Geology and mineral resources of the Northern Territory Ahmad M and Munson TJ (compilers) Northern Territory Geological Survey Special Publication 5 Chapter 41: Eromanga Basin BIBLIOGRAPHIC REFERENCE: Munson TJ, 2013. Chapter 41: Eromanga Basin: in Ahmad M and Munson TJ (compilers). ‘Geology and mineral resources of the Northern Territory’. Northern Territory Geological Survey, Special Publication 5. Disclaimer While all care has been taken to ensure that information contained in this publication is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of its information. The Northern Territory of Australia gives no warranty or assurance, and makes no representation as to the accuracy of any information or advice contained in this publication, or that it is suitable for your intended use. You should not rely upon information in this publication for the purpose of making any serious business or investment decisions without obtaining independent and/or professional advice in relation to your particular situation. The Northern Territory of Australia disclaims any liability or responsibility or duty of care towards any person for loss or damage caused by any use of, or reliance on the information contained in this publication. Eromanga Basin Current as of May 2012 Chapter 41: EROMANGA BASIN TJ Munson INTRODUCTION geology and regolith). However, the southwestern margins of the basin are exposed in SA and the northeastern part of The ௘Cambrian±"Devonian Warburton Basin, the basin in central Qld is also exposed and has been eroding Carboniferous±Triassic 3edirNa Basin and Jurassic± since the Late Cretaceous. The surface elevation of the basin Cretaceous Eromanga Basin are three stacNed basins in is highest over central Qld, where it is ca 300 m above present- the southeastern corner of the Northern Territory that also day sea-level, but elevations decrease towards the southwest extend over areas of adjoining Queensland, South Australia to below present-day sea level (Waschbusch et al 2009). and New South Wales (Figure 41.1). The Eromanga, Surat The stratigraphic nomenclature of the Eromanga Basin and Carpentaria basins together form the bulN of the Great is complex and has evolved over a century. Units of the Australian Basin1 (Green 1997, Draper 2002b) of central same lithology and in the same stratigraphic position have and northeastern Australia. Other interconnected eastern been given different names in different parts of the basin. Australian basins (eg Clarence-Moreton, Nambour and The stratigraphic succession in the Northern Territory is Laura basins) could also be considered to be a part of this summarised in Table 41.1 and a correlation chart that includes vast depositional system. The Northern Territory part of successions from other portions of the Great Australian the Eromanga Basin contains about 2300 m of Jurassic to Basin is presented in Figure 41.2. The Jurassic succession is Cretaceous strata overlying 3rotero]oic (Aileron 3rovince mainly terrestrial and comprises Àuviatile Tuart] sandstone and Musgrave 3rovince), 3alaeo]oic (AmadeusWarburton interbedded with carbonaceous shale. The Early Cretaceous and Georgina basins, ,rindina 3rovince) and 3ermian±Triassic succession is largely marine, whereas late Early Cretaceous (3edirNa Basin) successions. Elsewhere, the Eromanga strata were deposited in a regressive sea. The early Late Basin also overlies the Bowen, Cooper, Galilee, ArcNaringa Cretaceous part of the Eromanga Basin succession was laid and older basins, and crystalline basement rocNs. Most of down in a mix of environments, including shallow marine, the succession is in the subsurface and in the NT is largely paralic, lacustrine, paludal and Àuviatile. overlain by Ceno]oic and 5ecent sedimentary rocNs of the Numerous studies have been published on the Eromanga LaNe Eyre Basin and other sur¿cial deposits (see Cenozoic Basin, of which some of the more signi¿cant include Whitehouse (1955), Day (1964, 1966, 1967, 1968, 1969), 1 These basins were originally de¿ned by Mott (1952) as portions Vine and Day (1965), Vine et al (1967), Senior et al (1969, of the Great Artesian Basin, a term best restricted to hydrogeology as portions of the artesian system are within sedimentary rocNs of 1978), Casey (1970), Exon and Senior (1976), Haig and other basins (eg Bowen, Galilee basins). Barnbaum 1978, Burger and Senior (1979), Habermehl 133° 135° 137° 139 ° Aileron Province Georgina 23° Basin Ngalia Irindina Basin Province Warumpi Province Alice Springs Aileron NT Amadeus QLD Province (Warburton Basin) Basin Pedirka 25° Basin (Pedirka ? Basin) NT QLD SA SA Musgrave (Warburton Figure 41.1. 