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| | | | Geological Survey of Western Australia |
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| | | | HM Howard, RH Smithies, and R Quentin de Gromard | | | | | Type | Sub-basin | Lithology | sedimentary and volcanic rocks | Parent unit | | Child units | No child units | Constituent lithostratigraphic units | | Affected by events | | Tectonic setting | | basin: intracratonic basin |
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| | | Summary | The Talbot Sub-basin lies on the western side of the Musgrave Province, west of Jameson Community. It contains the most widely exposed and best-preserved bimodal volcanic sequences in the Musgrave region. These volcanic rocks belong to the widespread Bentley Supergroup that is divided into several groups. In the eastern part of the Talbot Sub-basin, the Mount Palgrave Group represents the preserved stratigraphic base of the sub-basin, and is overlain by mainly ignimbritic rocks of the Kaarnka Group. Outcrop of the Kaarnka Group is almost entirely restricted to a discrete north-northwesterly trending oval-shaped basin, up to 27 km wide and 46 km long. This basin is interpreted to define the extent of the Kaarnka caldera cluster. The Mount Palgrave and Kaarnka Groups are in turn overlain by the upper part of the Bentley Supergroup sequence, namely the Pussy Cat, Cassidy and Mission Groups, which form a south- to southwest-dipping, southwest-younging stratigraphy. | | | Distribution | The Talbot Sub-basin lies on the western side of the west Musgrave Province, west of Jameson Community, and extends west beyond Warburton Community and under the Gunbarrel Basin. To the north it overlies the older units (mostly preserved in the Blackstone Sub-basin) of the Bentley Supergroup and Musgrave Province. To the south it extends to the Townsend Ridges where it is overlain by the Officer Basin. | | | Description | The Talbot Sub-basin contains the largest exposure of rocks of the Bentley Supergroup. Daniels (1974) proposed two geographically restricted ‘associations’ of volcanic rocks — the Palgrave Volcanic Association in the east and the Scamp Volcanic Association in the north — and related these to two separate calderas. Our current stratigraphic interpretation does not recognize the Scamp caldera and requires modification of the extent of the postulated caldera in the Palgrave region. Rocks of the Palgrave Volcanic Association are now divided between two rhyolite-dominated groups: the effusive and ignimbritic rocks of the Mount Palgrave Group, representing the preserved stratigraphic base of the Talbot Sub-basin, and the overlying predominantly ignimbritic rocks of the Kaarnka Group. Outcrop of the Kaarnka Group is almost entirely restricted to a discrete north-northwesterly oval-shaped basin, up to 27 km wide and 46 km long. This basin is interpreted to define the extent of the Kaarnka caldera structure which likely comprises at least three separate calderas, forming the Kaarnka caldera cluster. Rocks of the Scamp Volcanic Association are all assigned to the Mount Palgrave Group, correlating units from both of the former associations into a single group with a preserved outcrop strike length of more than 200 km.
Depositional layering within the Mount Palgrave Group generally dips gently (≤30º) between south (in the northern part of the sub-basin) and west (in the eastern part of the sub-basin), but is locally steep (up to 85º) adjacent to the Barrow Range anticline and adjacent to the Winburn granite. Nowhere is the stratigraphy overturned. The thickest preserved section of the Mount Palgrave Group is in the northeastern Talbot Sub-basin, where up to 4500 m of volcanic sequence is preserved. In the southwestern Talbot Sub-basin, rocks of the Pussy Cat Group directly overlie the Mount Palgrave and Kaarnka Groups and are in turn overlain by rocks of the Cassidy Group. Both the Pussy Cat and Kaarnka Groups comprise bimodal volcanic rocks and less-common sedimentary units with gentle dips (≤30º) to the south and southwest, and form continuous packages that can be traced for more than 100 km along strike.
The Cassidy Group, in particular, comprises four major mafic–felsic volcanic cycles with a combined thickness of more than 3400 m. Both the size (extent and volume) and facies association of volcanic rocks within the Mount Palgrave, Kaarnka, and Cassidy Groups (i.e. the lower Talbot Sub-basin rocks) are unusual. Many of the felsic volcanic units of these stratigraphic groups have volumes that reflect supervolcano eruptions. Magma compositions are water-poor, but rich in F, alkalis, and FeO, reflecting very high eruptive temperatures (>900°C), as confirmed by Zr-saturation thermometry (Smithies et al., 2013). These high eruption temperatures are evident in outcrop from well-developed and continuous flow banding (in highly felsic rocks), including extensive evidence of rheomorphism, and high-temperature contact metamorphic assemblages in interflow sedimentary units. In terms of eruptive temperature, magma compositions, and volcanic textures, Miocene volcanic rocks in the central Snake River Plain area of northwestern North America provide a close analogue for the lower Talbot Sub-basin volcanic rocks.
