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| | | Bitter Springs Group (P_-BS-xk-s) | PW Haines and HJ Allen | | | Legend narrative | Dolomite, stromatolitic dolomite, siltstone, and sandstone; evaporites in subsurface | | | | | | GSWA status | Formal | Rank | | Parent unit | _Top Of Litho-Stratigraphic Order | Child units | | Tectonic units | |
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| | | Summary | The Bitter Springs Group, previously 'Bitter Springs Formation' before 2015, is widespread throughout the Amadeus Basin. The group comprises the Gillen, Loves Creek and Johnnys Creek Formations in ascending order. It is dominated by carbonates (principally dolomite and stromatolitic dolomite, with local dolomitic limestone), fine-grained siliciclastic rocks and evaporites. Mafic volcanics form a minor local component in the upper part of the group in the Northern Territory. Such rocks are inferred to extend into Western Australia in the subsurface where they are mapped as an informal basalt member of Johnnys Creek Formation (P_-BSj-bb) based only on aeromagnetic evidence. Evaporites in the lower part of the group (Gillen Formation), principally halite, are very important for the structural evolution of the basin. Although the Bitter Springs Group is inferred to be widespread under thin sand cover in Western Australia, outcrop is sparse in this part of the basin. Most outcrops in Western Australia comprise carbonate or silicified carbonate, with more recessive lithologies rarely exposed. In many areas, any outcrop is largely covered by calcrete. Without exposure of recessive lithologies, or the discovery of formation-specific stromatolites, it is difficult to distinguish individual formations, therefore the group generally remains undifferentiated in Western Australia. In areas where assumed equivalents of the group are metamorphosed, they are mapped as informal metamorphic unit (P_-BS-mlp). Such outcrops are dominated by sheared and tightly folded phyllite and schist, probably representing metamorphosed siltstones and shale low in the group (Gillen Formation?). This unit is equivalent to Pinyinna beds in the Northern Territory. There are no direct radiometric dates on the Bitter Springs Group in Western Australia. Age constraints from elsewhere indicate a Tonian age in the range of 900–720 Ma, and the group belongs to Supersequence 1 of the Centralian Superbasin. | | | Distribution | The Bitter Springs Group is distributed throughout the entire Amadeus Basin (Wells et al., 1970; Edgoose, 2013). The best exposures are in the northeastern Amadeus Basin in the Northern Territory. In Western Australia, it is inferred to be widely distributed although often covered by surficial deposits. The best exposure is in the Bonython Range (eastern edge of MACDONALD 1:250 000 sheet), although in this outcrop the group is complexly folded due to salt tectonics. | | | Derivation of name/Formal lithostratigraphy | The name of the group is derived from Bitter Springs Gorge, about 64 km east-northeast of Alice Springs in the Northern Territory (Zone 53, MGA 446550E 7397550N). What is now the Bitter Springs Group was originally named 'Bitter Springs Limestone' by Joklik (1955), and revised to 'Bitter Springs Formation' by Ranford et al. (1965). Upgrading to group status was first proposed by Normington et al. (2015), and subsequently adopted basinwide. The type section, about 800 m thick, lies along the eastern bank of Ellery Creek, about 83 km west of Alice Springs in the Northern Territory (base approximately at Zone 53, MGA 303750E 7369050N). The group comprises the Gillen, Loves Creek and Johnnys Creek Formations in ascending order, although it generally remains undifferentiated in Western Australia due to poor exposure. | | | Lithology | The Bitter Springs Group is a thick succession of dolomite, stromatolitic dolomite, siltstone, and minor sandstone, with evaporites present in the lower part in the subsurface. In Western Australia, the Bitter Springs Group generally outcrops very poorly and is often largely covered by surficial calcrete, obscuring recessive lithologies. Thus most outcrops are restricted to dolomite, which may be partly or totally silicified. Some outcrops, such as those north of the Mu Hills and Sir Frederick Range, are composed mainly of dolomite breccia, perhaps generated through mobilization and dissolution of evaporites. The lithological character of the component formations is summarized below. These summaries rely heavily on information from better outcrops and drillcore in the Northern Territory, and individual formations are generally not differentiated in Western Australia.
