Explanatory notes ANGLEDOOL 1:250 000 GEOLOGICAL SHEET SH/55–7 2nd Edition G.R. Burton Editor and contributing author: N.S. Meakin Published 2011 B.W. Mullard, Executive Director Mineral Resources Geological Survey of New South Wales Geological Survey of New South Wales Cartography (figures): Cheryl Hormann and Cassie Bambach Photography: Gary Burton (unless otherwise stated) Layout: Carey Martin Production management and index: Geneve Cox Printed by: Union Offset Printers, Canberra Bibliographic reference: BURTON G.R. 2011. Angledool 1:250 000 Geological Sheet SH/55–7, 2nd edition, Explanatory Notes. Geological Survey of New South Wales, Maitland, NSW. Cover photograph: Aerial shot of opal workings in the Preserved Opal Fields, taken in 1994. Underground mining is evidenced by mullock heaps. (Photographer: David Barnes). iii DISCLAIMER Copyright statement © State of New South Wales through NSW Department of Trade and Investment, Regional Infrastructure and Services 2011. 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ISSN 1321–828X ISBN 0 7347 1710 5 contents iv Abstract .................................................................................................................................................................................................. vii Acknowledgments ............................................................................................................................................................................... vii Editorial and explanatory notes....................................................................................................................................................... viii INTRODUCTION ......................................................................................................................................................................................... 1 Regional geological setting ................................................................................................................................................................. 1 Mapping method ................................................................................................................................................................................... 1 Quaternary stratigraphic subdivision ............................................................................................................................................... 2 MESOZOIC TO TERTIARY STRATIGRAPHY .......................................................................................................................................... 5 Cretaceous ............................................................................................................................................................................................... 5 Griman Creek Formation (Krg) of the Rolling Downs Group ................................................................................................. 5 Stratigraphic nomenclature and constituent units ............................................................................................................. 5 Type section, boundaries and thickness ................................................................................................................................ 6 Lithology ........................................................................................................................................................................................ 6 Palaeontology and age ............................................................................................................................................................... 6 Environment of deposition ........................................................................................................................................................ 8 Miocene .................................................................................................................................................................................................... 8 Gravels ................................................................................................................................................................................................. 8 Representative localities, boundaries and thickness .......................................................................................................... 8 Lithology ........................................................................................................................................................................................ 9 Palaeontology and age ............................................................................................................................................................. 10 Environment of deposition ...................................................................................................................................................... 10 Silcrete gravel with or without in situ silcrete ......................................................................................................................... 10 QUATERNARY STRATIGRAPHY ............................................................................................................................................................. 11 Units confined to the ridge system ................................................................................................................................................. 12 Colluvium (Qc) .................................................................................................................................................................................. 13 Dunes developed upon colluvium (Qcd) ..............................................................................................................................11 ‘Box hollow’ facies (Qb) .................................................................................................................................................................. 12 Units of the plains ................................................................................................................................................................................ 12 Riverine plain morphology .......................................................................................................................................................... 12 Bugwah Formation (Qr) ................................................................................................................................................................. 12 Channel facies (Qrc) ................................................................................................................................................................... 13 Meander plain facies (Qrm) ..................................................................................................................................................... 14 Crevasse splay facies (Qrl) ........................................................................................................................................................ 15 Backplain facies (Qrb) ................................................................................................................................................................ 15 Nullawa Member (Qrn) ............................................................................................................................................................. 15 Channel facies (Qrnc) .......................................................................................................................................................... 15 Splay facies (Qrns) ................................................................................................................................................................. 16 Backplain facies (Qrnb) ........................................................................................................................................................ 16 Marra Creek Formation (Qm) ....................................................................................................................................................... 17 Channel facies (Qmc) ................................................................................................................................................................ 17 Meander plain facies (Qmm) .................................................................................................................................................. 17 Backplain facies (Qmb) ............................................................................................................................................................ 17 Channelised backplain facies (Qmbc) .............................................................................................................................. 18 Flood basin backplain facies (Qmbf) ................................................................................................................................ 18 Ridge-bounded flood basin facies (Qmr) ............................................................................................................................. 18 Flood basin facies (Qmf) .......................................................................................................................................................... 19 Lake facies (Qmk) ...................................................................................................................................................................... 19 Source-bordering dunes (Qd) ..................................................................................................................................................... 20 STRUCTURE ................................................................................................................................................................................................. 21 Surface features .................................................................................................................................................................................... 21 Structures observed in opal workings and drillcore.................................................................................................................... 23 ‘Box hollows’ and other circular features ....................................................................................................................................... 23 ‘Blows’ ..................................................................................................................................................................................................... 24 Basement structures ............................................................................................................................................................................ 25 v BASEMENT GEOLOGY .............................................................................................................................................................................27 Palaeozoic .............................................................................................................................................................................................. 27 Structures affecting the Mesozoic sequence ................................................................................................................................ 28 WEATHERING ............................................................................................................................................................................................ 31 ECONOMIC GEOLOGY .............................................................................................................................................................................33 Opal ......................................................................................................................................................................................................... 33 Geological setting of opal deposits ........................................................................................................................................... 33 Timing of opal formation ............................................................................................................................................................. 40 Opal formation models ................................................................................................................................................................. 40 Weathering processes and passive structural control ...................................................................................................... 40 Upwelling fluids with active structural control .................................................................................................................. 40 Biological processes .................................................................................................................................................................. 41 Relationship of opal workngs to surface structures .............................................................................................................. 41 Gravel deposits ..................................................................................................................................................................................... 45 Sand and loam deposits .................................................................................................................................................................... 45 Water resources .................................................................................................................................................................................... 45 Petroleum ............................................................................................................................................................................................... 45 Coal .......................................................................................................................................................................................................... 45 Diamonds ............................................................................................................................................................................................... 45 GEOLOGICAL HISTORY .......................................................................................................................................................................... 47 Basement ................................................................................................................................................................................................ 47 Surat Basin, Tertiary and Quaternary systems ............................................................................................................................... 47 REFERENCES ..............................................................................................................................................................................................49 APPENDIXES ..............................................................................................................................................................................................53 Appendix 1 ............................................................................................................................................................................................. 53 Geological sites data ...................................................................................................................................................................... 54 Appendix 2 ............................................................................................................................................................................................. 71 Thin section descriptions .............................................................................................................................................................. 71 Appendix 3 ............................................................................................................................................................................................. 72 Soil sample descriptions ................................................................................................................................................................ 72 Appendix 4 ............................................................................................................................................................................................. 82 Rock sample descriptions ............................................................................................................................................................. 82 Appendix 5 ............................................................................................................................................................................................. 83 Thermoluminescence (TL) dating ............................................................................................................................................... 83 Appendix 6 ............................................................................................................................................................................................. 84 Palaeontology .................................................................................................................................................................................. 84 Fossil fauna .................................................................................................................................................................................. 84 Fossil flora .................................................................................................................................................................................... 84 LOCALITY INDEX ......................................................................................................................................................................................87 Tables table 1: Subunits of the Griman Creek Formation ....................................................................................................................... 5 table A: Geological sites data .......................................................................................................................................................... 54 table B: Thin section descriptions .................................................................................................................................................. 71 table c: Descriptions of alluvial material based on binocular microscope examination ................................................. 73 table D: Percentage estimate and description of clay component in alluvial samples .................................................... 79 table e: PIMA analysis of Quaternary alluvium ........................................................................................................................... 81 table F: PIMA analysis of rock samples ......................................................................................................................................... 82 table G: Thermoluminescence data .............................................................................................................................................. 83 table H: Cretaceous fossil list .......................................................................................................................................................... 85 Figures Figure 1. Location of the Angledool 1:250 000 map sheet area (Angledool) ......................................................................... 1 Figure 2. Regional geological setting of Angledool ..................................................................................................................... 2 Figure 3. Stratigraphic column for Angledool ............................................................................................................................... 3 vi angledool 1:100 000 geological sheet Figure 4. Stratigraphic column for the Surat Basin rocks .......................................................................................................... 4 Figure 5. Schematic representation of Tertiary and Quaternary sediments at Cumborah quarries .............................. 8 Figure 6. Schematic diagram showing riverine morphological terms used in this study ................................................ 12 Figure 7. Characteristics of the different Quaternary alluvial systems ................................................................................. 13 Figure 8. Interpreted surface lineaments for Angledool ........................................................................................................... 21 Figure 9. Interpreted radial and concentric lineaments in the Narran Lake area .............................................................. 22 Figure 10. Sketch of ‘blow’ structure at Grawin Creek . ............................................................................................................. 24 Figure 11. Aeromagnetic image for Angledool ............................................................................................................................. 25 Figure 12. Gravity map for Angledool .............................................................................................................................................. 26 Figure 13. Interpreted basement stratotectonic units of Angledool ....................................................................................... 27 Figure 14. Interpreted basement structure for Angledool ......................................................................................................... 29 Figure 15. Basement time structure contours across the Lightning Ridge Shelf ................................................................ 29 Figure 16. Opal fields of Grawin, Glengarry and Carters Rush area on a Landsat image .................................................. 35 Figure 17. Map of opal fields in the Coocoran area on a Landsat image ............................................................................... 36 Figure 18. Map of opal fields in the Lightning Ridge area on a Landsat image ................................................................... 37 Figure 19. Map of opal fields in the Wyoming area on a Landsat image ............................................................................... 38 Figure 20. Map of opal fields in the Muttabun area on a Landsat image .............................................................................. 39 Figure 21. Map of opal fields in the Mehi area on a Landsat image ....................................................................................... 39 Figure 22. Map of opal fields and interpreted lineaments in the map sheet area ....................................................... 42–43 Figure 23. Schematic models: Natalies Dream Lineament and opal localisation ................................................................ 44 Figure A. SWIR spectra of Quaternary alluvial samples ............................................................................................................. 72 Figure B. SWIR spectra of rock samples ....................................................................................................................................... 82 Photographs Plate 1. Early Cretaceous opalised fossils of the Griman Creek Formation ............................................................. 7 Photograph 1. Claystone rip-up clasts in sandstone ................................................................................................................. 6 Photograph 2. Quartz-rich gravels at Cumborah ....................................................................................................................... 9 Photograph 3. Quartz-rich gravels overlain by sandy unit, Site 237 ..................................................................................... 9 Photograph 4. Porcellanite band in Tertiary gravels at Cumborah ........................................................................................ 9 Photograph 5. ‘Knobby’ silcrete in the Grawin Creek area .................................................................................................... 10 Photograph 6. Typical colluvium (Qc), dominated by red sand ............................................................................................11 Photograph 7. Dunes developed upon colluvium (Qcd), eastern side of Narran Lake ...................................................11 Photograph 8. Typical ‘box hollow’ (Qb) .................................................................................................................................... 12 Photograph 9. Geomorphic expression: Bugwah Formation channel facies (Qrc) ......................................................... 14 Photograph 10. Geomorphic expression: Bugwah Formation channel facies (Qrc) .......................................................... 14 Photograph 11. Geomorphic expression: Bugwah Formation meander plain facies (Qrm) ............................................ 14 Photograph 12. Geomorphic expression: Bugwah Formation meander plain facies (Qrm) ............................................ 14 Photograph 13. Geomorphic expression: Bugwah Formation backplain facies (Qrb) ...................................................... 15 Photograph 14. Geomorphic expression: Nullawa Member channel facies (Qrnc) ........................................................... 16 Photograph 15. Geomorphic expression: Nullawa Member splay facies (Qrns) ................................................................. 16 Photograph 16. Geomorphic expression: Nullawa Member backplain facies (Qrnb) . ...................................................... 16 Photograph 17. The Birrie River representing Marra Creek Formation channel facies (Qmc) ........................................ 17 Photograph 18. Geomorphic expression: Marra Creek Formation backplain facies (Qmb) ............................................ 18 Photograph 19. Geomorphic expression: Marra Creek Formation channelised backplain facies (Qmbc) .................. 18 Photograph 20 Geomorphic expression: Marra Creek Formation flood basin backplain facies (Qmbf) ..................... 18 Photograph 21. Geomorphic expression: Marra Creek Formation ridge-bounded flood basin facies (Qmr) ............. 19 Photograph 22. Coocoran Lake — Marra Creek Formation flood basin facies (Qmf) ....................................................... 19 Photograph 23. Eastern edge of Narran Lake — Marra Creek Formation lake facies (Qmk) ........................................... 19 Photograph 24. Geomorphic expression: Dune system developed on Bugwah Fm. meander plain facies (Qd) ...... 20 Photograph 25. Partly ferruginised and laminated sandstone and siltstone, Griman Creek Formation . .................... 23 Photograph 26. ‘Blow’ breccia ......................................................................................................................................................... 25 Photograph 27. Opal ......................................................................................................................................................................... 33 Photograph 28. Three Mile opal field ............................................................................................................................................ 34 Photograph 29. Nebia Hill opal mine ............................................................................................................................................ 34 Photograph 30. Opal mining — sorting through opal dirt ...................................................................................................... 34 Photograph 31. Ellipsoidal fracture in Cretaceous sandstone ................................................................................................ 34 Photograph 32. ‘Steel band’ grading into opaline silica veinlets in claystone ..................................................................... 34 Photograph A. Arrangement for TL sample collection ........................................................................................................... 83 Photograph B. Angiosperm leaf impression — a broad-leaved dicot showing pinnate venation ............................... 