The Mission Group conformably overlies the Cassidy Group and represents the youngest preserved stratigraphic interval of the Bentley Supergroup. It is subdivided into a sedimentary lower part (Gamminah Conglomerate, Frank Scott Formation and Lilian Formation), and an upper basalt-dominated part (Milesia Formation). No evidence of felsic volcanism has yet been found. The Mission Group is conformably to unconformably overlain by the Townsend Quartzite. Daniels (1974) reported a total thickness for the Mission Group of about 4000 m.
The combined maximum stratigraphic thickness of units in the Talbot Sub-basin is estimated to be about 18.6 km, although this is never reached in any given region. Of this 18.6 km, basaltic magmas represent about 3.7 km, and felsic magmas about 9 km, giving a total preserved maximum thickness of igneous stratigraphy of approximately 12.7 km. | | | | | | Geochronology | | | Talbot Sub-basin | Maximum age | Minimum age | Age (Ma) | 1085 | 1030 | Age | Mesoproterozoic | Mesoproterozoic |
| A crystallization age of 1077 ± 6 Ma (GSWA 174662, Kirkland et al., 2010) was obtained from a weakly to moderately foliated granitic unit of the Winburn granite pluton. However, it is recognized that this pluton includes both pre- and synvolcanic granitic intrusions. Several samples of the Mount Palgrave Group have given dates also interpreted as igneous crystallization ages. These include: 1070 ± 6 Ma (GSWA 194800; Kirkland et al., 2012a), 1069 ± 6 Ma (GSWA 195116; Kirkland et al., 2014c) and 1068 ± 6 Ma (GSWA 195114; Kirkland et al., 2014a) from the Eliza Formation; 1070 ± 10 Ma (GSWA 195115; Kirkland et al., 2014b) and 1064 ± 5 Ma (GSWA 195678; Kirkland et al., 2014e) from the Scamp Formation; and 1065 ± 9 Ma (GSWA 195230; Kirkland et al., 2014d) from the Mount Waugh Formation.
The depositional or eruption age of the Kaarnka Group has been broadly constrained between 1064 ± 7 Ma (GSWA 194637; Kirkland et al., 2011a), for a porphyritic intrusion that cuts the lower part of the stratigraphy, and 1052 ± 5 Ma (GSWA 185415; Kirkland et al., 2013), for a volcaniclastic unit near the stratigraphic top of the group.
The basal contact of the Pussy Cat Group is a conformable, though locally faulted, contact with the Mount Waugh Formation at the top of the Mount Palgrave Group. Thus, a date of 1065 ± 9 Ma (GSWA 195230; Kirkland et al., 2014d) obtained directly from a sample of the Mount Waugh Formation possibly represents the maximum age constraint on the deposition of rocks of the Pussy Cat Group. The upper contact of the Pussy Cat Group with the overlying Wururu Rhyolite of the Cassidy Group is conformable. A date of 1065 ± 5 Ma (GSWA 174690, Kirkland et al., 2011b) obtained directly from a sample of the Wururu Rhyolite possibly represents the minimum age constraint on the deposition of rocks of the Pussy Cat Group. The Kathleen Ignimbrite has locally peperitic contacts with volcaniclastic sedimentary rocks of the Pussy Cat Group, indicating that the entire depositional sequence was essentially synchronous. However, although a 1062 ± 8 Ma date (GSWA 195001, Medlin et al., 2014a) obtained from feldspar-phyric rhyolite underlying the Kathleen Ignimbrite is consistent with the minimum and maximum age bracket of the Pussy Cat Group, older dates from the ignimbrite (1071 ± 5 Ma, GSWA 195723, Kirkland et al., 2011c) and from feldspar-phyric rhyolite that overlies it (1076 ± 5 Ma, GSWA 195031, Medlin et al., 2014b; 1078 ± 5 Ma, GSWA 195058, Medlin et al., 2014c) are at the older extreme of, or exceed, that age bracket. This highlights a problem common to dating of all igneous rocks of the Talbot Sub-basin: all felsic igneous rocks of the Talbot Sub-basin may include a large proportion of recycled cognate material (i.e. zircon antecrysts). The unavoidable inclusion of these in dated zircon samples means that all previously interpreted crystallization ages have likely been variably overestimated (i.e. true ages of volcanic deposition or intrusive crystallization could be younger). Dating of individual zircons interpreted to be antecrysts indicates a maximum possible range from 1116 ± 28 to 1010 ± 20 Ma. Smithies et al. (2013) suggested that the most conservative age range for magmatic activity within the Talbot Sub-basin is probably c. 1077 to 1047 Ma. However, the interpreted presence of the 1085–1075 Ma Kunmarnara Group at the base of this succession to the north, provides a more realistic maximum age for the Talbot Sub-basin of c. 1085 Ma.