Gillen Formation: The basal unit of the group is dominated by grey to buff-coloured dolomite in outcrop, with interbedded siltstone and minor fine-grained sandstone (mainly at the base). The dolomite may be locally stromatolitic and commonly displays chert laminae. Thick halite and sulfate evaporites have been intersected in the upper part of the formation in deep petroleum wells in the Northern Territory, although no halite has been observed in outcrop (Lindsay, 1987). Massive outcrops of gypsum occur locally in the Northern Territory, but have not been observed in Western Australia. Outcrops are often contorted and brecciated due to salt movement (halotectonics) and later dissolution. The stromatolite Tungussia erecta (Walter, 1972) is considered a diagnostic marker of the Gillen Formation, but in Western Australia has only been located in the Pollock Hills (southwest WEBB 1:250 000 sheet) (Allen et al., 2012).
Loves Creek Formation: The middle unit of the group is composed mainly of grey to buff and brown dolomite, locally varying to dolomitic limestone. The formation is characterized by an abundance and diversity of stromatolites of the Acaciella australica Assemblage (Allen et al., 2012; Grey et al., 2012; Haines and Allen, 2014). Stromatolites commonly form discrete bioherms. Silicification is common, and stromatolites may be partly replaced by chert. Chert also replaces nodules after sulfate evaporites. The carbonates are locally oolitic. Minor interbeds of siltstone are present, although poorly exposed. Most outcrops in Western Australia are poorly exposed and variably obscured by surficial calcrete.
Johnnys Creek Formation: Based on outcrops and drillcore in the Northern Territory, this upper formation of the group is characterized by red dolomitic siltstone, cyclically interbedded with units of grey dolomite and dolomitic limestone that may be chert bearing and locally stromatolitic. Fine-grained sandstone interbeds are present locally. Halite pseudomorphs are commonly present in the dolomitic siltstone. Black chert lenses in the carbonates may contain well-preserved microfossils (Schopf, 1968). Weathered mafic volcanic interbeds are a local and usually minor component in the northeastern part of the basin in the Northern Territory, with correlative mafic rocks inferred to extend into Western Australia under cover based on aeromagnetic data (informal sub-unit P_-BSj-bb).
An informal metamorphic unit (P_-BS-mlp) along the tectonized southern margin of the basin, is dominated by phyllite and schist that are commonly sheared and tightly folded. These rocks probably represent metamorphosed siltstones and shale low in the Bitter Springs Group (Gillen Formation?). | | | | Age code | Proterozoic | P_ | Stratigraphic code | BS | BS | Mixed rock type | mixed | x | | sedimentary carbonate | k | Rock type 2 | sedimentary siliciclastic | s | ROCK CODE | | P_-BS-xk-s |
| | | | | | Depositional environment | Depositional environment | Depositional environment | Depositional environment qualifier | - | shallow marine | inner shelf | - | lacustrine | playa |
| The Bitter Springs Group was initially deposited under shallow-marine, shelf conditions, and later non-marine lacustrine environments. Conditions were restricted during deposition of the Gillen Formation, allowing thick evaporites to accumulate. Evaporative lacustrine conditions (including playas) have been suggested for the Johnnys Creek Formation (Southgate, 1991), and supported by geochemical evidence (Hill et al., 2000). | | | | | | | | | | | Unit name | Unit code | Contact type | Contact relationship | Angas Hills Formation | | angular unconformity | | Bitter Springs Group | | gradational | | Kulail Sandstone | | thrust | is juxtaposed to P_-BS-xk-s | Paterson Formation | | angular unconformity | | Carnegie Formation | | unconformable | | Areyonga Formation | | angular unconformity | | Wallara Formation | | disconformable | | Heavitree Formation | | concordant | | Dean Quartzite | | concordant | | Mu Formation | | angular unconformity | | Larapinta Group | | angular unconformity | | Dean Quartzite | | concordant | | Ordovician sedimentary rocks, Amadeus Basin | | angular unconformity | | Amadeus Basin mafic unit | | unknown | is juxtaposed to P_-BS-xk-s |
