Woodleigh impact structure

The structure is not exposed at the surface and therefore its size is uncertain. The original discovery team stated in 2000 that it may be up to {{convert|120|km}} in diameter, but others argue it may be much smaller, with one 2003 study suggesting a diameter closer to {{convert|60|km}}.{{cite journal | doi=10.1111/j.1945-5100.2003.tb00301.x | vauthors=Reimold WU, Koeberl C, Hough RM, Mcdonald I, Bevan A, Amare K, French BM | title=Woodleigh impact structure, Australia: Shock petrography and geochemical studies | journal=Meteoritics & Planetary Science | volume=38 | issue= 7| year=2003 | pages=1109–1130 |bibcode = 2003M&PS...38.1109R | doi-access=free }} [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003M%26PS...38.1109R&db_key=AST&data_type=HTML&format=&high=44810356c609136 Abstract and full PDF] The larger estimate of {{convert|120|km}}, if correct, would make this impact structure tied for the fourth largest confirmed impact structure in the world, and imply a bolide (asteroid or comet) about {{convert|5|to|6|km}} in diameter.{{cite book | vauthors=Mory A, Iasky R | title=Woodleigh — Australia's largest impact structure? | journal=Fieldnotes, Geological Survey of Western Australia |isbn=978-0-7307-5642-2 | volume=16 | year=2000 | pages=1–2 }} [http://www.doir.wa.gov.au/documents/gswa/gsd_fld_woodleigh.pdf PDF] {{webarchive|url=https://web.archive.org/web/20060823134752/http://www.doir.wa.gov.au/documents/gswa/gsd_fld_woodleigh.pdf |date=23 August 2006 }} A more recent study in 2010 suggests the structure could be between {{convert|60|and|160|km}} or more, and was produced by a comet or asteroid {{convert|6|to|12|km}} wide.{{cite web |url=http://archive.cosmosmagazine.com/news/giant-impact-crater-found-south-australia/ |title=Giant crater may have been extinction trigger |author=Gareth Barton |date=27 October 2010 |publisher=Cosmos |access-date=15 August 2012 |url-status=dead |archive-url=https://web.archive.org/web/20161012144013/http://archive.cosmosmagazine.com/news/giant-impact-crater-found-south-australia/ |archive-date=12 October 2016}}

The central uplift, interpreted to be {{convert|20|km}} in diameter, was first intersected by drilling activities in the late 1970s; however its significance as an impact structure was only realised in 1997 during a gravity survey. In 1999, a new core sample was taken. The thin veins of melted glass, breccia, and shocked quartz found would have formed under pressures 100,000 times greater than atmospheric pressure at sea level, or between 10 and 100 times greater than those generated by volcanic or earthquake activity. Only a large impact could have generated such conditions. The reported discovery in 2018 of the extremely rare mineral reidite in a drillcore sample from the central uplift zone, supports the interpretation of the original crater as being over {{convert|100|km}} in diameter, and possibly the largest in Australia.[https://www.abc.net.au/news/2018-10-16/rare-mineral-reidite-found-in-woodleigh-meteorite-crater-in-wa/10382888 Discovery of reidite, one of the rarest minerals on Earth, may reveal Australia's biggest crater] ABC News, 16 October 2018. Retrieved 17 October 2018.

The Woodleigh impact event, originally thought in the early 2000s to have occurred between 259 Ma to 201 Ma (or between the Late Permian and Late Triassic) is now thought to date from 364{{nbsp}}±{{nbsp}}8 million years (Late Devonian).{{cite Earth Impact DB |name=Woodleigh |access-date=2017-10-09}} This time corresponds approximately to the Late Devonian extinction of about 370 million years ago. There is evidence for other large impact events at around the same time, such as the East Warburton Basin, so if the extinction is related to impact, perhaps more than one crater was involved.

Of the two dozen or more impact structures known in Australia, the three largest are Woodleigh, Acraman, and Tookoonooka. The Gnargoo structure, which has remarkable similarities to Woodleigh, is a nearby proposed impact crater on the Gascoyne platform.R. Iaskty and A. Glikson (2005). "Gnargoo: a possible 75 km-diameter post-Early Permian – pre-Cretaceous buried impact structure, Carnarvon Basin, Western Australia", Australian Journal of Earth Sciences, Vol 52, 2005

• Carnarvon Basin
• East Warburton Basin

{{reflist}}

• [http://www.dmp.wa.gov.au/Meteorite-impacts-craters-1642.aspx WA Geological Survey Meteorite Impacts in Western Australia]

{{Impact cratering on Earth}}

Category:Impact craters of Western Australia

Category:Carboniferous impact craters

Category:Devonian impact craters

Category:Carboniferous Australia

Category:Paleozoic Australia

Category:Shark Bay