84 vii Abstract The Angledool 1:250 000 map sheet area (Angledool) is located in northern New South Wales, and includes the opal fields around Lightning Ridge. This report discusses the results of the second generation of geological mapping of the map sheet. The area covers part of the Mesozoic Surat Basin, a sub-basin of the Great Australian Basin, which overlies rocks of the Palaeozoic Lachlan Orogen. Rocks of the Surat Basin in Angledool are overlain by Tertiary (Miocene) gravels, which are commonly silicified. Much of the area is covered by Quaternary alluvium. The oldest exposed rocks in Angledool belong to the Early Cretaceous Griman Creek Formation of the Rolling Downs Group. They consist of sandstone, claystone and siltstone and form a north-northeasterly trending ridge system through the central part of the area, as well as another ridge system in the eastern part, west of Collarenebri. Miocene gravels are also only exposed on the ridge areas, where they are generally silicified to silcrete and form resistant plateaus which shield the less resistant Cretaceous rocks. The ridge systems are blanketed by Quaternary colluvium, consisting of red sand, iron oxide pisoliths and a variable amount of rock fragments. Surrounding the ridges is an essentially flat plain consisting of Quaternary alluvium which has been subdivided into two morphostratigraphic units. The oldest is the Late Pleistocene Bugwah Formation which is characterised by wide, large wavelength, meandering channels. The broad meander plains formed from the deposition of a mixed bed load and suspended load in a moderate energy system. Within Angledool the lower part of the Bugwah Formation has been assigned to the Nullawa Member (nov.), which generally has a medial to distal distributive morphology but in places has characteristics more typical of the parent Bugwah Formation. The Holocene Marra Creek Formation overlies both of these units and constitutes the current drainage system, characterised by narrow, tightly meandering channels with a narrow meander plain facies and a broad backplain facies. The Marra Creek Formation represents deposition of a suspended load by a low energy system. Flow in all cases was from northeast to southwest. Lineaments interpreted from aerial photographs generally trend northeasterly, with a few orthogonal conjugate lineaments trending northwesterly. These structures are related to the northeast-trending Darling River Lineament, which was active during the Tertiary. A system of radial and concentric curvilinear structures in the southwestern part of Angledool occurs to the south and southeast of a positive magnetic anomaly which is interpreted to correspond to a granite intrusion forming a basement topographic high. A less likely interpretation is that the structure is related to a buried impact crater. Apart from this system there is no direct correlation between interpreted surface structures and basement structures detectable in regional geophysical data. The Angledool 1:250 000 map sheet area is economically significant as it contains the opal fields of the Lightning Ridge, Coocoran, Grawin–Glengarry, Muttabun, Wyoming and Mehi areas, which collectively constitute the world’s premier black opal fields. Opal occurs in the top 30 m of the Cretaceous rocks of the ridge system and has formed by the weathering (kaolinisation) of those rocks, probably during the Late Cretaceous to early Tertiary. Opal generally occurs in the top 1 m of claystone layers beneath sandstone beds. Surface structures appear to have influenced the distribution of some known opal occurrences, though the relationship between opal and structure remains unclear. Structures may have influenced the flow of silica-bearing fluids during opal formation and/or may have influenced (via uplift and down-faulting) the preservation of opal. Structures may also have influenced the distribution of sandstone, either during or after its deposition, which in turn may have affected the localisation of opal. Acknowledgments Bob and Shannon Barratt supplied samples from their opal mine for analysis. Dave Price (University of Wollongong) carried out the thermoluminescence dating of the sand material from the Nullawa Member. Staff of the Lightning Ridge office of the Division of Resources and Energy, are thanked for their assistance, particularly Warwick Schofield who helped validate the list of named opal working areas in the region. The Australian Opal Centre is thanked for providing photographs and advice on fossils. Bob Brown is thanked for editing the draft version of this report. John Watkins is thanked for technical assistance and assisting with peer review. Ian Percival is also thanked for peer reviewing part of the manuscript. Careful scrutiny by Simone Meakin has greatly improved an earlier version of the manuscript. viii angledool 1:100 000 geological sheet Resources and Energy) corporate Sites database. All of the sites referred to in these notes are prefixed by 8439GRB (the number referring to the Lightning Ridge 1:100 000 map sheet), regardless of where they lie within the Angledool 1:250 000 map sheet area. The letters indicate the initials of the geoscientist who collected the data (G.R. Burton). Classification of rocks and sediments For the sediments and sedimentary rocks described in these notes the Udden–Wentworth grain size scale was used, prefixed by prominent clast components (more dominant towards the right hand lithological name). For example, sandy clayey silt refers to sediment composed mostly of silt with lesser, but significant, clay and even less sand. Timescale In these notes the ages of eras, periods and epochs are based on those given in Gradstein et al. (2004). However, the term Tertiary is used herein to refer to the time period between 65.5 and 1.81 Ma and the term Quaternary is used herein to refer to the time period between 1.81 Ma and the present. Editorial and explanatory notes Map versions These notes accompany the second edition of the Angledool 1:250 000 geological map (Burton 2011). The first edition of the Angledool 1:250 000 geological map sheet was produced by Offenberg (1968) and accompanied by a set of explanatory notes (Offenberg 1967). Grid references Grid references were collected relative to the Map Grid of Australia (using the Geodetic Datum of Australia 1994, Zone 55) and all azimuths are with respect to true north. In these notes and related maps, grid references are represented by 13 digits (e.g. GR 575300 6736200) and are generally considered to be accurate to ± 20 m. A Global Positioning System (GPS) receiver was used for positioning field sites during the course of field mapping. Field locality numbers Field locality, or site, numbers are referred to in these notes. These numbers relate to those in the Geological Survey of New South Wales (Division of 1 IntRoDUctIon 100 m and also resulted in local surface silicification of the Cretaceous rocks (Taylor 1976, 1978). Unconformably overlying the Griman Creek Formation are Tertiary sands and gravels, commonly cemented by silica to form silcrete caps. It is largely these caps which have shielded the underlying Cretaceous rocks, leaving the ridges which exist today. The gravels correlate with the Cumborah Gravel (Taylor 1972) which has been assigned a Middle to Late Miocene age (Taylor 1978; Martin 1980, 1981). The silicification event (the Mount Charlotte Silcrete) was assigned a Pliocene age (Taylor 1976). Surrounding the ridges is unconsolidated Quaternary alluvium of the Bugwah Formation (including the Nullawa Member) and Marra Creek Formation. The ridges are immediately surrounded by, and variably covered in, red sand which is apparently derived from the breakdown of the ferruginous silcrete caps, though there is probably also a minor aeolian component. For example, Tate et al. (2004) identified aeolian sand deposits up to 0.1 m thick on plateaus of Miocene volcanics in the Byrock area, some 100 km southwest of Angledool. Mapping method The second edition of the Angledool 1:250 000 geological map sheet has been produced using two The Angledool 1:250 000 map sheet area (Angledool) is located in northern New South Wales, with the Queensland border marking its northern edge (Figure 1). The Castlereagh Highway is the main access route through the largely agricultural area and is one of the few sealed roads present. Most access is via unsealed tracks. Lightning Ridge, Goodooga, Cumborah and Angledool constitute all of the built-up areas. The terrain covered by Angledool is mostly flat-lying and dominated by the present day alluvial systems including the Bokhara, Narran, Barwon, Birrie and Culgoa rivers (Figure 1). The central part of the area is dominated by a north-northeasterly trending ridge system, which rises to about 20 m above the surrounding plain. The plain itself ranges from about 120 to 140 m above sea level. Another north- northeasterly trending ridge system is present in the eastern part of area, west of Collarenebri. Regional geological setting The study area is situated within the Mesozoic Surat Basin, a sub-unit of the Great Australian Basin (Figure 2). The exposed Mesozoic rocks in Angledool area were assigned by Byrnes (1977) to the Cretaceous Griman Creek Formation of the Rolling Downs Group (Figure 3). An Early Eocene weathering event caused kaolinisation and ferruginisation to a depth of about SYDNEY Angledool 1:250 000 map sheet area New South Wales DUNUMBRAL 8539 NARRAN 8338 CUMBORAH 8438 DUNGALEAR 8538 GOODOOGA 8339 LIGHTNING RIDGE 8439 Angledool SH/55-7 Lightning Ridge Goodooga Cumborah New Angledool Walgett 4km Narran Lake Coocoran Lake Angledool Lake Bir rie Riv er Cu lgo a Riv er Bo kha ra Riv er Ba rw on Riv er Na rra n Ri ve r Th e Bi g W ar ra m bo ol 0 40 km20 2010_03_0015 N 147°00’E 29°00’S 29°30’S 30°00’S 147°30’E 148°00’E 148°30’E Figure 1. Location of the Angledool 1:250 000 map sheet area (Angledool) showing main roads, tracks and drainage 2 angledool 1:100 000 geological sheet mapping methods — based on aerial photograph and Landsat7 image interpretation. Fieldwork was conducted from 2001 to 2003, with supporting data provided in Appendixes 1 to 5. The ridge systems, including all the exposed consolidated rocks of the area, have been mapped by stereographic interpretation of aerial photographs. The following photo sets were used: • Dunumbral 1968, approx. 1:50 000 black and white • Narran 1969, approx. 1:60 000 black and white • Dungalear 1967, approx. 1:50 000 black and white • Cumborah 1959, approx. 1:60 000 black and white • Cumborah 1978, approx. 1:60 000 black and white • Lightning Ridge 1978, approx. 1:60 000 black and white The aerial photographs, with geological interpretation overlays, were scanned and then rectified to the GDA 94 MGA Zone 55 grid using panchromatic Landsat 7 imagery as a base. Rectification was carried out using a triangulation method in ER Mapper 6.2 and this was found to be accurate to better than 100 m. The rectified images were imported into Arcview 3.2 and the line work was digitised on-screen at 1:20 000 scale. Interpretation of aerial photographs allowed reasonably accurate delineation of the Cretaceous, Tertiary and colluvial units, as well as the identification of structures. The resolution of the aerial photographs, combined with the ability to study them stereographically, made them the best data set for geological mapping of the ridge system. The surrounding plain was mapped by on-screen interpretation in Arcview 3.2 of Landsat 7 imagery at 1:40 000 scale. This method was employed as it was quicker and just as, if not more, accurate than aerial photo interpretation of the alluvial systems. It was found that the most useful combination for geological interpretation was a red–green–blue (RGB) combination of bands 3, 2 and 1. To a lesser extent band combinations 1, 5 and 7 and 1, 4 and 7 were also used. The following table shows the wavelength range for each of the Landsat 7 bands. (Source: Landsat 7 website — landsat.gsfc.nasa.gov/ index.html, viewed 2006) Radioelement imagery, released by the (then) NSW Department of Mineral Resources in 1995 as part of its Discovery 2000 initiative, was found to be of limited use due to the low resolution of the data (400 m line spacing, 80 m flight height). Some mapped units have a characteristic radiometric signature in this data set, but generally most do not. Once compiled, the mapping was checked by visiting key areas in the field. It was found that the interpretations were accurate to ± 100 m, with little revision of the line work required after field work. The principal purpose of the field work was to collect sufficient information to describe the various mapped units. Appendix 1 tabulates the geological site data. Overall it was found that this method of mapping was very effective and has great potential for application to similar terrain elsewhere in northern NSW. Quaternary stratigraphic subdivision The Quaternary alluvial systems of Angledool area have herein been subdivided following the terminology of Watkins and Meakin (1996), who mapped the Quaternary units of the Walgett and Nyngan 1:250 000 map sheet areas. Those workers defined the Marra Creek Formation and Bugwah Formation, which are also recognised within Angledool. The Nullawa Member is a newly defined stratigraphic unit. Landsat band Wavelength (μm) 1 0.45N0.52 2 0.53N0.61 3 0.63N0.69 4 0.75N0.90 5 1.55N1.75 6 10.40N12.50 7 2.09N2.35 8 (panchromatic) 0.52N0.90 Surat Basin (Mesozoic) Lachlan Orogen (Palaeozoic) Sydney and Gunnedah Basin (Mesozoic) N ew England O rogen (Palaeozoic) 147°00’E 148°00’E 149°00’E 30°00’S 150°00’E 146°00’E 29°00’S 31°00’S 32°00’S 2010_03_0016 Bourke Lightning Ridge Walgett Coonamble Gunnedah Cobar Dubbo Coonabarabran 0 200 km N Figure 2. Regional geological setting of Angledool; geological boundaries after Hawke and Cramsie (1984) and Shaw (2002) 3 introduction ? ? ? ? ? ? ? ? ? STRATIGRAPHIC UNITSERIESEPOCHER A C E N O ZO IC Q U AT E R N A R Y N E O G E N E TE R TI A R Y PA LA E O G E N E C R E TA C E O U S JU R A S S ICM E S O ZO IC HOLOCENE PLEISTOCENE PLIOCENE MIOCENE OLIGOCENE EOCENE PALEOCENE LATE LATE EARLY MIDDLE Marra Creek Formation Bugwah Formation undifferentiated sediments Rolling Downs Group Bungil Formation Mooga Sandstone Orallo Formation Pilliga Sandstone Purlawaugh Formation L L L L L L M M M E E E E E E ES TI M AT ED AG E ‘Canaway’ weathering event ‘Morney’ weathering event SYSTEM/ PERIOD Ma Llanillo silcrete Nullawa Member Mount Charlotte Silcrete Early Miocene weathering (McQueen et al. 2007) 0.01 0.126 0.78 1.81 5.3 23 33.9 55.8 65.5 99.6 145.5 161.2 175.6 2010_03_0017 Figure 3. Stratigraphic column for Angledool. Mesozoic units after Shaw (2002); Tertiary sediments after Taylor (1978) and Martin (1980, 1981); Mount Charlotte Silcrete and Llanillo Silcrete after Taylor (1976, 1978); Morney and Canaway weathering events after Indurm and Senior (1978); Early Miocene weathering event after McQueen et al. (2007); Marra Creek and Bugwah formations after Watkins and Meakin (1996); Nullawa Member (this study) is shown as Late Pleistocene based on overprinting by Bugwah Formation, although a single thermoluminescence (TL) sample (this study) returned an age of approximately 2600 years BP. It is possible that either the TL date is not indicative of the true depositional age of the Nullawa Member and/or the top of the Bugwah Formation is younger than previously recognised. Numerical ages are after Gradstein et al. (2004). 4 angledool 1:100 000 geological sheet 2010_03_0018 Griman Creek Formation Surat Siltstone Fine-grained sandstone, siltstone and claystone. Intraformational conglomerate and coal present in upper part. Interbedded siltstone and carbonaceous and pyritic mudstone Siltstone interbedded with mudstone and minor, very fine- to fine-grained lithic sandstone. Thin coal seams in places. Mudstone with subordinate siltstone Fine-grained lithic sandstone, siltstone and mudstone with surbordinate coarse-grained quartzose sandstone. Thin coal seams in places. Quartzose, sub-labile sandstone, minor siltstone, shale, mudstone and coal Medium-grained, sub-lithic sandstone and interbedded siltstone and mudstone with minor coal Medium- to coarse-grained, well sorted quartzose sandstone with minor interbeds of mudstone, siltstone and fine-grained sandstone Siltstone, mudstone, kaolinitic claystone interbedded with carbonaceous to coaly shale, thin coal seams and fine- to medium-grained lithic–labile sandstone. The coal is stratigraphically equivalent to the Walloon Coal Measures of the southern Surat Basin. Coreena MemberR ol lin g D ow ns G ro up Ea rly C re ta ce ou s W al lu m bi lla Fo rm at io n Bungil Formation Mooga Sandstone Orallo Formation Pilliga Sandstone Purlawaugh Formation Doncaster Member La te J ur as si c M id dl e Ju ra ss ic Figure 4. Stratigraphic column for the Surat Basin rocks within Angledool; after Shaw (2002) and references therein. 5 MesoZoIc to teRtIARY stRAtIGRAPHY The Griman Creek Formation is the only Mesozoic unit which crops out within Angledool. The cross- sections on the Angledool 1:250 000 map face, depict the stratigraphic relationships of the units underlying the Griman Creek Formation. Figure 4 illustrates the stratigraphic column and presents a brief description of the Mesozoic units interpreted to exist within the study area after Shaw (2002). Cretaceous Griman Creek Formation (Krg) of the Rolling Downs Group (defined by Reiser 1970) The outcropping Cretaceous rocks of Angledool have been assigned to the Griman Creek Formation. Stratigraphic nomenclature and constituent units The name comes from Griman Creek, near Surat in southeastern Queensland, where the unit crops out, mainly in an area referred to as the Surat Inlier, defined as the area of Cretaceous outcrop mainly to the south and east of Surat, bounded by the Cenozoic sediments of the Condomine, Balonne and Moonie rivers (Reiser 1970; Exon 1976). Stratigraphic nomenclature of sub- units of the Griman Creek Formation is shown in Table 1. Whiting and Relph (1961) referred to the top 30 m of the Cretaceous rocks in the local area of Lightning Ridge as the ‘Lightning Ridge Group’. They subdivided this into the ‘Coocoran Claystone’, a fine-grained white to cream claystone, which Byrnes (1977) described as a laminite comprising alternating sandy and clayey laminae of 10 mm or less thickness; the ‘Wallangulla Sandstone’, a fine-grained, white, clayey sandstone; and the ‘Finch Clay–Shale’ or ‘Finch Claystone’, a grey to buff-coloured clay shale, commonly called ‘opal dirt’. Byrnes (1977) also recognised the ‘Coocoran Claystone’ and the ‘Wallangulla Sandstone’ but referred to them as members of the Griman Creek Formation, while he assigned the ‘Finch clay’, consisting of numerous clay beds interbedded with sandstone, to a facies within the ‘Wallangulla Sandstone’. Offenberg (1967) noted that while the units of Whiting and Relph (1961) can be observed in shafts at Lightning Ridge it would be very difficult to map those subdivisions for any distance. Similarly, MacNevin (1975) considered those subdivisions as useful within the opal workings of the immediate Lightning Ridge area but not mappable on a regional scale. Byrnes (1977) considered that the sequence of Whiting and Relph (1961) was recognisable Griman creek Formation ta bl e 1: s tr at ig ra ph ic n om en cl at ur e of th e up pe r 3 0  m o f t he G ri m an c re ek F or m at io n in th e Li gh tn in g Ri dg e ar ea (m od ifi ed fr om H aw ke & B ou rk e 19 84 ) st ra ti gr ap hi c no m en cl at ur e Li th ol og y th ic kn es s ty pe s ec ti on (n ew ) W hi tin g an d Re lp h 19 61 By rn es 1 97 7 an d he re in H aw ke a nd B ou rk e 19 84 Li gh tn in g Ri dg e G ro up Co oc or an C lay sto ne G rim an C re ek Fo rm at io n (u pp er p ar t) Co oc or an C la ys to ne M em be r Fi ne -g ra in ed , p al e, ka ol in iti c cla ys to ne ; o fte n sil ici fie d to po rc el la ni te (‘ sh in cr ac ke r’) ; t hi n sa nd y a nd cl ay ey la m in ae Th e c om pl et e G rim an Cr ee k Fo rm at io n is 19 6. 5  m th ick in b or eh ol e (B ou rk e 1 97 3) Th e C oo co ra n Cl ay sto ne M em be r i s 0 –3 .6  m th ick (W hi tin g & R elp h 19 61 ) Lu na tic H ill o pe n cu t ( G R 59 39 40 m E 67 40 35 4m N ) e xp os es al l u ni ts of th e f or m at io n in it s ea ste rn w al ls. W al la ng ul la Sa nd sto ne W al la ng ul la Sa nd st on e M em be r ( in clu di ng F in ch cl ay fa ci es ) Fi ne - t o m ed iu m -g ra in ed , p al e, cla ye y s an ds to ne ; c lay sto ne pe lle ts ; s om e c ro ss -b ed di ng 4– 19  m th ick (W hi tin g & Re lp h 19 61 ) Fi nc h Cl ay sto ne ‘O pa l d irt ’, g re y t o bu ff m on tm or ill on ite -r ich cl ay sto ne Le ns es o f t he cl ay fa ci es ar e 1 .2 –6  m th ick (W hi tin g & R elp h 19 61 ), bu t u su al ly 1– 2  m . 6 angledool 1:100 000 geological sheet between the opal fields of Coocoran, Mehi and Lightning Ridge but not in the Grawin and Glengarry opal fields although he noted the similarity in rock types between those areas. Type section, boundaries and thickness Reiser (1970) defined the type section of this formation to be within the cored section of Geological Survey of Queensland drillhole Surat 3 between 25’ and 1135’ (7.6 m and 346 m). Exon (1976) stated that the maximum thickness is 400 m in the Surat Inlier but thins towards the margins of the Surat Basin. Bourke (1973) described a sequence of siltstone interbedded with poorly sorted sandstone between 16.7 and 213.2 m depth in (vertical) bore hole 34677 Lightning Ridge which he assigned to the Griman Creek Formation. This thickness (196.5 m) would be an approximate maximum thickness for the unit in Angledool. The unit is conformable with the underlying Surat Siltstone (Reiser 1970; Bourke 1973), while it is unconformably overlain by Tertiary gravels. Lithology In Angledool the rocks of this formation consist of interbedded sandstone, claystone and siltstone. In outcrop the Cretaceous rocks are kaolinised and white. Observations from opal workings indicate that the kaolinisation extends to a depth of at least 25 m (Burton 2003a), while in drillcore Burton (2003a) recognised it to at least 50 m. Taylor (1978) stated that weathering effects in the Cretaceous rocks extend to 100 m depth. The sandstone is generally fine- to medium-grained and rarely coarse-grained. Unweathered sandstone is generally grey (as observed in drillcore, Burton 2003a). Thin section observation indicates that the sandstone consists of at least 60% feldspar grains (now altered to kaolinite); approximately 20% quartz grains; up to 10% lithic grains, which are apparently very fine-grained rhyolitic fragments; and up to 10% matrix material which is very fine-grained and difficult to identify. The grains are commonly angular and of low sphericity and the rocks are generally moderately well sorted. A felsic volcanic origin for the material is evident. Sandstone beds range in thickness from several centimetres to at least 6 m and fining-upward units with erosional bases are common. However, these features are best observed within opal workings and drillcore, as outcrop of the Cretaceous rocks is generally not coherent. Rounded to irregularly- shaped claystone rip-up clasts and disaggregated claystone horizons within sandstone units are common (Photograph 1). Sandstone is generally massive to rarely laminated. In places the sandstone is cross- bedded and Burton (2003a) reported ripple patterns in interlaminated sandstone and claystone. Siltstone is laminated to massive. In places it forms gradational tops to fining-upward sandstone beds. It occurs interbedded with sandstone and claystone and in places is finely interlaminated with claystone to form laminite. Claystone forms beds from several centimetres to about 10 m in thickness. Below the kaolinised zone, claystone ranges from light grey to grey in colour (Burton 2003a). In places (generally at depth and rarely at the surface) weathering has turned the claystone to a purple to mottled purple and white/ grey colour. Burton (2003a) suggested that this colour change may represent part of a palaeosol profile. In places the upper part of the Cretaceous sequence has been silicified. Silicification appears to be mainly associated with the Pliocene silcrete-forming event (Figure 3), though it probably also occurred in the Early Eocene (Llanillo Silcrete, Taylor 1978), before deposition of the Tertiary gravels. Silicification usually extends to no more than 10 m below the surface. Where the silicified Cretaceous rock is very hard, particularly where claystone has been converted to porcellanite, the rock is locally referred to by miners as ‘shincracker’. Sporadically at depth, not far above the opal levels, silicified sandstone, or ‘steel band’ occurs, ranging in thickness from several millimetres to about 1 m. ‘Steel band’ is not always associated with opal, but observations (this study, see Economic Geology section) suggest that it formed contemporaneously with opal deposits. Palaeontology and age Fossil remains are relatively abundant within the Griman Creek Formation. It is renowned for yielding a diversity of rare opalised fossils (e.g. see Plate 1), Photograph 1. Claystone rip-up clasts in a displaced block of sandstone, Site 20 (GR 572044 6735350). Lens cap is 50 mm in diameter. 7 mesozoic to tertiary stratigraphy Plate 1. Early Cretaceous opalised fossils recovered from discarded surface dirt at Lightning Ridge. Fossils are from the collection of the Australian Opal Centre except C and F from the collection of the Australian Museum. A. Fish palate with finely-preserved, sharply-pointed teeth. B. Corbiculid bivalve, one of the smallest and most rare bivalve taxa in the Lightning Ridge fauna. C. Turtle shell fragment with ornamentation. D. Pine cone with scales dessicated prior to fossilisation. E. Sauropod dinosaur tooth. F. Lower jaw fragment of the monotreme mammal Steropodon galmani, one of the most significant fossils ever found in Australia, featured on the cover of the journal Nature. Scale bar = 5 mm. Photographer Robert A. Smith. Photographs and caption courtesy of the Australian Opal Centre. 8 angledool 1:100 000 geological sheet 2010_03_0019 ground level erosional boundary gradational boundary Friable conglomerate; quartz pebbles up to 30 mm, generally less than 15 mm diameter, in fine-to medium- grained quartz sand matrix Hard siliceous (porcellanite) lens up to 10 mm thick Friable sandstone with sporadic quartz pebbles and granules up to 5 mm; weak horizontal laminae Quaternary colluvium; red sand with silcrete boulders 1 m Figure 5. Schematic representation of Tertiary gravels and sands overlain by Quaternary colluvium at Cumborah gravel quarries some of which are shown in Smith and Smith (1999), and is the only significant dinosaur locality in New South Wales. Many workers have described fossils from the area, including monotremes (Archer et al. 1985; Flannery et al. 1995, Musser 2005), crocodiles (Molnar 1980; Molnar and Willis 2001), bivalves (Hocknull 2000; Kear 2006), gastropods (Hamilton- Bruce et al. 2002; Hamilton-Bruce and Kear 2010), echinoderms, crustaceans, cartilaginous and bony fishes and lungfish (Smith and Smith 1999; Kemp and Molnar 1981), plesiosaurs, dinosaurs (Molnar and Galton 1986; Rich and Vickers-Rich 1994; Molnar 2010), pterosaurs, birds (Molnar 1999), turtles (Smith 2009; 2010), foraminifera (Scheibnerova 1974; 1984), plants (White 1986) and pollen (Morgan 1984). A palaeontological listing for the unit is provided in Appendix 6. Cylindrical cavities after reeds and sedges are common, ranging from several millimetres to about 1 cm in diameter, generally less than 10 cm in length and lying perpendicular, or at a high angle, to bedding. In places claystone units contain abundant plant fossils. Reiser (1970) concluded that the Griman Creek Formation was of early to middle Albian age, which accords with palynological age determinations by Burger (1980) and Morgan (1984). Exon (1976) noted that Laing and Allen (1955) had identified fossils of Dimitobelus sp. (a mollusc), indicating that the lower part of the Griman Creek Formation in southwestern Queensland is no older than Albian (112.0–99.6 Ma according to Gradstein et al. 2004), while spores of middle Albian age were identified by Burger (1976). Exon (1976) concluded that the Griman Creek Formation is probably of middle Albian age but possibly ranges into the late Albian. Environment of deposition The basal part of the Griman Creek Formation has been interpreted to have been deposited within a beach or near-shore marine environment, based on lithological, sedimentological and fossil evidence (Reiser 1970). The upper part of the Griman Creek Formation reflects terrestrial deposition within a flood plain environment (Reiser 1970) and includes freshwater pelecypods, coal and intraformational conglomerate (Exon 1976). Reiser (1970) interpreted the middle part of the formation to represent deposition within a paralic/deltaic environment, transitional from marine to freshwater. Lightning Ridge is unique among Australian opal fields in producing opalised fossils of predominantly freshwater and terrestrial plants and animals (Smith 2007, 2009) Miocene Gravels (Tg) Representative localities, boundaries and thickness The Griman Creek Formation is unconformably overlain by Tertiary gravels and sands, the majority of which have been silicified to silcrete. A quarry centred at GR 578003 6737351 exposes the unconformity. The silcrete is situated at the top of the plateau and has shielded the underlying, less resistant Cretaceous rocks. Its thickness ranges from less than 1 m to about 4 m and the unconformity is probably undulating. The Tertiary deposits consist of gravel and pebbly to granule-bearing quartz-rich sand. Sand and gravel are interbedded, with beds ranging from 1 cm to about 3 m in thickness. The best exposures of Tertiary gravel occur at Cumborah (Figure 5 and Photograph 2) and about 10 km southwest of Gravels 9 mesozoic to tertiary stratigraphy Photograph 2. Approximately 3 m thick layer of quartz-rich gravels at Cumborah with hammer on upper left side indicating location of Photograph 4; Site 237 (GR 574741 6708827), looking northwest. Collarenebri. In the Cumborah area, the gravel beds fine upwards into sand (Photograph 3). Another quarry, 6.5 km west of Angledool, contains silicified gravel which exhibits imbrication of flat pebble clasts. Photograph 3. Gradational contact from quartz-rich gravels (foreground) to overlying sandstone with sporadic quartz pebbles up to 5 mm across. The sandstone is weakly laminated, with laminae dipping about 18º to the southwest. Site 237 (GR 574741 6708827), looking west. Lithology The sand ranges from fine- (rare) to medium- to coarse-grained. The gravel is usually matrix- supported by coarse- to medium-grained sand. The clasts are dominantly quartz granules to pebbles, commonly up to about 20 mm in diameter, though pebbles up to about 0.1 m across are present. The clasts are always well-rounded, but of variable sphericity. They are usually white in colour, but an estimated 10% are black, with a very small fraction being red or brown. Petrified wood is present and white clasts (either chert and/or rhyolite — see Appendix 2) occur sporadically. Topaz has also been identified (R.E. Brown, Geological Survey of New South Wales, 2008 pers. comm.). It is noted that the proportions of the minor components vary from one locality to another, but no systematic trends in the proportions of pebble types were recognised in this study. The Tertiary sediments are mostly silicified to silcrete. Unweathered Tertiary sediments are commonly white, being almost completely comprised of quartz. A thin coating of red-brown iron oxide, commonly less than 1 mm thick, is generally developed on weathered surfaces of silcrete. Unconsolidated gravels occur sporadically intercalated with silicified gravels (Burton 2003a) suggesting either that silicification occurred along particular beds, or was contemporaneous with deposition. In the Cumborah area, a thin (up to 10 mm thick) porcellanite layer is present within otherwise unsilicified gravels (Photograph 4). In the Grawin Creek area (GR 565800 6728030) some silcrete has a ‘knobby’ texture (Photograph 5) consisting of an indurated ‘matrix’ of red-brown coloured, poorly sorted, coarse- to very coarse-grained quartz-rich sand and rounded, semi-spherical to irregularly shaped white ‘clasts’ ranging in size from about 5 mm to more than 0.1 m consisting of harder sand of identical composition to the ‘matrix’. The larger ‘clasts’ are more irregular Photograph 4. Porcellanite band in Tertiary gravels at Cumborah; Site 237 (GR 574741 6708827), looking southeast. The lens cap is approximately 50 mm in diameter. See Photograph 2 for location. 10 angledool 1:100 000 geological sheet in shape. It is here considered that locally variable degrees of silicification of the Tertiary sand has produced this ‘pseudo clastic’ texture in situ and it is not the result of reworking and recementing of earlier silcrete material. Although laterally extensive, most silcrete is obscured by colluvium. Exposures generally consist of rubbly subcrop and only via aerial photo interpretation can the silcrete be accurately mapped out. Most silcrete exposures are found at the edge of the silcrete plateau. Several sinuous ridges on the plateau have been identified on aerial photographs (Burton 2003a) and found to comprise rubbly piles of silcrete. These features are interpreted as remnant, inverted palaeochannels. Palaeontology and age Carpenter et al. (in press) describe a rich array of plant fossils in silcrete of the Grawin area. During the current mapping, angiosperm leaf fossils were found in loose blocks of fine-grained sandstone associated with Tertiary gravels and possibly underlying Cretaceous rock at Cumborah (Appendix 6). A precise identification of them has not yet been made, and they may be of Cretaceous to Tertiary age. Taylor (1978) stated that the age of the gravels at Cumborah (which he referred to as the Cumborah Gravels) was unknown, except that they post-date the Eocene and pre-date the oldest fluvial deposits of late Pliocene age. Taylor (1978) attributed their age to Late Miocene. Palynological dating of Tertiary sediments from the Namoi River and Gwyder River valleys (Martin 1980) and the Castlereagh River valley (Martin 1981) indicated that Tertiary deposition did not begin until the Middle to Late Miocene. Environment of deposition The gravel depsoits are thought to have been deposited by a braided river system, with some silcrete ridges representing inverted palaeochannels. Some bedding is thin and lenticular, indicating frequent changes in current strength during deposition. Silcrete gravel with or without in situ silcrete (T–Qg) In some areas of the ridge system there are deposits composed of Tertiary silcrete boulders and gravel which are variably overlain by colluvium. They form flat plateaus but on aerial photographs the plateau boundaries lack discernible sharp edges, characteristic of areas of intact silcrete. Without reliable drilling data it is not clear whether this material represents a disaggregated silcrete layer, which may be intact, though thin, beneath the boulders, or whether the material has been entirely transported. These areas are presented as T–Qg on the map face to indicate this uncertainty. silcrete gravel with or without in situ silcrete Photograph 5. Silcrete with a ‘knobby’ texture at Grawin Creek (GR 565800 6728030). 