Ages from the Cassidy Group include 1065 ± 5 Ma for the Wururu Rhyolite at Mount Weir (GSWA 174690, Kirkland et al., 2011b), and 1057 ± 6 Ma for the Thomas Rhyolite at Day Hill (GSWA 174691, Kirkland et al., 2012b).
Constraints on the minimum depositional age of the Mission Group are from the 825–800 Ma depositional age for the Bitter Springs Formation (Maidment et al., 2007), which overlies sedimentary units in the Amadeus Basin that are equivalent of the Townsend Quartzite in the Officer Basin. However, the youngest crystallization age for rocks belonging to the Warakurna Supersuite (which includes all magmatic rocks of the Bentley Supergroup) is c. 1030 Ma (e.g. Quentin de Gromard et al., 2017) and this is likely a realistic minimum age for deposition of the Mission Group. | | | | No contact relationship narrative found. | | | Tectonic setting | Rocks of the Talbot Sub-basin and Blackstone Sub-basin, and the Tjauwata Group (which together make up the larger Bentley Basin), form part of the Bentley Supergroup which were deposited within the Mesoproterozoic Ngaanyatjarra Rift in central Australia. This long-lived, but failed, intracontinental rift (Evins et al., 2010) is the main crustal expression of the Giles Event that was responsible for producing almost 50 Ma of continued magmatism in the west Musgrave region. The Giles Event does not, therefore, reflect a simple single event, rather a protracted and complex geodynamic setting. The event included the c. 1075 Ma Warakurna Large Igneous Province (LIP), the associated granites of which have volcanic equivalents in the Smoke Hill Volcanics, and emplacement of the regional Alcurra Dolerite dyke swarm and its volcanic equivalent in the Hogarth Formation (Blackstone Sub-basin).
The long duration of mantle-derived mafic and felsic magmatism included the development of a silicic LIP over a period of >30 Ma, formed by a series of large rhyolite eruptions, including some of supervolcano size, interleaved with regional tholeiitic basalt flows. These formed the Talbot Sub-basin, the most extensive volcanic succession of the Bentley Basin. | BookMark | | | | | Constituent lithostratigraphic units | | | Unit name | Unit code | Rank | GSWA status | | | Formation | Informal | | | Formation | Informal | | | Group | Formal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Formation | Formal | | | Member | Informal | | | Formation | Formal | | | Formation | Formal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Formation | Formal | | | Formation | Formal | | | Formation | Formal | | | Formation | Formal | | | Member | Informal | | | Formation | Informal | | | Formation | Informal | | | Formation | Informal | | | Formation | Informal | | | Formation | Informal | | | Formation | Informal | | | Formation | Informal | | | Formation | Informal | | | Formation | Informal | | | Formation | Informal | | | Formation | Informal | | | Group | Formal | | | Formation | Informal | | | Formation | Informal | | | Formation | Informal | | | Formation | Informal | | | Formation | Formal | | | Formation | Formal | | | Member | Informal | | | Member | Informal | | | Formation | Formal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Formation | Formal | | | Member | Informal | | | Member | Informal | | | Formation | Formal | | | Member | Informal | | | Group | Formal | | | Group | Formal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Formation | Formal | | | Member | Informal | | | Formation | Informal | | | Formation | Informal | | | Formation | Informal | | | Formation | Informal | | | Formation | Informal | | | Group | Formal | | | Formation | Informal | | | Formation | Formal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Formation | Formal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Member | Informal | | | Formation | Formal | | | Formation | Formal |
