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Woodleigh is a large
/ref>
/ref> The larger estimate of , if correct, would make this impact structure tied for the fourth largest confirmed impact structure in the world, and imply a
A more recent study in 2010 suggests the structure could be between or more, and was produced by a comet or asteroid wide. The central uplift, interpreted to be 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,
WA Geological Survey Meteorite Impacts in Western Australia
{{Impact cratering on Earth Impact craters of Western Australia Carboniferous impact craters Devonian impact craters Carboniferous Australia Paleozoic Australia Shark Bay
Woodleigh is a large meteorite
A meteorite is a rock (geology), rock that originated in outer space and has fallen to the surface of a planet or Natural satellite, moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical ...
impact structure
An impact structure is a generally circular or craterlike geologic structure of deformed bedrock or sediment produced by impact on a planetary surface, whatever the stage of erosion of the structure. In contrast, an impact crater is the surface e ...
(astrobleme) in Western Australia
Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...
, centred on Woodleigh Station east of Shark Bay
Shark Bay () is a World Heritage Site in the Gascoyne region of Western Australia. The area is located approximately north of Perth, on the westernmost point of the Australian continent.
UNESCO's listing of Shark Bay as a World Heritage S ...
in the Gascoyne
The Gascoyne region is one of the nine regions of Western Australia. It is located in the northwest of Western Australia, and consists of the local government areas of Carnarvon, Exmouth, Shark Bay and Upper Gascoyne. The Gascoyne has about of ...
region. A team of four scientists at the Geological Survey of Western Australia
The Geological Survey of Western Australia is an authority within the Department of Mines and Petroleum of the Government of Western Australia that is responsible for surveying and exploration of Western Australia's geological resources.
The ...
and the Australian National University
The Australian National University (ANU) is a public university, public research university and member of the Group of Eight (Australian universities), Group of Eight, located in Canberra, the capital of Australia. Its main campus in Acton, A ...
, led by Arthur J. Mory, announced the discovery in the 15 April 2000 issue of ''Earth and Planetary Science Letters''.Abstract/ref>
Description
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 in diameter, but others argue it may be much smaller, with one 2003 study suggesting a diameter closer to .Abstract and full PDF/ref> The larger estimate of , if correct, would make this impact structure tied for the fourth largest confirmed impact structure in the world, and imply a
bolide
A bolide is normally taken to mean an exceptionally bright meteor, but the term is subject to more than one definition, according to context. It may refer to any large Impact crater, crater-forming body, or to one that explodes in the atmosphere. ...
(asteroid or comet) about in diameter.PDFA more recent study in 2010 suggests the structure could be between or more, and was produced by a comet or asteroid wide. The central uplift, interpreted to be 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
Breccia ( , ; ) is a rock composed of large angular broken fragments of minerals or Rock (geology), rocks cementation (geology), cemented together by a fine-grained matrix (geology), matrix.
The word has its origins in the Italian language ...
, and shocked quartz
Shocked quartz is a form of quartz that has a microscopic structure that is different from normal quartz. Under intense pressure (but limited temperature), the crystalline structure of quartz is deformed along planes inside the crystal. These pla ...
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 in diameter, and possibly the largest in Australia.
The Woodleigh impact event
An impact event is a collision between astronomical objects causing measurable effects. Impact events have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or meteoroids and have minimal effe ...
, originally thought in the early 2000s to have occurred between 259 Ma to 201 Ma (or between the Late Permian
Late or LATE may refer to:
Everyday usage
* Tardy, or late, not being on time
* Late (or the late) may refer to a person who is dead
Music
* ''Late'' (The 77s album), 2000
* Late (Alvin Batiste album), 1993
* Late!, a pseudonym used by Dave Groh ...
and Late Triassic
The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch a ...
) is now thought to date from 364±8 million years (Late Devonian
The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...
). This time corresponds approximately to the Late Devonian extinction
The Late Devonian mass extinction, also known as the Kellwasser event, was a mass extinction event which occurred around 372 million years ago, at the boundary between the Frasnian and Famennian ages of the Late Devonian period.Racki, 2005McGh ...
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
See also
*Carnarvon Basin
The Carnarvon Basin is a geological basin located in the north west of Western Australia which extends from the Dampier Archipelago to the Murchison bioregion, and is the main geological feature that makes up the North West Shelf. The onsho ...
* East Warburton Basin
References
External links
WA Geological Survey Meteorite Impacts in Western Australia
{{Impact cratering on Earth Impact craters of Western Australia Carboniferous impact craters Devonian impact craters Carboniferous Australia Paleozoic Australia Shark Bay