11 QUAteRnARY stRAtIGRAPHY Units confined to the ridge system Colluvium (Qc) Unconsolidated red, quartz-rich sand and iron oxide pisoliths covers the ridge system (Photograph 6), defined by the elevated areas of Griman Creek Formation and overlying Tertiary gravels. In places the colluvium contains fragments of Cretaceous rock and/or silcrete, several centimetres to tens of centimetres across. It is postulated that the red sand and pisoliths were derived from the weathering of the ridge system, especially the ferruginised silcrete cap. Exposed silcrete is ubiquitously ferruginised but exposed Cretaceous rocks within Angledool are generally not ferruginised. By contrast, to the west of Collarenebri, where there is minimal Tertiary gravel cover, the Cretaceous rocks are ferruginised to a depth of approximately 1 m. Pisoliths are generally several millimetres in diameter with a small proportion being magnetic. The larger pisoliths comprise small silcrete fragments with concretionary iron oxide coatings. Colluvium commonly conceals the silcrete on the ridge system. It commonly covers the Cretaceous rocks along the edges of the ridge, where the sand may be at least 1 m thick, as indicated by exposures in erosion gullies. On top of the ridge the sand is also about 1 m thick, but is usually intermixed with silcrete rubble. A borehole collared about 25 km west- southwest of Cumborah penetrated red sand to a thickness of approximately 8 m (Watkins 1985). This relatively thick deposit may reflect local reworking of colluvium by fluvial processes. The geological map does not show the full extent of the Quaternary colluvium, as it was considered preferable to indicate the bedrock type on the map, where it can be reasonably interpreted. The map only indicates where relatively thick deposits of colluvium are interpreted to be present on the margins of the ridges. At the base of the ridge there is a transition zone between colluvium and Quaternary alluvial material. Samples of colluvium collected during this study include medium- to coarse-grained sand; poorly- sorted, silty, fine-grained sand; well-sorted medium- grained sand; clayey silt; and poorly-sorted, silty medium-grained sand. Colluvium generally has a red- brown colour, though a minor amount is grey brown. Dunes developed upon colluvium This unit is recognised in several areas along the eastern edge of the Narran Lake system, adjacent to the Cretaceous–Tertiary ridge. The material was originally colluvial but it appears to have been significantly reshaped by aeolian processes into low, irregular sand dunes hosting tussocky grasses and saltbush on the elevated areas (Photograph 7). On the eastern edge of Narran Lake, about 1.5 km east- southeast of Narran Lake homestead, the soil consists of a veneer (up to 10 mm thick) of reddish brown, medium- to very coarse-grained quartz-rich sand. This layer contains abundant carbonate nodules from less than 1 mm to approximately 20 mm across, as well as silcrete fragments, quartz pebbles and pisoliths (a small proportion being magnetic). This material overlies pale yellow–brown silt to fine-grained sand. It is probable that the material has also undergone wave action in times when Narran Lake contained substantial amounts of water. The terrain has the appearance of a beach landscape. colluvium Qcd Photograph 6. Typical colluvium (Qc), dominated by red sand, adjacent to a buried ridge formed of Cretaceous and Tertiary rocks. Site 253 (GR 584968 6780958), looking south. Base of photograph is approximately 4 m wide. Photograph 7. Low dunes developed upon colluvium (Qcd) on the eastern side of Narran Lake. Site 347 (GR 542095 6695699), looking northwest. Base of photograph is approximately 4 m wide. 12 angledool 1:100 000 geological sheet ‘Box hollow’ facies (Qb) On the plateau there are circular features up to about 200 m in diameter which are locally referred to as ‘box hollows’ (Photograph 8). The material within the hollows consists of black to grey clay with a hummocky appearance. Vegetation within the ‘box hollows’ is commonly a thin, sparse cover of grass. Around the edges of the ‘box hollows’ silcrete rubble is common, though it rarely occurs within them. One of the best examples of a ‘box hollow’ occurs at GR 575300 6736200, about 2.9 km north–northeast of Gurley homestead, south of the Coocoran opal field. It is not clear what ‘box hollows’ are. In some areas, particularly south of the Coocoran opal field, they appear to be associated with interpreted lineaments (Burton 2003a), however, in many areas they have no obvious relationship with identified structures. They may be internal drainage points where faults have acted locally as fluid conduits. However, it is not known what these features look like at depth, so it is difficult to interpret them. The lack of vegetation within them may indicate that water is not retained, suggesting that they are internal drainage systems. Units of the plains Riverine plain morphology Most of the Quaternary units of Angledool are associated with fluvial (riverine) systems. Figure 6 is a schematic diagram indicating the morphological features which make up these systems. The thickness variation of the Quaternary material within the study area has been estimated from drillhole logs. Most of the data has come from water bore logs (those for which adequate geological information is provided) from the New South Wales Department of Water and Energy (data available online at http://nratlas.nsw.gov.au) while some is available from holes drilled by Rio Tinto Exploration Pty Limited (Doe & Palmer 1997a). The average thickness of the Quaternary material away from the outcropping bedrock is 56 m, ranging to a local maximum thickness of 120 m. Appendix 3 contains descriptions of selected soil samples collected during this study, based on binocular microscope examination, clay content estimation and Portable Infrared Mineral Analyser (PIMA) analysis. Bugwah Formation (Qr) (defined by Watkins & Meakin 1996) The Bugwah Formation typically consists of a relatively wide meander plain facies flanking the channel and a bordering backplain facies. The channel forms a gentle depression within the meander plain, which gently slopes down to the backplain (Figure 7). An alluvial system with a medial to distal distributary pattern ‘Box hollow’ facies Bugwah Formation Photograph 8. A typical ‘box hollow’ (Qb facies) — a flat, sparsely vegetated area ringed by trees; Site 154 (GR 576156 6731948), looking east. Base of photograph is approximately 4 m wide. Lake Channelised backplain Ridge Ridge-bounded flood basin Flood basin backplain Backplain Backplain Meander plain Flood basin Oxbow (abandoned channel) Crevasse splay Channel several km (generalised scale) 2010_03_0020 Figure 6. Schematic diagram showing riverine morphological terms used in this study 13 quaternary stratigraphy underlies the typical Bugwah Formation deposits within Angledool. While grossly morphologically different, its composition is very similar to that of typical Bugwah Formation material and locally it shares some morphological traits with that unit. The underling deposits have therefore been defined as the Nullawah Member of the Bugwah Formation. Watkins and Meakin (1996) estimated the age of the Bugwah Formation to be between 13 400 years BP and 6 400 years BP, based on thermoluminescence dating documented by Watkins (1992). Channel facies Bugwah Formation meander channels are large and sinuous, with amplitudes and wavelengths in the order of a kilometre. The channels are relatively wide, ranging from 100 m to about 500 m. Abandoned channels, or oxbows, occur in places. Although generally sinuous internally, the channel systems follow grossly straight courses with minor bifurcation. Flow within the channels in the study area has always been from northeast to southwest. Sediments of the meander plain facies ubiquitously flank the channels. Qrc Qrb Qrb 2010_03_0021 B A Al Bl Cl C approx 500 m to 2 km 50 m to 300 mapprox 200 m to 2 km approx 1 m approx 1 m approx 1 to 10 km 50 m to 500 m approx 200 m to 2 km approx 1 km to >10 km approx 200 m to 1 km approx 50 m (several 100 m max) Nullawa Member Bugwah Formation Marra Creek Formation A Al B Bl C Cl cross-section cross-section cross-section Qrnc Qrnc Qrns Qrns Qrnb Qrnb Qrb Qrm Qrc Qrc Qrm Qmm Qmm Qmc Qmc Qmb Qmb Figure 7. Characteristics of the Quaternary alluvial systems identified in the area 14 angledool 1:100 000 geological sheet In the field, the channels are distinguished by sinuous lines of trees and associated vegetation, which contrast with less-vegetated meander plain and backplain facies (Photograph 9). The soil contained within the channels varies from pale to dark grey, to pale yellow–grey to pale brownish grey. It comprises variable proportions of silty medium-grained sand, sandy silt, sandy clayey silt, and clayey silt. Carbonate nodules up to about 5 mm in diameter are present in places. The ground is commonly cracked and has gilgai, though in places it is more even and flat and cracking is less common (Photograph 10). Vegetation, which varies from sparse to dense, includes grass (mainly tussocky), saltbush, shrubs and gum trees. Meander plain facies The meander plain facies of the Bugwah Formation is characterised by broad point bar deposits, commonly with scroll bars, ranging from several hundred metres to about 4 km in width. They generally flank the Bugwah Formation channel facies. In places, isolated remnants of Bugwah Formation meander plain facies up to 3 km wide and 8 km long are surrounded by Marra Creek Formation floodplain material. In some places the Bugwah Formation meander plain facies is overprinted by Marra Creek Formation deposits, but the geomorphic expression of Bugwah Formation meander plain facies is still evident on satellite imagery and aerial photographs. Such areas are shown on the Angledool 1:250 000 geological map as Bugwah Formation meander plain facies deposits. Examples of this occur adjacent to the Bokhara River. Bugwah Formation meander plain facies material includes well-sorted, fine- to medium-grained sand; silty sand; sandy silt; clayey sandy silt; silty clay; and clay. The clay content generally increases with depth in the soil profile. The soil colour varies from dark to pale grey to grey–brown, reddish brown, yellow–brown and orange to beige. Uncommon carbonate nodules up to 4 mm diameter are present in some areas. Qrm Photograph 9. Geomorphic expression of the Bugwah Formation channel facies (Qrc; defined by the line of gum trees) within the meander plain facies (Qrm; orange–brown plain). Site 245 (GR 579238 6704398), looking southwest. Photograph 10. Geomorphic expression of Bugwah Formation channel facies (Qrc) near Site 245 (GR 579370 6704290), looking southwest. Base of photograph is approximately 5 m wide. Photograph 12. Geomorphic expression of Bugwah Formation meander plain facies (Qrm) showing typical scalded texture-contrast soil consisting of sandy ridges and low, more clay-rich flat areas with little vegetation; Site 309 (GR 504589 6784130), looking north-northwest. Base of photograph is approximately 4 m wide. Photograph 11. Geomorphic expression of Bugwah Formation meander plain facies (Qrm); Site 230 (GR 585639 6738609), looking north-northwest. Base of photograph is approximately 4 m wide. 15 quaternary stratigraphy The terrain representative of the Bugwah Formation meander plain facies is generally flat, even and firm (Photograph 11). Texture-contrast soils are typical of the facies, consisting of a sandy upper layer, about 0.3 m thick and variably undulating, and a lower, more clay-rich layer. Commonly these soils are eroded (scalded), leaving a surface expression of low sandy ridges which are usually well vegetated with grass, shrubs and trees; and more clay-rich flat areas which are barren to poorly vegetated with grass and saltbush (Photograph 12). Crevasse splay facies Crevasse splay deposits consist of the same material as described for the Bugwah Formation meander plain facies but they have been produced by sudden breaches of the river channel, producing fan-shaped lobes. This facies has only been recognised adjacent to Little Yamba Creek at GR 526457 6751449, 9 km east of Leander homestead, and southeast of Lexington homestead at GR 530801 6681544 from satellite imagery interpretation. Neither area was inspected in the field. Backplain facies The backplain facies of the Bugwah Formation flanks the meander plain facies, lying between river systems. These zones are several kilometres wide, ranging up to 10 km in the area of Lourney homestead (GR 615400 6726100), between the Twenty Nine Mile Warrambool and the Mungaroo Warrambool. The backplain terrain (Photograph 13) varies from flat and even, to gently undulating with an irregular surface, to having common gilgai with abundant desiccation cracks. Vegetation varies from sparse to dense and consists of low grass, tussocky grass, saltbush, shrubs and trees. The soil material which constitutes the Bugwah Formation backplain facies consists of pale yellow– grey to dark grey, clayey silt to clayey, sandy silt. Carbonate nodules 3–5 mm across are sparsely present in places. Nullawa Member (new name) The Nullawa Member is composed of the same constituent materials as those in the Bugwah Formation but it has different geomorphological features. While the Bugwah Formation deposits are mostly part of an aggrading riverine plain system, the Nullawa Member has the geomorphic expression of a medial to distal fluvial distributary system (e.g. Nichols & Fisher 2007). It is characterised by a dendritic system of numerous branching channels with associated splay facies and backplain facies (Figure 7). However, it also exhibits some geomorphic features typical of Bugwah Formation, suggesting that it is part of that system, rather than a separate formation. This member occurs at the base of the Bugwah Formation and is overprinted by the more typical riverine plain units. Examples of this are exhibited in the areas east and north of Goodooga, where broad meander bars with scrolls, typical of Bugwah Formation deposits, of the ancestral Bokhara River, overprint the dendritic pattern of the Nullawa Member. Localities at GR 612516 6733970 and GR 618675 6743835, along the Twenty Nine Mile Warrambool, present other examples where the Nullawa Member is overprinted by more typical Bugwah Formation deposits. Between Goodooga and Nullawa homestead, the Nullawa Member forms a distinct fan-shaped system, but elsewhere it is closely associated with more typical Bugwah Formation deposits. The member is interpreted as an early distributary phase of the Bugwah Formation, prior to establishment of a meandering riverine plain system. A thermoluminescence (TL) analysis was carried out on material from the Nullawa Member splay facies (see Appendix 5). The calculated age from this analysis was 2.6 ± 0.15 ka. This age conflicts with previous ages of 13 400–6 400 years BP (Watkins 1992) for the Bugwah Formation. The most likely reason for the relatively young age calculated here is that the material was remobilised, quite possibly by aeolian processes. Less likely is the possibility that material near the base of the Bugwah Formation in the Angledool area is much younger than similar units further south and that the minimum age of the Bugwah Formation in the Angledool area extends to less than 2 600 years BP. Channel facies The channels of the Nullawa Member range in morphology from straight or irregular, to a more Qrl Qrn QrncPhotograph 13. Geomorphic expression of the Bugwah Formation backplain facies (Qrb); Site 277 (GR 637280 6731353), looking north. Base of photograph is approximately 4 m wide. Qrb 16 angledool 1:100 000 geological sheet regular, sinuous shape similar to that of typical Bugwah Formation channels. Sinuous channels may have wavelengths and amplitudes of several hundred metres. The channels commonly bifurcate and have a distributive morphology. Flow has been from northeast to southwest throughout the area. The channels are weakly topographically depressed corridors, ranging in width from about 50–300 m (Photograph 14). The surface is commonly flat with minor undulation, though some channels have an irregular, gilgaid surface with dessication cracking. They are generally well vegetated with abundant grasses, trees and shrubs. Channel material comprises medium-grained sand; silty, fine- to medium-grained sand; silty clay; and clayey silt. Its colour varies from grey to beige to red–brown. At Site 260, 4 km southeast of Finger Post bore, a trace amount of carbonate nodules up to 2 mm across occurs in the soil. Splay facies The splay facies flanks the channels and also occurs in isolated domains surrounded by later Marra Creek Formation backplain facies. This facies extends about 500 m to 2 km away from the channels and exhibits a gentle slope downward from the channel areas to the adjacent floodplain. The material is interpreted to have formed as sheet flood deposits by avulsion from channels in a distributary system. Locally it has the characteristics of a meander plain facies with scroll bars. The Nullawa Member splay facies has the same overall compositional variations as the Bugwah Formation meander plain facies. The soil varies in colour from pale grey to brown, red–brown and orange. Texture-contrast soils are commonly developed (Photograph 15) and these are generally scalded, exposing elevated sandy ridges about 0.3 m high, upon a harder, flatter, more clayey sand plain. The ridges support tussocky grass and tree cover which varies from dense to open, while the lower- lying areas tend to be bare or sparsely vegetated. Backplain facies The backplain facies of the Nullawa Member is generally restricted to relatively small, irregular domains, several hundred metres across, between deposits of the splay facies which are associated with separate channels. In a few areas the backplains are more than 1 km wide, but have an overall irregular shape. The material making up this facies consists of poorly sorted sandy, clayey silt with sporadic carbonate nodules up to 3 mm in diameter. It has a pale to dark grey to pale yellow–grey colour. The terrain varies from flat with minor undulation, to gilgaid Qrns Qrnb Photograph 14. Geomorphic expression of the Nullawa Member channel facies (Qrnc; grey material) with splay facies (Qrns; orange) in left distance. Site 260 (GR 573498 6787423), looking south. Base of photograph is approximately 5 m wide. Photograph 15. Geomorphic expression of the Nullawa Member splay facies (Qrns). Typical scalded texture contrast soil consists of sandy ridges (foreground) and more clay-rich depressions (background). Site 366 (GR 576855 6785975), looking northwest. Base of photograph is approximately 4 m wide. Photograph 16. Geomorphic expression of the Nullawa Member backplain facies (Qrnb); Site 258 (GR 577580 6785772), looking south. Base of photograph is approximately 3.5 m wide. 17 quaternary stratigraphy Meander plain facies The meander plain facies flanks the major Marra Creek Formation channels. The meander belts are relatively narrow, being generally no more than 1 km wide. The banks of Marra Creek Formation channels are marked by abundant trees as well as shrubs and grasses. However, the banks do not have a marked elevation above the surrounding floodplain. The topography of the meander plains is flat and varies from firm and even to gilgaid, where the ground is collapsed in places with cracks being tens of centimetres across and tens of centimetres deep. The material making up this unit is clayey silt varying in colour from dark to pale grey to pale yellow–grey. Away from the channel edges, the meander plains host variable grass cover, saltbush and variable densities of trees. In places there is thick shrub cover. Backplain facies The Marra Creek Formation backplain facies forms extensive, flat terrain, commonly referred to as the ‘black soil plain’. The backplains are several kilometres wide between river channels, to over 15 km wide in places (mainly in the area between the Culgoa River and Birrie River; the Birrie River and Yamba Creek; and Yamba Creek and the Bokhara River). Between the Bokhara River and Narran Lake the Marra Creek Formation backplain is approximately 30 km wide. The material which constitutes the backplain facies comprises clayey sandy silt, silty clay, and clay. The colour varies from dark to pale grey, beige and pale yellowish grey. Carbonate nodules from 1–13 mm in diameter are commonly present. The terrain is typically undulating and gilgaid, exhibiting desiccation cracks which are up to 1 m wide and at and cracking soils are common (Photograph 16). Vegetation, which is generally sparse, consists of patchy low grass with minor to, less commonly, moderate tree cover. Saltbush is present in places, along with other low shrubs. Marra Creek Formation (Qm) (defined by Watkins & Meakin 1996) The Marra Creek Formation consists of narrow channels flanked by relatively narrow meander belts and broad backplains. The meander plains are not noticeably elevated above the flood plain and the channels have a ‘U’ shaped cross-section within the meander belt (Figure 7). The backplain material overlies older alluvial material in places, resulting in remnants of earlier deposits surrounded by Marra Creek Formation backplain. The Marra Creek Formation has a maximum age of 6 400 years BP, based on thermoluminescence dating (Watkins 1992) and has been active to the present day. Channel facies Marra Creek Formation channels are of two types. The first type consists of narrow, linear to curvilinear belts of meandering channels with wavelengths and amplitudes of hundreds of metres. This morphology is typified by such water courses as the Narran River, Culgoa River, Birrie River, Bokhara River and Barwon River. The second type of channel, which is minor, varies from straight to sinuous but does not form major drainage channels and generally does not have an associated meander plain facies. Some major Marra Creek Formation channels, such as the Bokhara River and Yamba Creek, occupy older Bugwah Formation channel courses. Throughout Angledool, water flow in the Marra Creek Formation channels is grossly from northeast to southwest. Abandoned channels and oxbows are common. Channels are generally about 50 m wide but range in width from several hundred metres to about 30 m (Photograph 17). A single sample of channel fill material from Site 267, from the Fifteen Mile Warrambool, 4.7 km northeast of Tysons bore (GR 563400 6767000), consists of grey, silty clay. This is considered to be fairly typical, though in some places the river beds are lined with boulders and pebbles of Cretaceous and Tertiary rock. Carbonate nodules to 2 mm across are present in places. The channel material is pale to dark grey, in places pale brownish grey. The surface varies from flat and even to undulating, to gilgaid with desiccation cracking. Vegetation, where present, consists of tussocky grass, shrubs and moderate tree cover. Photograph 17. The Birrie River represents the Marra Creek Formation channel facies (Qmc) with the meander plain facies (Qmm) on the banks. Site 304 (GR 541575 6780642), looking south. Base of photograph is approximately 5 m wide. Qmc Qmm Qmb Marra creek Formation 18 angledool 1:100 000 geological sheet least 0.5 m deep (Photograph 18). Less commonly the plain is fairly even with shallow depressions. Vegetation is commonly sparse, consisting of low, grassy cover and tussocky grass, and/or saltbush, though in places it is densely vegetated with shrubs and trees. Channelised backplain facies This facies has only been delineated in the south- eastern corner of Angledool, where it occurs on the southeastern margin of the main Barwon River channel. The area is up to 5 km wide and around 30 km in length. It is recognised on Landsat imagery as a plain containing abundant, arcuate to irregular, anastomosing channels, each several tens of metres across. At Site 361, 3 km west-northwest of Eurie Eurie, the terrain consists of a gently rolling plain with variable tree cover (Photograph 19). The ground is firm and even, with slight undulations over hundreds of metres. The soil consists of grey sandy clayey silt and contains minor white carbonate nodules up to 5 mm in diameter. Flood basin backplain facies The flood basin backplain facies is defined as flood basin areas flanking river channels along their course (not at their termini). In Angledool this facies chiefly occurs along the Culgoa River, in the area of Cawwell homestead, and along the Narran River in the area of Amaroo homestead and Mureabun homestead (Photograph 20). The areas are up to 8 km wide and at least 20 km long. Such areas are flat to undulating with cracked and collapsed ground. They are generally well vegetated with tussocky grasses, shrubs and trees. The soil colour varies from dark grey to pale yellow–grey. A sample of this material from Site 341, 5.4 km northwest of Moordale homestead, consists of silty clay to clay. At Site 311, immediately south of Weilmoringle, adjacent to the Culgoa River (on the Enngonia 1:250 000 map sheet) there are irregular carbonate nodules, several centimetres across, in the subsurface. Ridge-bounded flood basin facies Ridge-bounded flood basins occur adjacent to the ridges formed by Cretaceous and Tertiary rocks. These ephemeral basins are not fed by any conspicuous stream channels, thus Coocoran Lake, which is fed from Weetalibah Creek, is not included within this geomorphic category. Angledool Lake, Rotten Plain and Morendah Plain are included within this Qmbc Qmbf Qmr Photograph 18. Geomorphic expression of the Marra Creek Formation backplain facies (Qmb); Site 293 (GR 555602 6756162), looking north. Base of photograph is approximately 3.5m wide. Photograph 19. Geomorphic expression of Marra Creek Formation channelised backplain facies (Qmbc); Site 361 (GR 616000 6684303), looking north. Base of photograph is approximately 4 m wide. Photograph 20. Geomorphic expression of Marra Creek Formation flood basin backplain facies (Qmbf), Site 341 (GR 540772 6724139), looking west. Base of photograph is approximately 7 m wide. 19 quaternary stratigraphy often used as a cropping area. A sample of material from Coocoran Lake consists of dark grey clayey silt with carbonate nodules to 7 mm across. Lake facies This unit only occurs in the Narran Lake area and is characterised by semi-permanent bodies of water. The main Narran Lake is a broad, flat basin approximately 20 km across. The floor of the basin forms flat, even ground (Photograph 23) consisting of dark grey, poorly sorted sandy silt with common carbonate nodules up to 5 mm across. The lake is ridge-bounded at its eastern and northeastern margins and the basin is also associated with flood basin material (Qmf). The basin forms the terminus of the Narran River. classification. The areas are commonly characterised on radioelement imagery by elevated potassium compared to surrounding areas. A PIMA study of this material (see Appendix 3) did not identify the presence of any potassium-bearing minerals, such as illite. However, the material may contain a minor amount of feldspar (not detectable with a PIMA unit), derived from the surrounding Cretaceous rocks. The basins are irregularly shaped and are several kilometres across, extending to more than 10 km in places. The Morendah Plain embayment is more than 15 km wide. The ground surface tends to be generally flat and even (Photograph 21) but in places is gently undulating to gilgaid. Cracking soils are common. Vegetation varies from barren to dense and comprises tussocky grass, shrubs, saltbush and trees. In places there is abundant cane grass. Angledool Lake is a cultivated area. The ridge-bounded flood basin facies includes sandy silt, clayey sandy silt and clayey silt. The colour varies from dark to pale grey to beige and pale yellow–grey. White carbonate nodules to 10 mm are common. Flood basin facies This unit is represented by Coocoran Lake and the area north of Narran Lake. These ephemeral flood basins are elongate and fed by stream channels. Coocoran Lake is approximately 5 km wide and 10 km long, while the area around Narran Lake is over 15 km long. Similar to the ridge-bounded flood basins, they are characterised by elevated potassium relative to surrounding areas, discernible on radioelement images. Flood basin terrain is flat and even. As an ephemeral basin, the Coocoran Lake floor (Photograph 22) is Qmk Qmf Photograph 21. Geomorphic expression of Marra Creek Formation ridge-bounded flood basin facies (Qmr); Site 228 (GR 572175 6737685), looking southwest. Base of photograph is approximately 3.5 m wide. Photograph 22. The ephemeral Coocoran Lake, shown here under cultivation, represents the Marra Creek Formation flood basin facies (Qmf). Site 286 (GR 580498 6749835), looking north. Base of photograph is approximately 3.5 m wide. Photograph 23. The eastern edge of Narran Lake represents the Marra Creek Formation lake facies (Qmk). Site 346 (GR 541824 6695611), looking west. Base of photograph is approximately 5 m wide. 20 angledool 1:100 000 geological sheet Source-bordering dunes (Qd) This facies occurs principally in the southwestern part of Angledool, located up to 20 km northwest of Narran Lake, with some also occurring in the area around Burranbaa homestead (GR 607800 6754390) and Carinya homestead (GR 605900 6744190). They are developed upon Bugwah Formation meander plain facies. The convex margins of many of these domains suggest their origin as remobilised Bugwah Formation meander deposits which have subsequently been surrounded by Marra Creek Formation backplain material. The dune material consists of medium to coarse- grained sand and sandy, clayey silt. The colour varies from red–brown to grey–brown. The terrain is gently undulating with a dune wavelength of about 500 m, forming low, broad hills (Photograph 24). The dunes are heavily vegetated with grass, shrubs and trees. source-bordering dunes Photograph 24. Geomorphic expression of the dune system developed upon Bugwah Formation meander plain facies (Qd). This undulating terrain reflects a dune wavelength of about 500 m. Site 300 (GR 557099 6733146), looking east. Base of photograph is approximately 4 m wide. 21 structures are shown on the geology map, but others only shown on the interpretation diagram (Figure 8) as their positions cannot be defined accurately. No surface exposures of faults were recognised during this study. Cretaceous rock exposures show some jointing, but this is rarely observed as the rocks generally occur as rubbly outcrop and subcrop. Most of the interpreted structures trend in a northeasterly direction, as does the Darling River Lineament, a structure which has strongly influenced the course of the Darling River and passes through Surface features Surface structures in Angledool were interpreted from aerial photographs during this mapping project. They are confined to the ridge areas as the Quaternary deposits mask any structures elsewhere. Some structures have been identified directly on aerial photographs as distinct linear features, but many have been identified from the compiled geological mapping. Linear boundaries on geological units have been inferred to be caused by the presence of linear structures (faults or joints). Many such stRUctURe 148°30'E 29°00’S 147°00'E 29°00'S 147°00'E 30°00'S 148°30'E 30°00'S N Na rra n Ri ve r Ri ve r Bok har a River Bir rie Th e Bi g W ar ra m bo ol Ba rwo n Ri ve r 0 20 km Wyoming tank “Lourney” “Oxley Park” “Carinya” “Amaroo”“Carinya” “Mureabun” “Leander” “Moordale” “Gurley” “Burranbaa” “Nullawa” “Narran Lake” “Calgary” “Angledool” “Lexington” “Cawwell” “Kia-ora” REFERENCE Darling River Lineament Lineament interpreted from aerial photographs Locality; homestead Watercourse; tank 2010_03_0022 Lightning Ridge Narrandool Cumborah New Angledool Mount Charlotte Goodooga Figure 8. Lineaments interpreted from aerial photographs and mapped distribution of rock units for Angledool. The Darling River Lineament (after O’Sullivan et al. 1998) is shown. Background Landsat7 image ©Commonwealth of Australia (Geoscience Australia) 2011. This material is released under the Creative Commons Attribution 3.0 Australia Licence. 22 angledool 1:100 000 geological sheet Wilcannia and Bourke. The Darling River Lineament also passes through Angledool, in the vicinity of Leander homestead and Oxley Park homestead (Figure 8) and transects the road from Goodooga to Lightning Ridge approximately 6.7 km southeast of Goodooga. The structure does not transect exposed rocks within the mapped area. The lineament has been active for hundreds of millions of years and was most recently active during the Tertiary (O’Sullivan et al. 1998). It joins with the Cato fracture zone in the Tasman Sea, off the Queensland coast (O’Sullivan et al. 1998). Northwesterly trending lineaments are much less common in the study area and are considered to be an orthogonal conjugate set to the northeasterly trending structures. This orthogonal, northeasterly and northwesterly trending structural fabric is dominant throughout the exposed Cretaceous rocks of the Great Australian Basin in northern New South Wales. There are two substantial, north-northeasterly trending lineaments in the southern part of Angledool, immediately west of Mount Charlotte, which have had a strong influence on the outcrop pattern of the Cretaceous and Tertiary rocks. No other similar structures are evident in the study area. The eastern edges of Narran Lake have been controlled by lineaments that trend north-northwest and east-northeast. These structures appear to be part of a set of concentric and radial structures, which are centred approximately on an area in the vicinity of Amaroo homestead and Wyoming tank. An elliptical magnetic high feature (with an associated weak low gravity anomaly) is present in that area (Figure 9). While there is no apparent surface feature 29°30’S 147°00'E 29°30'S 147°00'E 30°00'S 148°00'E 30°00'S N 148°00'E 0 20 km Narran Lake Lake Coocoran Riv er Bo kha ra Ri ve r Na rra n REFERENCE Lineament interpreted from aerial photographs Watercourse; tank Locality; homestead 2011_02_0014 Lightning Ridge Mount Charlotte Cumborah “Leander” “Narran Lake” “Kia-ora” “Carinya” “Lexington” “Amaroo” “Gurley” “Mureabun” “Moordale” Wyoming tank Figure 9. Radial and concentric lineaments interpreted from aerial photographs and mapped distribution of rock units in the southwestern part of Angledool, superimposed upon a regional Total Magnetic Intensity image. The structures are apparently focussed on the magnetic high centred near Wyoming tank. 23 structure corresponding to the magnetic high in that area, there is a nearby subcircular domain of Marra Creek flood basin backplain facies (Qmbf) centred 7 km southeast of Amaroo homestead and about 8 km south of the centre of the magnetic feature. One interpretation of this system, though speculative, is that it is associated with a buried astrobleme. However, no other surface features (either topographic or outcrop scale) are presently recognised which support this interpretation. The speculated impact most likely would have occurred after deposition of the Griman Creek Formation but prior to deposition of the Quaternary alluvium. A more probable explanation is that the body causing the magnetic high, previously interpreted as an Alaskan-type intrusion beneath the Surat Basin by Scheibner (1997), formed a topographic high prior to deposition of the Great Australian Basin and became buried. Later compaction of the Mesozoic sedimentary rock has lead to flexing and fracturing around the basement high. The Cretaceous rocks and the Tertiary gravel are effectively flat lying, though there is gentle tilting which can be deduced from aerial photograph interpretation. Qualitative dips (which are only gentle, i.e. several degrees) of the gravel layers are plotted on the Angledool 1:250 000 geological map face. It is common for the strikes of the gravel layer to lie parallel (or in some cases orthogonal) to nearby interpreted linear features, possibly suggesting that the dips are attributable to differential uplift/down- dropping adjacent to faults. This would suggest that the faults are dominantly dip-slip structures, consistent with faults observed in the sub-surface. At Site 273, 21 km southwest of Collarenebri, Cretaceous siltstone laminae have a vertical dip (Photograph 25). The laminae strike 140º, sub- parallel to an interpreted lineament (which trends approximately 150º) occurring about 800 m to the northwest. It is speculated that bedding has been dragged and rotated along a nearby dip-slip fault, possibly a subsidiary structure to the interpreted lineament. Nowhere else in the study area were such steep dips observed within Cretaceous rock. Drilling in the southern part of the Coocoran opal field (Burton 2003a) indicates that opal mineralisation in that area apparently terminates against a northeasterly trending fault, referred to by Burton (2003b) as the Natalies Dream Lineament. Burton (2003a) estimated a dip-slip displacement of about 10 m along that structure. The possibility that other opal fields are influenced by similar structures is discussed below in the Economic Geology section. Structures observed in opal workings and drillcore In opal mine workings and in drillcore (Burton 2003a) macro scale faults are common. Fault planes dip at various angles though generally they dip at about 60º. Commonly they are lined either with brick-red to brown iron oxide-stained clay, which may be up to several centimetres thick, or a thin veneer of brick-red iron oxide. The coatings contain lineations which always indicate dip-slip movement. No systematic study of these fault planes has been undertaken, hence questions regarding the distribution of fault orientations, displacement, sense of movement and timing of movement remain unanswered. It is considered that the displacement on most faults has probably been less than 1 m, and probably only tens of centimetres. These structures have only been observed cross-cutting Cretaceous rocks, not Tertiary material, though this is strongly biased by a lack of exposure. In drillcore, several faults displacing ferruginised zones have been observed (Burton 2003a). Although it is possible that ferruginisation post-dates faulting and occupies previously displaced favourable beds, the author is of the opinion that the faulting post- dates the ferruginisation event. ‘Box hollows’ and other circular features ‘Box hollow’ is an informal miners’ term. A small proportion of ‘box hollows’ (Qb) either line up along lineaments, or are confined to, linear zones (e.g. Burton 2003a). A circular feature occurs 2 km east of Bobs tank, centred at GR 551505 6716243. It has a radius of Photograph 25. Partly ferruginised, laminated fine- grained sandstone and siltstone of the Griman Creek Formation. The laminae are approximately vertical and strike 140º. Compass (22 cm full length) points to the north. Site 273 (GR 635374 6719195). 