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| | | | | | References | Daniels, JL 1974, The geology of the Blackstone region, Western Australia: Geological Survey of Western Australia, Bulletin 123, 257p. View Reference | Evins, PM, Smithies, RH, Howard, HM, Kirkland, CL, Wingate, MTD and Bodorkos, S 2010, Redefining the Giles Event within the setting of the 1120-1020 Ma Ngaanyatjarra Rift, west Musgrave Province, central Australia: Geological Survey of Western Australia, Record 2010/6, 36p. View Reference | Kirkland, CL, Wingate, MTD and Howard, HM 2010, 174662.1: granophyre, Eliza Rocks; Geochronology Record 909: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD and Howard, HM 2013, 185415.1: dacite, Mount Palgrave; Geochronology Record 1127: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD, Howard, HM and Smithies, RH 2012a, 194800.1: rhyolite, Mount Grace; Geochronology Record 1144: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD, Howard, HM, Smithies, RH and Werner, M 2011b, 174690.1: rhyolite, Mount Weir; Geochronology Record 995: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD, Howard, HM, Smithies, RH and Werner, M 2012b, 174691.1: rhyolite, Mount Weir; Geochronology Record 1048: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD and Smithies, RH 2011a, 194637.1: feldspar-porphyritic microgranite, Windich Hill; Geochronology Record 963: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD, Smithies, RH, Howard, HM and Quentin de Gromard, R 2014a, 195114.1: dacite, Domeyer Hill; Geochronology Record 1176: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD, Smithies, RH, Howard, HM and Quentin de Gromard, R 2014b, 195115.1: felsic volcaniclastic rock, Bentley Hill; Geochronology Record 1177: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD, Smithies, RH, Howard, HM and Quentin de Gromard, R 2014c, 195116.1: dacite, Mount Squires; Geochronology Record 1178: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD, Smithies, RH, Howard, HM and Quentin de Gromard, R 2014d, 195230.1: rhyolite, Mount Elvire; Geochronology Record 1179: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD, Smithies, RH, Howard, HM and Quentin de Gromard, R 2014e, 195678.1: rhyolite, Mount Elvire; Geochronology Record 1201: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Kirkland, CL, Wingate, MTD and Werner, M 2011c, 195723.1: rhyolitic ignimbrite, Mount Glyde; Geochronology Record 939: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Maidment, DW, Williams, IS and Hand, M 2007, Testing long-term patterns of basin sedimentation by detrital zircon geochronology, Centralian Superbasin, Australia: Basin Research, v. 19, p. 335–360. | Medlin, CC, Kirkland, CL, Wingate, MTD and Smithies, RH 2014a, 195001.1: porphyrititc rhyolite, Mount Glyde; Geochronology Record 1163: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Medlin, CC, Kirkland, CL, Wingate, MTD and Smithies, RH 2014b, 195031.1: porphyritic rhyolite, Mount Glyde; Geochronology Record 1164: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Medlin, CC, Kirkland, CL, Wingate, MTD and Smithies, RH 2014c, 195058.1: porphyritic rhyolite, Mount Kathleen; Geochronology Record 1165: Geological Survey of Western Australia, <www.dmpe.wa.gov.au/geochron>. View Reference | Quentin de Gromard, R, Howard, HM, Smithies, RH, Wingate, MTD and Lu, Y 2017, The deep seismic reflection profile 11GA-YO1 in the west Musgrave Province: An updated view: Geological Survey of Western Australia, Record 2017/8, 20p. | Smithies, RH, Howard, HM, Kirkland, CL, Werner, M, Medlin, CC, Wingate, MTD and Cliff, JB 2013, Geochemical evolution of rhyolites of the Talbot Sub-basin and associated felsic units of the Warakurna Supersuite: Geological Survey of Western Australia, Report 118, 74p. |
| | | | Recommended reference for this publication | Howard, HM, Smithies, RH and Quentin de Gromard, R 2019, Talbot Sub-basin (PTBNT): Geological Survey of Western Australia, WA Geology Online, Explanatory Notes extract, viewed 05 August 2025. <www.dmp.wa.gov.au/ens> |
| | | This page was last modified on 14 June 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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