5egional geological Province setting of Eromanga Basin. NT Basin) geological regions slightly modi¿ed 27° from NTGS 1:2.5M geological regions GIS dataset. Queensland geological Officer regions simpli¿ed and slightly modi¿ed Basin (Arckaringa (Cooper Basin) from Denaro and Dhnaram (2009) and Basin) Geoscience Australia (GA) Geological 5egions National Geoscience Dataset. Mesozoic–Cenozoic Basins (under cover): SA geological regions simpli¿ed and Neoproterozoic– (Pedirka Basin); Carpentaria Palaeozoic Basin slightly modi¿ed from Department for (Amadeus Basin) Euroka Manufacturing, Innovation, Trade, Palaeo–Mesoproterozoic Arch 5esources and Energy (DMIT5E), orogens (Warburton Basin); Eromanga Basin (other – as labelled) South Australia 5esources Information EROMANGA BASIN Nebine Geoserver (SA5IG: http://www. Road Ridge Location of Figure 40.941.9 Surat sarig.dmitre.sa.gov.au/) and from GA Rail Basin Geological 5egions National Geoscience State boundary Dataset. Ceno]oic covering strata (eg 02125 50 km Alice Locality LaNe Eyre Basin) not shown. Springs A12-097.ai Geology and mineral resources of the Northern Territory 41:1 Special publication 5 Eromanga Basin (1980, 1986), papers in Moore and Mount (1982), Burger Eromanga Basin in that area (Gray et al 2002). Elsewhere, it (1986), papers in GravestocN et al (1986), John and Almond unconformably overlies earlier 3alaeo]oic sedimentary and (1987), papers in O’Neil (1989), Questa (1990), Green et al metasedimentary basement rocNs. In the western Eromanga (1991, 1992), Krieg et al (1995), Draper (2002a, b), Gray Basin in the NT and northern SA, the 3oolowanna Formation et al (2002), Gray and Draper (2002), McKellar (2002), intertongues with and is conformably overlain by the Ambrose et al (2002, 2007), Ambrose (2006), Cotton et al AlgebucNina Sandstone. To the east on the Birdsville TracN (2006), Waschbusch et al (2009) and Ambrose and Heugh 5idge, it is conformably overlain by the Hutton Sandstone, (2010, 2011). The distribution of outcrops in the NT portion which is a lateral eTuivalent of the lower AlgebucNina of the basin is shown in Figure 41.3. Sandstone, and in the Cooper Basin area further to the east, it intertongues with and is conformably overlain by JURASSIC–EARLY CRETACEOUS the Hutton Sandstone (Krieg et al 1995, Gray et al 2002). The 3oolowanna Formation is a lateral eTuivalent of the In the NT portion of the Eromanga Basin, the Jurassic and 3recipice Sandstone and overlying Evergreen Formation older part of the Early Cretaceous succession is divided of the northeastern Eromanga Basin and Surat Basin into two units (Figure 41.2, Table 41.1), the 3oolowanna (McKellar 2002). The main depocentre for the formation )ormation and AlgebucNina Sandstone. is the 3oolowanna Trough, where it reaches a maximum thicNness of 206 m in drillhole 3oolowanna-1 in SA (Krieg Poolowanna Formation et al 1995). ThicN sections are also present to the east and The entirely subsurface 3oolowanna )ormation (Moore northeast of the trough in southwestern Qld, where the 1986b µ3oolowanna beds’ of Wiltshire 1978) is the basal formation reaches a thicNness of 165 m in drillhole DIO unit in the Eromanga Basin succession in the NT in the Curalle-1 (Gray et al 2002). In the NT, the 3oolowanna 3oolowanna, Madigan and Eringa troughs. However, it Formation reaches maximum thicNnesses of 205 m in thins to the west and is absent along the western ÀanNs of Thomas-1 (Wiltshire 1982) and 193 m in 3oeppels Corner-1 the latter two depocentres, where it is overlapped by the (Arco Australia 1985), but it thins to the north and west to AlgebucNina Sandstone (Figure 41.4). The 3oolowanna be 109.4 m thicN in Colson-1 (Beach 3etroleum 1979), 39 m )ormation unconformably overlies 3ermian and Triassic in Simpson-1 (Central 3etroleum 2009a) and less than 10 m sedimentary rocNs of the 3edirNa Basin in the NT and in Blamore-1 (Central 3etroleum 2008, Figure 41.5). SA and the Cooper Basin in SA and Qld. In the Cooper An informal two-fold division of the 3oolowanna Basin, it also unconformably overlies the Late Triassic Formation is recognised in Qld, where a lower interval Cuddapan Formation, which is the lowermost unit of the of medium to very coarse sandstone, grading in places to Unit, max thickness Lithology Depositional environment Stratigraphic relationship Cretaceous ROLLING DOWNS GROUP MANUKA SUBGROUP Winton Formation Claystone, siltstone and mudstone with Fluviatile to paludal to Conformable on MacNunda Formation. 620 m interbedded sandstone and minor coal lacustrine. 3aralic, estuarine, Unconformable beneath Ceno]oic sediments, seams. deltaic and Àuviatile near base. including those of LaNe Eyre Basin. Mackunda Formation Labile lithic sandstone, siltstone Shallow marine and paralic. Conformable on Allaru Mudstone. 144 m and mudstone, lesser mud-clast intraformational