24 angledool 1:100 000 geological sheet about 280 m. Outside of the circumference the ground slopes away from the structure, while inside it slopes down to the centre. Grey clayey soil (Qmr) occupies an inner zone with a radius of about 160 m. A similar, but larger (approximately 1.5 km diameter) feature occurs to the southeast, centred on GR 553409 6714831, but was not inspected during this study. Both of these circular structures may be resting on a northwesterly trending radial fracture associated with regional flexure, as discussed previously under Surface features. The possibility that these circular structures are astroblemes, particularly the southeastern one, is not discounted, but further supporting evidence would need to be acquired before that interpretation could be seriously considered. They appear more likely to be related to box hollow features and probably represent areas of internal drainage. ‘Blows’ ‘Blow’ is an informal miners’ term for a breccia zone consisting of clasts of Cretaceous rock and/or silcrete and/or quartz pebbles and granules, cemented by a hard to friable matrix of white, quartz-rich sand and grey clay. These structures are exposed at the surface at numerous localities and they are commonly observed within mine workings and in drillcore (Burton 2003a). The breccias occur in irregular to linear zones which are vertical in orientation (overall) and range from a few millimetres to about 2 m in width. They can extend to over 20 m in depth. The breccia zones are commonly oriented parallel to vertical fracturing in the adjacent Cretaceous rock. This indicates either that the breccia has been controlled by pre-existing fractures in the Cretaceous rock, or, more likely, the fracturing has been induced during the weathering event which produced the ‘blow’. ‘Blow’ structures are well exposed at Grawin Creek (Site 208, Figure 10); 6 km southeast of Kia Ora homestead (Site 345, Photograph 26); and 4 km northwest of Mehi (Site 368). Some opal miners believe that ‘blows’ are good indicators for opal and cite that some opal seams have been found adjacent to ‘blows’. However, it is apparent that ‘blows’ post-date both opal formation Ground surface Silcrete with pebbly horizons Quartz pebbles to 30mm Cretaceous siltstone with laminae Vertical fractures in silicified claystone Clast-supported breccia with matrix of hard sand. Indurated. Floor level of gully Clasts (mainly silcrete) vary from irregular to rounded 1.6m 2011_02_0010 Figure 10. Sketch of ‘blow’ structure exposed in southern side of Grawin Creek (GR 565800 6728030) showing the irregular shape that some of these structures have. Note also the vertical fracturing in the Cretaceous rocks adjacent to the ‘blow’. Most of the contained clasts are silcrete and the structure cross-cuts Tertiary silcrete, clearly indicating that it post-dates silcrete formation. 25 structure and the last silicification event. Some cross-cut opal/potch seams and contain angular opal/potch fragments (observed by the author in a mine in the Mulga field, GR 563880 6719641) indicating that they post-date the seams. The fact that the ‘blows’ are rich in present-day surface material indicates that they are recent features. A PIMA examination of three samples of ‘blow’ matrix indicated that the grey clay is most probably a mixture of kaolinite (halloysite) and montmorillonite (Table F in Appendix 4). Basement structures Figure 11 is the aeromagnetic image for Angledool while Figure 12 shows the gravity image. In both figures surface structures from Figure 8 are overlain for comparison. The geophysical imagery reflects Photograph 26. ‘Blow’ breccia consisting mainly of quartz pebbles up to 10 mm across and lesser rounded silcrete clasts, in a matrix of medium-grained quartz- rich sand and grey clay. The breccia cross-cuts flat-lying, interbedded siltstone and claystone of the Griman Creek Formation. The hammer lies across the contact. Site 345 (GR 544194 6682216), looking northeast. 148°30'E 29°00’S 147°00'E 29°00'S 147°00'E 30°00'S 148°30'E 30°00'S N 0 20 km Narran Lake Coocoran Lake Angledool Lake Riv er Bo kha ra Ri ve r Na rra n Ri ve r Ba rw on REFERENCE Lineament interpreted from aerial photographs Watercourse; tank Locality; homestead 2011_02_0015 “Angledool” “Lourney” “Leander” “Oxley Park” “Calgary” Wyoming tank “Amaroo” “Nullawa” “Burranbaa” “Carinya” “Cawwell” “Lexington” “Narran Lake” “Moordale” “Kia-ora” “Gurley” “Mureabun” “Narrandool” Goodooga Cumborah New Angledool Mount Charlotte Lightning Ridge Figure 11. Aeromagnetic image for Angledool. The data reflect lithological and structural features in the basement to the Surat Basin. Surface lineaments from Figure 8 are overlain and show little relationship to basement structures. 26 angledool 1:100 000 geological sheet rock types and structures in the underlying basement to the Great Australian Basin with the flat-lying Mesozoic sedimentary rocks displaying no discernible gravity or magnetic features. Generally, there is no direct correlation of geophysical features with structures interpreted on the surface. Exposures of Cretaceous and Tertiary rock are grossly coincident with a positive magnetic anomaly which trends north- northeast through the middle of Angledool and broadly corresponds with a gravity ridge. The association of the concentric and radial fractures with an interpreted intrusion (or impact structure?) in the southwestern part of the study area has been discussed. Other than that system, it seems likely that most of the interpreted surface structures are related to the Darling River Lineament, rather than any basement structures reflected in the regional geophysical data sets. The Darling River Lineament itself does not have a conspicuous geophysical expression in either the aeromagnetic or gravity imagery over Angledool. 148°30'E 29°00’S 147°00'E 29°00'S 147°00'E 30°00'S 148°30'E 30°00'S N 0 20 km Narran Lake Coocoran Lake Angledool Lake Riv er Bo kha ra Ri ve r Na rra n Ri ve r Ba rw on “Narrandool” Goodooga Cumborah New Angledool Mount Charlotte Lightning Ridge “Angledool” “Lourney” “Leander” “Oxley Park” “Calgary” Wyoming tank “Amaroo” “Nullawa” “Burranbaa” “Carinya” “Cawwell” “Lexington” “Narran Lake” “Moordale” “Kia-ora” “Gurley” “Mureabun” REFERENCE Lineament interpreted from aerial photographs Watercourse; tank Locality; homestead 2011_02_0016 Figure 12. Gravity image for Angledool. The data reflect lithological and structural features in the basement to the Surat Basin. Surface lineaments from Figure 8 are overlain and show little relationship to basement structures. 27 BAseMent GeoLoGY The geology of the basement to the Great Australian Basin in the Angledool has been deduced mainly from regional geophysical data, particularly aeromagnetic and gravity imagery. Several seismic surveys have been carried out and a small number of bore holes have penetrated through the Mesozoic sedimentary rocks and into the basement. Palaeozoic Figure 13 illustrates an interpretation of the basement geology after Scheibner (1997). Following that interpretation, the Ordovician to Early Carboniferous basement rocks, with minor exception as discussed below, belong to the Lachlan Orogen. ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ??? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 148°30’E 29°00’S 147°00’E 29°00’S 147°00’E 30°00’S 148°30’E 30°00’S “Calgary” Mount Charlotte Cumborah “Amaroo” Wyoming tank “Leander ” “Oxley Park” Goodooga Lightning Ridge New Angledool Angledool Lake Coocoran Lake Narran Lake 2010_03_0026 REFERENCE S–Dv S–Dv C– PsD–Cs S–Ds S–Dm S–Dd C–Pv Ds ΘvΘg Θg Θg Na rra n Ri ve r Ri ve r Ba rw on Ri ve r Bok har a Redbeds, conglomerate, sandstone, quartzite, shale and possibly coal I-type granite (age uncertain) I-type granite Redbeds, conglomerate, sandstone, quartzite shale Quartzose sediments Undifferentiated sedimentary rocks Undifferentiated sedimentary rocks Undifferentiated sedimentary rocks Mafic volcanic rocks Quartz-rich sedimentary rocks C–Ps C–Pv D–Cs Ds S–Dv S–Dd S–Ds S–Dm Θa Θa Θg Θv Alaskan type intrusion Devonian to Carboniferous Carboniferous to Permian Devonian Siluro - Devonian Ordovician Siluro- Devonian W ar ra m bo ol Th e B ig Riv er Bir rie “Nullawa” “Angledool” “Carinya” “Lourney” “Kia-ora” “Lexington” “Mureabun” “Moordale” “Gurley” N 0 20 km Figure 13. Interpreted basement stratotectonic units of Angledool (modified from Scheibner 1997) 28 angledool 1:100 000 geological sheet The main elements are as follows. 1. A northerly trending belt of Ordovician to Early Silurian basic volcanic rocks lies in the centre of Angledool. This is flanked by: 2. Ordovician to Early Silurian quartz-rich turbidites with an interpreted Alaskan-type intrusion, probably of Ordovician age, in the area of Wyoming tank. Similar turbidites are interpreted to occur in the extreme northwestern corner of Angledool. 3. Silurian to Middle Devonian shallow marine sedimentary rocks and intrusions are interpreted to occur 20 km to the south of Cumborah. 4. Silurian to Middle Devonian deep water sedimentary rocks occur in the southeastern corner of the area. 5. Silurian to Middle Devonian deep to shallow water sedimentary rocks form most of the eastern third of Angledool. 6. A Silurian to Middle Devonian or Late Early Carboniferous to Early Permian intrusion is interpreted to occur around 12 km southwest of Collarenebri, in the area of Calgary homestead. 7. Late Silurian to Early Devonian shallow marine sedimentary rocks occur in the western part of Angledool, flanked by: 8. Early Devonian to Early Carboniferous terrestrial sedimentary rocks of the Paka Tank Trough to the northwest. 9. A small graben filled with Late Early Carboniferous to Early Permian continental sedimentary rock is interpreted to occur immediately west of Goodooga (the Goodooga Graben). However, where Scheibner (1997) interpreted a northerly trending belt of Ordovician to Early Silurian volcanic rocks through the centre of Angledool, Glen et al. (2006) suggested an alternative basement interpretation, with the southern half of that zone consisting of Siluro-Devonian granites. North and east of that they interpreted the presence of Siluro-Devonian sedimentary and volcanic rocks with Carboniferous(?) granite intrusions in the eastern part of Angledool. West of that central zone Glen et al. (2006) interpreted the basement rocks as being part of the Thomson Orogen. Scheibner (1997) interpreted Thomson Orogen to be present in the extreme northwestern corner of Angledool, including the interpreted turbidites in that area. Burton (2010) has questioned the presence of the Thomson Orogen in New South Wales. By that interpretation all the basement rocks shown on Angledool belong to the Lachlan Orogen. Burton (2010) also favoured Scheibner’s (1997) interpretation of a northerly trending belt of Ordovician to Early Silurian basic volcanic rocks through the Angledool area. Structures affecting the Mesozoic sequence The Palaeozoic basement is considered to have been effectively levelled by erosion prior to deposition of the Mesozoic sediments of the Great Australian Basin (Shaw 2002), although, as noted in the section on Structure, it is possible that an intrusion in the area of Wyoming tank formed a basement topographic high. Figure 14 shows the major structural domains which form the basement to the Surat Basin within Angledool. These features are generally superimposed upon, but in some instances include, the older Palaeozoic units described above. The main structures are the: • Lightning Ridge Shelf • Nebine Ridge • Paka Tank Trough • Coonamble Embayment • Goodooga Graben • Collarenebri Graben (which lies just east of Angledool). Figure 15 is a contour map of two-way seismic travel time showing interpreted graben structures across a substantial part of northern Angledool, after Shaw (2002). 29 basement geology Pa ka T an k Tro ug h G oodooga G raben Ne bi ne R id ge Co on am ble E mb aym en t Lig htn ing R idg e Sh elf 2010_03_0027 Probable Devonian rocksBasement topographic boundary Interpreted faults Undifferentiated Ordovician to Permian rocks REFERENCE C ol la re ne br i G ra be n Area of Figure 15 148°30' 148°45'E 29°01'S 29°30'S 147°18'E147°00'E 29°00'S 147°00'E 30°00'S 148°45'E 30°00'S 0 25 km N Figure 14. Interpreted Middle Devonian to pre-Jurassic basement structure beneath the Surat Basin in Angledool (after Shaw 2002). 148° 30' E147° 18' E 148° 45' E 29° 30' S 29° 01' S 147° 30' E 148° 00' E 08 0 6 8 82 0048 880 840 88 0 900 1020 1 08 7 00 8 067 087 087 008 008 0 8 8 028 048 068 9 6 0 029 028 048 86 0 98 0 0201 0 069 000 001 00 0 8 8 0 8 8 088 99 20 940 049 029 900 0 0 4 99 6 029 049 069 940 009 8 8 0 0 8 8 900 029 9 20 920 90 0 860 088 920 049 0 6 9 9 009 920 8 8 8 0 0 0 9 1040 102 01000 0 4 7 76 0 7 2 0 840 98 0 009 900 02 069 0 4 8 960 008 08 7 8 2 0 9 2 0 900 840 660 0 68 980 049 049 920 0 27 067 08 7 80 0 6 8 820 02 9 04 9 9 6 0 880 720 029 94 0 08 7 82 0 0 4 7 780 76 0 8 8 0 068 78 0 80 06 800 048 84 0 0 82 0 00 8 840 06 8 0 8 8 720700 06 704 7 8 2 0 8 40 008 700 6 8 0 02 7 0 6 6 82 0 7 00 9 02 98 20 04 8 048 088 009 Lightning Ridge Collyblue 1 Bangate Dungle Ridge Eulalie Dunumbral Goondablui 1Goondablui 4 Muckerawa Wilby WilbyWillawillingbah Llanillo 2 2010_03_0028 20 km0 Figure 15. Two-way time contours to basement across the Lightning Ridge Shelf, showing graben structuring identified from seismic coverage acquired during the Collyblue, Lightning Ridge, Angledool and Angledool Extension seismic surveys; from Shaw (2002). Contours are in 20 msec intervals. See Figure 14 for location. 30 angledool 1:100 000 geological sheet 31 WeAtHeRInG Idnurm and Senior (1978) distinguished two periods of deep weathering in southwestern Queensland. They differentiated the Morney Profile, which is Maastrichtian to Early Eocene in age (60 ± 10 Ma), and the Canaway Profile, which is approximately Eocene to Miocene in age (30 ± 15 Ma). Both events are shown on Figure 3. McQueen et al. (2002) carried out palaeomagnetic dating on ferruginous weathering profiles in the Cobar area and determined that there had been a period of widespread stable iron fixation in the latest Cretaceous to early Eocene (60 ± 10 Ma) and another in the Middle Miocene (12 ± 3 Ma). McQueen et al. (2007) later refined the timing of the latter event, via further radiometric dating, to the Early Miocene. The former event is correlatable with Idnurm and Senior’s (1978) Morney Profile, while the latter corresponds to Idnurm and Senior’s (1978) Canaway Profile. Based on these data it is reasonable to assume that both weathering events were widespread and affected the area of Angledool. In the Upper Darling Basin, Taylor (1976, 1978) identified the Early Eocene Llanillo Silcrete, which he attributed to the culmination of a weathering event equivalent to Idnurm and Senior’s (1978) Morney Profile. Taylor (1978) attributed the weathering of the Cretaceous rocks of the area (including Angledool) to this event — producing deep kaolinisation (to 100 m) and local ferruginisation. The Pliocene event which formed the Mount Charlotte Silcrete (Taylor 1976) is much younger than Idnurm and Senior’s (1978) Canaway Profile. However, Taylor (1978) noted that a third silicification event which has been recorded in central Queensland probably does correlate with the Mount Charlotte Silcrete. Taylor (1978) was unable to differentiate a weathering event equivalent to the Canaway Profile in the Upper Darling Basin area. In Angledool, surface ferruginisation is present as a thin film of iron oxide on Tertiary gravels and silcrete. The only known Cretaceous rocks in Angledool, which display surface ferruginisation, are those exposed in the area west of Collarenebri, where they are ferruginised to a depth of about 1 m. Diamond drilling in the Coocoran area (Burton 2003a) indicates that significant ferruginisation of Cretaceous rock occurs at about 20 to 30 m below the surface. Ferruginisation takes the form of discontinuous red to chocolate brown, hard layers from approximately 1 to 10 cm thick, and nodules of goethite/limonite. Above this, the rocks are variably stained brown, orange or yellow (ochre) by iron oxide, commonly within the basal parts of sandstone layers underlain by claystone. The evidence suggests that iron has moved down from the surface and precipitated out at permeability barriers. Ferruginous horizons have been displaced by faults (Burton 2003a). Similar ferruginisation has been recognised in drillholes RC97BK001–012, drilled by Rio Tinto Exploration Pty Limited in the area northwest of Narran Lake (Doe & Palmer 1997a), where goethite–hematite alteration has been recorded starting at depths of 25 to 40 m and extending to about 75 m deep. The exposed Cretaceous rocks in Angledool have been pervasively kaolinised such that feldspars and clay minerals have broken down to form kaolinite, resulting in the rocks having a bleached white appearance. Burton (2003a) reported that visible kaolinisation extends below 20 m depth in opal workings of the Coocoran area, while in drillcore from the same area it extends to at least 50 m, being less easy to see but detectable with a Portable Infrared Mineral Analyser (PIMA). Silicification occurred at the surface and has resulted in the induration of the Tertiary gravels to form silcrete. Cretaceous rocks have also been variably silicified at the surface and below the silcrete to form ‘shincracker’. In the Coocoran area, Burton (2003a) noted that silicification extends from the surface to about 10 m depth. ‘Steel band’ is sporadic at depth, consisting of silicified Cretaceous sandstone and ranging in thickness from several millimetres to about 1 m. It occurs at the base of the sandstone, immediately above claystone lenses, which are the main hosts for opal mineralisation. It is apparent that ‘steel band’ has been produced by the pooling of siliceous fluid at the base of the sandstone where fluid flow has been retarded by the underlying, impermeable claystone. Burton (2003a) noted that where the silicified sandstone contains claystone rip-up clasts, the clasts are not silicified, indicating that silica has only pooled in the interconnected pore spaces of the sandstone. Burton (2003a) noted that manganese oxide coatings are common on exposed Cretaceous rocks. He also reported that, at depth, manganese oxide blebs and stains are concentrated in the basal parts of sandstone units, above claystone layers, suggesting that manganese, like silica in the ‘steel band’, has migrated downward and precipitated at an impermeable barrier. The timing relationships between the various types of weathering/alteration are not clear from the available data. However, as the region has experienced more than one phase of weathering there is probably a complex overprinting of kaolinisation, silicification, ferruginisation and manganese oxide precipitation. 32 angledool 1:100 000 geological sheet 33 econoMIc GeoLoGY Opal The opal of the Lightning Ridge area, as with all opal hosted within the rocks of the Great Australian Basin, consists of amorphous, hydrated silica (e.g. MacNevin & Holmes 1977). The silica is in the form of spheres which generally range in size from 0.1 μm to 0.5 μm (Jones et al. 1964; Sanders 1964). The microstructure of precious opal consists of a regular array of stacked spheres of equal diameter (Jones et al. 1964; Gaillou et al. 2008). The regular lattice so produced diffracts light to produce the play of colours characteristic of precious opal. Potch, or common opal, does not produce a play of colours as the spheres are either of unequal size and/or are not perfectly shaped and/or are not stacked uniformly (Gaillou et al. 2008). Black opal (Photograph 27) is so named for the dark body colour which enhances the play of colour (MacNevin & Holmes 1977). The dark colouration is due to the presence of carbon (Webb et al. 1999). The distribution of opal workings is shown on the Angledool 1:250 000 map face. The main areas where opal is mined are the Coocoran, Lightning Ridge, Carters Rush–Grawin–Glengarry, Wyoming, Muttabun–Allawah and Mehi areas. Figures 16, 17, 18, 19, 20 and 21 are more detailed maps showing the named fields. The opal fields of Angledool currently produce the world’s highest quality black opal. The production figures for any one mine or for any one opal field are not determinable and the all-time value of opal production from the area is difficult to estimate, due to the changing value of opal and the informal means of keeping records. The field value of opal (i.e. the amount that miners receive) produced from all of the Lightning Ridge fields for 2001/02 is estimated to have been $15 million (Lightning Ridge Miners’ Association 2003 pers. comm.). The retail value is estimated to have been about $45 million. Since the late 1990s, following the East Asian Financial Crisis, the value of opal has declined. Geological setting of opal deposits Opal occurs as horizontal seams, nodules (nobbies) and as replacements and cast fillings after fossils. It commonly occurs within the upper parts (approximately the upper 1 m) of the ‘Finch clay’ facies lenses (refer to Mesozoic to Tertiary Stratigraphy chapter). The claystone lenses are referred to by miners as ‘levels’ and the claystone itself is referred to as ‘opal dirt’. Recoverable opal is found within 30 m of the surface and has been worked mainly by underground methods, though some open cut mining has been carried out. Photographs 28 to 30 show opal mining operations carried out in the region. Seam opal consists of mainly horizontal (lesser vertical) seams of opaline silica. Nobby type opal consists of nodular masses of opal. The nodules may be rounded or have various conical shapes, in particular the ‘Chinaman’s hat’ type structure, and they vary in size from a few millimetres to several tens of centimetres in diameter. Nobby type opal is particularly common in the opal fields around Lightning Ridge and in the Coocoran area, while to the south in the Grawin–Glengarry area nobbies are rare and seam opal dominates. The origin of nobbies is uncertain. Watkins (1985) suggested that they may be opal replacements of ball and pillow structures, following on from the proposal of Heirn (1964) that they are opal infills of cavities after sand pockets. Byrnes (1975; 1976) speculated that ‘Chinaman’s hat’ nobbies may be opal casts of guilielmites formed from concretions. Pecover (1999b) suggested that they are boudins formed by deformation of once continuous opal seams. Anecdotal evidence suggests that nobbies commonly have sand coatings, supporting the model that they are opal replacements after sand pillows. The author alternatively proposes that some nobbies may be opal fills of spherical and ellipsoidal fractures, which may have formed during weathering. The author has observed naturally fractured rocks in outcrop which consist of a cup-like hollow on one side of the fracture and a corresponding dome on the other. Also, upon breaking with a hammer, the Cretaceous rocks commonly split with identical ellipsoidal fractures. The poles of the ellipsoid are commonly marked by a small tabular indentation, which appears to be a fossil wood imprint, which may have acted Photograph 27. Nobbies and polished black opal from Lightning Ridge. (Photographer: David Barnes). 34 angledool 1:100 000 geological sheet Photograph 30. Processing opal dirt. (Photographer David Barnes). Photograph 29. Nebia Hill opal mine. (Photographer David Barnes). Photograph 31. Naturally occurring ellipsoidal shaped fracture in Cretaceous sandstone. Note tabular fossil wood imprint in top left side of cavity. Site 216 (GR 563364 6737557). Photograph 32. Hand specimen from the contact between white kaolinised and silicified sandstone (‘steel band’) (top) and kaolinised claystone. Silica in the sandstone has preferentially pooled at the bottom of the unit and has an opaline character with opaline silica veinlets extending into the claystone. This sample clearly demonstrates a link between the ‘steel band’ and opal mineralisation. Opal mine located at GR 563944 6719824. Photograph 28. Three Mile opal field. (Photographer David Barnes). as a focus for the fracturing (Photograph 31). If such fractures became filled with opal, the resulting cast would be a shell- or conical-shaped cast, similar to an opal nobby. ‘Steel band’ is silicified sandstone which locally occurs above opal levels. Samples of ‘steel band’ in contact with potch (hosted by claystone) from the Grawin area (Photograph 32) have been petrographically examined (see Appendix 2). The contact between ‘steel band’ and potch is gradational and the ‘steel band’ exhibits flashes of weak ‘colour’, indicating that it is composed of opaline silica. It is apparent that the ‘steel band’ has formed at the same time as the potch. 35 economic geology Okhei Baikes Warning Riddles Lummo's Dijoe's Wild Cat Spinifex Shield's Lynfield Grawin F Sheepyard Gravesend GlengarryBenz Hill Blind Freddies Blazed Tree Mozzie Gully Grawin Creek Hardy's Crack Olympic Dribble New Glengarry 2 Central Station Grawin (east) (Richard's Hill) Carters Rush Wee Warra (part) New Glengarry Gotham City Millionaires Gully Chinaman's Gully Williamson's Corner Wee Warra (part) Shield's East Mulga RushFire Chief Grawin C Czinners Zac's Corner Wayne Manor Grawin (west) (Hammond's Hill) 2010_03_0029 6730000mN 6720000mN 560000mE 570000mE REFERENCE Opal mine N 0 5 km 6725000mN 6715000mN 565000mE555000mE Figure 16. Carters Rush, Grawin and Glengarry area — opal fields shown on a Landsat7 Enhanced Thematic Mapper Plus panchromatic image. Image © Commonwealth of Australia (Geoscience Australia) 2011. This material is released under the Creative Commons Attribution 3.0 Australia Licence. 36 angledool 1:100 000 geological sheet 6470000mN 6475000mN 570000mE 575000mE 580000mE KK CC Olga's Cody's Tyrones Sceek's Red Eye Rainbow Marie's Klaus's Kevin's Jenny's The Nest Red Post Martin's Dawson's White Peg Kellie's 6 Kellie's 5 Kellie's 1 Greenacres Warrengulla Old Coocoran New Coocoran Greenacres 2 Norway (south) Natalies Dream 2 Natalies Dream 1 T Bone Rainbow West Greenacres 3 Granny's Flat T Bone 2 extension Emu's Norway (north) Joyce's Moonshine Steen's Three Trees Hard Hill Smith's Dead Bird Ken's Retreat Molyneux's The Rocks Ormies Luck Allah's Rush (Kellie's 3) Kellie's 4 Extension Cheryl's (Kellie's 4) Long's Rush (Kellie's western fall) Steen's Greenacres 3 REFERENCE Opal mine N 0 5 km 2010_03_0030 Figure 17. Coocoran area — opal fields sown on a Landsat7 Enhanced Thematic Mapper Plus panchromatic image. Images © Commonwealth of Australia (Geoscience Australia) 2011. This material is released under the Creative Commons Attribution 3.0 Australia Licence. 37 economic geology JC Dave's Wyoming Hornet's Rush Rosso's Darby's Walshe's Ten Mile Pig Hill Ironbark Holden's Canada's The Gully Red RobinNine Mile Beckett's Bald Hill Angledool Power Pole Nebia Hill Con's Rush Bullockies Tom's Gully Frog Hollow Snowy Browns Deep Four Mile Steve's Bee Eaters Dentist Hill Jim Taylor's Rush Foley's Six Mile Seven MileMatson's Rush Shearer's Rush Berlin Rush Bishop's Rush Newtown and New Year Rush Vertical Bill's Airport Rush Water Tower Field and Reward Rush New Four Mile Shallow Belars and Four Mile Flat Three Mile Western Falls Three Mile Three Mile Flat Old Nobby Palestine Bullock's Head Deep Belars Hidden Valley Grassy Hollow Hawks Nest and Frying Pan Hart's and Spicer's Phil Herbert's Rush McNamara's Pumpkin Flat Old Chumand New Chum Dry Rush, Poverty Point and New Nobby Telephone Line and Pony Fence Canfell's Hill Sim's Hill (includes Hatter's Flat, Old Town Butterfly, Indian Lookout and Kingfisher) Potch Point Thorley's Six Mile McDonald's Six Mile Bill the Boer Lightning Ridge 2010_03_0031 674000mN 675000mN 674500mN 590000mE585000mE 595000mE 600000mE REFERENCE Opal mine N 0 5 km Figure 18. Lightning Ridge area — opal fields superimposed on a Landsat7 Enhanced Thematic Mapper Plus panchromatic image. 38 angledool 1:100 000 geological sheet JC CC Gema D & D Miro's Dunn's Dave's Wyoming Marie's Goulash Ten Mile Pot Luck Ironbark Boredrain Allawah 3 Allawah 2 Speck Hill Power Pole Lee's Luck Boggy Hill Warrengulla Tom's Gully Snake Gully Scandanavia Great Eastern Crusty's LuckCrusty's Luck 2 Les's Eight MileFraser Island Anderson's Folly Weetalibah Frankstone 3 Frankstone 1 Great Eastern Extension Stoney's Steve's Bee Eaters Dentist Hill Foley's Six Mile Seven MileMatson's RushBerlin Rush 580000mE 585000mE 590000mE 6760000mN 6755000mN 6750000mN 2010_03_0032 Bishop’s Rush REFERENCE Opal mine N 0 5 km Figure 19. Wyoming area — opal fields shown on a Landsat7 Enhanced Thematic Mapper Plus panchromatic image. Images © Commonwealth of Australia (Geoscience Australia) 2011. This material is released under the Creative Commons Attribution 3.0 Australia Licence. 39 economic geology Gema Eagle D & D Rednex Miro's Dunn's Dave's Brooks Goulash Jag Hill Wedge Tail Tyrone's 2 Knightlife Kitty Hawk Boggy Hill Scandinavia Roses and Chocolates Jag Hill 2 Jag Hill 3 Muttabun (Brown's) Fraser Island Weetalibah Steve's Tom’s Gully Steve's 2010_03_0033 570000mE 580000mE 6760000mN 6750000mN 6755000mN 575000mE Figure 20. Muttabun area — opal fields shown on a Landsat7 Enhanced Thematic Mapper Plus panchromatic image. Castlereagh Hwy Billy Goat Hill The Springs and Harrison's Folly Mehi Watson's Reward Spiders Rainah's Itchy and Scratchy Mehi 7 Eagle's Nest Mehi 2010_03_0034 6790000mN 590000mE Opal mine REFERENCE 595000mE 6785000mN 5 km0 N Figure 21. Mehi area — opal fields shown on a Landsat7 Enhanced Thematic Mapper Plus panchromatic image. 