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| | | | | | | | | | | | | | | | | | | | | | | | Department of Mines, Industry Regulation and Safety |
| | | | Geological Survey of Western Australia |
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| | | | DMcB Martin | | | | | Type | Basin | Lithology | sedimentary rocks | Parent unit | | Child units | No child units | Constituent lithostratigraphic units | | Affected by events | | Tectonic setting | |
| | | Summary | Recent subdivision of the ‘Wyloo Group’, as originally defined, into the Shingle Creek Group (upper Turee Creek Basin), Wooly Formation and a revised Wyloo Group (Ashburton Formation), has led to the recognition of the Wooly Basin. The Wooly Basin is a c. 2031–2008 Ma failed rift that has been identified on the basis of a wider regional distribution of the Wooly Formation than originally identified, and the recognition of a post-Ophthalmian, normal-fault network along the southern and western margins of the Hamersley province that appears to control thickness trends. | | | Distribution | The Wooly Basin is present along the southern and western margins of the Hamersley province on PANNAWONICA, MOUNT STUART, HARDEY, ROCKLEA, ASHBURTON and PARABURDOO (Krapež et al., 2015). This distribution is also strongly controlled by a recently recognized normal fault network along the southern and western margins of the Hamersley province that post-dates the Ophthalmia Orogeny (Dalstra, 2005, 2014; Martin, 2020), and by post-Wooly Formation, open upright folds that predate the unconformity at the base of the Mount McGrath Formation. | | | Description | The Wooly Basin contains the recently revised Wooly Formation (Martin, 2020) whose wide regional extent was first identified by Krapež et al. (2015). Present-day outcrop and thickness distributions of the Wooly Formation appear to be controlled by an extensive network of moderate to steep, southwesterly and northeasterly dipping, curvilinear normal faults, with throws of several hundreds to thousands of metres (Dalstra, 2005, 2014). These faults are locally intruded by c. 2008 Ma Panhandle Dolerite dykes, further indicating that they are probably related to formation of the Wooly Basin. Five depositional sequences have been recognized in the Wooly Formation by Krapež et al. (2015), although they differ in their tectonic interpretation in assigning this formation to the top of their Horseshoe Basin, which also includes the Shingle Creek Group. The difference in age between the base of the Wooly Basin and the top of the Turee Creek Basin implies a hiatus of about 172 Ma, so Wooly Basin extension cannot be the consequence of orogenic collapse of the Ophthalmia Orogeny. Folding of the Wooly Formation is parallel to the controlling normal faults, and must be younger than c. 2031 Ma, making it possible that this deformation may be due to reactivation and inversion of these faults during the 2002–1947 Ma Glenburgh Orogeny. | | | | | | Geochronology | | | Wooly Basin | Maximum age | Minimum age | Age (Ma) | 2031 | 2008 | Age | Paleoproterozoic | Paleoproterozoic |
| The Wooly Basin is younger than the 2031 ± 6 Ma maximum depositional age obtained from a pumice-bearing tuffaceous siltstone near the base of the formation, and older than the c. 2008 Ma Panhandle Dolerite dykes (Müller et al., 2005). However, nowhere do these dykes intrude the Wooly Formation (Martin, 2020), but they do intrude normal faults that appear to control its distribution. | | | | | | | Contact relationships | | | | Tectonic unit name | Unit code | Contact type | Contact relationship | | AS | angular unconformity | overlies WY | | TK | unconformable | underlies WY |
| The Wooly Basin unconformably overlies the Turee Creek Basin and is, in turn, unconformably overlain by the Ashburton Basin, especially in the vicinity of DMMHAM001041. | | | Tectonic setting | The close association with normal faults, and preservation within narrow fault-bound blocks, combined with the absence of extensive volcanic rocks and lack of evidence for a thermal subsidence phase, suggests that the Wooly Basin is a failed rift on the southern margin of the Pilbara Craton that post-dated accretion of the Glenburgh Terrane during the Ophthalmia Orogeny by about 172 Ma. The tectonic driver for this extension has not been identified, and the basin is interpreted to have been later inverted during the Glenburgh Orogeny, and then reactivated by strike-slip deformation during the latter stages of the Capricorn Orogeny. | BookMark | | | | | Constituent lithostratigraphic units | | | Unit name | Unit code | Rank | GSWA status | | | Formation | Formal |
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| | | | | | References | Dalstra, HJ 2005, Structural controls of bedded iron ore in the Hamersley Province, Western Australia — An example from the Paraburdoo Ranges, in Iron Ore 2005, Fremantle, 19–21 September: Australian Institute of Mining and Metallurgy; Conference proceedings vol. 8, p. 49–55. | Dalstra, HJ 2014, Structural evolution of the Mount Wall region in the Hamersley province, Western Australia and its control on hydrothermal alteration and formation of high-grade iron deposits: Journal of Structural Geology, v. 67, p. 268–292, doi:10.1016/j.jsg.2014.03.005. | Krapež, B, Müller, SG and Bekker, A 2015, Stratigraphy of the Late Palaeoproterozoic (~2.03 Ga) Wooly Dolomite, Ashburton Province, Western Australia: A carbonate platform developed in a failed rift basin: Precambrian Research, v. 271, p. 1–19, doi:10.1016/j.precamres.2015.09.022. | Martin, DMcB 2020, Geology of the Hardey Syncline — The key to understanding the northern margin of the Capricorn Orogen: Geological Survey of Western Australia, Report 203, 62p. View Reference | Müller, SG, Krapež, B, Barley, ME and Fletcher, IR 2005, Giant iron-ore deposits of the Hamersley province related to the breakup of Paleoproterozoic Australia: new insights from in situ SHRIMP dating of baddeleyite from mafic intrusions: Geology, v. 33, no. 7, p. 577–580, 4p., doi:10.1130/G21482.1. |
| | | | Recommended reference for this publication | Martin, DMcB 2022, Wooly Basin (WY): 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 20 September 2022. | | | | | 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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