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| The Bitter Springs Group overlies the Heavitree Formation along the northern margin of the basin, and the Dean Quartzite in the south. The contact is very poorly exposed in Western Australia, thus its nature in this area is uncertain, although it appears to be concordant. At one location on the RAWLINSON 1:250 000 sheet (PWHRAW000038, Zone 52, MGA 394547E 7253795N) the contact between the Dean Quartzite and a basal sandstone unit of informal Bitter Springs Group metamorphic unit (P_-BS-mlp) is concordant although very abrupt, and has the potential to be a disconformity, but this is not certain. In the Northern Territory, this contact is variably described as sharp or gradational in different areas, although once again is typically poorly exposed. The upper contact with the Wallara Formation is erosional based on drillcore evidence in the Northern Territory. In Western Australia, this contact is very poorly exposed, but at one location in the Boord Ridges (PWHBOO000100, Zone 52, MGA 466342E 7424978N) the base of the Wallara Formation is marked by a poorly exposed lithic sandstone with chert clasts probably eroded from the underlying Bitter Springs Group, suggesting a disconformable contact. Elsewhere in Western Australia, the Bitter Springs Group is overlain by significantly younger units such as Carnegie and Mu Formations, and Ordovician sedimentary rocks, with the contact varying from disconformable to a pronounced angular unconformity. The Bitter Springs Group is also unconformably overlain by the Paterson Formation of the onlapping Canning Basin. | | | | | | Geochronology | | | P_-BS-xk-s | Maximum age | Minimum age | Age (Ma) | 900 | 720 | Age | Tonian | Tonian | Age data type | Inferred | Biostratigraphic | References | | Wyborn et al. (1998) | Kositcin et al. (2015) |
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| The age of the base of the Bitter Springs Group is not well constrained. However, it is younger than the underlying Heavitree Formation, which is in turn younger than the Central Desert Dolerite that has yielded dates of 976 ± 3 Ma (zircon) and 972 ± 8 Ma (baddeleyite) (Wyborn et al., 1998). A detrital zircon sample from a sandstone unit within the Gillen Formation at the base of the group in the northeastern Amadeus Basin (Northern Territory) gave a maximum depositional age of 896 ± 12 Ma (2σ), based on the youngest date (Kositcin et al., 2015). The global Bitter Springs Anomaly (negative δ¹³C isotope anomaly), which in the Amadeus Basin is encompassed by the Loves Creek Formation, is constrained to approximately 810–790 Ma based on dating overseas, although the anomaly boundaries may have some local paleoenvironmental controls (Klaebe et al., 2017, and references therein). The age of the top of the Bitter Springs Group is not well constrained, although the group is considered to be entirely Tonian on biostratigraphic grounds, thus a minimum age of c. 720 Ma is applied. In summary, the group is given a broad Tonian age of approximately 900–720 Ma. | Blank Line | | | | | | Child units | Unit name | Unit code | Age (Ma) | Rank | GSWA status | Bitter Springs Group | | 900–720 | Formation | Informal | Johnnys Creek Formation | | 800–720 | Formation | Formal | Loves Creek Formation | | 810–790 | Formation | Formal | Gillen Formation | | 900–800 | Formation | Formal | Bitter Springs Group | | 900–720 | Formation | Informal |
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| | References | Allen, H-J, Grey, K and Haines, PW 2012, Neoproterozoic stromatolite biostratigraphy in the western Amadeus Basin, in Symposium proceedings edited by Ambrose, GJ and Scott, J: Central Australian Basins Symposium III, Alice Springs, Northern Territory, 16–17 July 2012: Petroleum Exploration Society of Australia. | Edgoose, CJ 2013, Ngalia Basin, in Geology and mineral resources of the Northern Territory edited by Munson, TJ, Johnston, KJ and Fuller, MH: Northern Territory Geological Survey, Darwin, Special Publication 5, p. 24:1–24:24. | Grey, K, Allen, H-J, Hill, A and Haines, PW 2012, Neoproterozoic biostratigraphy of the Amadeus Basin, in Symposium proceedings edited by Ambrose, GJ and Scott, J: Central Australian Basins Symposium III, Alice Springs, Northern Territory, 16–17 July 2012: Petroleum Exploration Society of Australia. | Haines, PW and Allen, HJ 2014, Geology of the Boord Ridges and Gordon Hills: Key stratigraphic section in the western Amadeus Basin, Western Australia: Geological Survey of Western Australia, Record 2014/11, 21p. View Reference | Hill, AC, Arouri, K, Gorjan, P and Walter, MR 2000, Geochemistry of marine and non-marine environments of a Neoproterozoic cratonic carbonate/evaporite: The Bitter Springs Formation, Central Australia, in Carbonate sedimentation and diagenesis in