40 angledool 1:100 000 geological sheet Timing of opal formation Byrnes (1981) reported the occurrence of opal clasts in gravels overlying the Cretaceous rocks but pre- dating the Tertiary gravels in the White Cliffs area. He concluded that opal formation in that area must have preceded deposition of the Tertiary gravels. Similarly, Watkins (1985), citing Whiting and Relph’s (1961) observation of opal float in gravels, interpreted the gravels at the Old Chum opal field (GR 595000 6745800) as being Tertiary in age. He concluded that opal formation in the Lightning Ridge area must have occurred prior to the deposition of the Tertiary gravels. On the basis of these observations it is likely that opal in the Lightning Ridge region must have formed in the Maastrichtian to Early Eocene ‘Morney’ weathering event (Idnurm & Senior 1978) (see chapter on Weathering and Figure 3). However, the boulder opal deposits of southwestern Queensland are considered to have formed in the ‘Canaway’ weathering event (Senior et al. 1977), even though some opal occupies ironstone concretions formed during the ‘Morney’ event. MacNevin and Holmes (1977) reported that rare opal veins within Tertiary silcrete occur to the north of White Cliffs but Byrnes (1981) advised that this required further investigation. It may be the case that opal throughout the southwest Queensland–northern New South Wales region has formed at more than one time. Dowell and Mavrogenes (2003a, 2003b, 2004) and Dowell et al. (2002) carried out carbon dating of black (carbon-rich) nobby-type opal samples and determined that they formed between 1740 and 7 790 years B.P. These ages conflict with the field evidence which suggests that opal formation is much older. Gallacher (1999) has suggested that the structure of opal is open and hence its trace element and isotopic characteristics are susceptible to re-equilibration with groundwater. If correct, this casts doubt upon all isotopic work carried out on opal. Amelin and Back (2006) have attempted to date opal and define a standard using the U-Pb method. However, they concluded that precious opal is not suitable for dating by this method as it contains very low levels of U and has very low ratios of U/204Pb. Hence not enough radiogenic Pb is produced to give accurate dates of its formation. Their best results were from opals originating in Nevada which consist of opal-CT (i.e. non-amorphous or crystalline silica). Hence, the possibility of directly dating opal formation in the Lightning Ridge area remains low. Opal formation models Weathering processes and passive structural control A process involving silica mobilisation during weathering is the most likely explanation for the origin of opal in the Lightning Ridge district. Darragh, Gaskin and Sanders (1976) proposed this model for the origin of opal at Andamooka, South Australia and Watkins (1985) applied it to the Lightning Ridge district. This model proposes that deep weathering, leading to kaolinisation of the feldspathic sedimentary rock, liberated silica. The silica-rich ground water migrated downward via faults and fractures and other permeability pathways until reaching an impermeable barrier. In most cases this barrier was provided by claystone lenses, though voids after fossils and various fractures also acted as fluid traps. Once trapped, the water evaporated, creating a silica gel. Microscopic silica spheres — up to 0.0005 mm diameter (Darragh, Gaskin & Sanders 1966) — then precipitated from the gel to form opaline silica. Where the spheres were of uniform size and were regularly packed, precious opal was formed. Where the spheres were variable in size and not regularly packed, potch, or common opal, developed. Dowell and Mavrogenes (2003a, 2003b, 2004) argued that the weathering model was untenable because the δ18O values of opal are higher than those in the weathered Cretaceous host rocks and are much higher than meteoric water values. However, the weathering model predicts that opal precipitates from a fluid derived from fresh Cretaceous rock which has reacted with meteoric water. After weathering it would be expected that the silica-bearing fluid would be enriched in 18O and the δ18O of the weathered host would be lowered. Dowell and Mavrogenes (2003a, 2003b, 2004) did not present any isotopic data for fresh Cretaceous rocks, which would be expected to have a higher δ18O than their weathered counterparts. Given that the Cretaceous rocks are derived from a volcanic provenance, a high δ18O value would be expected. The present author’s contention is that Dowell and Mavrogenes (2003a, 2003b, 2004) data support the weathering model. Rondeau et al. (2004), in their study of Slovakian opals, undertook oxygen isotope analysis which also included an opal from Coober Pedy for comparison. They concluded that the maximum temperature of formation was 45 °C which is consistent with the weathering model. Pewkliang et al. (2008) have studied the opalisation of plesiosaur bones from Andamooka. They concluded that the opal most likely formed from a gel which had occupied open spaces within the already fossilised bone and that this was consistent with the opal having formed during a post-Cretaceous weathering event. Upwelling fluids with active structural control Pecover (1996, 1999a, 1999b) has proposed that opal in the Lightning Ridge region formed in dilational sites by crack-seal processes in high-strain zones 41 economic geology opal formation and hydrothermal processes are unlikely to have been responsible. They determined that the δ13C and δ18O in black opal fits with a biological origin. Though these observations show that biological material is included within black opal there is no evidence that biological processes were responsible for its formation. Previous studies have shown that the weathering of feldspars can be enhanced by bacteria (e.g. Barker et al. 1998; Rogers et al. 1998; Hutchens et al. 2003), so it is possible that bacteria may have played a role in the liberation of silica into the weathering environment. However, there is no evidence that the microstructure of opal was in any way produced by bacteria. Amorphous opal formed in geothermal environments is also composed of silica spheres which precipitate from silica-rich water (e.g. Channing and Butler 2007 — Yellowstone, USA; Jones and Renaut 2007 — Geysir, Iceland; Smith et al. 2003 — Wairakei, New Zealand). While microorganisms in those areas have been encased in amorphous opal and thereby acted as a substrate in some instances, they have not been actively involved in the precipitation of opal. Smith et al. (2003) suggested that microbes may have influenced the precipitation of opal from hydrothermal fluids in geothermal power station discharge pipes and a naturally occurring geothermal field. However, they also acknowledged that salinity was an important factor and that the textures present were consistent with those produced in abiogenic laboratory systems of similar physical and chemical properties. Channing and Butler (2007) produced synthetic amorphous opal and were able to reproduce microstructures analogous to those found in naturally occurring opal at Yellowstone, indicating that bacteria are not a necessary part of the process. Aubrecht et al. (2008) described siliceous speleothems which occur within a cave in Venezuela. These structures are stromatolitic, produced by the precipitation of opal via evaporation of condensed cave moisture with several types of microbes and spider threads acting as substrates. The fact that not all opal produced from the Great Australian Basin is black opal also indicates that organic material is not necessary for its formation. Relationship of opal workings to surface structures Burton (2003a) presented evidence to show that opal occurrences in the Coocoran area are bounded to the southeast by a northeasterly trending lineament which passes close to the Natalies Dream workings. Burton (2003b) referred to this structure as the Natalies Dream Lineament (NDL) (Figure 22). Opal has been during active faulting and folding. He considered that the silica-rich fluids were either derived from intraformational water and/or from aquifers within the Great Australian Basin and invoked fluid temperatures greater that 100 ºC. In this scenario the kaolinisation and silicification of the host rocks are interpreted as hydrothermal alteration effects and ‘blows’ are interpreted to represent hydrothermal breccias. One problem with this model is that the conditions described are essentially the same as those within a high sulphidation epithermal vein system but it does not adequately explain why precious opal formed instead of quartz veins. It also does not adequately explain why kaolinisation and silicification decrease with depth and why opal seams are not surrounded by silicification haloes but rather are overlain by silicified rocks. Work by Dowell and Mavrogenes (2003a) does not support a hydrothermal origin for the fluids. Pecover (1996) interpreted the presence of large scale open anticlines within the Lightning Ridge region and considered that opal had been emplaced into high-strain hinge zones, in order to explain why opal occurs primarily within claystone rather than sandstone. However, high- strain indicators such as tight folding or attenuation or shearing were not evident in opal workings examined by the author. Rey et al. (2003) proposed that opal formed during a widespread extensional deformation event. They considered that the ‘steel band’ was in existence prior to opal deposition and acted as a permeability barrier to over-pressured fluids which precipitated opal into fractures in the underlying claystone. This contrasts with observations by the author which shows a strong association between ‘steel band’ and opal (as noted above). Their model does not adequately explain the common occurrence of opal in horizontal fractures — extensional fractures would be more likely to have vertical orientations in a horizontally extending regime. Biological processes Behr et al. (2000) and Behr (2001) found that black opal contains aerobic bacteria that commonly live in soil at temperatures of between 23 and 35 °C and at neutral pH. They considered that the bacteria originally lived in a muddy, organic-rich environment and excreted enzymes and acids that helped break down clay minerals and feldspar, producing, among other components, Si(OH)4. They considered that opal nobbies originated as gas bubbles formed within the sediments. The gas bubbles became filled with silica- rich formation water which later precipitated opal. Deuterium and oxygen isotope analyses by Dowell and Mavrogenes (2003a) indicated that present day ground water and bore water were not involved in 42 angledool 1:100 000 geological sheet “Calgary” Mount Charlotte Cumborah “Amaroo” “Wyoming tank” “Leander” “Oxley Park” Goodooga Lightning Ridge New Angledool Coocoran Lake Narran Lake 2010_03_0037 148°45'E147°00'E 29°00'S 30°00'S (a) 0 20 km Angledool Lake 0 4 8km 2010_03_0035 147°40’ E 147°50’ E 148°00’ E 29°20’ S 29°30’ S barren block? prospective block? Natalies dream lineament Na rra n Riv er W ar ra m bo ol Bi g The R. Lightning Ridge Dentist Hill Wyoming Jag Hill Wedge tail Coocoran Lake Seven Mile (b) 43 economic geology Figure 22. Opal fields (red dots) and lineaments (black lines) interpreted from mapped distribution of rock units in Angledool. Figures (b), (c) and (d) show areas with further interpretation. Opal working (some named) Lineament interpreted from aerial photographs REFERENCE Speculative bounding structure N 6km0 3 147°30’ E 29°40’ S Grawin Carters Rush Glengarry 147°40’ E 147°50’ E 2010_03_0036 (c) New Angledool Angledool Lake 2010_03_0038 29°00’S 29°10’S 147°50’E 148°00’E Queensland (d) New South Wales 0 5 km 44 angledool 1:100 000 geological sheet found on the northwestern side of the structure but, despite the drilling of numerous exploratory holes, none has been found to the southeast. Burton (2003a) interpreted the NDL as a dip-slip fault, analogous to other faults observed in opal workings. Based on diamond drilling data and investigations of opal workings, it was considered that sandstone is a minor component of the rock sequence on the southeastern side of the structure but more significant on its northwestern side. Three following reasons could explain why the NDL appears to have controlled opal distribution (Figure 23). 1. The NDL was a growth fault active during deposition of the Griman Creek Formation and controlled the location of river channels, such that more sandstone was deposited northwest of the structure than to its southeast. If the weathering model of opal formation is correct, it suggests that a thicker sandstone unit is likely to produce more silica-rich fluid during weathering, resulting in increased likelihood of opal deposition in the underlying claystone (Watkins 1985). 2. The NDL was active after deposition of the Griman Creek Formation but before opal formation, such that sandstone units were uplifted and eroded or, conversely, were more deeply buried, on the southeastern side of the structure. As in (1) the sandstone-poor sequence near the surface on the southeastern side of the NDL was less favourable for opal formation. 3. The NDL was active after opal formation such that opal on the southeastern side of the structure was uplifted and eroded away. Conversely, another possibility is that opal was more deeply buried on the southeastern side of the structure, but this is considered less likely. It is also possible that any combination of the above three scenarios occurred. Perhaps the dip-slip displacements along faults have affected opal prospectivity elsewhere within Angledool for similar reasons to those outlined above. However, the difficulty in identifying faults from surface studies makes it impossible to derive a reliable structural interpretation. Consequently, no well-constrained model for identifying prospective blocks is presented herein. The opal fields of the Coocoran area appear to be confined to a wedge-shaped block defined by the northeasterly extension of the Natalies Dream Lineament and other (non-parallel) northeasterly trending structures up to 8 km to the northwest (Figure 22). However, some opal occurrences occur immediately northwest of this block, reducing the validity of this interpretation. Conversely, in the Muttabun area no opal has been found within a Mudstone (floodplains etc.) Natalies Dream Lineament Sandstone (channels) confined to graben/half-graben prospective zone ‘barren’ zone Present ground surface enoz ’nerrab‘ enoz evitcepsorp Removed by erosion Present ground surface Removed by erosion Opal deposit enoz ’nerrab‘ enoz evitcepsorp ferruginised zone (assumed to be related to opal formation) (c) (b) (a) NW SE 2011_02_0009 Figure 23. Schematic models showing how the Natalies Dream Lineament could have controlled the localisation of opal deposits in the Coocoran area. A) the structure may have been a growth fault active during deposition of the Griman Creek Formation which controlled deposition of sandstone (channel) units, confining them largely to the northwestern side of the structure. B) dip-slip movement along the structure after deposition of the Griman Creek Formation may have resulted in uplift and erosion of sandstone layers on its southeastern side. C) dip-slip movement along the structure after the formation of opal may have resulted in uplift and erosion of opal on its southeastern side. It is also possible that any combination of these processes may have occurred. 45 economic geology Petroleum The Angledool 1:250 000 map sheet area, particularly the northeastern part, has been explored for petroleum. Seismic surveys have been conducted by exploration companies and the (former) Department of Mineral Resources and a test hole, Collyblue No.1, was drilled by a joint venture between Consolidated Petroleum Australia NL and The Australian Gas Light Company in 1987 (Lawrence & Harris 1988). The hole tested an anticline produced by draping of the Mesozoic sedimentary sequence over Lachlan Orogen basement rocks. The hole failed to detect any hydrocarbons (Lawrence & Harris 1988; Shaw 2002). In general, the Mesozoic rocks in the Angledool area are not considered to have high potential to host a petroleum resource, as any potential source rocks have probably not been sufficiently matured (buried deeply enough) and no favourable trap structures have been recognised (Shaw 2002). Shaw (2002) speculated that the Goodooga Graben and the Collarenebri Graben could be favourable source areas. Bamberry and Kouzmina (1995) postulated that the Goodooga Graben and the Collarenebri Graben are Permian half- grabens. They interpreted the graben fill as comprising three distinct seismic facies — a basal facies of non- marine sedimentary rocks, possibly coal-bearing; a middle facies of mixed character; and a top facies of coastal plain sedimentary rocks. The graben fill may be up to 750 m thick, which allows the possibility that the rocks have reached sufficient maturity for petroleum to form. However, no exploration work has been carried out to test this. Coal There are no known coal resources within Angledool. Bourke (1973) reported occurrences of coal from several formations penetrated during the drilling of the Lightning Ridge Town Water Supply bore. In drillhole Collyblue No.1, coal was identified in the Bungil Formation (Lawrence & Harris 1988). Coal has been reported from several water bores in the area, mainly as bands and lenses with shale or sandstone. Some bores, scattered over Angledool, have penetrated coal seams over 1 m thick, including (with depths below collar indicated): GW004164 (288.04–291.69 m); GW008372 (457.5–460.55 m), GW027499 (92.96–94.49 m and 99.06–100.58 m) and GW800002 (427–432 m). Coal may be present in the Goodooga Graben and the Collarenebri Graben (Bamberry & Kouzmina 1995). Diamonds Exploration for diamonds has been conducted in the southwestern area of Angledool in the vicinity northeasterly trending zone which occurs south of the Jag Hill opal field and north of the Wedge Tail opal field. This zone corresponds to an area of significant Quaternary alluvial cover, where probably little or no exploration has been carried out. Watkins (1985) postulated that in some instances pre-existing faults in the Lightning Ridge area acted as pathways for silica-bearing fluids which, once trapped at impermeable barriers, precipitated opal. This interpretation is supported by the occurrence of some opal deposits along interpreted structures, such as in the Mehi area, the northern edge of the Coocoran area, and the opal fields extending from Dentist Hill to Seven Mile, northwest of Lightning Ridge (Figure 22). Gravel deposits Gravel has been quarried at several locations. The largest quarries are situated in unconsolidated Tertiary gravels, with examples at Cumborah; about 11 km northwest (Gamalally or 9 Mile pit) and about 10 km (Mount Brandon pit) and 19 km southwest of Collarenebri; and 6.5 km west of Angledool. Smaller quarries exploit silcrete at various places. An extensive quarry in Cretaceous sandstone, siltstone and claystone is developed at the Calgary pit, 26 km southwest of Collarenebri. Small borrow pits are situated in Cretaceous rocks in several areas. Sand and loam deposits The abundance of Quaternary alluvium throughout Angledool presents an enormous potential for deposits of sand and loam. Presently, sand and loam are extracted from deposits of Bugwah Formation meander plain facies at the Mission (Ginghi) pit (GR 602702 6682402) and from splay facies deposits of the Nullawa Member at the Heathfield pit (GR 603777 6725276). Well-sorted sands in some colluvial material (Qc) and some dune deposits (Qd) may have potential for construction purposes, however, the presence of iron oxides in such materials may be problematic for some uses. Water resources The Pilliga Sandstone and the Mooga Sandstone (see cross section on map) constitute the main artesian aquifers in Angledool. Minor aquifers have been intersected in water bore drilling within the Orallo Formation and Bungil Formation. Water bore locations are shown on the map face. Further information on these bores can be obtained from the New South Wales Department of Water and Energy (available online at http://nratlas.nsw.gov.au). 46 angledool 1:100 000 geological sheet that contamination from the drilling had occurred, or that if diamonds are naturally present, they are not significantly concentrated to constitute a resource. There is no reliable estimate of the age of the breccia. Doe and Palmer (1997b) described it as occurring within basement rocks to the Surat Basin — mainly phyllite with lesser meta-arenite and meta-siltstone. An interpretation by consultant Peter Temby (pers. comm. 2003), based on palynological data (Price 1997), suggests that the diatreme is immediately overlain by the Doncaster Member and that it probably cross-cuts Cretaceous rocks of the Surat Basin. This implies that the intrusion is no older than Cretaceous. Oxiana Resources NL has carried out subsequent drill testing of isolated aeromagnetic anomalies. of Lynrae (GR 506700 6711600) and Glenallyn (GR 517100 6714700) stations. Work focused on drill testing discrete positive aeromagnetic anomalies apparent on the (former) Department of Mineral Resources’ regional aeromagnetic map of the Angledool 1:250 000 sheet. Rio Tinto Exploration Pty Limited identified the Penarie 4472-1 anomaly as the most prospective target for a diamondiferous intrusion (Doe & Palmer 1997b). Three holes were drilled to target the inferred intrusion. The target was identified as a ‘variably magnetic basalt breccia with ultramafic and meta-sedimentary xenoliths’ and was interpreted to be a diatreme. While three microdiamonds were recovered from the breccia, the sampling results could not be reproduced, suggesting 47 GeoLoGIcAL HIstoRY to (west of) a volcanic arc which extended along the Queensland coast (Veevers 1984). The Middle Jurassic Purlawaugh Formation (Figures 3 & 4) is the oldest recognised stratigraphic unit of the basin in Angledool. The depositional environment of the Purlawaugh Formation is considered to have been a low-energy fluvial to paludal, perhaps swampy, aggradational plain or valley infill (Shaw 2002). The Pilliga Sandstone is considered to have been deposited by a braided to meandering river system with extensive flood plains (Shaw 2002). Further fluvial sedimentation occurred to form the Orallo Formation and Mooga Sandstone and a marine incursion took place during deposition of the Bungil Formation (Shaw 2002). The Wallumbilla Formation is interpreted to have been deposited mainly within a marine environment (Byrnes 1973), as too was the Surat Siltstone (Shaw 2002). The provenance area for the Pilliga Sandstone and Mooga Sandstone was an exposed upland area in southern Australia, while material constituting the other Mesozoic formations described herein was derived mainly from the volcanic arc to the east (Veevers 1984). While the lower part of the Griman Creek Formation is interpreted to have been deposited in a shallow marine environment (Reiser 1970) most of the unit probably reflects deposition within a terrestrial (riverine) environment (Reiser 1970; Exon 1976). Abundant fossils (many of which are opalised) include aquatic and terrestrial animal remains and plant material. Disarticulated remains of fish, molluscs, sharks, lungfish, monotremes, aquatic reptiles, plesiosaurs, dinosaurs and birds have been found (Smith & Smith 1999). After deposition of the lower part of the Griman Creek Formation the sea retreated to the north. In the Late Cretaceous to early Palaeogene there was a widespread weathering event (Idnurm & Senior 1978) which resulted in kaolinisation and silicification of the Cretaceous sedimentary rocks in Angledool. It is considered by the author that opal was produced during this event. A second weathering event occurred in the Oligocene to Miocene (Idnurm & Senior 1978; McQueen et al. 2007). During the Miocene an extensive braided river system covered the region, depositing sand and gravel. The provenance of this material is not well constrained but its deposition was probably related to uplift of the eastern highlands. Further weathering and silicification occurred in the Pliocene, cementing the gravels to form silcrete (Taylor 1976). It is assumed that tectonism, most likely block faulting, Basement The following account of the geological history of the Palaeozoic (basement) rocks is mainly based on the work of Scheibner and Basden (1996, 1998), except where indicated otherwise. The basement is composed of rocks of the Lachlan Orogen. The oldest rocks of the Lachlan Orogen are at least Early Ordovician in age and the youngest are middle Carboniferous intrusions. A deep-water turbidite succession is interpreted to have been deposited on what was the Cambro-Ordovician continental margin, and in a backarc environment associated with a subduction zone in the Ordovician to Early Silurian. The belt of Ordovician to Early Silurian volcanic rocks represents part of the volcanic arc with deep water turbidites to the east representing forearc basin deposits. Subduction ended in the Early Silurian, as the subduction front migrated eastward, and the volcanic arc was rifted, producing deep grabens which became filled with sedimentary and volcanic material throughout the remainder of the Silurian, until the Middle Devonian. Granites were also emplaced during this interval. The Tabberabberan Orogeny occurred in the Middle Devonian. Subsequent to this deformation event the area was overlain by Late Devonian to Early Carboniferous terrestrial sediments, including those of the Paka Tank Trough. The middle Carboniferous Kanimblan Orogeny, caused by the docking of the New England Orogen to the east with the Lachlan Orogen, was a major deformational event which affected most of New South Wales. Granites were also emplaced during the middle Carboniferous. During the Early Permian, rifting in the Goodooga Graben and Collarenebri Graben is considered to have been part of an extensional phase, caused by backarc rifting behind the still-active volcanic arc further east (Shaw 2002 and references therein). It is speculated that these grabens contain mainly terrestrial sedimentary rocks (Shaw 2002; Scheibner 1997). Surat Basin, Tertiary and Quaternary systems Following deposition in the Early Permian, the region underwent a long period of erosion, levelling most of the topography. Sedimentation within the Surat Basin commenced in the Early Jurassic, to the east of Angledool (Shaw 2002). The Surat Basin is considered to have formed a foreland basin adjacent 48 angledool 1:100 000 geological sheet by relatively narrow meander plain deposits with little, if any, elevation above the surrounding back plain. The Quaternary alluvial systems directly reflect the prevailing climatic regimes at the time of their deposition. The Bugwah Formation formed during the waning stages of the last glacial maximum, which occurred at 18 ka. The climate during this period was characterised by wet, cool winters, in which the alluvial systems were active, and dry, hot and windy summers, in which some alluvial material was reworked into source-bordering dunes (Williams 2000). The Marra Creek Formation reflects a climate following the last interglacial maximum (at 9 ka), in which rainfall is less seasonal (Williams 2000). In all of the Quaternary systems recognised within the Angledool, sediment was derived from the highlands of southeastern Queensland and transported towards the southwest. The exposed Cretaceous and Tertiary rocks have been weathered and eroded throughout the Quaternary. occurred in the region before, during and after deposition and silicification of the gravels. Since the Late Pleistocene the area has been dominated by riverine deposition. 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The origin of Murillo gravels in northwestern New South Wales. Joint Specialist Group Meeting Geological Society of Australia, G7–G11. taylor g. 1976. The Barwon River, New South Wales — a study of basin fill by a low gradient stream in a semi-arid climate. Unpublished PhD thesis, Australian National University, Canberra. taylor g. 1978. A brief Cainozoic history of the Upper Darling Basin, pp. 53–59. Royal Society of Victoria, Proceedings 90(1). veevers J.J. (ed.) 1984. Phanerozoic earth history of Australia, Clarendon Press, Oxford. watkins J.J. 1985. Future prospects for opal mining in the Lightning Ridge region, Geological Survey of New South Wales, Report GS1985/119. watkins J.J. 1992. Thermoluminescence dating of Quaternary sediments from the Nyngan–Walgett area’, Geological Survey of New South Wales, Quarterly Notes, 89, 23–29. watkins J.J. & meakin n.s. 1996. Nyngan and Walgett 1:250 000 geological sheets SH/55-15 & SH/55-11: explanatory notes, Geological Survey of New South Wales, Sydney. webb J.a., pigram p.J., prince k., gong b. & scott s.m. 1999. The presence of carbon in Lightning Ridge black potch. First National Opal Mining Symposium, 30–31 March, Lightning Ridge, (not paginated). white m.e. 1986. The Greening of Gondwana. Reed Books, Sydney. whiting J.w. & relph r.e. 1961. The occurrence of opal at Lightning Ridge and Grawin, with geological notes on County Finch. Department of Mines New South Wales, Technical Report 6 (for 1958), 7–21. williams m.a.J. 2000. Quaternary Australia: extremes in the last glacial–interglacial cycle. In: J.J. Veevers (ed.), Billion-year earth history of Australia and neighbours in Gondwanaland. GEMOC Press, Macquarie University, Sydney. 53 APPenDIxes Appendix 1 Geological sites data Table A lists the geological sites that were visited during the course of this study. It is a subset of information derived from the corporate Sites database of the Division of Resources and Energy. 54 angledool 1:100 000 geological sheet ta bl e A : G eo lo gi ca l s it es d at a si te ea st in g M G A e n or th in g M G A n Lo ca lit y Li th ol og y si te fe at ur es 1 57 79 20 67 37 45 2 Q ua rr y / sc ra pe sil cr et e, cla ys to ne 2 57 52 83 67 36 17 8 Ci rc ul ar d ep re ss io n (a pp ro x. 2 00  m di am et er ) v isi bl e o n ae ria l p ho to gr ap h so il H um m oc ky g ro un d, su rr ou nd ed b y t re es an d gr ee n gr as s; so m e s ilc re te b ou ld er s b ut m ai nl y d ry , g re y s oi l w ith tu ss oc ks o f b ro w n/ gr ey g ra ss . 3 57 87 81 67 37 23 1 Pa ve m en t e xp os ur e o n ro ad sa nd sto ne 4 57 94 25 67 37 10 8 Pa ve m en t e xp os ur e o n ro ad sa nd sto ne , s ilt sto ne 5 57 55 31 67 36 27 2 Ru bb ly ex po su re o n ris e sil cr et e D ril l h ol e a t t hi s s ite ; a li ne o f h ol es tr en ds ap pr ox . n or th ea st. 6 57 53 40 67 35 75 8 Lo w ex po su re o n ro ad sil cr et e 7 57 52 92 67 35 55 1 Lo w ex po su re o n ro ad sa nd sto ne 8 57 50 64 67 35 06 3 G ur ley ga te in fl at , s an dy ar ea sa nd Re d sa nd w ith fr ag m en ts of si lcr et e; so m e d ril l h ol es . 9 57 52 53 67 35 37 4 Lo w ru bb ly su bc ro p ex po su re sil cr et e 10 57 47 70 67 36 25 7 Lo w, ru bb ly ex po su re sil cr et e 11 57 40 03 67 36 00 7 SW co rn er o f c la im 37 40 4, N at al ie s D re am sil cr et e Cl ai m h as a tip pe r a nd a bl ow er n ea rb y; sh ee t o f i ro n ov er sh aft an d an ai r s ha ft; so m e ru bb le of sh in cr ac ke r ( lig ht b ro w n/ ta n po rc el la ni te) fr om w or ki ng s. 12 57 38 22 67 35 94 6 W oo de d, h um m oc ky g ro un d so il 13 57 37 33 67 35 96 8 Lo w ru bb ly ar ea sil cr et e 14 57 31 60 67 35 95 3 Fl at , r ub bl y a re a sil cr et e 15 57 27 13 67 35 91 9 Lo w ru bb ly ex po su re sil cr et e 16 57 23 68 67 35 85 8 La rg e, po or ly ve ge ta te d, o pe n ar ea w ith ru bb ly ex po su re sil cr et e 17 57 20 44 67 35 48 4 Tw o fe nc es jo in w ith ga te o n no rt h- tre nd in g fe nc e sil cr et e, sa nd sto ne , cla ys to ne , s ilt sto ne Bo un da ry b et we en T er tia ry si lcr et e a nd C re ta ce ou s r oc ks . 18 57 20 56 67 35 45 2 Cr ee k ex po su re sa nd sto ne , cla ys to ne , s ilt sto ne Cr et ac eo us ro ck s a re o ve rla in b y r ed sa nd w ith fe rr ug in ou s s ilc re te cl as ts ; o nl y e xp os ur e is in cr ee k. 19 57 20 26 67 35 40 9 O ut cr op in cr ee k sa nd sto ne , cla ys to ne Aw ay fr om cr ee k th er e i s o nl y r ed so il w ith fe rr ug in ou s s ilc re te cl as ts . 20 57 20 44 67 35 35 0 O ut cr op in cr ee k sa nd sto ne , s ilt sto ne O nl y o ut cr op is in cr ee k; aw ay fr om cr ee k th er e i s o nl y r ed sa nd . 21 57 52 51 67 36 37 1 Pi le of ru bb le w ith p os ts an d w ire ; p os sib le wo rk in g Po ss ib le in fil led w or ki ng . 22 57 94 65 67 37 10 0 G ul ly o n so ut h sid e o f r oa d sa nd sto ne , s ilt sto ne 23 57 94 15 67 36 99 7 Fl at , o pe n ar ea w ith tr ee s; lo w ri se to so ut h sa nd Be tw ee n he re an d sit e 0 02 2 t he re is su bc ro p to o ut cr op o f C re ta ce ou s s an ds to ne in re d so il. 55 appendixes 24 57 93 81 67 36 90 8 Bo un da ry o f s ilc re te , lo w o ut cr op sil cr et e 25 57 93 18 67 36 79 4 Fl at ar ea w ith ab un da nt p in e t re es sa nd Re d so il w ith fe rr ug in ou s s ilc re te cl as ts ; t yp ic al o f t op o f t he ri dg e. 26 57 91 89 67 36 75 7 Fl at , s po ng y, ci rc ul ar ar ea ap pr ox . 5  m X 10  m ac ro ss . so il So m e s ilc re te b ou ld er s. 27 57 91 50 67 36 59 6 Fl at ar ea ge nt ly sl op in g do w n to so ut h; re d sa nd w ith go od tr ee co ve r sa nd Be tw ee n th is sit e a nd si te 0 02 6 th er e i s o nl y s an d w ith ra re si lcr et e c la sts . 28 57 92 38 67 36 35 7 Fl at ar ea , g en tly sl op in g do w n to so ut h sa nd Re d sa nd w ith p in e t re es b et we en h er e a nd si te 0 02 7. 29 57 92 51 67 35 96 9 N or th ea ste rly tr en di ng ro ad , v er y c lo se to ed ge o f b la ck so il (< 10 0  m to th e s ou th ) sa nd Sp ar se ve ge ta tio n of tu ss oc ky g ra ss an d fe w tr ee s; no ru bb le. 30 57 93 39 67 36 00 6 Fl at ar ea ge nt ly sl op in g do w n to w es t sa nd , s ilc re te N um er ou s s m al l p in e t re es ; r ed sa nd w ith ab un da nt si lcr et e fl oa t; ed ge o f s ilc re te ru bb le. 31 57 94 66 67 36 09 8 Fl at ar ea sil cr et e Re d sa nd w ith si lcr et e c la sts an d tre es ; s ilc re te ru bb le be co m es m or e a bu nd an t a bo ut 5 0  m up sl op e t o N N W ; r ed so il be co m es m or e c om m on d ow n slo pe to th e S SE . 32 57 95 31 67 36 18 5 Fl at ar ea ge nt ly sl op in g do w n to ea st an d so ut he as t sa nd sto ne Ve ry p oo r o ut cr op to su bc ro p; fr ag m en ts of sa nd sto ne , s ilc re te cl as ts an d re d sa nd . 33 57 95 74 67 36 13 2 Ru bb ly ar ea ge nt ly sl op in g do w n to ea st sa nd sto ne 34 57 97 62 67 36 07 5 Ed ge o f p ad do ck — fi eld to ea st , t re es to we st so il G re y, cla ye y s oi l; we t, sp on gy to b og gy in p la ce s w ith cl as ts of C re ta ce ou s s an ds to ne an d sil cr et e; tu ss oc ky g ra ss , h um m oc ky g ro un d. 35 57 96 17 67 36 21 9 G en tly sl op in g do w n to ea st sa nd sto ne Cr et ac eo us sa nd sto ne ru bb le in so il. 36 57 95 08 67 36 35 4 N or th -n or th ea st tre nd in g sh al lo w tr en ch sa nd sto ne 37 57 94 17 67 36 48 5 sil cr et e Ed ge o f a bu nd an t s ilc re te fl oa t; no t a m ar ke d ch an ge in sl op e a t t he ed ge o f t he si lcr et e b ut gr ou nd sl op es d ow n to so ut h aw ay fr om it . 38 57 95 38 67 36 59 9 sa nd sto ne A bu nd an t s ilc re te ru bb le w ith so m e c la sts o f p re su m ab ly u nd er ly in g Cr et ac eo us sa nd sto ne . 39 57 96 73 67 36 79 0 G en tle sl op e t o ea st sa nd sto ne , s ilt sto ne O ut cr op st op s j us t e as t o f h er e a nd g re y c lay ey so il is pr es en t. 40 57 94 78 67 36 95 4 sil cr et e Si lcr et e p ro ba bl y f or m s a th in ve ne er ab ov e C re ta ce ou s s an ds to ne . 