Regions of western australia nine plus perth

Woodleigh is a large

meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the ...

impact crater An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters ...

(astrobleme) in

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

, centred on Woodleigh Station east of

Shark Bay Shark Bay (Malgana: ''Gathaagudu'', "two waters") is a World Heritage Site in the Gascoyne region of Western Australia. The http://www.environment.gov.au/heritage/places/world/shark-bay area is located approximately north of Perth, on the ...

Gascoyne The Gascoyne region is one of the nine administrative 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 Gasc ...

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. Th ...

and the

Australian National University The Australian National University (ANU) is a public research university located in Canberra, the capital of Australia. Its main campus in Acton encompasses seven teaching and research colleges, in addition to several national academies and ...

, led by Arthur J. Mory, announced the discovery in the 15 April 2000 issue of ''Earth and Planetary Science Letters''.Abstract
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Description

The crater 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 120 km, if correct, would make this crater 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 crater-forming body, or to one that explodes in the atmosphere. It can be a ...

(asteroid or comet) about in diameter.PDF
A more recent study in 2010 suggests the crater 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 rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of di ...

, 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 Reidite is a rare polymorph of ZrSiO4 created when zircon experiences high pressure and temperature. Reidite is denser than zircon and has the same crystal structure as scheelite. All natural occurrences of reidite are associated with meteorite i ...

in a drillcore sample from the central uplift zone, supports the interpretation of the crater as being over 100 km 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 physical consequences and have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or me ...

, originally thought in the early 2000s to have occurred between 259 Ma to 201 Ma (or between the

Late Permian Late may refer to: * LATE, an acronym which could stand for: ** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia ** Local-authority trading enterprise, a New Zealand business law ** Local average treatment effect, ...

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 ...

) is now thought to date from 364 ± 8 million years (Late

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

). This time corresponds approximately to the

Late Devonian extinction The Late Devonian extinction consisted of several extinction events in the Late Devonian Epoch, which collectively represent one of the five largest mass extinction events in the history of life on Earth. The term primarily refers to a major exti ...

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 The East Warburton Basin in South Australia is the site of a hypothesised large impact crater of the Carboniferous period (around 360-300 million years ago). The subterranean structure lies buried at a depth of ~4 km, and measures a minimu ...

, so if the extinction is related to impact, perhaps more than one crater was involved. Of the two dozen or more impact craters 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

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

Description

See also

References

External links