the evolving Precambrian world edited by Grotzinger, JP and James, N, SEPM Special Publication 67, p. 327–344. | Joklik, GF 1955, The geology and mica-fields of the Harts Range, central Australia: Bureau of Mineral Resources, Geology and Geophysics, Bulletin 26, 226p. | Klaebe, RM, Kennedy, MJ, Jarrett, AJM and Brocks, JJ 2017, Local paleoenvironmental controls on the carbon-isotope record defining the Bitter Springs Anomaly: Geobiology, v. 15, p. 65–80, doi:10.1111/gbi.12217. | Kositcin, N, Normington, V and Edgoose, CJ 2015, Summary of results. Joint NTGS-GA geochronology project: Amadeus Basin, July 2013-June 2014: Northern Territory Geological Survey, Record 2015–001, 56p. | Lindsay, JF 1987, Upper Proterozoic evaporites in the Amadeus basin, central Australia, and their role in basin tectonics: Geological Society of America Bulletin, v. 99, no. 6, p. 852–865. | Normington, VJ, Donnellan, N and Edgoose, C 2015, Neoproterozoic evolution of the Amadeus Basin: evidence from sediment provenance and mafic magmatism, in Annual geoscience exploration seminar (AGES) 2015. record of abstracts edited by MacDonald, GC: AGES 2015, Alice Springs, Northern Territory, Australia, 17–18 March 2015: Northern Territory Geological Survey; NTGS Record 2015-002, p. 73–78. | Ranford, LC, Cook, PJ and Wells, AT 1965, The geology of the central part of the Amadeus Basin, Northern Territory: Bureau of Mineral Resources, Geology and Geophysics, Report 86, 48p. | Schopf, JW 1968, Microflora of the Bitter Springs Formation, late Precambrian, central Australia: Journal of Paleontology, v. 42, no. 3, p. 651–688. | Southgate, PN 1991, A sedimentological model for the Loves Creek Member of the Bitter Springs Formation, northern Amadeus Basin, in Geological and geophysical studies in the Amadeus Basin, central Australia edited by Korsch, RJ and Kennard, JM: Bureau of Mineral Resources, Geology and Geophysics, Bulletin 236, p. 113–126. | Walter, MR 1972, Stromatolites and the biostratigraphy of the Australian Precambrian and Cambrian: The Palaeontological Association, London, U.K., Special Papers in Palaeontology 11, 190p. | Walter, MR, Veevers, JJ, Calver, CR and Grey, K 1995, Neoproterozoic stratigraphy of the Centralian Superbasin, Australia: Precambrian Research, v. 73, no. 1–4, p. 173–195, doi:10.1016/0301-9268(94)00077-5. | Wells, AT, Forman, DJ, Ranford, LC and Cook, PJ 1970, Geology of the Amadeus Basin, central Australia: Bureau of Mineral Resources, Geology and Geophysics, Bulletin 100, 222p. | Wyborn, LAI, Hazell, M, Page, R, Idnurm, M and Sun, S-S 1998, A newly discovered major Proterozoic granite-alteration system in the Mount Webb region, central Australia, and implications for Cu-Au mineralisation: Australian Geological Survey Organisation, Research Newsletter 28, 7p. |
| | | Recommended reference for this publication | Haines, PW and Allen, HJ 2019, Bitter Springs Group (P_-BS-xk-s): Geological Survey of Western Australia, WA Geology Online, Explanatory Notes extract, viewed 18 October 2025. <www.dmp.wa.gov.au/ens> | | | This page was last modified on 12 April 2019. | | | | | Grid references in this publication refer to the Geocentric Datum of Australia 1994 (GDA94). Locations mentioned in the text are referenced using Map Grid Australia (MGA) coordinates, Zones 49 to 52. All locations are quoted to at least the nearest 100 m. Capitalized names in text refer to standard 1:100 000 map sheets, unless otherwise indicated. WAROX is GSWA’s field observation and sample database. WAROX site IDs have the format ‘ABCXXXnnnnnnSS’, where ABC = geologist username, XXX = project or map code, nnnnnn = 6 digit site number, and SS = optional alphabetic suffix (maximum 2 characters). All isotopic dates are based on U–Pb analysis of zircon and quoted with 95% uncertainties, unless stated otherwise. U–Pb measurements of GSWA samples were conducted using a sensitive high-resolution ion microprobe (SHRIMP) in the John de Laeter Centre at Curtin University, Perth, Western Australia. Digital data related to WA Geology Online, including geochronology and digital geology, are available online at the Department’s Data and Software Centre and may be viewed in map context at GeoVIEW.WA. | | | Further details of geological publications and maps produced by the Geological Survey of Western Australia are available from: Information Centre Department of Mines, Industry Regulation and Safety 100 Plain Street EAST PERTH, WA 6004 Telephone: +61 8 9222 3459 Facsimile: +61 8 9222 3444 |
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