41 57 89 36 67 37 00 4 N ea r g at e a nd b elo w p ow er li ne sil cr et e Si lcr et e s ub cr op an d ru bb le; fe rr ug in ou s. 42 57 81 57 67 36 36 3 O n po we rli ne ro ad w ith sl op e d ow n to th e so ut h sil cr et e Be tw ee n th is sit e a nd si te 0 04 1 th e t er ra in is fl at an d co ns ist s o f r ed sa nd w ith si lcr et e ru bb le; o nl y r ed sa nd o cc ur s t o th e s ou th we st. 43 57 75 05 67 35 84 1 Lo ck ed ga te a lo ng p ow er li ne ro ad ; lo we st pa rt o f g ul ly sa nd , c lay sto ne 44 57 75 63 67 35 55 1 Fl at ar ea w ith ve ry ge nt le slo pe u p to th e so ut h sa nd , f er ric re te 45 57 77 07 67 35 38 4 Fl at ar ea n ea r d ril l h ol e sil cr et e 46 57 78 08 67 35 14 7 Er os io n gu lly in re d sa nd p la in sa nd sto ne , s ilt sto ne 47 57 77 81 67 34 91 3 G en tle sl op e d ow n to ea st sa nd sto ne , sil tst on e, cla ys to ne Ru bb ly o ut cr op o f C re ta ce ou s r oc ks in re d sa nd . 56 angledool 1:100 000 geological sheet si te ea st in g M G A e n or th in g M G A n Lo ca lit y Li th ol og y si te fe at ur es 48 57 76 45 67 34 77 5 Fl at ru bb ly ar ea sil cr et e Ed ge o f s ilc re te . 49 57 74 70 67 34 58 1 Re d sa nd p la in sl op es d ow n to so ut he as t sa nd Be tw ee n th is sit e a nd si te 0 04 8 te rr ai n co ns ist s o f r ed sa nd w ith ra re C re ta ce ou s c la sts an d Cr et ac eo us su bc ro p in g ul lie s. 50 57 72 34 67 34 63 8 sil cr et e Ed ge o f s ilc re te ; m ar ke d by ab un da nt si lcr et e r ub bl e. 51 57 68 59 67 34 68 6 sil cr et e Ru bb ly o ut cr op to su bc ro p. 52 57 67 14 67 34 75 8 Fl at , s pa rs ely ve ge ta te d ar ea ; c irc ul ar st ru ct ur e ( ap pr ox . 2 00  m d ia m et er ) v isi bl e on ae ria l p ho to gr ap h so il A re a c om po se d of w et , g re y s oi l w ith lo w gr ee n gr as s a nd sp ar se tr ee s; rin ge d by tr ee s. 53 57 73 23 67 37 26 1 H ea vi ly ti m be re d (y ou ng p in e) ar ea w hi ch co rr es po nd s t o cr es ce nt -s ha pe d rid ge o n ae ria l p ho to sil cr et e Ri dg e i s n ot o bv io us o n th e g ro un d; si lcr et e r ub bl e b ec om es le ss co m m on aw ay fr om th e ar ea . 54 57 76 98 67 37 66 4 Q ua rr y o n no rt h sid e o f r oa d sil cr et e 55 57 76 73 67 37 75 1 Lo w o ut cr op in q ua rr y cla ys to ne 56 57 81 35 67 37 91 7 sil cr et e A pp ar en t n or th er n ed ge o f s ilc re te ; s lo pe d ro ps aw ay (s ha llo w ly) to n or th . 57 57 82 79 67 38 11 4 Fl at p la in ge nt ly sl op in g do w n to n or th ; su bc ro p in ro ad g ul ly sil tst on e Su rr ou nd in g ar ea is co m po se d of re d sa nd w ith tr ee s. 58 57 87 78 67 37 31 3 Ru bb ly o ut cr op n or th o f r oa d sa nd sto ne 59 57 88 64 67 37 39 2 Fl at ar ea ge nt ly sl op in g do w n to n or th sa nd Bo un da ry b et we en re d sa nd an d Cr et ac eo us ro ck o ut cr op . 60 57 89 21 67 37 32 1 sa nd sto ne 61 57 90 36 67 37 47 1 N ea r d am sa nd , s an ds to ne Cr et ac eo us cl ay sto ne ar ou nd d am ; b la ck so il to n or th o f d am . 62 57 86 78 67 37 21 1 Fl at ar ea w ith ru bb ly o ut cr op sa nd sto ne Sm al l o ut cr op in re d sa nd . 63 57 83 79 67 36 97 9 Fl at ar ea w ith tr ee s; ve ry ge nt le slo pe u p to so ut h sil cr et e M ai nl y r ed sa nd an d tre es w ith m in or si lcr et e fl oa t; so m e f er ru gi no us p iso lit hs . 64 57 80 82 67 38 29 3 Lo w ru bb ly o ut cr op w ith n um er ou s d ril l ho les ar ou nd sa nd sto ne Ed ge o f C re ta ce ou s r oc k ou tc ro p; re d sa nd to n or th . 65 57 74 77 67 38 20 6 Fl at ar ea o f r ed sa nd an d ed ge o f t hi ck tim be r sa nd 66 57 73 11 67 38 26 4 Fl at ar ea ge nt ly sl op in g up to w es t sa nd Fr ag m en ts of m ai nl y fi ne -g ra in ed si lcr et e w ith so m e p eb bl es ; s ub cr op o f p eb bl y, m at rix su pp or te d sil cr et e l ie s i m m ed ia te ly to w es t a nd sc re e b ec om es le ss co m m on to th e e as t. 67 57 69 52 67 38 24 3 H ea vi ly ti m be re d (p in e) , fl at ar ea , n ea r t op of ri dg e sil cr et e Si lcr et e fl oa t i n re d sa nd . 68 57 65 67 67 38 48 0 Fl at ar ea ge nt ly sl op in g do w n to w es t sa nd Re d sa nd w ith si lcr et e fl oa t. 57 appendixes 69 57 62 63 67 38 41 1 Fl at g ro un d so il 70 57 58 88 67 38 27 3 Fl at ar ea ge nt ly ri sin g to w es t; so m e d ril l ho les sa nd 71 57 58 41 67 38 28 0 Ve ry lo w o ut cr op in re d sa nd cla ys to ne 72 57 56 77 67 38 37 4 Ed ge o f h ea vi ly w oo de d ar ea (t o we st) ; slo pe s t o we st sil cr et e 73 57 54 17 67 38 40 1 Fl at ar ea , g en tly sl op in g up to w es t sil cr et e Ed ge o f s ilc re te ca p. 74 57 56 44 67 38 21 9 Fl at , g en tle sl op e u p to ea st sil cr et e 75 57 57 44 67 38 00 7 Fl at ar ea w ith ab un da nt q ua rt z p eb bl es an d fe rr ug in ou s s ilc re te fl oa t i n re d sa nd sil cr et e, pe bb les 76 57 58 50 67 38 00 1 G en tle sl op e d ow n to ea st , s pa rs e o ut cr op sil tst on e, cla ys to ne 77 57 66 52 67 37 92 5 Fl at , h ea vi ly ti m be re d (p in e) ar ea sil cr et e 78 57 68 58 67 38 02 2 Fl at , h ea vi ly ti m be re d (p in e) ar ea sil cr et e 79 57 73 59 67 38 20 1 sa nd W es te rn b ou nd ar y o f r ed sa nd . 80 57 46 87 67 37 61 1 M id dl e o f r oa d 81 57 40 61 67 37 79 4 N or w ay w or ki ng s A bu nd an t s ilc re te ru bb le an d re d so il on su rf ac e; Cr et ac eo us sa nd sto ne o n du m ps . 82 57 42 12 67 37 83 4 Fl at ar ea w ith d ril l h ol es sa nd 83 57 44 51 67 38 06 2 Fl at ar ea w ith m od er at e d en sit y o f t im be r sa nd W or ki ng s a nd d ril l h ol es o cc ur ab ou t 5 0  m to th e s ou th we st. 84 57 43 46 67 38 39 8 Fl at ar ea at so ut he rn ed ge o f A lla hs wo rk in gs sil cr et e 85 57 40 73 67 38 36 1 sa nd 86 57 40 51 67 37 92 0 N or th er n en d of N or w ay w or ki ng s sa nd Cr et ac eo us ro ck ru bb le ar ou nd w or ki ng s b ut n o ou tc ro p. 87 57 33 78 67 37 89 7 A pp ro x. 5  m n or th o f g at e o n ro ad h ea di ng no rt h sa nd 88 57 34 13 67 38 10 4 Ex po su re in g ul ly a lo ng w es te rn si de o f ro ad sa nd sto ne , sil tst on e, cla ys to ne 89 57 34 78 67 38 37 4 Ro ad at to p of sl op e sil cr et e 90 57 28 74 67 39 11 0 ‘Y ’ ju nc tio n in tr ac k w ith fe nc e o n we st sid e; da m > 10 0  m to th e n or th we st sa nd Ed ge o f b la ck so il pl ai n w ith n o ex po se d Cr et ac eo us ro ck ; m an y d ril lh ol es . 91 57 25 07 67 38 51 6 Be nd in ro ad an d fe nc e. Fl at ar ea w ith th ick sc ru bb y v eg et at io n sa nd Re d sa nd w ith sc ru b. 92 57 25 19 67 38 31 1 To p of sm al l r ise sil cr et e W es te rn ri dg e F 12 9 of si lcr et e c ov er . 93 57 25 55 67 37 77 7 ‘T ’ ju nc tio n w ith m ai n ro ad sa nd Re d sa nd g ra di ng in to b la ck so il pl ai n. 94 57 40 37 67 37 64 5 N or th er n en d of so ut he rn N or w ay wo rk in gs sa nd Re d sa nd w ith m od er at e v eg et at io n pu nc tu at ed b y o pa l w or ki ng s. 58 angledool 1:100 000 geological sheet 95 57 43 29 67 37 28 0 G en tle sl op e u p to n or th ea st , m od er at e t re e co ve r sil cr et e 96 57 46 00 67 37 34 3 W es t s id e o f a re a w ith m in e d um ps an d po ss ib le wo rk in gs sil cr et e 97 57 44 66 67 37 15 1 G en tle sl op e d ow n to so ut hw es t, m od er at e tre e c ov er (m os tly p in e) sil cr et e 98 57 42 59 67 36 84 9 Fl at ar ea , g en tly sl op in g do w n to so ut h sil cr et e Fe rr ug in ou s p iso lit hs fr om a fe w m ill im et re s t o se ve ra l c en tim et re s i n di am et er ; l ar ge r on es ar e s ilc re te cl as ts w ith fe rr ug in ou s c ru sts ; s om e s m al ler o ne s a re m ag ne tic . 99 57 42 31 67 36 41 2 Fl at , o pe n ar ea w ith ve ry ge nt le ris e t o th e so ut h sil cr et e 10 0 57 42 42 67 36 25 5 Fl at , f ai rly o pe n ar ea sil cr et e Ir on sto ne p iso lit hs co m m on ; d ril l h ol es in ar ea an d a p os sib le wo rk in g ab ou t 1 00  m to th e no rt he as t. 10 1 57 39 95 67 36 41 1 Fl at ar ea ge nt ly sl op in g do w n D1 36 to no rt hw es t sil cr et e Ir on sto ne p iso lit hs co m m on ; m ar ks th e e dg e o f s ilc re te ru bb le an d pi so lit hs in re d sa nd ; on ly re d sa nd li es to th e n or th we st. 10 2 57 35 27 67 36 76 6 Fl at ar ea w ith m od er at e t re e c ov er sa nd Sh aft w ith co ve r o f w oo d, g ril l a nd co rr ug at ed ir on . 10 3 57 52 22 67 36 88 6 Fl at ar ea w ith m od er at e t im be r sil cr et e 10 4 57 48 54 67 36 81 3 Fl at ar ea w ith h ea vy ti m be r ( m ai nl y p in e) sa nd 10 5 57 44 93 67 36 25 0 D um ps o f C re ta ce ou s r oc k fro m o pa l wo rk in gs sil cr et e 10 6 57 33 63 67 36 30 5 Fl at ar ea w ith m od er at ely th ick ti m be r; al on g di rt tr ac k sil cr et e 10 7 57 30 53 67 36 55 9 sil cr et e 10 8 57 29 94 67 36 59 2 G en tle sl op e d ow n to w es t. Ru bb ly o ut cr op an d w as h ou t g ul lie s w ith C re ta ce ou s fr ag m en ts sa nd sto ne Re d sa nd is at le as t 1  m th ick , w ith ra re C re ta ce ou s o ut cr op s; re d sa nd co nt ai ns fe rr ug in ou s s ilc re te fr ag m en ts an d iro ns to ne p iso lit hs . 10 9 57 22 32 67 36 08 7 Fl at ar ea sil cr et e Re d sa nd w ith fe rr ug in ou s s ilc re te ru bb le an d iro ns to ne p iso lit hs . 11 0 57 16 98 67 35 93 6 Fl at ar ea , n ot fa r f ro m b la ck so il; d am ab ou t 2 00  m to so ut hw es t sa nd Re d sa nd w ith w as h- ou t g ul lie s. 11 1 57 17 06 67 35 88 6 Sm al l p ile o f r ub bl e o n fla t a re a sa nd sto ne Ru bb le ov er ab ou t 4  m 2 ; ro un de d ro ck s o f C re ta ce ou s s an ds to ne ap pe ar to b e n at ur al (n ot m an m ad e) . 11 2 57 18 11 67 35 92 0 (B as e o f?) ge nt le slo pe u p to ea st sil cr et e 11 3 57 22 23 67 35 49 2 G en tle sl op e u p to ea st ; m od er at e t im be r co ve r ( no p in e) sil cr et e A bu nd an t s ilc re te ru bb le. 11 4 57 25 28 67 35 57 2 Sm al l o ut w as h gu lly w ith C re ta ce ou s s cr ee (n o ou tc ro p) sa nd sto ne Re d sa nd w ith si lcr et e r ub bl e i n pl ac es ; a fe w ro un de d sto ne s s ev er al te ns o f c en tim et re s ac ro ss . 11 5 57 27 32 67 35 47 3 H ea vy sc ru b on re d sa nd w ith n o ou tc ro p sa nd si te ea st in g M G A e n or th in g M G A n Lo ca lit y Li th ol og y si te fe at ur es 59 appendixes 11 6 57 25 56 67 35 83 5 O n pl at ea u sil cr et e Ex te ns iv e s ilc re te ru bb le oc cu rs in g ul ly to so ut h, ab ou t 1 00 m aw ay . 11 7 57 46 40 67 35 79 6 Tr ac k sil cr et e 11 8 57 46 32 67 35 36 6 Sl op es d ow n to so ut h, th ick sc ru b sa nd 11 9 57 44 45 67 35 37 7 Fl at ar ea o f m os tly re d sa nd ; l ie s o n no rt h- so ut h lin ea m en t i nt er pr et ed fr om ae ria l ph ot og ra ph sa nd sto ne , s ilt sto ne W es te rn ed ge o f s ub cr op ; d ril l h ol e n ea rb y. 12 0 57 39 83 67 35 44 9 Fl at ar ea ge nt ly ri sin g to w es t; lo w ru bb ly ou tc ro p/ su bc ro p sa nd sto ne , cla ys to ne Lo ca te d on an in te rp re te d ae ria l p ho to li ne am en t b ut n o st ru ct ur e i s e vi de nt o n th e gr ou nd . 12 1 57 39 12 67 35 29 9 G en tle sl op e u p to n or th we st ; lo w ru bb ly su bc ro p cla ys to ne Cr et ac eo us ru bb le co nt in ue s a pp ro x. 10 0  m u p hi ll to w es t b ef or e s ilc re te ru bb le be co m es do m in an t. 12 2 57 36 90 67 35 28 7 Cl um p of tr ee s n ea r e as t-t re nd in g fe nc e; ne ar to p of h ill sil cr et e Re as on ab le slo pe b ut n o sig ni fic an t o ut cr op . 12 3 57 36 86 67 35 19 3 G en tle sl op e d ow n to so ut h; lo w ru bb ly ou tc ro p sil tst on e 12 4 57 36 86 67 34 96 2 G en tle sl op e d ow n to so ut h; m ai nl y r ed sa nd w ith m od er at e t im be r/s cr ub sa nd 12 5 57 36 63 67 35 02 5 O ut cr op in g ul ly sa nd sto ne , cla ys to ne 12 6 57 35 14 67 35 10 8 G en tle sl op e t o so ut h sa nd sto ne , cla ys to ne 12 7 57 34 34 67 35 11 8 Lo w ru bb ly o ut cr op ; g en tle sl op e d ow n to so ut h cla ys to ne 12 8 57 34 20 67 35 41 3 V irt ua lly o n to p of ri se +D 15 6 sil cr et e 12 9 57 49 34 67 34 87 6 Ro ad w ith lo w ru bb ly su bc ro p sil cr et e 13 0 57 47 57 67 34 88 6 G en tle sl op e d ow n to w es t; co m m on p in e tre es ; m od er at e d en sit y t im be r sil cr et e Lo w ru bb ly su bc ro p; re d sa nd , s ilc re te fr ag m en ts an d iro ns to ne p iso lit hs . 13 1 57 45 90 67 34 84 2 M od er at e t o he av ily ti m be re d ar ea sa nd sto ne , cla ys to ne Ru bb le of C re ta ce ou s r oc k on re d sa nd , s lo pi ng ge nt ly w es t. 13 2 57 44 92 67 34 52 4 G en tle sl op e d ow n to w es t w ith m od er at e sc ru b co ve r sa nd In te rs ec tio n of tw o in te rp re te d lin ea m en ts on ae ria l p ho to gr ap h; n o ou tc ro p. 13 3 57 44 95 67 34 45 9 G en tle sl op e d ow n to w es t; lo w ru bb ly ou tc ro p sa nd sto ne , cla ys to ne 13 4 57 44 87 67 34 28 8 Fl at ar ea o n pl at ea u sil cr et e Ir on sto ne p iso lit hs p re se nt o n su rf ac e. 13 5 57 51 66 67 34 28 4 Fl at , g en tly sl op in g do w n to ea st. O n we st sid e o f n or th -s ou th fe nc e w ith ab un da nt pi ne tr ee s o n ea st sid e a nd p in e a nd sc ru b to w es t sa nd 13 6 57 52 30 67 35 10 6 Fl at ar ea w ith m od er at e s cr ub . P lat ea u sa nd 60 angledool 1:100 000 geological sheet 13 7 57 47 20 67 34 17 9 Ro ad sil cr et e 13 8 57 46 89 67 33 76 9 Ro ad o n slo pe d ow n to so ut h; su bc ro p in gu lli es an d ru bb le sa nd sto ne , cla ys to ne , s ilc re te N ea r c on ta ct b et we en si lcr et e a nd C re ta ce ou s r oc ks . 13 9 57 44 90 67 33 78 1 Fl at ar ea sl op in g do w n to so ut h sa nd 14 0 57 44 92 67 33 92 3 G en tle sl op e d ow n to so ut h an d we st sa nd sto ne A sm al l r ub bl y s ub cr op in re d sa nd w ith ab un da nt p iso lit hs an d fe rr ug in ou s s ilc re te gr av el; an er os io n gu lly ap pr ox . 1 00  m to N W in di ca te s t ha t r ed sa nd is at le as t 1  m th ick . 14 1 57 42 58 67 33 95 5 Fl at p la in cla ys to ne Ru bb ly o ut cr op in re d sa nd ; a n er os io n gu lly 5  m aw ay in di ca te s t ha t s an d is at le as t 0 .5  m th ick . Th e f ac t t ha t C re ta ce ou s r oc ks ar e e xp os ed n ea rb y s ug ge sts th at th e t op o f t he Cr et ac eo us m us t b e a n irr eg ul ar su rf ac e. 14 2 57 41 07 67 33 95 1 Ex te ns iv e r ub bl y o ut cr op /su bc ro p w ith slo pe ri sin g to n or th we st ; c re st of sl op e i s ab ou t 5 0  m aw ay sa nd sto ne , cla ys to ne 14 3 57 36 69 67 33 71 1 Fl at ar ea o n pl at ea u; d ril l h ol es n ea rb y sil cr et e Th in , e ro de d, si lcr et e c ap w ith C re ta ce ou s r oc k no t f ar b elo w th e t op o f t he p lat ea u; ab un da nt ir on sto ne p iso lit hs an d fe rr ug in ou s g ra ve l. 14 4 57 34 36 67 33 29 1 Sm al l p lat ea u w ith si lcr et e r ub bl e sil cr et e Si lcr et e c ap fo rm s a th in ve ne er ; C re ta ce ou s r oc k is no t f ar b elo w th e t op o f t he p lat ea u; ab un da nt ir on sto ne p iso lit hs . 14 5 57 34 44 67 32 98 6 Ro ad sid e sa nd sto ne 14 6 57 46 29 67 31 74 0 A bo ut 2 0  m ea st of ga te so il 14 7 57 47 15 67 31 64 3 G en tle sl op e u p to ea st w ith lo w ru bb ly ou tc ro p sa nd sto ne 14 8 57 50 75 67 31 16 8 To p of ri dg e sa nd sto ne , cla ys to ne 14 9 57 54 22 67 31 20 9 G en tle sl op e d ow n to ea st sa nd 15 0 57 54 47 67 31 39 1 Si de o f r id ge , s lo pi ng d ow n to so ut he as t sil cr et e Re d sa nd w ith fe rr ug in ou s s ilc re te fr ag m en ts ; t he si lcr et e r id ge (a li ne am en t i nt er pr et ed on ae ria l p ho to ) i s a th in , s ke let al re m na nt . 15 1 57 55 67 67 31 45 2 G en tle sl op e d ow n to ea st ; lo w ru bb ly su bc ro p sa nd sto ne Sm al l s ub cr op o f C re ta ce ou s s an ds to ne in re d sa nd w ith ir on sto ne p iso lit hs an d fe rr ug in ou s s ilc re te ru bb le. 15 2 57 60 86 67 31 58 5 Br oa d, fl at o pe n ar ea sil cr et e Si lcr et e f ra gm en ts w ith ir on sto ne p iso lit hs an d so m e s ilc re te b ou ld er s u p to 1  m ac ro ss . 15 3 57 64 58 67 31 78 3 Co rr es po nd s t o rid ge o n ae ria l p ho to sil cr et e Fo rm s a ge nt le ris e a nd a su bt le ar cu at e p la n sh ap e. 15 4 57 61 56 67 31 94 8 Bo x ho llo w so il O pe n, ci rc ul ar o r o vo id ar ea su rr ou nd ed b y t re es an d lo os e s ilc re te ru bb le; in te rn al ly it co ns ist s o f p al e g re y, cla ye y s oi l s up po rt in g ve ry lo w fi ne g ra ss . 15 5 57 58 67 67 32 05 4 G en tle sl op e d ow n to w es t; lo w ru bb ly ou tc ro p sa nd sto ne , cla ys to ne Su rr ou nd in g ar ea is ju st re d sa nd an d sc ru b. 15 6 57 51 05 67 32 42 5 G en tle sl op e d ow n to w es t sa nd 15 7 57 46 12 67 32 87 0 W es te rn en d of d am cla y A n or th -s ou th ae ria l p ho to li ne am en t i s i nt er pr et ed to ru n th ro ug h th is po in t, bu t f ou nd no C re ta ce ou s f ra gm en ts sh ow in g ev id en ce o f s he ar in g/ fa ul tin g. si te ea st in g M G A e n or th in g M G A n Lo ca lit y Li th ol og y si te fe at ur es 61 appendixes 15 8 57 59 82 67 33 36 3 G en tle sl op e u p to ea st sa nd 15 9 57 61 95 67 33 52 6 G en tle sl op e u p to ea st , n ea r t op o f r id ge sil cr et e 16 0 57 66 30 67 33 67 0 Ro ad sil cr et e 16 1 57 61 73 67 33 96 3 G en tle sl op e d ow n to so ut h, m od er at e t re e co ve r sa nd sto ne Ru bb le in re d sa nd . 16 2 57 58 42 67 34 27 3 Cl os e t o to p of p lat ea u sil cr et e O ut cr op o f s ilc re te . 16 3 57 80 24 67 32 66 5 Fl at ar ea , m od er at ely ti m be re d (n o pi ne s), ne ar lo ck ed ga te so il 16 4 57 75 47 67 32 39 9 Lo w o ut cr op sil cr et e 16 5 57 77 70 67 32 48 1 G en tle sl op e d ow n to ea st ; m od er at e t re e co ve r; lo w ru bb ly o ut cr op sa nd sto ne 16 6 57 84 85 67 33 39 2 G en tle sl op e d ow n to n or th cla ys to ne , s ilt sto ne , sa nd sto ne 16 7 57 83 08 67 33 36 4 N ea r t op o f p lat ea u w ith a ge nt le ris e t o th e we st sil cr et e 16 8 57 84 41 67 33 42 7 G ul ly o n so ut h sid e o f r oa d sil tst on e, cla ys to ne 16 9 57 74 54 67 33 55 0 Ro ad sil cr et e 17 0 57 65 41 67 30 16 0 O n ro ad ju st do w n fro m to p of p lat ea u sa nd sto ne , s ilt sto ne 17 1 57 59 68 67 29 90 5 G en tle sl op e u p to w es t sa nd sto ne , s ilt sto ne 17 2 57 57 52 67 29 92 7 To p of p lat ea u sil cr et e Cr et ac eo us ro ck s c ro p ou t j us t w es t o f h er e, su gg es tin g th at si lcr et e i s o nl y a th in ve ne er . 17 3 57 64 77 67 30 43 4 O n ro ad sil cr et e 17 4 57 68 34 67 30 52 0 Lo w sl op e d ow n to ea st sa nd sto ne 17 5 57 74 02 67 30 66 0 W es te rn si de o f s um m it of ro un d hi ll sa nd sto ne H ill is ri m m ed b y f er ru gi no us si lcr et e r ub bl e; so m e s ilc re te ru bb le on ap ex w ith q ua rt z pe bb les u p to 5 0  m m ac ro ss b ut b es t e xp os ur es ar e o n slo pe s o f t he h ill . Th e c en tr al p ar t of th e h ill is d om in at ed b y g re y c lay . 17 6 57 64 47 67 30 57 3 Ro ad in v al ley sa nd Re d sa nd w ith sc ru b. 17 7 57 61 42 67 31 33 7 sil cr et e In te rp re te d no rt he as te rly tr en di ng p ho to li ne am en t i s n ot ev id en t o n th e g ro un d. 17 8 57 59 97 67 31 15 9 Re d sa nd p la in w ith sc ru b slo pi ng d ow n to so ut hw es t sa nd sto ne 17 9 57 63 10 67 32 12 3 Fl at , c lea re d ar ea sil cr et e 18 0 57 65 94 67 33 04 3 Fl at ar ea — b ox h ol lo w/ sin k so il A pp ro x. 10 0  m × 5 0  m zo ne , e lo ng at e i n a n or th ea ste rly d ire ct io n an d su rr ou nd ed b y b ox tre es (a nd o th er ty pe s). Im m ed ia te ly n or th th er e i s a si m ila r a re a a bo ut 5 0  m × 5 0  m . G R gi ve n is be tw ee n th e t wo ar ea s. 18 1 57 71 38 67 33 26 0 Fl at ar ea — b ox h ol lo w/ sin k so il Bo w l-s ha pe d de pr es sio n co nt ai ni ng la rg e a nd sm al l t re es , b ut ge ne ra lly fa irl y s pa rs e ve ge ta tio n. S ilc re te is fo un d ou tsi de o f i ts m ar gi ns an d ra re p ie ce s o cc ur in sid e t he st ru ct ur e. 62 angledool 1:100 000 geological sheet si te ea st in g M G A e n or th in g M G A n Lo ca lit y Li th ol og y si te fe at ur es 18 2 57 56 30 67 35 94 1 Lo w ri se w ith ab un da nt si lcr et e r ub bl e sil cr et e Aw ay fr om th e r id ge , t er ra in co ns ist s o f r ed sa nd w ith v ar ia bl e v eg et at io n. Th e r id ge is de ns ely ve ge ta te d w ith p in e. Th e d om in an t s an d he re co ul d ex pl ai n w hy th is ar ea is co nd uc tiv e ( ac co rd in g to th e a irb or ne E M su rv ey ) a t t he su rf ac e, ev en th ou gh it is re sis tiv e a t d ep th . 18 3 57 60 88 67 35 53 4 Ri dg e+ D 21 3 ap pr ox . 5 0  m w id e w ith ab un da nt si lcr et e sil cr et e Th e r id ge is h ea vi ly ti m be re d w ith p in e a nd su rr ou nd ed b y r ed sa nd w ith sp or ad ic sil cr et e flo at . 18 4 58 53 90 67 46 24 6 H ill o n Ca st ler ea gh H ig hw ay sa nd sto ne , cla ys to ne , s ilt sto ne 18 5 58 61 23 67 46 60 6 O n a t ra ck sil cr et e, sa nd sto ne A bu nd an t s ilc re te ru bb le on C re ta ce ou s r oc k; su gg es ts a r em na nt si lcr et e c ap is p re se nt (a s i nt er pr et ed fr om ae ria l p ho to ). 18 6 58 66 61 67 45 99 3 O pa l w or ki ng s sa nd sto ne Sh aft s a nd o pe n cu ts . 18 7 58 26 33 67 58 04 2 A re a a pp ro x. 2 00  m n or th ea st of ri dg e so il A re a o f g re y, st ick y, cla ye y c ra ck in g so il fo rm in g hu m m oc ky g ro un d. S ilc re te ru bb le ra ng es fr om b ou ld er s a bo ut 1  m ac ro ss to fr ag m en ts se ve ra l c en tim et re s a cr os s. Ir on sto ne pi so lit hs ar e p re se nt in th e s oi l. 18 8 57 48 71 67 37 71 6 O pa l m in e a t J oy ce s R us h 18 9 57 44 16 67 38 59 0 O pa l m in e a t A lla hs R us h 19 0 57 43 23 67 38 56 3 O pa l m in e a t A lla hs R us h 19 1 57 39 62 67 36 03 5 O pa l m in e a t N at al ie s D re am 19 2 57 30 72 67 38 84 2 O pa l m in e a t K el lie s 5 19 3 57 29 86 67 38 87 4 O pa l m in e a t K el lie s 5 19 4 57 55 71 67 41 73 7 O n ro ad , a dj ac en t t o sc ra pe o n sil cr et e sil cr et e 19 5 57 69 66 67 41 41 1 Lo w ru bb ly o ut cr op o n tr ac k; w or ki ng s t o no rt h; d ril l h ol es to n or th an d so ut h sa nd sto ne , sil tst on e, cla ys to ne N ea r e as te rn ed ge o f s ilc re te ? 19 6 57 67 90 67 42 07 2 sa nd sto ne Ea ste rn ed ge o f e xt en siv e r ub bl y o ut cr op . 19 7 57 60 32 67 42 13 1 Pl at ea u; m in in g ar ea sil cr et e 19 8 57 70 55 67 44 12 9 Ro ad sid e g ul ly sa nd sto ne 19 9 57 99 45 67 43 99 9 N ea r t op o f h ill sil cr et e, sa nd sto ne , cla ys to ne 20 0 57 70 16 67 50 55 2 Sm al l b ul ld oz er p it on si de o f r oa d sil cr et e 20 1 57 32 91 67 47 49 7 Fl at ar ea sa nd 20 2 57 21 69 67 48 24 1 Sm al l b ul ld oz er -s cr ap ed q ua rr y sil cr et e Pe bb les w er e p ro ba bl y d er iv ed fr om b re ak do w n of si lcr et e, ra th er th an g ra ve l t ha t h as es ca pe d sil ici fic at io n. 20 3 56 97 17 67 32 42 6 Bu lld oz er sc ra pe sil cr et e, sa nd sto ne 20 4 56 97 73 67 29 67 0 To p of sm al l h ill sil cr et e, sa nd sto ne 63 appendixes 20 5 56 86 68 67 32 08 8 O n tr ac k sa nd 20 6 56 50 00 67 30 37 0 Sm al l r ise o n bl ac k so il pl ai n sil cr et e 20 7 56 50 22 67 29 61 9 La rg e b ut sh al lo w b ul ld oz er -s cr ap ed qu ar ry cla ys to ne , s ilc re te 20 8 56 59 11 67 28 21 1 G ra w in C re ek / G ra w in W at er ho le cla ys to ne , s ilc re te So m e s ha fts an d di gg in gs in cl iff fa ce s. 20 9 56 70 07 67 25 70 0 Ro ad sil cr et e Ed ge o f s ilc re te ; g en tle sl op e d ow n to so ut h fla nk ed b y r ed sa nd m er ge s i nt o a fl at p la in w ith d en se ve ge ta tio n. 21 0 56 75 05 67 24 93 5 Ro ad sc ra pe cla ys to ne 21 1 56 79 16 67 23 90 0 Q ua rr y sil cr et e, sa nd sto ne , cla ys to ne 21 2 56 87 68 67 22 27 8 Ro ad sid e g ul ly n ea r f en ce (e as te rn si de o f ro ad ) sa nd sto ne 21 3 57 09 34 67 23 50 3 Ro ad o n pl at ea u sil cr et e 21 4 57 10 23 67 25 22 4 Bu lld oz er sc ra pe sa nd sto ne , sil tst on e, cla ys to ne 21 5 56 75 36 67 36 17 2 Ro ad sil cr et e 21 6 56 33 64 67 37 55 7 Tr ac k slo pi ng d ow n to w es t; lo w ex po su re on tr ac k an d w as ho ut g ul ly ad ja ce nt to tr ac k sa nd sto ne , s ilt sto ne 21 7 56 47 34 67 22 78 8 N ea r t o ab an do ne d bu ild in gs sa nd sto ne 21 8 56 50 54 67 22 89 5 O n tr ac k sil cr et e, sa nd sto ne 21 9 56 40 96 67 21 80 5 Sm al l r ise sil cr et e 22 0 56 24 63 67 20 25 2 G ul ly ad ja ce nt tr ac k (o ld G len ga rr y R oa d) cla ys to ne , sa nd sto ne A th in si lcr et e p lat ea u (u p to 0 .2 5  m th ick ) c ro ps o ut le ss th an 5 0  m to th e s ou th an d in clu de s s po ra di c o ut cr op s o f C re ta ce ou s s ed im en ta ry ro ck s. 22 1 56 25 93 67 19 00 9 To p of ri se o n de to ur tr ac k fro m m ai n G len ga rr y R oa d sil cr et e 22 2 56 02 11 67 17 74 4 Sm al l b ul ld oz er ex ca va tio n im m ed ia te ly so ut h of ro ad sa nd sto ne 22 3 56 39 44 67 19 82 4 Sh an no n Ba rr et t’s m in e sa nd sto ne , cla ys to ne , b re cc ia 22 4 55 14 55 67 16 24 1 Ce nt re o f c irc ul ar fe at ur e ( ap pr ox . 2 80  m di am et er ) D 25 1 in te rp re te d fro m ae ria l ph ot og ra ph so il, ca lcr et e, sil cr et e Th is sa uc er -s ha pe d st ru ct ur e h as a ra di us o f a bo ut 2 80  m , b ey on d w hi ch th e g ro un d slo pe s d ow n, o ut w ar ds . Th e c en tr al zo ne , w ith a ra di us o f 1 60  m , c on sis ts of g re y, cla ye y so il. 22 5 54 96 30 67 12 99 8 Ro ad sid e e xp os ur e sa nd sto ne , s ilc re te 22 6 57 34 53 67 31 36 3 Fl at ar ea so il Th e a re a i s v er y s lig ht ly el ev at ed o ve r 1 00 s o f m et re s h or iz on ta l d ist an ce , r ela tiv e t o th e su rr ou nd in g pl ai n. It is fa irl y d en se ly ti m be re d ar ea w ith p at ch es o f o pe n, fl at g ro un d w ith p at ch y g ra ss . 64 angledool 1:100 000 geological sheet si te ea st in g M G A e n or th in g M G A n Lo ca lit y Li th ol og y si te fe at ur es 22 7 57 41 10 67 31 66 6 so il G ro un d is hu m m oc ky . C ol la ps ed ar ea s a re ir re gu la r i n sh ap e a nd a lte rn at e w ith sl ig ht ly ele va te d fla t a re as , e ac h se ve ra l m et re s a cr os s. Su pp or ts de ns e t o op en ve ge ta tio n co ve r w ith b ar e p at ch es an d sp or ad ic of lo w g re en co ve r. 22 8 57 21 75 67 37 68 5 Fl at ar ea a lo ng tr ac k so il G en tly u nd ul at in g pl ai n w ith co m m on co lla ps e h ol es an d sp ar se tu ss oc ky g ra ss . 22 9 58 35 33 67 38 43 5 O n tr ac k; fl at o pe n ar ea D 22 6 so il Ev en su rf ac e w ith u nd ul at io ns ca us ed b y c ol la ps e; lo w g ra ss co ve r w ith sp ar se sa lt bu sh . 23 0 58 56 39 67 38 60 9 Fl at ro ad sid e a re a so il Fl at p la in w ith h ar d so il, th in lo w g re en g ra ss an d ab un da nt tr ee s. 23 1 58 86 12 67 40 42 2 Ro ad sid e a re a so il Fl at to u nd ul at in g ar ea w ith lo w tu ss oc ky g ra ss an d so il co lla ps e f ea tu re s. 23 2 59 21 76 67 46 83 4 Fl at ro ad sid e a re a so il H um m oc ky so il w ith ab un da nt co lla ps e f ea tu re s a nd co m m on lo w w ee dy p la nt s. 23 3 59 19 25 67 43 67 5 Tr ac k on fl at p lat ea u sil cr et e 23 4 59 33 90 67 34 18 0 Ro ad sid e fl at p la in so il Fa irl y e ve n pl ai n w ith so m e v er y s ha llo w d ep re ss io ns ; p at ch y g ra ss an d lo w sh ru bs to re lat iv ely d en se tr ee co ve r. 23 5 58 34 77 67 22 30 3 Ro ad sid e so il Pl ai n is fla t a nd sm oo th w ith sp ar se g ra ss , s hr ub s a nd tr ee s. 23 6 58 03 26 67 19 63 1 Ro ad sid e fl at p la in so il Fl at , e ve n, sm oo th te rr ai n w ith ab un da nt sa ltb us h. 23 7 57 47 41 67 08 82 7 La rg e, sh al lo w g ra ve l q ua rr y n ea r g at e o n ro ad sid e co ng lo m er at e 23 8 57 48 19 67 06 44 5 Ro ad sid e so il Th e B ug w ah sy ste m is a pa le ye llo w g re y, hu m m oc ky , c ol la ps ed te rr ai n w ith sp ar se g ra ss , sa ltb us h an d ol d gu m tr ee s ( m an y d ea d) . Th e M ar ra C re ek sy ste m is a lso p al e y el lo w g re y bu t i s a pp ar en tly li gh te r t ha n th e B ug w ah . 23 9 55 65 74 67 05 33 6 Ed ge o f fl oo d ba sin , a lo ng tr ac k so il Fl at , e ve n pl ai n w ith p at ch y v eg et at io n; a lte rn at es fr om o pe n to d en se ly ti m be re d ar ea s. 24 0 55 29 72 67 08 13 9 Tr ac k so il Th ick ve ge ta tio n; m os tly p in e t re es , s om e b ox tr ee s e tc . 24 1 55 37 40 66 94 91 4 Fl at ca ne g ra ss te rr ai n so il Fl at , e ve n te rr ai n w ith ca ne g ra ss an d we ed s. 24 2 57 74 64 67 06 21 2 Ro ad sid e fl at p la in so il Co m m on co lla ps e f ea tu re s u p to ap pr ox . 1  m ac ro ss an d at le as t 0 .5  m d ee p, b ut th e te rr ai n is no t h um m oc ky ; a bu nd an t g ra ss , s al t b us h, sm al l t re es . 24 3 57 77 49 67 05 90 2 Ro ad sid e fl at p la in so il Fl at p la in ; v ar ia bl e g ra ss co ve r w ith sa lt bu sh , a bu nd an t d ea d tre es an d va rio us ty pe s an d de ns iti es o f l iv in g tre es . S im ila r t o sit e 2 42 . C ol la ps e f ea tu re s c om m on , b ei ng te ns o f ce nt im et re s a cr os s a nd te ns o f c en tim et re s d ee p. 24 4 57 83 87 67 05 01 1 M od er n ch an ne l w ith b rid ge so il Th e c ha nn el is a d ep re ss io n w ith an u nd ul at in g flo or w hi ch is n ot w el l d efi ne d. Th e ov er ba nk ar ea su pp or ts de ns e t re e c ov er an d is sli gh tly el ev at ed re lat iv e t o flo or o f t he ch an ne l, bu t a pp ar en tly n ot ra ise d ab ov e t he su rr ou nd in g pl ai n. 24 5 57 92 38 67 04 39 8 Ro ad sid e z on e o f r ela tiv ely d en se ti m be r so il Th e t re e- lin ed B ug w ah ch an ne l, fo llo w s a cu rv ili ne ar p at h. Th e c ha nn el m at er ia l i s hu m m oc ky / l um py . Th e s ur ro un di ng p la in is m ai nl y fl at w ith sp ar se g ra ss an d lo w sh ru b co ve r. 24 6 58 11 29 67 02 76 9 Ro ad sid e fl at p la in so il Pa le gr ey h um m oc ky /lu m py te rr ai n w ith ab un da nt co lla ps e s tr uc tu re s; tu ss oc ky g ra ss , sa lt bu sh an d a f ew tr ee s ( al l a liv e) ; c on tr as ts w ith th e s ur ro un di ng p la in o f b ro w ne r s oi l. 24 7 58 27 63 67 01 51 1 Ro ad sid e fl at p la in so il Pl ai n ha s d ep re ss io ns an d co lla ps e s tr uc tu re s; co nt ra sts w ith fl at b ro w ne r p la in o bs er ve d at la st fe w si te s; su pp or ts gr as s, tu ss oc ky g ra ss , s al t b us h an d a f ew tr ee s ( al l a liv e) . 65 appendixes 24 8 56 14 90 66 95 25 9 Ru bb ly p lat ea u at to p of h ill sil cr et e, gr av el 24 9 55 67 91 66 93 73 3 Fl at p la in so il Fl at , e ve n, p la in w ith sp or ad ic gr as s a nd tr ee co ve r. 25 0 58 66 27 67 64 97 9 Fl at p la in so il Si lcr et e b ou ld er sc re e f ro m n ea rb y r id ge ; a bu nd an t t re es b ut li ttl e g ra ss o r l ow sh ru b co ve r. 25 1 58 71 02 67 69 08 7 La ke A ng led oo l so il Cr op pe d ar ea w ith su bt le co lla ps e s tr uc tu re s b ut n o hu m m oc ks . 25 2 58 86 20 67 77 06 6 Fl at ar ea w ith ab un da nt tr ee s sa nd A bu nd an t t re es an d te rm ite m ou nd s; nu m er ou s a ug er h ol es in ge ne ra l a re a; sil cr et e ru bb le in p la ce s; pr ob ab ly o n a s ilc re te p lat ea u. 25 3 58 49 68 67 80 95 8 A lo ng tr ac k; fl at p la in so il Ev en , fl at g ro un d, w el l v eg et at ed w ith d iv er sit y o f t re es . 25 4 58 30 52 67 81 51 4 Ro ad sid e, ex te ns iv e s ha llo w sc ra pe s i n gr av el ex te nd n or th fo r a t l ea st 15 0 m sil cr et e W or ki ng s e xt en d to to p of h ill an d fu rt he r w es t o f h er e. 25 5 57 96 47 67 84 32 6 D ep re ss io n al on g ro ad so il Ch an ne l o n no rt h sid e o f r oa d ha s w at er w hi le it is dr y t o th e s ou th (d am m ed b y r oa d) ; ab un da nt tr ee s, gr as s, tu ss oc ky g ra ss ; r ela tiv ely fl at ; s om e u nd ul at io n bu t n ot h um m oc ky . 25 6 57 89 37 67 84 76 5 Fl at ro ad sid e a re a so il Fl at , e ve n te rr ai n, o pe n he re b ut h ea vi ly ti m be re d aw ay fr om ro ad . 25 7 57 82 09 67 85 24 0 Ro ad sid e, br oa d, lo w (d ee p? ) d ep re ss io n so il Ch an ne l i s u p to 3 00  m w id e; re lat iv ely fl at ; h ea vy ti m be r ( va rio us ty pe s o f t re e) ; n o gr as s or sh ru bs . 25 8 57 75 80 67 85 77 2 so il D ist in ct g re y c lay ey zo ne w ith in fl at te r, re dd ish b ro w n gr ey p la in . F ai rly fl at b ut un du lat es , w ith in cip ien t c ol la ps e- ty pe d ep re ss io ns . N o tre es , p at ch y l ow g ra ss an d ra re gr as s t us so ck s. 25 9 57 47 25 67 86 84 9 Fl at ar ea o f g re y s oi l so il Co lla ps e f ea tu re s c om m on an d gr ou nd u ne ve n; sp ar se tr ee s ( a f ew d ea d) ; a bu nd an t l ow ve ge ta tio n, so m e s al t b us h an d ot he r s hr ub s. 26 0 57 34 98 67 87 42 3 Ch an ne l t o lo w d ep re ss io n. so il D ep re ss io n ap pr ox . 5 0  m w id e; co lla ps e s tr uc tu re s a nd g ro un d is un ev en ; a bu nd an t t re es of v ar io us ty pe s; so m e g ra ss co ve r a nd tu ss oc ky g ra ss . 26 1 57 33 57 67 87 49 1 Ro ad sid e so il Lo w p at ch y g ra ss co ve r a nd sp or ad ic tre e c ov er . 26 2 56 70 82 67 89 80 5 Pl ai n w ith ab un da nt tr ee s so il H um m oc ky p la in w ith ab un da nt co lla ps e s tr uc tu re s, tu ss oc ky g ra ss an d ab un da nt an d ev en ly d ist rib ut ed tr ee s. O n th e s ou th si de o f t he ro ad , s oi l i s s lig ht ly g re ye r a nd is n ot hu m m oc ky o r c ol la ps ed . V eg et at io n is sim ila r b ut w ith m or e l ow le ve l s hr ub s a nd g ra ss . 26 3 54 95 53 67 75 06 2 Ro ad sid e so il Ve ry si m ila r t o sit e 2 62 . C ol la ps e s tr uc tu re s, hu m m oc ky g ro un d, tu ss oc ky g ra ss , s pa rs e (u nl ik e s ite 2 62 ) t o de ns e t re es , s om e s al t b us h. 26 4 55 25 83 67 74 25 8 Ro ad sid e so il H um m oc ky so il w ith co lla ps e s tr uc tu re s, sp or ad ic gr as s c ov er , s al tb us h an d m od er at e tre e c ov er ; c ar bo na te n od ul es to 3  m m d ia m et er . 26 5 55 44 37 67 74 09 4 Fl at p la in so il Fl at , e ve n pl ai n; lo w, sp ar se g ra ss co ve r; so m e d en se tr ee co ve r b ut ge ne ra lly o pe n co un tr y (a pp ar en tly ty pi ca l o f t hi s u ni t). 26 6 55 94 49 67 72 94 6 Fl at , o pe n pl ai n so il H um m oc ky w ith co lla ps e f ea tu re s, tu ss oc ky g ra ss co ve r, sp ar se tr ee s; te rr ai n is th e s am e as at si te 2 64 . 26 7 56 52 79 67 69 51 7 D ep re ss io n al on g ro ad so il Ch an ne l i s s ev er al h un dr ed m et re s w id e; hu m m oc ky so il w ith co m m on co lla ps e f ea tu re s; tu ss oc ky g ra ss , m od er at e t re e c ov er (d ea d an d al iv e) . 26 8 57 73 02 67 64 94 4 O pe n pl ai n; cr op pe d so ut h of ro ad , ve ge ta te d to n or th o f r oa d so il U nd ul at in g, h um m oc ky p la in ; c ol la ps e f ea tu re s c om m on ; c om m on tu ss oc ky g ra ss co ve r, ab un da nt w ee dy sh ru bs an d sp ar se tr ee s. 26 9 57 92 37 67 64 69 2 N ar ra n Ri ve r b ed so il Ch an ne l i s a bo ut 10 0  m w id e, w ith fl oo r c ov er ed in g ra ve l o f C re ta ce ou s m at er ia l a nd sil cr et e. 66 angledool 1:100 000 geological sheet si te ea st in g M G A e n or th in g M G A n Lo ca lit y Li th ol og y si te fe at ur es 27 0 57 91 11 67 64 76 0 W es t o f N ar ra n Ri ve r c ha nn el. so il M ea nd er p la in ; s om e c ol la ps e f ea tu re s a nd h um m oc ky (u ne ve n) in p la ce s; th ick co ve r o f we ed y b us he s ( ve ry si m ila r t o sit e 2 68 b ut m or e t re es h er e) . 27 1 63 10 71 67 12 69 9 Ro ad sid e fl at p la in so il Va ria bl e t re e c ov er ; s om e c ol la ps e s tr uc tu re s. 27 2 63 19 86 67 15 13 1 So ut he as te rn en d of g ra ve l p it; sh al lo w b ut ex te nd s o ve r s ev er al h un dr ed m et re s sa nd sto ne , s oi l 27 3 63 53 74 67 19 19 5 D am ex ca va tio n on w es t s id e o f h ig hw ay sa nd sto ne , s oi l 27 4 63 73 27 67 20 53 2 G ra ve l s cr ap e; ex te nd s f or h un dr ed s o f m et re s t o we st pe bb le, si lcr et e 27 5 63 94 12 67 21 75 6 Ro ad sid e pe bb les Sh al lo w sc ra pe s a bo ut 2 00  m ea st of h ig hw ay ; p eb bl es ar e p re se nt o n bo th si de s o f t he ro ad . 27 6 64 43 12 67 25 75 5 Ex te ns iv e q ua rr y o pe ra tio n sa nd sto ne , co ng lo m er at e Q ua rr y i s u p to 5  m d ee p an d se ve ra l h un dr ed m et re s i n di am et er . 27 7 63 72 80 67 31 35 3 Tr ac k so il H um m oc ky , lu m py p la in w ith co m m on co lla ps e f ea tu re s; sa ltb us h an d m od er at e t re e co ve r. 27 8 63 84 74 67 30 68 2 Fl at p la in so il Fl at , e ve n te rr ai n w ith sh ru bb y v eg et at io n an d va ria bl e d en sit y o f t re e c ov er ; s om e sa ltb us h. 27 9 64 02 57 67 27 26 3 Fl at ar ea w ith ab un da nt fe rr ug in ou s pe bb les pe bb les M od er at e d en sit y o f t re e c ov er ; p ro ba bl y e ro de d sil cr et e. 28 0 62 69 74 67 26 92 8 Co ns pi cu ou s c ha nn el, d ep re ss io n at le as t 10 0 m w id e so il Co lla ps e f ea tu re s c om m on ; i rr eg ul ar su rf ac e b ut n ot h um m oc ky ; a bu nd an t g ra ss co ve r, sp ar se tr ee s; so m e t us so ck y g ra ss an d pr ick ly p ea r. 28 1 62 71 33 67 26 75 1 Co ns pi cu ou s r ai se d ar ea th at ta pe rs d ow n to so ut he as t so il Ve ry w el l v eg et at ed w ith co m m on g ra ss co m m on an d m od er at e d en sit y o f t re es . 28 2 62 78 00 67 26 49 7 Fl at p la in so il Fl at , e ve n pl ai n; m in or co lla ps e f ea tu re s; w id es pr ea d gr as s a nd sp ar se tr ee co ve r. 28 3 62 98 89 67 23 30 4 W el l v eg et at ed , s lig ht ly su nk en zo ne so il G ro un d is fla t a nd ev en ; w el l v eg et at ed w ith d en se tr ee co ve r, sa ltb us h an d m in or g ra ss . 28 4 63 18 78 67 18 35 7 Fl at ar ea so il D en se ti m be r c ov er ; n o ev id en ce o f g ra ve l o r s ilc re te . 28 5 58 43 01 67 51 33 7 Sh al lo w sc ra pe s sil cr et e 28 6 58 04 98 67 49 83 5 Co oc or an L ak e; fla t, cu lti va te d so il 28 7 57 13 01 67 53 09 6 Fl at ar ea so il Fl at su rf ac e w ith cr ac ks ; s up po rt s t us so ck y g ra ss , s om e l ow , g re en g ra ss b ut n o tre es . 28 8 56 91 30 67 55 91 0 Fl at ar ea w ith n o ou tc ro p so il D en se p in e c ov er ; s ilc re te g ra ve l o n a s lo pe to th e s ou th ea st su gg es ts th at it u nd er lie s t he pl at ea u. 28 9 56 79 94 67 57 67 4 N ar ra n Ri ve r c ha nn el so il Ch an ne l i s a pp ro xi m at ely 5 0  m w id e. 29 0 56 80 06 67 57 71 8 N or th er n ba nk o f N ar ra n Ri ve r so il Fl at ar ea ; s m oo th an d ev en . 29 1 56 86 95 67 62 01 7 G ra ve l s tre w n ar ea a lo ng tr ac k sil cr et e 29 2 56 81 61 67 61 51 4 Fl at ve ge ta te d ar ea so il Co lla ps e f ea tu re s v er y c om m on ; s pa rs e t re e c ov er ; t us so ck y g ra ss . 67 appendixes 29 3 55 56 02 67 56 16 2 Fl at o pe n pl ai n so il Fl at te rr ai n w ith co lla ps e f ea tu re s; tu ss oc ky g ra ss , r ar e s al t b us h. 29 4 55 22 64 67 45 71 2 Fl at p la in n ea r c ro ss ro ad s so il Sm oo th , fl at ar ea ; c om m on g ra ss . 29 5 55 28 15 67 45 49 0 O pe n, fl at p la in so il Fl at , o pe n, b ut ex te ns iv ely co lla ps ed te rr ai n; ve ry sp ar se tr ee s a nd tu ss oc ky g ra ss . 29 6 55 38 65 67 45 07 3 W es t b an k of N ar ra n Ri ve r so il Ev en te rr ai n w ith la rg e t re es , s al tb us h et c.; n ea rb y c ha nn el is ab ou t 5 0  m w id e. 29 7 55 67 45 67 38 62 5 Sh al lo w sc ra pe o n ea st sid e o f r oa d sil tst on e, sil cr et e Sc ra pe (a bo ut 1 m d ee p) o n Te rt ia ry si lcr et e h as ex po se d Cr et ac eo us ro ck s; sil cr et e po ss ib ly ca m e f ro m fu rt he r u p slo pe . 29 8 55 77 01 67 37 56 0 Fl at p la in so il Fl at , s m oo th te rr ai n w ith ab un da nt g ra ss an d va ria bl e t re e c ov er ; c on tr as ts w ith th e gr ou nd to so ut h w hi ch is p al e g re y a nd h as co lla ps e s tr uc tu re s. 29 9 56 23 62 67 33 67 6 Fl at ar ea so il Fl at , e ve n bu t s lo pe ri se s g en tly to so ut h; v ar ie s f ro m o pe n to re lat iv ely d en se tr ee co ve r. 30 0 55 70 99 67 33 14 6 Lo w, h ill y a re a so il A pp ar en tly p ar t o f a d un e s ys te m ; g ro un d su rf ac e g en tly u nd ul at es o ve r a bo ut 5 00  m in w av ele ng th ; a bu nd an t t re es , m os tly p in e; pa tc hy g ra ss 30 1 56 40 65 67 31 09 2 Fl at ar ea a lo ng ro ad so il Ve ry ir re gu la r, hu m m oc ky su rf ac e w ith ex te ns iv e c ol la ps e s tr uc tu re s; tu ss oc ky g ra ss (e xc ep t i n pl ou gh ed p ad do ck ). 30 2 57 02 51 67 20 26 1 Fl at ar ea so il O ve r t he fe nc e t o th e n or th ea st th e g ro un d is cu lti va te d. B et we en th e r oa d an d th e f en ce th e g ro un d is co ve re d in g ra ss . Th e g ro un d ha s c ol la ps e s tr uc tu re s i n pl ac es b ut o ve ra ll lo ok s fl at . 30 3 54 22 30 67 80 39 1 Fl at , w el l v eg et at ed p la in so il Fl at w ith co m m on co lla ps e f ea tu re s; ab un da nt g ra ss , a fe w sm al l b us he s a nd sc at te re d tre es . 30 4 54 15 75 67 80 64 2 Bi rr ie Ri ve r; dr y r iv er b ed so il Ch an ne l i s a bo ut 3 0  m w id e w hi le ov er ba nk ar ea is ab ou t 4 0  m w id e. Th e o ve rb an k ar ea ha s c om m on co lla ps e s tr uc tu re s b ut th e g ro un d is no t h um m oc ky an d is we ll ve ge ta te d w ith b us he s a nd g um tr ee s. Th e c ha nn el ha s m in or g ra ss o n it. 30 5 52 94 40 67 89 19 9 Cu lg oa R iv er ch an ne l so il Th e c ha nn el su pp or ts va rio us ty pe s o f l ow sh ru b. Th e g ro un d is fla t a nd sm oo th . Th e ov er ba nk ar ea h os ts ab un da nt tr ee s a nd sh ru bs an d gr as sy p la nt s. It is a fl at , e ve n ar ea b ut is cr ac ke d w ith in cip ien t c ol la ps e f ea tu re s. 30 6 52 81 42 67 91 28 1 Fl at p la in so il U nd ul at in g te rr ai n w ith sh al lo w co lla ps e f ea tu re s; we ll ve ge ta te d w ith tr ee s a nd lo w bu sh es . 30 7 51 04 84 67 91 80 2 Fl at , v er y w el l t im be re d te rr ai n so il Fl at , fi rm , e ve n gr ou nd ; a bu nd an t t re e c ov er w ith m in or sa ltb us h. 30 8 50 86 49 67 88 47 3 Fl at p la in , w el l v eg et at ed so il Ve ry u ne ve n gr ou nd ; h um m oc ky b ut n o co lla ps e f ea tu re s; ab un da nt tr ee co ve r w ith m in or tu ss oc ky g ra ss . 30 9 50 45 89 67 84 13 0 Fl at ar ea w ith d en se to o pe n tre e c ov er so il Th e t er ra in ap pe ar s t o be ab lat ed , d isp lay in g ro un de d rid ge s w ith st ee p er os io na l e dg es ap pr ox . 0 .3  m h ig h an d up to te ns o f m et re s a cr os s, an d lo w fl at ar ea s. Th e r id ge s a re sta bi lis ed b y g ra ss an d tre es . Th e fl at ar ea s a re h ar d an d ev en . 31 0 50 21 89 67 80 74 7 Fl at p la in w ith d en se ti m be r so il U ne ve n, h um m oc ky so il w ith so m e s ub du ed co lla ps e f ea tu re s; ab un da nt tr ee s, lo w tu ss oc ky g ra ss an d so m e b us he s. 31 1 49 28 19 67 64 38 3 A pp ro x. 10 0  m ea st of C ul go a R iv er ch an ne l so il, ca lcr et e A bu nd an t t re es an d bu sh y w ee ds (e sp ec ia lly o n ba nk ); gr ou nd is u ne ve n bu t n ot ob vi ou sly co lla ps ed ; t he ch an ne l i s e ph em er al . 31 2 50 02 57 67 56 66 0 Fl at p la in so il Fl at , e ve n pl ai n; m od er at ely d en se , c on tin uo us tr ee co ve r a nd lo w b us he s. 31 3 50 50 99 67 54 98 6 Fl at p la in so il Ir re gu la r, lu m py o pe n pl ai n w ith tu ss oc ky g ra ss an d sp ar se tr ee co ve r. 68 angledool 1:100 000 geological sheet 31 4 51 38 74 67 54 12 5 Fl at p la in so il G en tly u nd ul at in g pl ai n w ith ve ry sh al lo w (0 .1  m ) c ol la ps e s tr uc tu re s a nd ab un da nt tu ss oc ky g ra ss b ut n o tre es . 31 5 52 20 33 67 58 78 7 Fl at ar ea so il Fl at , e ve n, o pe n pl ai n w ith p at ch y g ra ss co ve r a nd n o tre es . 31 6 52 67 25 67 64 07 8 Fl at p la in so il Fl at , s m oo th , e ve n pl ai n; b ar e w ith sp or ad ic gr as s c ov er an d no tr ee s; th e g ro un d su rf ac e slo pe s d ow n to th e s ou th . 31 7 52 65 30 67 64 74 7 Fl at p la in so il D ist in ct iv ely cr ac ke d in a po ly go na l p at te rn w ith ‘i sla nd s’ of so il (1  m o r m or e a cr os s), se pa ra te d by la rg e c ra ck s ( te ns o f c en tim et re s d ee p) ; r ar e t re es b ut ab un da nt tu ss oc ky gr as s. 31 8 59 98 45 67 46 14 5 Fl at p la in so il Ve ry u ne ve n, u nd ul at in g an d hu m m oc ky te rr ai n; sp ar se co lla ps e f ea tu re s; ab un da nt tr ee s an d so m e s al tb us h. 31 9 60 53 98 67 45 65 6 Fl at p la in so il Fl at , e ve n pl ai n; ve ry w el l v eg et at ed w ith n um er ou s t yp es o f t re e. 32 0 60 56 58 67 55 25 7 Fl at p la in so il Fl at p la in ; s om e c ol la ps e s tr uc tu re s; co m m on g ra ss an d m od er at ely d en se sa lt bu sh ; sp ar se tr ee co ve r. 32 1 61 05 23 67 60 54 0 Fl at p la in w ith sa nd d un es ap pr ox . 1 50  m to ea st an d so ut he as t so il Th e s an dy ri dg e i s a bo ut 1  m ab ov e t he p la in an d is we ll ve ge ta te d w ith tr ee s a nd g ra ss . Th e p la in is fl at an d sp ar se ly ve ge ta te d. 32 2 61 84 43 67 57 49 0 Fl at p la in so il Re as on ab ly fl at p la in , g en tly u nd ul at in g; n um er ou s c ol la ps e f ea tu re s; sp or ad ic , lo w g ra ss y co ve r; ab un da nt tu ss oc ky g ra ss ; t re e c ov er v ar ie s f ro m sp ar se to m od er at e. 32 3 62 08 55 67 55 38 6 Fl at p la in ap pr ox . 1 50  m w es t o f c ha nn el so il Fl at , e ve n, fi rm su rf ac e; ba re w ith p at ch y g ra ss co ve r. 32 4 62 09 65 67 55 33 3 D ep re ss io n on ro ad sid e so il Sm oo th , e ve n, fi rm su rf ac e; ab un da nt tr ee s e xt en d be yo nd th e c ha nn el; tu ss oc ky g ra ss , ra re sh ru bs . Th e c ha nn el is ab ou t 1 00  m w id e a nd , a w ay fr om it , t he g ro un d slo pe s s lig ht ly do w n to th e p la in . 32 5 62 22 15 67 53 63 3 Fl at p la in so il G en tly u nd ul at in g, a lm os t h um m oc ky , t er ra in w ith su bd ue d co lla ps e f ea tu re s c om m on . Th e s un ke n ar ea s c on ta in g ra ss w hi le th e r ai se d ar ea s h os t l ow , g re y g ra ss (d ea d? ). A bu nd an t r oo ts m ak e t he su rf ac e h ar d. 32 6 62 57 82 67 49 53 9 Fl at p la in so il Fl at , e ve n, fi rm te rr ai n; ve ry w el l v eg et at ed w ith a di ve rs ity o f t re es ; n o gr as s o r l ow sh ru bs ; v er y s im ila r t o sit e 3 23 . 32 7 62 63 66 67 48 90 9 Sl ig ht ly d ep re ss ed ar ea so il G en tly u nd ul at in g te rr ai n; sp or ad ic co lla ps e f ea tu re s; sp or ad ic tu ss oc ky g ra ss an d va ria bl e t re e c ov er (o pe n to d en se ); ch an ne l i s a bo ut 15 0  m w id e. 32 8 62 89 79 67 46 05 6 Fl at p la in so il Ty pi ca l o f t he p la in in th is ar ea ; g en tly u nd ul at in g, ir re gu la r s ur fa ce w ith ab un da nt sh ru bs an d tre es . 32 9 63 15 78 67 44 08 7 Ve ry sl ig ht d ep re ss io n so il G en tly u nd ul at in g; ab un da nt tr ee co ve r a nd sa lt bu sh (a nd o th er sh ru bs ?). Th e c ha nn el de pr es sio n is ba re ly n ot ice ab le on th e g ro un d. 33 0 63 33 78 67 43 73 4 Fl at p la in so il Fl at p la in w ith sp ar se to m od er at e t re e c ov er , g oo d gr as s c ov er , v er y m in or sa ltb us h an d ot he r s hr ub s. 33 1 63 52 04 67 43 49 3 Fl at p la in so il Fl at , s m oo th , e ve n, p la in w ith p at ch y g ra ss co ve r; de ns e t re e c ov er an d so m e s hr ub s o n th e u ne ve n, sl ig ht ly u nd ul at in g ele va te d ar ea s. 33 2 63 58 75 67 43 47 2 Sh al lo w d ep re ss io n so il H um m oc ky , u nd ul at in g, u ne ve n gr ou nd ; h um m oc ky su rf ac e c au se d by cr ac ki ng ; lo w tu ss oc ky g ra ss co ve r; pa tc hy tr ee co ve r; m in or sm al l t re es /sh ru bs . si te ea st in g M G A e n or th in g M G A n Lo ca lit y Li th ol og y si te fe at ur es 69 appendixes 33 3 63 83 16 67 42 51 5 Fl at p la in so il Fl at , e ve n, b ut lo os e s ur fa ce w ith sp or ad ic su bd ue d co lla ps e f ea tu re s; ab un da nt tu ss oc ky gr as s, so m e d en se tr ee co ve r a nd so m e o pe n ar ea s; m in or sh ru bs . 33 4 64 36 09 67 37 71 4 G en tle sl op e u p to th e e as t so il, p eb bl es Re d sa nd co nt ai ni ng w hi te q ua rt z p eb bl es . 33 5 64 51 92 67 37 45 1 Lo w ex po su re o n ro ad sa nd sto ne O ve rla in b y a pp ro x. 0 .5  m o f r ed sa nd w ith b la ck ir on o xi de p iso lit hs . 33 6 64 46 57 67 38 36 3 Ex te ns iv e s ha llo w sc ra pe s/s ha llo w q ua rr y co ng lo m er at e M at er ia l r ep re se nt s n on -s ili ci fie d Te rt ia ry g ra ve ls. 33 7 62 75 13 67 58 87 9 Fl at p la in so il Er os io na l l an ds ca pe o f p lat ea us su pp or tin g tre es an d sh ru bs o r l ow tu ss oc ky g ra ss , su rr ou nd ed b y l ow er b ar e, m or e c lay ey , p la in ar ea s. 33 8 62 62 93 67 83 92 4 Fl at , m od er at e t o he av ily ti m be re d ar ea so il Re d sa nd w ith ou t r oc k fr ag m en ts . 33 9 62 12 54 67 85 09 4 Sm al l h ill , c lea rly el ev at ed ab ov e p la in so il W el l-t im be re d hi ll ris es se ve ra l m et re s a bo ve p la in . 34 0 61 04 96 67 76 29 5 Th ick ly ti m be re d sa nd p la in so il Ex te ns iv e s an d sh ee t w ith ab un da nt tr ee s. 34 1 54 07 72 67 24 13 9 Fl at b ut h ea vi ly ti m be re d te rr ai n so il G en tly u nd ul at in g; co m m on co lla ps e f ea tu re s; ab un da nt ve ge ta tio n co ns ist in g of tr ee s, tu ss oc ky g ra ss an d sh ru bs . 34 2 54 27 66 67 24 01 3 W el l v eg et at ed , fl at ar ea so il Fl at , e ve n te rr ai n; n ot d un es ; a bu nd an t g ra ss ; t re es (i nc lu di ng p in e) . 34 3 54 36 20 67 23 87 3 Tr ac k sil cr et e Lo w su bc ro p on tr ac k. 34 4 54 42 18 67 22 87 0 Fl at p la in pe bb le Si lcr et e c la sts sc at te re d ov er h un dr ed s o f m et re s b ut n o ou tc ro p. 34 5 54 41 94 66 82 21 6 Sm al l b or ro w p it on n or th si de o f r oa d sil tst on e, br ec ci a Pi t a pp ro x. 10  m w id e a nd 1. 5  m d ee p; g ro un d slo pe s u p to n or th an d is re d, su gg es tin g a pr ob ab le sil cr et e c ap ex ist s t he re . 34 6 54 18 24 66 95 61 1 N ar ra n La ke so il Fl at te rr ai n w ith lo w g ra ss co ve r. 34 7 54 20 95 66 95 69 9 U nd ul at in g pl ai n so il Te rr ai n is irr eg ul ar ; lo w ar ea s a lte rn at e w ith ra ise d ar ea s s up po rt in g sm al l a m ou nt o f l ow gr as s + /− sa ltb us h or tu ss oc ky g ra ss ; a pp ar en tly an er os io na l l an ds ca pe . 34 8 53 50 94 66 91 38 9 Bo ul de r- st re w n pl ai n so il, si lcr et e Fl at , e ve n, fi rm su rf ac e; ab un da nt sm al l t re es , s al tb us h an d gr as s. 34 9 53 58 52 67 16 22 4 Fl at , d en se ly ve ge ta te d pl ai n so il A bu nd an t t re e c ov er . 35 0 53 24 09 67 12 43 4 Br oa dl y u nd ul at in g pl ai n so il U nd ul at in g te rr ai n w ith ab un da nt tr ee s a nd g ra ss ; p ro ba bl e d un e s ys te m . 35 1 53 34 67 67 12 37 7 Fl at p la in so il Fl at p la in ; c ra ck ed w ith sh al lo w co lla ps e f ea tu re s; m od er at e t o de ns e t re e c ov er , lo w g ra ss an d sh ru bs . 35 2 59 58 68 67 35 28 1 Fl at p la in so il Fl at , e ve n, p la in w ith ab un da nt tr ee s a nd lo w sh ru bs . 35 3 60 22 11 67 28 06 0 Fl at p la in so il Fl at , fi rm , e ve n pl ai n; ab un da nt tr ee co ve r a nd lo w tu ss oc ky g ra ss ; p os sib ly in flu en ce d by th e B ug w ah sy ste m m ea nd er p la in fa ci es . 35 4 60 41 27 67 26 19 1 W ea k de pr es sio n on p la in w ith d en se tr ee co ve r so il G ro un d is fir m an d ev en , w ith ab un da nt tr ee s a nd lo w sh ru bs . 35 5 60 40 75 67 24 02 2 Fl at p la in so il Ir re gu la r, un du lat in g, h um m oc ky su rf ac e; ab un da nt co lla ps e f ea tu re s; sp ar se ve ge ta tio n of lo w tu ss oc ky g ra ss an d ve ry m in or lo w sh ru bs . 35 6 61 01 22 67 31 13 8 Fl at p la in so il G en tly u nd ul at in g w ith si gn ifi ca nt co lla ps e f ea tu re s; co ve r o f l ow g ra ss an d sp ar se , lo w sh ru bs ; v ar ia bl e t re e c ov er an d ab un da nt d ea d tre es . 70 angledool 1:100 000 geological sheet si te ea st in g M G A e n or th in g M G A n Lo ca lit y Li th ol og y si te fe at ur es 35 7 60 70 96 67 27 30 1 Fl at p la in so il U nd ul at in g, ir re gu la r s ur fa ce (a lm os t h um m oc ky ); sig ni fic an t c ol la ps e f ea tu re s; va ria bl e tre e c ov er (s pa rs e t o de ns e) , m od er at ely d en se sa lt bu sh , s hr ub s a nd tu ss oc ky g ra ss ; sim ila r t o Si te 35 6. 35 8 60 52 81 67 20 31 9 Ve ry sl ig ht ly d ep re ss ed ar ea w ith tr ee s so il U nd ul at in g, h um m oc ky te rr ai n; m od er at e t o de ns e t re e c ov er an d sp or ad ic , t us so ck y gr as s. Th e b ro ad ch an ne l’s b an ks sl op e u p to so ut h to th e o ve rb an k fa ci es , w hi ch th en ge nt ly sl op es d ow n to w ar ds th e p la in o ve r h un dr ed s o f m et re s. 35 9 60 61 87 67 16 48 5 U nd ul at in g te rr ai n w ith ab un da nt tr ee s so il U nd ul at in g, h um m oc ky te rr ai n w ith si gn ifi ca nt co lla ps e f ea tu re s; de ns e t re e c ov er (v ar io us ty pe s); so m e t us so ck y g ra ss an d lo w sh ru bs . Th is br oa d ar ea is o nl y v er y s lig ht ly lo we r ( if at a ll) th an th e s ur ro un di ng p la in . 36 0 60 70 97 67 13 21 7 Fl at p la in so il U nd ul at in g te rr ai n, a lm os t h um m oc ky ; m in or in co ns pi cu ou s c ol la ps e f ea tu re s; sp ar se to de ns e t re e c ov er ; m od er at e g ra ss co ve r a nd co m m on sh ru bs 36 1 61 60 00 66 84 30 3 Fl at p la in so il Fl at , fi rm , e ve n gr ou nd ; s lig ht u nd ul at io n ov er h un dr ed s o f m et re s; ab un da nt , lo w g ra ss co ve r a nd sp ar se to d en se tr ee co ve r. 36 2 61 24 03 66 89 93 7 Fl at p la in so il Cr op pe d pa dd oc k on w es te rn si de o f r oa d an d sp ar se to m od er at e t re e c ov er w ith ab un da nt g ra ss o n ea ste rn si de o f r oa d. E ith er si de o f r oa d ar e fl at ar ea s w ith cr ac ke d su rf ac es d ue to sp or ad ic co lla ps e f ea tu re s. 36 3 60 96 93 66 98 61 0 Fl at p la in so il D en se tr ee co ve r, m od er at e s al t b us h co ve r; fla t, ev en su rf ac e. 36 4 60 63 97 67 15 05 6 Fl at p la in so il Fl at , e ve n pl ai n w ith p at ch y g ra ss co ve r a nd lo w sh ru bs ; t re e c ov er n il to d en se . 36 5 59 40 97 67 36 96 9 Lo w h ill (‘ Li gh tn in g Ri dg e’) ; r es t a re a a nd hi sto ric si te cla ys to ne , b re cc ia Sm al l h ill w ith ve ne er o f s ilc re te ru bb le, tr an se ct ed b y r oa d an d su rr ou nd ed b y p la in . 36 6 57 68 55 67 85 97 5 El ev at ed , s an dy ar ea so il Ir re gu la r t er ra in ; s an dy ri dg e s ur ro un ds h ar de r, fla tte r, cla ye y s an d pl ai n; ri dg e s up po rt s tu ss oc ky g ra ss an d pa tc hy tr ee co ve r ( de ns e t o op en ); TL d at in g sit e. 36 7 58 70 38 67 82 23 0 Lo w h ill o n ro ad sid e gr av el 36 8 58 43 95 67 86 42 7 Ro ad cu tti ng sil tst on e, br ec ci a Sh al lo w sh aft b y r oa ds id e w ith tr ee n ea rb y. Si lcr et e g ra ve l o ve rli es th e C re ta ce ou s r oc ks an d fo rm s t he g ro un d su rf ac e. Th e s ur fic ia l g ra ve l l ay er is ap pr ox 0 .5  m th ick , c om pr isi ng re d sa nd w ith p eb bl es an d sil cr et e b ou ld er s. 36 9 59 97 57 67 73 50 8 Fl at ar ea o n ro ad sa nd sto ne , cla ys to ne Su bc ro p on ro ad sid e. 37 0 59 92 04 67 73 82 3 Sh al lo w g ra ve l q ua rr y co ng lo m er at e 71 appendixes Appendix 2 Thin section descriptions Table B gives descriptions of thin sections of rock samples which were collected during the course of the geological mapping. The thin sections are held by the Division of Resources and Energy. ta bl e B: t hi n se ct io n de sc ri pt io ns th in se ct io n no . Fi el d no . M G A e (m ) M G A n (m ) Lo ca lit y Fo rm at io n /u ni t G eo co nt ex t th in se ct io n de sc ri pt io n se co nd ar y m in er al og y T7 32 28 SH AN 01 -1 56 39 35 67 19 83 1 op al m in e Gr im an Cr ee k F m sil ici fie d sa nd sto ne wi th n on - sil ici fie d cla ys to ne cla sts (‘ ste el ba nd ’) Sa nd sto ne w ith gr ai ns u p to 0. 2 m m ac ro ss , a ng ul ar an d of lo w sp he ric ity , po or ly so rte d; ab ou t 2 0% q ua rtz , 5 % rh yo lit e ( ?) cla sts , 6 0% al te re d fel ds pa r gr ai ns , 1 5% m at rix (i so tro pi c m at er ia l — si lic a ( ?) or im pr eg na tin g m ed iu m (?) ); tra ce am ou nt s o f c hl or ite an d op aq ue gr ai ns . C lay sto ne cl as ts co ns ist of an ex tre m ely fi ne -g ra in ed m at rix co nt ai ni ng q ua rtz gr ai ns u p 0.1  m m . Cl ay sto ne cl as ts ar e i rr eg ul ar an d re as on ab ly an gu lar . M in or op al in e s ili ca in vo id s i n cla ys to ne T7 32 29 SH AN 01 -2 56 39 35 67 19 83 1 op al m in e Gr im an Cr ee k F m sa nd sto ne wi th cla ys to ne cla sts ; n on - sil ici fie d ve rs io n of SH AN 01 -1 M os tly cl ay sto ne cl as ts (a s a bo ve ) w ith m in or sa nd sto ne (a s a bo ve ) a s m at rix . Cl as ts ar e i rr eg ul ar , a ng ul ar an d ra ng e i n siz e f ro m < 1 m m to ab ou t 8  m m lo ng . M in or q ty op al in e s ili ca in ve ry sm al l vo id s i n cla ys to ne T7 48 17 GB 36 7 58 70 38 67 82 23 0 ro ad cu tti ng ne ar An gl ed oo l Te rti ar y gr av els wh ite cl as ts fro m T er tia ry gr av els A ll cla sts co ns ist of ex tre m ely fi ne -g ra in ed q ua rtz -ri ch m at er ia l ( ch er t o r rh yo lit e? ) c ro ss -c ut by gr an ul ar q ua rtz ve in let s. T7 48 36 M U LG A 2 56 39 44 67 19 82 4 op al m in e Gr im an Cr ee k F m po tc h ve in s in cl ay sto ne be ne at h ‘st ee l b an d’ (si lic ifi ed sa nd sto ne ) Sa nd sto ne (‘ ste el ba nd ’) — q ua rtz is th e d om in an t m in er al an d is hi gh ly an gu lar w ith lo w to m od er at e s ph er ici ty . G ra in s a re ab ou t 0 .2  m m ac ro ss . Cl ay sto ne cl as ts ar e a bu nd an t i n sa nd sto ne , b ein g w ell ro un de d wi th h ig h to m od er at e s ph er ici ty , u p to 0. 75  m m bu t c an b e m uc h sm al ler . M in or al te re d pl ag io cla se gr ai ns u p to 0. 75  m m an d pr ob ab ly so m e m ica , a lso al te re d. M in or li th ic cla sts ar e g ra nu lar , p ro ba bl y r hy ol iti c. Th e s an ds to ne m at rix is re pl ac ed by o pa lin e s ili ca an d in p lac es th e g ra in s a re su pp or te d by it . N o fin e- gr ai ne d cla sti c m at rix is p re se nt . ‘C ol ou r’* is p re se nt in th e s ili ca in th e l ow er p ar t o f t he sa nd sto ne an d ne ar th e c on ta ct w ith cl ay sto ne th er e is a b ou nd ar y b et we en ‘c ol ou r’ an d bl ac k p ot ch . B lac k p ot ch fo rm s v ein let s wi th in cl ay sto ne an d th e c lay sto ne is br ok en u p in to an gu lar fr ag m en ts wi th in p ot ch . M in or ‘c ol ou r’ is ev id en t i n th e p ot ch in p lac es . T7 48 37 M U LG A 3 56 39 44 67 19 82 4 op al m in e Gr im an Cr ee k F m po tc h ve in s in cl ay sto ne be ne at h ‘st ee l b an d’ (si lic ifi ed sa nd sto ne ) Sa nd sto ne (‘ ste el ba nd ’) — q ua rtz gr ai ns to ab ou t 0 .2  m m , a ng ul ar to su b- an gu lar an d lo w to m od er at e s ph er ici ty ; c lay sto ne cl as ts up to 2  m m , a nd m an y m uc h sm al ler , w ell ro un de d wi th lo w to h ig h sp he ric ity ; m in or fe ld sp ar an d m ica (b ot h alt er ed ). Th e m at rix is o pa lin e s ili ca , w hi ch is p ale br ow n in pl an e p ol ar ise d lig ht an d do es n ot ex hi bi t a ny ‘c ol ou r’. In p lac es th e c las ts ar e m at rix -su pp or te d. Th er e i s n o cla sti c m at rix . S ili ca in va de s c lay sto ne at th e ba se , w he re th er e i s a p at ch of ‘c ol ou r’. * ‘ co lo ur ’ r efe rs to th e ‘ pl ay of co lo ur ’ c au se d by th e d iff ra ct io n of li gh t w ith in pr ec io us op al str uc tu re an d th e s ub se qu en t r ef ra ct io n at th e o pa l-a ir in ter fa ce (D ar ra gh & Sa nd er s 1 96 5) 72 angledool 1:100 000 geological sheet The other mineral identifications seem reasonable and are consistent with information gleaned from microscopic examination and the behaviour of the samples when immersed in water. It must be stressed that the only minerals identified are those which contribute to the spectrum. Minerals such as quartz (which is the most abundant component in most of the samples) and feldspar do not give a characteristic SWIR response and hence are not determinable by this method. The PIMA is particularly useful for the identification of clays as well as some other minerals. Appendix 3 Soil sample descriptions During the field investigations carried out as part of this study, soil samples from Quaternary alluvial units were collected. For each Quaternary facies, as described in previous chapters, representative samples were chosen for detailed examination. Each selected sample was examined under a binocular microscope and described in Table C. One weakness of this method is that it is difficult to estimate the amount of clay in the samples. To better establish the proportion of clay, portions of each sample were placed into plastic specimen bottles with water. The bottles were then shaken to disaggregate the sand and silt grains from the clay component and then left to settle for several days. By measuring the height of the sand and silt component within each bottle and comparing it to the initial height before shaking, the proportion of silt and sand was estimated and hence the proportion of clay could be inferred. However, this method is considered to be indicative only, as it is unlikely that the clay fraction was completely separated from the sand/silt fraction. Given that swelling clays are commonly present, there is much potential for the measured sand/silt proportion to be inaccurate. However, the method is considered useful as a semi-quantitative estimate of the proportion of clay. Noting the behaviour of the samples when immersed in water was also helpful in determining the type of clays present. The results of this analysis are given in Table D. Each selected sample was also analysed by a PIMA (Portable Infrared Mineral Analyser), which measures the short wavelength infrared reflectance (SWIR) spectra of materials. The PIMA device measures a circular area of the specimen with a diameter of about 10 mm. Portions of each sample were placed into petri dishes, which were then placed over the PIMA window for measurement. The measured SWIR spectrum for each sample is given in Figure A. The PIMA acquisition software attempts an identification of the minerals that contribute to each spectrum. The results of this are given in Table E along with ‘confidence’ — a qualitative estimate of the accuracy of the determination. Anhydrite (CaSO4) has been identified in most samples, however some of that is probably gypsum (CaSO4.2H2O). 2010_03_0039 1540 1780 2020 2260 Wavelength (nm) Qc 1 Qc 2 Qc 3 Qc 4 Qc 5 Qcd 1 Qd 1 Qd 2 Qd 3 Qmb 1 Qmb 2 Qmb 3 Qmb 4 Qmbc 1 Qmbf 1 Qmc 1 Qmf 1 Qmk 1 Qmm 1 Qmr 1 Qmr 2 Qmr 3 Qmr 4 Qmr 5 Qrnb 1 Qrnc 1 Qrnc 2 Qrnc 3 Qrnc 4 Qrnm 1 Qrb 1 Qrb 2 Qrc 1 Qrc 2 Qrc 3 Qrc 4 Qrm 1 Qrm 2 Qrm 3 Qrm 4 Qrm 5 Qrm 6 Qrm 7 Qrm 8 Qrm 9 S am ple Figure A. Stacked SWIR spectra of Quaternary samples; no vertical scale is implied. 73 appendixes ta bl e c: D es cr ip ti on s of a llu vi al m at er ia l b as ed o n bi no cu la r m ic ro sc op e ex am in at io n c o M P o n e n t s sa m pl e ID si te n o. U ni t sy m bo l co lo ur co he re nc e D es cr ip ti on sa nd si lt cl ay ca rb on at e no du le s or ga ni c m at te r ot he r Q c1 34 8 Q c gr ey ish br ow n clu m pe d to un co ns ol id at ed (c lay ey ) s ilt m in or co m po ne nt ; a ve ra ge gr ai n siz e a bo ut 0 .6 m m , ra re ly u p to 1m m ; c lea r, w hi te an d re d- sta in ed cl ea r qu ar tz do m in an t co m po ne nt ; cle ar , w hi te an d re d- sta in ed cle ar q ua rt z pr ob ab ly a m in or co m po ne nt no ne m in or ro ot let s tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q c2 24 0 Q c re d br ow n m ai nl y un co ns ol id at ed w ith m in or clu m pi ng po or ly so rt ed , sil ty m ed iu m - gr ai ne d sa nd m ajo r c om po ne nt ; a ve ra ge gr ai n siz e a bo ut 0 .3 m m , ra ng es fr om si lt up to 1. 5m m ; m ai nl y c lea r q ua rt z, re d- sta in ed cl ea r q ua rt z a nd so m e w hi te q ua rt z sig ni fic an t co m po ne nt , co m po se d of qu ar tz pr ob ab ly a m in or co m po ne nt no ne no ne tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q c3 34 0 Q c re d br ow n un co ns ol id at ed we ll so rt ed m ed iu m - gr ai ne d sa nd m ai n co m po ne nt ; g ra in s av er ag e a bo ut 0 .3 m m ac ro ss , ra ng e f ro m 0 .2 5m m u p to 1.0 m m (r ar e) ; c om po se d of cle ar q ua rt z, re d- sta in ed cle ar q ua rt z a nd m in or w hi te qu ar tz ve ry m in or , i f an y no ne no ne no ne tr ac e a m ou nt of b la ck , s hi ny gr ai ns Q c4 34 2 Q c re d br ow n un co ns ol id at ed m ed iu m - t o co ar se -g ra in ed sa nd av er ag e g ra in si ze is ab ou t 0. 5m m ac ro ss , r an gi ng fro m 0 .15 m m u p to 2 m m ; pr ob ab ly fa irl y w el l s or te d; co m po se d w ho lly o f q ua rt z, m os tly cl ea r, so m e w hi te an d a t ra ce am ou nt re d; g ra in s ha ve a va ria bl e c oa tin g of re d cla y o r r ed ir on o xi de , im pa rt in g an o ve ra ll re d co lo ur m in or co m po ne nt o f sil t-s iz e q ua rt z gr ai ns no ne no ne m in or am ou nt of p la nt m at er ia l on sa m pl e su rf ac e tr ac es o f irr eg ul ar , b la ck gr ai ns Q c5 25 3 Q c re d br ow n un co ns ol id at ed po or ly so rt ed , sil ty , fi ne - gr ai ne d sa nd do m in an t c om po ne nt ; av er ag e g ra in si ze ab ou t 0. 2m m , g ra di ng to si lt- siz ed ; cle ar , w hi te an d re d qu ar tz gr ai ns (c lea r q ua rt z w ith re d iro n ox id e s ta in in g) sig ni fic an t co m po ne nt , co m po se d of qu ar tz pr ob ab ly no ne no ne tr ac e a m ou nt of ro ot let m at er ia l tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e 74 angledool 1:100 000 geological sheet c o M P o n e n t s sa m pl e ID si te n o. U ni t sy m bo l co lo ur co he re nc e D es cr ip ti on sa nd si lt cl ay ca rb on at e no du le s or ga ni c m at te r ot he r Q d1 30 0 Q d re d br ow n un co ns ol id at ed m ed iu m - t o co ar se -g ra in ed sa nd m ai n co m po ne nt ; g ra in siz e a ve ra ge s a bo ut 0 .5 m m , ra ng in g fro m 0 .3 m m u p to 1. 5m m (r ar e) ; c om po se d of cle ar , w hi te an d m in or re d qu ar tz ; g ra in s a pp ea r t o be we ll- ro un de d an d of h ig h to m od er at e s ph er ici ty lit tle , i f a ny no ne no ne m in or am ou nt of p la nt m at er ia l on sa m pl e su rf ac e tr ac e s an d- siz ed lim on ite g ra in s Q d2 29 9 Q d br ow n gr ey clu m pe d, h ar d sa nd y, cla ye y sil t sig ni fic an t c om po ne nt ; av er ag e g ra in si ze is ab ou t 0. 4m m ; c lea r, w hi te an d m in or re d qu ar tz pr ob ab ly do m in an t; co m po se d of qu ar tz sig ni fic an t; pa le br ow n- gr ey no ne no ne tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q d3 35 0 Q d re d br ow n un co ns ol id at ed m ed iu m - gr ai ne d sa nd do m in an t c om po ne nt ; av er ag e g ra in si ze is ab ou t 0. 5m m , r an gi ng fr om 0 .3 m m up to 1. 5m m (r ar e) ; c lea r, w hi te an d re d- sta in ed cl ea r qu ar tz m in or co m po ne nt no ne no ne no ne tr ac e a m ou nt of b la ck , s hi ny gr ai ns Q m b1 26 3 Q m b da rk g re y ve ry cl um pe d, ha rd sil ty cl ay m in or co m po ne nt ; g ra in si ze up to ab ou t 0 .2 5m m ; c lea r, m in or w hi te an d tr ac e r ed qu ar tz pr ob ab ly a sig ni fic an t co m po ne nt pr ob ab ly th e do m in an t co m po ne nt ; kh ak i m in or co m po ne nt , up to 1m m m in or ro ot let s tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q m b2 36 3 Q m b gr ey b ei ge clu m pe d to un co ns ol id at ed cla ye y, sa nd y sil t m in or co m po ne nt ; g ra in si ze up to ab ou t 0 .3 m m ; c lea r qu ar tz , m in or w hi te an d tr ac e r ed q ua rt z pr ob ab ly th e m ai n co m po ne nt ; co m po se d of cle ar q ua rt z cla y pr ob ab le to ac co un t f or clu m pi ng m in or co m po ne nt , up to 3m m m in or ro ot let s tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q m b3 31 8 Q m b da rk g re y clu m pe d to un co ns ol id at ed sa nd y, cla ye y sil t sig ni fic an t c om po ne nt ; gr ai ns av er ag e 0 .2 5m m ac ro ss ; c lea r t o w hi te an d tr ac e r ed q ua rt z pr ob ab ly th e do m in an t co m po ne nt , co m po se d of cle ar q ua rt z pr ob ab ly a sig ni fic an t co m po ne nt m in or co m po ne nt , up to 5 m m m in or ro ot let s tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q m bf 1 34 1 Q m bf da rk g re y clu m pe d, h ar d cla ye y, sa nd y sil t sig ni fic an t c om po ne nt ; av er ag e g ra in siz e i s a bo ut 0. 2m m ; m ai nl y c lea r, w hi te an d ve ry m in or re d- sta in ed cle ar q ua rt z pr ob ab ly th e do m in an t co m po ne nt , co m po se d of qu ar tz sig ni fic an t, da rk g re y no ne ab un da nt , th in p la nt ro ot s tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e 75 appendixes Q m c1 26 7 Q m c da rk g re y clu m pe d, h ar d sil ty cl ay ve ry m in or co m po ne nt ; qu ar tz g ra in s t o 0, 25 m m ; m ai nl y w hi te an d cle ar qu ar tz pr ob ab ly sig ni fic an t, co m po se d of qu ar tz pr ob ab le do m in an t co m po ne nt ; pa le kh ak i- gr ey to p al e gr ey no ne ab un da nt , th in p la nt ro ot s a nd so m e ga st ro po d sh el ls tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q m f1 28 6 Q m f da rk g re y clu m pe d, fr ia bl e cla ye y s ilt m in or co m po ne nt ; a ve ra ge gr ai n siz e i s a bo ut 0 .2 5m m , ra re ly u p to 0 .5 m m ; c lea r, w hi te an d ve ry m in or re d- sta in ed q ua rt z pr ob ab ly th e do m in an t co m po ne nt , co m po se d of qu ar tz sig ni fic an t; pa le gr ey m in or no du les to ab ou t 7 m m m in or ro ot let s tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q m k1 34 6 Q m k da rk g re y clu m pe d to un co ns ol id at ed po or ly so rt ed sa nd y s ilt av er ag e g ra in si ze is ab ou t 0; 3m m , r an gi ng fr om 0 ;1m m to 1m m ; q ua rt z c ol ou r i s m os tly cl ea r t o w hi te b ut a m in or am ou nt is re d ab un da nt si lt siz e p ar tic les ; se em s t o co ns ist m ai nl y o f qu ar tz cla y i s ev id en t fro m th e ag gr eg at ed sil t p ar tic les un co m m on no du les to ab ou t 3 m m m in or ro ot m at er ia l tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q m m 1 30 5 Q m m da rk g re y clu m pe d, h ar d sil ty cl ay m in or co m po ne nt ; g ra in s u p to 0 .3 m m ac ro ss ; w hi te , c lea r, m in or re d qu ar tz sig ni fic an t, po ss ib ly do m in an t, co m po ne nt ; co m po se d of qu ar tz sig ni fic an t; pa le gr ey no ne tr ac e a m ou nt of ro ot let m at er ia l tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q m r1 23 9 Q m r be ig e t o pa le gr ey clu m pe d to un co ns ol id at ed cla ye y s ilt m in or co m po ne nt ; g ra in s t o ab ou t 0 .3 m m ac ro ss ; m os tly cle ar to w hi te q ua rt z, tr ac e re d do m in an t co m po ne nt ; m ai nl y c lea r qu ar tz g ra in s, so m e r ed pr ob ab le no ne no ne tr ac e s ilt si ze d bl ac k sh in y irr eg ul ar g ra in s Q m r2 23 6 Q m r re dd ish br ow n clu m pe d to un co ns ol id at ed sa nd y s ilt sig ni fic an t c om po ne nt ; av er ag e g ra in si ze is ab ou t 0. 5m m , r ar ely u p to 1. 5m m ; cle ar , w hi te an d m in or re d qu ar tz g ra in s do m in an t co m po ne nt ; co m po se d of qu ar tz m in or cl ay co m po ne nt pr ob ab le, to ac co un t f or clu m pi ng ; pa le gr ey ? no ne m in or ro ot let s tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e 76 angledool 1:100 000 geological sheet c o M P o n e n t s sa m pl e ID si te n o. U ni t sy m bo l co lo ur co he re nc e D es cr ip ti on sa nd si lt cl ay ca rb on at e no du le s or ga ni c m at te r ot he r Q m r4 22 7 Q m r gr ey clu m pe d to un co ns ol id at ed sa nd y, cla ye y sil t sig ni fic an t c om po ne nt ; av er ag e g ra in si ze is ab ou t 0. 3m m ac ro ss ; c lea r, w hi te an d ve ry m in or re d qu ar tz gr ai ns pr ob ab ly th e do m in an t co m po ne nt , co m po se d of qu ar tz sig ni fic an t; pa le gr ey no ne m in or ro ot let s tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q m r5 22 8 Q m r da rk g re y clu m pe d, h ar d to fr ia bl e cla ye y s ilt m in or co m po ne nt ; a ve ra ge siz e i s a bo ut 0 .4 m m ac ro ss ; cle ar , w hi te an d m in or re d- sta in ed cl ea r q ua rt z pr ob ab ly th e do m in an t co m po ne nt , co m po se d of qu ar tz sig ni fic an t; pa le br ow n- gr ey co m m on , up to 7m m ac ro ss m in or ro ot let s tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q ra b1 25 9 Q ra b da rk g re y clu m pe d to un co ns ol id at ed po or ly so rt ed sa nd y s ilt M in or sa nd p ar tic les to ab ou t 0. 2m m ac ro ss ; c om po se d of qu ar tz , m os tly cl ea r b ut a tr ac e a m ou nt is re d do m in an t co m po ne nt ; m os t s ilt g ra in s ar e q ua rt z cla y pr ob ab le to ac co un t f or clu m pi ng m in or co m po ne nt , up to 3m m m in or , ro ot let m at er ia l tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q ra c1 26 0 Q ra c da rk g re y ve ry cl um pe d, ha rd sil ty cl ay m in or co m po ne nt ; g ra in si ze up to ab ou t 0 .2 5m m ; c lea r, m in or w hi te an d tr ac e r ed qu ar tz pr ob ab ly a sig ni fic an t co m po ne nt ; co m po se d of qu ar tz pr ob ab le do m in an t co m po ne nt ; pa le gr ey - gr ee n tr ac e am ou nt , up to ab ou t 2m m m in or ro ot let s tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q ra c2 25 5 Q ra c gr ey br ow n m ai nl y clu m pe d to m in or un co ns ol id at ed cla ye y s ilt m in or co m po ne nt ; g ra in si ze up to ab ou t 0 .3 m m ; c lea r, m in or w hi te an d tr ac e r ed qu ar tz m ajo r co m po ne nt co m po se d of qu ar tz g ra in s pr ob ab ly a sig ni fic an t co m po ne nt no ne tr ac e a m ou nt of ro ot let m at er ia l tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q ra c3 25 7 Q ra c re dd ish br ow n m os tly un co ns ol id at ed w ith m in or clu m pi ng sil ty , fi ne -F 39 to m ed iu m - gr ai ne d sa nd do m in an t c om po ne nt ; av er ag e s iz e a bo ut 0 .2 5m m , ra ng es fr om si lt to ab ou t 0. 5m m (r ar e) ; m ai nl y c lea r qu ar tz , m in or w hi te an d tr ac e r ed sig ni fic an t co m po ne nt ; cle ar , m in or w hi te an d les s re d qu ar tz m in or if an y no ne tr ac e a m ou nt of ro ot let m at er ia l tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q ra m 1 26 5 Q ra m re dd ish br ow n clu m pe d, h ar d cla ye y s ilt m in or co m po ne nt ; g ra in s u p to 0 .2 m m ac ro ss ; c lea r, w hi te an d m in or re d gr ai ns pr ob ab ly th e do m in an t co m po ne nt , co m po se d of qu ar tz pr ob ab ly sig ni fic an t; pa le gr ey no ne tr ac e a m ou nt of ro ot let m at er ia l tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e 77 appendixes Q rb 1 33 0 Q rb gr ey clu m pe d to un co ns ol id at ed cla ye y s ilt m in or co m po ne nt ; a ve ra ge gr ai n siz e i s a bo ut 0 .3 m m , ra ng in g to 1. 5m m (r ar e) ; cle ar , w hi te an d ve ry m in or re d- sta in ed q ua rt z pr ob ab ly th e do m in an t co m po ne nt , co m po se d of qu ar tz sig ni fic an t co m po ne nt ; pa le gr ey to gr ey -g re en m in or , t o ab ou t 3 m m m in or ro ot let s tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q rb 2 35 6 Q rb da rk g re y clu m pe d, h ar d cla ye y, sa nd y sil t sig ni fic an t c om po ne nt ; av er ag e g ra in siz e i s a bo ut 0. 3m m ; m ai nl y c lea r, w hi te an d ve ry m in or re d- sta in ed cle ar q ua rt z pr ob ab ly th e do m in an t co m po ne nt , co m po se d of qu ar tz sig ni fic an t; pa le gr ey tr ac e am ou nt , up to ab ou t 3m m m in or ro ot let s a nd sp ira l-s ha pe d ga st ro po d sh el ls tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q rc 1 24 6 Q rc da rk g re y clu m pe d, h ar d cla ye y s ilt m in or co m po ne nt , a ve ra ge siz e o f a bo ut 0 .3 m m ; co m po se d of cl ea r, w hi te an d m in or re d- sta in ed cl ea r qu ar tz pr ob ab ly th e do m in an t co m po ne nt , co m po se d of qu ar tz sig ni fic an t; pa le br ow n- gr ey m in or no du les to ab ou t 3 m m m in or ro ot let s tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q rc 2 35 4 Q rc gr ey b ei ge to g re y br ow n clu m pe d to un co ns ol id at ed sil ty , m ed iu m - gr ai ne d sa nd pr ob ab ly th e d om in an t co m po ne nt ; a ve ra ge p ar tic le siz e i s 0 .4 m m ; c lea r, w hi te an d m in or re d qu ar tz sig ni fic an t co m po ne nt , co m po se d of qu ar tz pr ob ab le m in or co m po ne nt no ne no ne tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q rc 3 28 3 Q rc gr ey b ei ge m ai nl y un co ns ol id at ed w ith m in or clu m pi ng sa nd y s ilt sig ni fic an t c om po ne nt ; g ra in siz e a ve ra ge s 0 .4 m m ac ro ss ; co m po se d of cl ea r, w hi te an d m in or re d gr ai ns po ss ib ly th e m ai n co m po ne nt , co m po se d of qu ar tz po ss ib ly a m in or am ou nt no ne no ne tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q rc 4 33 2 Q rc da rk g re y clu m pe d cla ye y, sa nd y sil t m in or co m po ne nt ; g ra in si ze up to ab ou t 0 .3 m m ; c lea r qu ar tz , m in or re d qu ar tz m ajo r co m po ne nt co m po se d of cle ar an d tr ac e re d qu ar tz gr ai ns cla y pr ob ab le to ac co un t f or clu m pi ng no ne ab un da nt , th in ro ot let s an d so m e ga st ro po d sh el ls tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q rm 1 28 1 Q rm gr ey br ow n un co ns ol id at ed sil ty , m ed iu m - gr ai ne d sa nd m os tly q ua rt z s an d; av er ag e pa rt icl e s iz e i s a bo ut 0 .3 m m ; qu ar tz g ra in s a re m os tly cle ar , m in or re d on es pa rt icl es u p to 0. 02 m m ar e co m pr ise d of qu ar tz ? ( pr ob ab ly no t m uc h) no ne sm al l am ou nt o f ro ot m at er ia l an d ot he r pl an t m at te r tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q rm 2 29 8 Q rm re dd ish br ow n clu m pe d po or ly so rt ed sa nd y s ilt so m e q ua rt z g ra in s u p to ab ou t 0 .4 m m ; m os tly cl ea r, m in or re d gr ai ns do m in an t co m po ne nt , co m pr ise d m ai nl y o f qu ar tz cla y pr ob ab le to ac co un t f or clu m pi ng no ne no ne tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e 78 angledool 1:100 000 geological sheet c o M P o n e n t s sa m pl e ID si te n o. U ni t sy m bo l co lo ur co he re nc e D es cr ip ti on sa nd si lt cl ay ca rb on at e no du le s or ga ni c m at te r ot he r Q rm 4 24 3 Q rm gr ey br ow n clu m pe d cla ye y, sa nd y sil t sig ni fic an t c om po ne nt ; av er ag e s iz e i s a bo ut 0 .2 5m m ; cle ar , w hi te an d m in or re d qu ar tz pr ob ab ly th e do m in an t co m po ne nt , co m po se d of qu ar tz sig ni fic an t; pa le br ow n gr ey no ne tr ac e a m ou nt of ro ot let m at er ia l tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q rm 5 23 1 Q rm re d br ow n clu m pe d to un co ns ol id at ed sa nd y s ilt sig ni fic an t c om po ne nt ; av er ag e g ra in si ze o f a bo ut 0. 3m m ; m os tly cl ea r q ua rt z, m in or w hi te an d ra re re d gr ai ns pr ob ab ly th e m ai n co m po ne nt ; co m po se d of cle ar q ua rt z w ith re d iro n ox id e c oa tin gs cla y pr ob ab le to ac co un t f or clu m pi ng no ne m in or ro ot s a nd ot he r p la nt m at er ia l tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q rm 6 33 1 Q rm pa le gr ey ish br ow n clu m pe d to un co ns ol id at ed po or ly so rt ed sa nd y s ilt sig ni fic an t c om po ne nt ; gr ai ns u p to 0 .3 m m ac ro ss ; cle ar to w hi te q ua rt z, so m e re d gr ai ns do m in an t co m po ne nt ; m ai nl y c lea r qu ar tz cla y pr ob ab le to ac co un t f or clu m pi ng no ne tr ac e a m ou nt of ro ot let m at er ia l tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e Q rm 7 26 2 Q rm da rk g re y clu m pe d cla ye y s ilt ve ry m in or co m po ne nt ; qu ar tz g ra in s t o 0. 3m m do m in an t co m po ne nt ; ap pa re nt ly m ai nl y q ua rt z pr ob ab le ra re , u p to 3m m m in or ro ot let s a nd ot he r p la nt m at te r tr ac es o f irr eg ul ar , b la ck gr ai ns Q rm 8 30 9 Q rm be ig e un co ns ol id at ed we ll so rt ed fin e- to m ed iu m - gr ai ne d sa nd m ajo r c om po ne nt ; g ra in si ze av er ag es 0 .2 5m m ; m os tly cle ar to w hi te , s om e m in or re d gr ai ns ; f ai rly w el l s or te d pr ob ab ly m in or , if an y no ne no ne m in or , ro ot let m at er ia l tr ac e a m ou nt of b la ck , s hi ny gr ai ns Q rm 9 30 9 Q rm be ig e t o pa le gr ey clu m pe d to un co ns ol id at ed cla ye y, sil ty fin e- to m ed iu m - gr ai ne d sa nd do m in an t c om po ne nt ; av er ag e s iz e a bo ut 0 .2 5m m ; m ai nl y c lea r q ua rt z, m in or w hi te an d tr ac e r ed sig ni fic an t co m po ne nt , m ai nl y c lea r qu ar tz cla y pr ob ab le to ac co un t f or clu m pi ng no ne no ne tr ac e a m ou nt of b la ck , s hi ny gr ai ns , r an gi ng fro m sa nd to sil t s iz e 79 appendixes table D: Percentage estimate and description of clay component in Quaternary samples sample no. clay % estimated from size fraction in water Description (microscope examination; see table c) Description of clay component Qc1 20 clayey silt weakly swelling, very dark brown clay Qc2 7 poorly sorted, silty medium-grained sand dark to moderate grey clay Qc3 3 well sorted medium-grained sand moderate swelling, very dark grey/brown clay Qc4 1 medium to coarse-grained sand very dark brown clay Qc5 8 poorly sorted, silty, fine-grained sand weakly swelling, very dark brown clay Qcd1 5 poorly sorted, silty, fine- to very coarse-grained sand swelling, moderate brown clay Qd1 4 medium- to coarse-grained sand swelling, very dark brown clay Qd2 11 sandy, clayey silt weakly swelling, moderate brown clay Qd3 3 medium-grained sand weakly swelling, very dark brown clay Qmb1 substantial component silty clay clay is a substantial component; swelling, moderate grey clay Qmb2 20 clayey, sandy silt swelling, moderate grey clay; possibly 2 clay layers — upper (light) 7 mm thick and lower (dark) 10 mm thick Qmb3 7 sandy, clayey silt swelling, dark grey clay Qmb4 clay forms most of the sample clayey silt sample is probably a silty clay or clay; clay forms most of sample — swelling, moderate grey clay Qmbc1 7 sandy, clayey silt swelling, moderate grey clay Qmbf1 26 clayey, sandy silt swelling, moderate grey clay Qmc1 60 silty clay swelling, dark grey clay Qmf1 80 clayey silt sample is probably a silty clay or clay; clay is a substantial component — swelling, moderate grey clay Qmk1 11 poorly sorted sandy silt swelling, dark grey clay Qmm1 23 silty clay sample is probably a clayey silt; swelling, dark grey clay Qmr1 5 clayey silt swelling, moderate grey clay Qmr2 10 sandy silt swelling, dark brown clay Qmr3 7 poorly sorted sandy silt weakly swelling, very dark grey clay Qmr4 4 sandy, clayey silt swelling clay, dark to pale grey clay Qmr5 20 clayey silt clay is a substantial component — swelling, dark grey clay Qrab1 18 poorly sorted sandy silt sample is probably a sandy, clayey silt; swelling, moderate grey clay Qrac1 20 silty clay sample is probably a clayey silt; swelling, dark grey clay 80 angledool 1:100 000 geological sheet Qrac2 16 clayey silt swelling, dark grey/brown clay Qrac3 6 silty, fine- to medium-grained sand swelling, very dark brown clay Qrac4 2 medium-grained sand dark grey clay Qram1 8 clayey silt swelling, dark to light brown clay Qrb1 18 clayey silt swelling, dark grey clay Qrb2 30 clayey, sandy silt swelling, dark grey clay; two clay layers — an upper light grey clay (10 mm thick ) and a lower, slightly darker layer (13 mm thick). Qrc1 18 clayey silt swelling, dark grey clay Qrc2 6 silty, medium-grained sand swelling, dark grey clay Qrc3 7 sandy silt weakly swelling, very dark brown clay Qrc4 20 clayey, sandy silt swelling, moderate grey clay Qrm1 6 silty, medium-grained sand slightly swelling, very dark brown clay Qrm2 15 poorly sorted sandy silt swelling, dark to pale brown clay Qrm3 15 poorly sorted sandy silt swelling, moderate grey clay Qrm4 10 clayey, sandy silt swelling, dark to pale brown clay Qrm5 17 sandy silt swelling, reddish brown clay Qrm6 7 poorly sorted sandy silt swelling, dark grey to pale brown clay Qrm7 60 clayey silt sample is probably a silty clay or clay; clay is a significant component — swelling, moderate grey clay. Qrm8 5 well sorted fine- to medium-grained sand dark grey clay Qrm9 25 clayey, silty fine- to medium-grained sand swelling, pale grey clay sample no. clay % estimated from size fraction in water Description (microscope examination; see table c) Description of clay component 81 appendixes table e: PIMA analysis of Quaternary alluvium PIMA analysis — mineral % (computer estimate) confidence Sample no. montmorillonite anhydrite halloysite nontronite water Qc1 16 46 38 good Qc2 34 54 12 excellent Qc3 35 59 6 poor Qc4 31 69 excellent Qc5 16 40 43 excellent Qcd1 49 26 25 excellent Qd1 48 52 excellent Qd2 23 33 44 excellent Qd3 33 59 8 good Qmb1 37 42 21 excellent Qmb2 40 45 16 excellent Qmb3 43 43 15 excellent Qmb4 38 38 24 excellent Qmbc1 39 44 17 excellent Qmbf1 26 27 47 excellent Qmc1 39 41 21 excellent Qmf1 33 39 28 excellent Qmk1 44 42 14 excellent Qmm1 36 45 19 excellent Qmr1 73 27 good Qmr2 26 40 34 excellent Qmr3 15 51 34 excellent Qmr4 33 49 18 excellent Qmr5 47 37 16 excellent Qrab1 34 39 27 excellent Qrac1 9 26 66 good Qrac2 29 47 24 excellent Qrac3 9 42 49 excellent Qrac4 47 37 16 excellent Qram1 37 36 27 excellent Qrb1 32 43 24 excellent Qrb2 31 42 27 excellent Qrc1 29 41 29 excellent Qrc2 16 46 39 excellent Qrc3 11 51 38 excellent Qrc4 29 40 31 excellent Qrm1 52 48 excellent Qrm2 26 42 33 excellent Qrm3 39 38 24 excellent Qrm4 36 43 22 excellent Qrm5 18 25 57 excellent Qrm6 19 43 38 excellent Qrm7 33 39 28 excellent Qrm8 22 43 36 excellent Qrm9 73 27 good 82 angledool 1:100 000 geological sheet Appendix 4 Rock sample descriptions Several rock samples were analysed using a PIMA in order to glean information on the clay minerals present. Appendix 3 describes the rationale and limitations of the PIMA method. Table F gives the results of the mineral determinations made by the PIMA acquisition software, while Figure B presents the measured SWIR spectra for the rock samples. table F: PIMA analysis of rock samples sample description PIMA analysis — mineral % (computer estimate) confidence halloysite montmorillonite kaolinite water white claystone rich in plant fossils 54 46 excellent white siltstone with potch seams 70 10 20 excellent grey, hard ‘blow’ matrix 77 13 10 excellent white K siltstone with elliptical fracture 68 8 24 excellent blow’ matrix material from Grawin area 60 31 8 excellent pale grey, hard ‘blow’ matrix material 56 44 excellent 1540 1780 2020 2260 Wavelength (nm) 2010_03_0040 Site 199 Site 211 Site 345 Site 216 Site 223 Site 208 S am ple Figure B. Stacked SWIR spectra of rock samples; no vertical scale is implied. 83 appendixes The specific activity of the specimen was measured by means of calibrated thick source alpha counting over a 42 mm scintillation screen. The values shown assume secular equilibrium for both the U and Th decay chains. The uncertainty levels indicated represent one standard deviation. The sample was analysed by means of the combined regenerative and additive methods using the 90–125 μm quartz grain size fraction. This technique ensures that there has been no change in TL sensitivity due to the particular laboratory procedure adopted. The age indicated is not corrected for surface residual TL as no suitable sample was provided for that purpose. Hence it has been assumed that the TL starting point, at the time of deposition, is that level attained following a minimum 24 hour prepared sample exposure beneath a laboratory ultraviolet lamp (Philips MLU 300W). The TL characteristics exhibited suggest that any error introduced as a result of this assumption is negligible. These characteristics lend considerable confidence to the final depositional age derived for this sample. Appendix 5 Thermoluminescence (TL) dating One sample was submitted for thermoluminescence (TL) dating. It consisted of fine-grained, reddish brown sand of the Nullawa Member splay facies (GR 576855 6785975 — Site 366, see Appendix 1). The sample was obtained by digging a hole to 0.3 m depth and then inserting a PVC pipe horizontally into the ground to extract a sample without exposure to light (Photograph A). The TL analysis was carried out by David M. Price at the School of Geosciences, University of Wollongong. The following details (Table G) and the discussion were provided by him on 30 June 2003. table G: thermoluminescence data specimen no. W3424 Reference MGA Zone 55/0.30Sm Plateau region (°C) 300N500 Analysis temp. (°C) 375 Palaeodose (Grays) 6.90H±H0.30 K content (% by AES) 1.15H±H0.05 Rb content (ppm assumed) 100H±H25 Moisture content (% by weight) 2.5H±H3 Specific activity (Bq/kg U+Th) 63.6H±H1.4 Cosmic contribution (μGy/yr assumed) 185H±H25 Annual radiation Dose (μGy/yr) 2670H±H61 TL age (yearsSBP) 2600H±H0.15 Photograph A. TL sample collection site in the Nullawa Member meander plain facies (GR 576855 6785975). The sample was collected in a PVC pipe to prevent exposure to light. 84 angledool 1:100 000 geological sheet (Burger 1980, Morgan 1984). A petrified Cretaceous tree trunk with opal-filled cavities and opalised cones of Araucaria from Lightning Ridge is preserved in the Galman Collection of the Australian Museum and another Cretaceous gymnosperm trunk exists in the Geological Survey of New South Wales fossil collection. Fossil plants have also been found at several sites around Lightning Ridge (e.g. Carpenter et al. in press), associated with silcrete of the Tertiary unit Tg. The fossil collection of the Geological Survey of New South Wales includes leaves, seeds and fruit/seed pods of probable Tertiary age. Fossil leaves found in fine-grained sandstone near Cumborah during the current mapping project (Photograph B) are difficult to date and could be Cretaceous or younger, but an age of Paleocene to Miocene age is possible and they are suggestive of vine forest (pers. comm. David Greenwood, Brandon University, Manitoba, Canada). Appendix 6 Palaeontology N.S. Meakin Lightning Ridge is world-renowned for its diversity of fossils that contribute greatly to our understanding of Early Cretaceous freshwater and land-dwelling life forms and environments. They provide a rare insight into the palaeogeography, palaeoclimate and biodiversity of Australia during that time. Dettman et al. (1992) discuss the Cretaceous terrestrial fossils within the context of palaeogeography and regional biostratigraphy. Cretaceous opalised fossils of the region are summarised by Smith and Smith (1999) and a selection is shown in Plate 1. Collaboration between miners and researchers is vital for fossil discovery and preservation. Palaeontologists consult with opal miners to assess what has been found, or to access spoil heaps and opal mines and guide excavation. Without the assistance of miners, many fossils would not have been recognised or preserved, and smaller and less spectacular fossils would tend to be thrown away. Museums and universities also provide support through research grants to support palaeontological work, and by purchasing important and valuable specimens. Fossil fauna A diverse range of fossils has been recovered from the Finch Claystone facies of the Wallungulla Sandstone Member of the Griman Creek Formation (Table H). Lightning Ridge is unique among Australian opal fields in producing opalised fossils of predominantly freshwater and terrestrial plants and animals (Smith 2007, 2009) and is the only significant dinosaur locality in New South Wales. Many workers have described fossils from the area, including monotremes (Archer et al. 1985; Flannery et al. 1995; Musser 2005), crocodiles (Molnar 1980; Molnar & Willis 2001), bivalves (Hocknull 2000; Kear 2006), gastropods (Hamilton-Bruce et al. 2002; Hamilton- Bruce & Kear 2010), echinoderms, crustaceans, cartilaginous and bony fishes and lungfish (Smith & Smith 1999; Kemp & Molnar 1981), plesiosaurs, dinosaurs (Molnar & Galton 1986; Rich & Vickers- Rich 1994; Molnar 2010), pterosaurs, birds (Molnar 1999), turtles (Smith 2009, 2010) and foraminifera (Scheibnerova 1974, 1984). Fossil flora Opalised plant remains have also been found in the region (Morgan 1984, White 1986). ). Using palynological analysis, the Griman Creek Formation has been assigned to the Coptospora paradoxa spore– pollen zone, indicating an early to middle Albian age Photograph B. Angiosperm leaf impression — a broad- leaved dicot showing pinnate semi-craspedodromous venation. Age range: Cretaceous? to Tertiary?. (Photographer: N.S. Meakin). 85 appendixes Table H: List of Cretaceous fossil fauna of the Griman Creek Formation, Lightning Ridge, from Smith (2007, 2009, 2010), with contributions from other sources. taxon source Chlorophyceae Charophyta indet. taxon Dr Adriana Garcia pers. comm.; Henk Godthelp pers. comm. Foraminifera Hyperammina sp. Scheibnerova 1984 Ramulina tetrahedralis Ludbrook 1966 Scheibnerova 1984 Radiolaria radiolarian? Scheibnerova 1984 Polychaeta indet. taxon Smith Mollusca Pelecypoda Alaythyria jaqueti Newton 1915 Smith Megalovirgus wintonensis Hocknull 1997 Smith Hyridella macmichaeli Hocknull 1997 Smith Hyridella (Protohyridella) goondiwindiensis Hocknull 1997 Smith Palaeohyridella godthelpi Hocknull 2000 Smith Coocrania hamiltonbrucei Kear 2006 Smith large hyriid? Smith sphaeriid Smith ‘tellen’ or nut shell Smith corbiculid — river pea shell Smith strongly ridged, subcircular unioid Smith clam with spines, narrow rippled margins Smith Gastropoda Albianopalin benkeari Hamilton-Bruce et al. 2002 Smith Albianopalin lizsmithae Hamilton-Bruce et al. 2002 Smith Notopala sp. Hamilton-Bruce et al. 2002 Smith Melanoides godthelpi Hamilton-Bruce et al. 2004 Smith Fretacaeles gautae Hamilton-Bruce and Kear 2006 Smith Suratia marilynae Hamilton-Bruce and Kear 2010 Smith Crustacea Decapoda freshwater crayfish — indet. taxon Anura frog — indet. taxon Dr Mike Tyler and Henk Godthelp pers. comm. Pisces Chondrichthyes small shark cf. Isurus or Cretolamna small shark cf. Isurus or Cretolamna Actinopterygia — Teleostei indet. taxa x 4 Dr Sue Turner pers. comm. aspidorhynchid cf. Richmondichthys sweeti Etheridge and Smith Woodward 1891 Smith freshwater eel — indet. taxon Dr Peter Forey and Dr Tom Rich, pers. comm. Dipnoi – lungfish Ceratodus wollastoni Chapman 1914 Kemp and Molnar 1981 Ceratodus diutinus Kemp 1993 Kemp 1993 Neoceratodus forsteri Kreftt 1870 Kemp and Molnar 1981 Ichthyosauria ichthyosaur — indet. taxon Dr Benjamin Kear pers. comm. Sauropterygia Pliosauria Leptocleidid? pliosaur Dr Benjamin Kear pers. comm. Plesiosauria elamosaurid plesiosaur — indet. taxon Dr Benjamin Kear pers. comm. 86 angledool 1:100 000 geological sheet taxon source Testudines — turtles Chelidae indeterminate chelid pleurodires x 2 taxa Smith 2010 Testudines indet. meiolaniid-like taxon 1 — ‘Spook’s Turtle’ Smith 2009 meiolaniid-like taxon 2 — ‘Sunflash Turtle’ Smith 2009 Crocodilia Crocodylus selaslophensis Etheridge 1917 Smith crocodile — ziphodont Molnar and Willis 2001 crocodile — conical tooth form Molnar and Willis 2001 Pterosauria pterosaur — indet. taxon Henk Godthelp pers. comm. Dinosauria Ornithopoda stegosaurid Dr Benjamin Kear pers. comm. Muttaburrasaurus sp. Molnar 1991, 1996 Fulgurotherium australe von Huene 1932 (Molnar and Galton 1986) Smith Atlascopcosaurus loadsi Rich and Rich 1989 Smith Leallynasaurus? sp. Rich and Rich 1989 Smith very large hypsilophodontid Smith Sauropodomorpha indeterminate sauropods x 2—- ‘spoon tooth’ form, ‘sharp tooth’ form Smith small prosauropod? Smith Theropoda Rapator ornitholestoides von Huene 1932 Smith alvarezsaurid? or ceratosaurid — very large form Smith dromaeosaurid cf. Velociraptor Henk Godthelp pers. comm. ornithomimosaurid Henk Godthelp pers. comm. spinosaurid? Dr Benjamin Kear pers. comm. Aves unidentified ornithoracines — two taxa Molnar 1999 Mammalia Synapsida unidentified synapsid? Clemens et al. 2003 Monotremata Steropodontidae — Steropodon galmani Archer et al. 1985 Smith Kollikodontidae — Kollikodon ritchiei Flannery et al. 1995 Smith Ornithorhynchidae? — up to 3 unidentified taxa Smith 2009 87 locality index 9 Mile pit, 45 A Amaroo homestead, 18, 21, 22, 22, 23, 25, 26, 27 Angledool homestead, 21, 25, 26, 27 Angledool Lake, 1, 18, 19, 25, 26, 27 Angledool map sheet area, 1 B Balonne River, 5 Barwon River, 1, 1, 17, 25, 26, 27 Birrie River, 1, 1, 17, 27 Bobs tank, 23 Bokhara River, 1, 1, 14, 15, 17, 22, 25, 26, 27 Burranbaa homestead, 20, 21, 25, 26 C Calgary homestead, 21, 25, 26, 27 Calgary pit, 45 Carinya homestead, 20, 21, 22, 25, 26, 27 Carters Rush opal field, 33 Castlereagh Highway, 1 Cawwell homestead, 18, 21, 25, 26 Collyblue No.1, 45 Condomine River, 5 Coocoran Lake, 1, 18, 19, 22, 25, 26, 27 Coocoran opal field, 12, 31, 33, vii Culgoa River, 1, 17 Cumborah, 1, 9, 21, 22, 25, 26, 27 Cumborah map sheet area, 1 D Darling River, 21 Dentist Hill, 45 Dungalear map sheet area, 1 Dunumbral map sheet area, 1 E Eurie Eurie, 18 F Fifteen Mile Warrambool, 17 Finger Post bore, 16 G Gamalally pit, 45 Glenallyn station, 46 Glengarry, 33 Goodooga, 1, 15, 21, 25, 26, 27 Goodooga map sheet area, 1 Grawin, 33 Grawin Creek, 9, 24 Grawin–Glengarry opal field, vii Griman Creek, 5 Gurley homestead, 12, 21, 22, 25, 26, 27 H Heathfield pit, 45 J Jag Hill opal field, 45 K Kia-Ora homestead, 21, 22, 24, 25, 26, 27 L Leander homestead, 15, 21, 22, 22, 25, 26, 27 Lexington homestead, 15, 21, 22, 25, 26, 27 Lightning Ridge, 1, 21, 22, 25, 26, 27 Lightning Ridge map sheet area, 1 Lightning Ridge opal field, vii, 33 Lightning Ridge Town Water Supply bore, 45 Little Yamba Creek, 15 Lourney homestead, 15, 21, 25, 26, 27 Lynrae station, 46 M Marra Creek, 23 Mehi, 24 Mehi opal field, vii, 33 Mission (Ginghi) pit, 45 Moonie River, 5 Moordale homestead, 18, 21, 22, 25, 26, 27 Morendah Plain, 18, 19 Mount Brandon pit, 45 Mount Charlotte, 21, 22, 22, 25, 26, 27 Mungaroo Warrambool, 15 Mureabun homestead, 18, 21, 22, 25, 26, 27 Muttabun opal field, vii, 33 N Narran Lake, 1, 11, 17, 19, 22, 22, 26, 27, 31 Narran Lake homestead, 11, 21, 22, 25, 26 Narran map sheet area, 1 Narran River, 1, 1, 17, 22, 25, 26, 27 Narrandool homestead, 21, 25, 26 New Angledool, 1, 21, 25, 26, 27 Nullawa homestead, 15, 21, 25, 26, 27 O Old Chum opal field, 40 opal workings Airport Rush, 37; Allah’s Rush (Kellie’s 3), 36; Allawah 2, 38; Allawah 3, 38; Anderson’s Folly, 38; Angledool, 37; Baikes, 35; Bald Hill, 37; Beckett’s, 37; Bee Eaters, 37, 38; Benz Hill, 35; Berlin Rush, 37, 38; Bill the Boer, 37; Billy Goat Hill, 39; Bishop’s Rush, 37, 38; Blazed Tree, 35; Blind Freddies, 35; Boggy Hill, 38, 39; Boredrain, 38; Brooks, 39; Bullock’s Head, 37; Butterfly, 37; Canada’s, 37; Carters Rush mine, 35; CC, 36, 38; Central Station, 35; Cheryl’s (Kellie’s 4), 36; Chinaman’s Gully, 35; Cody’s, 36; Con’s Rush, 37; Crusty’s Luck, 38; Crusty’s Luck 2, 38; Czinners, 35; D&D, 38, 39; Darby’s, 37; Dave’s, 37, 38, 39; Dawson’s, 36; Dead Bird, 36; Deep Belars, 37; Deep Four Mile, 37; Dentist Hill, 37, 38; Dijoe’s, 35; Dry Rush, 37; Dunn’s, 38, 39; Eagle, 39; Eagle’s Nest, 39; Emu’s, 36; Fire Chief, 35; Foley’s Six Mile, 37, 38; Four Mile Flat, 37; Frankstone 1, 38; Frankstone 3, 38; Fraser Island, 38, 39; Frog Hollow, 37; Frying Pan, 37; Gema, 38, 39; Glengarry, 35; Goulash, 38, 39; Granny’s Flat, 36; Grassy Hollow, 37; Gravesend, 35; Grawin (east) (Richard’s Hill), 35; Grawin (west) (Hammond’s Hill), 35; Grawin C, 35; Grawin Creek, 35; Great Eastern, 38; Great Eastern Extension, 38; Greenacres, 36; Greenacres 2, 36; Greenacres 3, 36; The Gully, 37; Hard Hill, 36; Hardy’s Crack, 35; Harrison’s Folly, 39; Hart’s, 37; Hatter’s Flat, 37; Hawks Nest, 37; Hidden Valley, 37; Holden’s, 37; Hornet’s Rush, 37; Indian Lookout, 37; Ironbark, 37, 38; Itchy and Scratchy, 39; Jag Hill, 39; Jag Hill 2, 39; Jag Hill 3, 39; JC, 37, 38; Jenny’s, 36; Jim Taylor’s Rush, 37; Joyce’s, 36; Kellie’s 1, 88 angledool 1:100 000 geological sheet 36; Kellie’s 4 Extension, 36; Kellie’s 5, 36; Kellie’s 6, 36; Ken’s Retreat, 36; Kevin’s, 36; Kingfisher, 37; Kitty Hawk, 39; KK, 36; Klaus’s, 36; Knightlife, 39; Lee’s Luck, 38; Les’s Eight Mile, 38; Long’s Rush (Kellie’s western fall), 36; Lummo’s, 35; Lynfield, 35; Marie’s, 36, 38; Martin’s, 36; Matson’s Rush, 37, 38; McDonald’s Six Mile, 37; McNamara’s, 37; Mehi 7, 39; Millionaires Gully, 35; Miro’s, 38, 39; Molyneux’s, 36; Moonshine, 36; Mozzie Gully, 35; Mulga Rush, 35; Muttabun (Brown’s), 39; Natalies Dream, 36; Natalies Dream 1, 36; Nebia Hill, 37; New Chum, 37; New Coocoran, 36; New Four Mile, 37; New Glengarry, 35; New Glengarry 2, 35; New Nobby, 37; Newtown, 37; New Year Rush, 37; Nine Mile, 37; Norway (north), 36; Norway (south), 36; Okhei, 35; Old Chum, 37; Old Coocoran, 36; Old Nobby, 37; Old Town, 37; Olga’s, 36; Olympic Dribble, 35; Ormies Luck, 36; Palestine, 37; Phil Herbert’s Rush, 37; Pig Hill, 37; Pony fence, 37; Pot Luck, 38; Potch Point, 37; Poverty Point, 37; Power Pole, 37, 38; Pumpkin Flat, 37; Rainah’s, 39; Rainbow, 36; Rainbow West, 36; Red Eye, 36; Red Post, 36; Red Robin, 37; Rednex, 39; Reward Rush, 37; Riddles, 35; Roses and Chocolates, 39; Rosso’s, 37; Scandanavia, 38, 39; Sceek’s, 36; Seven Mile, 37, 38; Shallow Belars, 37; Shearer’s Rush, 37; Sheepyard, 35; Shield’s, 35; Shield’s East, 35; Sim’s Hill, 37; Smith’s, 36; Snake Gully, 38; Snowy Brown’s, 37; Speck Hill, 38; Spicer’s, 37; Spiders, 39; Spinifex, 35; Steen’s, 36; Steve’s, 37, 38, 39; Stoney’s, 38; T Bone, 36; T Bone 2 extension, 36; Telephone Line, 37; Ten Mile, 37, 38; The Nest, 36 ; The Rocks, 36; The Springs, 39; Thorley’s Six Mile, 37; Three Mile, 37; Three Mile Flat, 37; Three Mile Western Falls, 37; Three Trees, 36; Tom’s Gully, 37, 38, 39; Tyrones, 36; Tyrone’s 2, 39; Vertical Bill’s, 37; Walshe’s, 37; Warning, 35; Warrengulla, 36, 38; Water Tower Field, 37; Watson’s Reward, 39; Wayne Manor, 35; Wedge Tail, 39; Weetalibah, 38, 39; White Peg, 36; Wild Cat, 35; Williamson’s Gully, 35; Wyoming, 37, 38; Zac’s Corner, 35 Oxley Park homestead, 21, 22, 25, 26, 27 R Rotten Plain, 18 S Seven Mile, 45 Surat (QLD), 5 T The Big Warrambool, 1, 27 Twenty Nine Mile Warrambool, 15 Tysons bore, 17 W Wedge Tail opal field, 45 Weetalibah Creek, 18 Weilmoringle, 18 White Cliffs, 40 Wyoming opal field, vii, 33 Wyoming tank, 21, 22, 22, 25, 26, 28 Y Yamba Creek, 17 Resources Wwwamww‘i WW & Energy 5 Explanatory ANGLEDOOL 1:250 000 GEOLOGY Notes Sheet 5H/ssr7 www.industry.nsw.gov.aulminevals 2011 9% Q“. w WM” .‘Hw ”Lu“ v 10m 20 ya so an m mm m Amos wamma (5‘31; 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