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{{Short description|Geological and geophysical feature in Western Australia}}
{{For|the French Navy officer|Jacques Bedout}}
{{Use Australian English|date=May 2024}}
{{Infobox terrestrial impact site
| name = Bedout
| other_name = 
| photo = 
| photo_size = 
| photo_alt = 
| photo_caption = 
| map = Western Australia
| map_alt = 
| map_caption = Location of Bedout offshore Western Australia
| map_size = 
| location = [[Canning Basin]]
| label =
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| coordinates = {{coord|18|S|119|E|region:AU-WA_type:landmark_scale:10000000|display=inline,title}}
| coordinates_ref = 
| confidence = Possible
| diameter = {{convert|30|km|mi|abbr=on}}
| depth = 
| rise =
| imp_size =
| age = 250.1 ± 4.5 Ma<br>[[Permian-Triassic boundary]]
| exposed = No
| drilled = Yes
| bolide = 
| translation =
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| access = 
| country = {{AUS}}
| state = [[Indian Ocean]]
| province =
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| municipality = 
}}
'''Bedout''' {{IPAc-en|b|ᵻ|ˈ|d|uː}}, or more specifically the '''Bedout High''', is a [[geological]] and [[geophysical]] feature centered about {{convert|250|km|abbr=in}} off the northwestern coast of [[Australia]] in the [[Canning Basin|Canning]] and overlying [[Roebuck Basin|Roebuck]] basins. Although not obvious from sea floor topography, it is a roughly circular area about {{convert|30|km|abbr=in|sigfig=1}} in diameter where older rocks have been uplifted as much as {{convert|4|km|abbr=in}} towards the surface and may mark the centre of a very large buried [[impact crater]] up to {{convert|250|km|abbr=in}} in diameter.<ref name="Gorter1996">Gorter J.D. 1996. Speculation on the origin of the Bedout high - a large, circular structure of pre-Mesozoic age in the offshore Canning Basin, Western Australia. PESA News, October/November 1996, p. 32-34.</ref> The Bedout High was penetrated by two petroleum exploration wells (Bedout-1, Lagrange-1) in the 1970s and 1980s.  It is named after nearby [[Bedout Island]].

== Impact hypothesis ==
In 1996 Australian [[geologist]] John Gorter first suggested that the Bedout High might mark the centre of a very large buried impact crater up to {{convert|250|km|abbr=in}} in diameter, based mainly on its internal geological structure as revealed on a single [[Reflection seismology|seismic]] survey line, and suggested that it may be of near end [[Permian]] age, based on the reported age of volcanic rocks in Lagrange-1.<ref name="Gorter1996" /><ref name="Gorter1998">Gorter J.D. 1998. The petroleum potential of Australian Phanerozoic impact structures. The APPEA Journal 38, 159-187.</ref> The impact hypothesis was developed further by Luanne Becker ([[University of California]]) and coworkers who claimed to have confirmed that the supposed volcanic rocks in the petroleum wells are actually impact melt [[breccia]] showing evidence of [[shock metamorphism]], and re-dated these rocks at 250.1 ± 4.5 [[Annum|Ma]].<ref name="Becker2004">Becker L., Poreda R.J., Basu A.R., Pope K.O., Harrison T.M., Nicholson C. & Iasky R. 2004. Bedout: A possible end-Permian impact crater offshore of northwestern Australia. Science 304, 1469-1476. [http://www.sciencemag.org/cgi/content/abstract/1093925 Abstract]</ref> The new age is essentially coincident with the [[Permian]]–[[Triassic]] boundary and associated [[Permian-Triassic extinction event|extinction event]], and Becker speculates that there is a likely connection. It was subsequently reported, based on very limited preliminary data, that the impact hypothesis is further supported by [[chromium]] [[isotope]] evidence for the presence of extraterrestrial material.<ref name="Becker2006">Becker L., Shukolyukov A., Macassic C., Lugmair G. & Poreda R. 2006. Extraterrestrial Chromium at the Graphite Peak P/Tr boundary and in the Bedout Impact Melt Breccia. Lunar and Planetary Science XXXVII (2006), abstract # 2321.[http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2321.pdf PDF]</ref>

== Rebuttals to the impact hypothesis ==
The Bedout impact hypothesis has not been widely supported by impact cratering specialists. Specific counter claims include:
# The alleged impact melt breccia actually has the characteristics of a volcanic [[basalt]], in part altered by contact with sea water and [[metamorphism]] due to its deep burial, and the evidence for shock metamorphism is likely mistaken.<ref name="Glikson2004a">Glikson A. 2004. Comment on ‘‘Bedout: A possible end-Permian impact crater offshore of northwestern Australia’’. Science 306, 613b.[http://www.sciencemag.org/cgi/reprint/306/5696/613b.pdf PDF]</ref><ref name="Glikson2004b">Glikson A. 2004. Bedout basement rise, offshore northwestern Australia: evidence of an unshocked mafic volcanic hyaloclastite volcanic breccia. Eos Trans. AGU, 85(47), Fall Meet. Suppl., Abstract B33C-0269.
[http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm04&database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Ffm04%2Ffm04&maxhits=200&=B33C-0269  Abstract] {{Webarchive|url=https://web.archive.org/web/20070927192927/http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm04&database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Ffm04%2Ffm04&maxhits=200&=B33C-0269 |date=2007-09-27 }}</ref>
# A crater of the purported size would have produced a widespread layer of ejecta, but no such eject is evident at the nearest Permian-Triassic boundary sites in Australia.<ref name="Wignall2004">Wignall P., Thomas B., Willink R., Watling J., Becker L., Poreda R.J. & Pope K.O. 2004. Is Bedout an impact crater? Take 1. Science 306, 609-610.</ref>  
# The presented evidence for impact fails to meet established standards, and the dating methodology is flawed.<ref name="Renne2004">Renne P.R., Melosh H.J., Farley K.A., Reimold W.U., Koeberl C., Rampino M.R., Kelley S.P., Ivanov B.A., Becker L., Poreda R.J., Basu A.R., Pope K.O., Harrison T.M., Nicholson C. & Iasky R. 2004. Is Bedout an impact crater? Take 2. Science 306, 610-612.</ref>
# A detailed re-evaluation of the geophysical data indicates that the evidence is not consistent with the expected properties of a giant impact crater, but rather the Bedout High was likely the result of episodes of continental rifting.<ref name="Muller2005">Müller R.D., Goncharov A. & Kristi A. 2005. Geophysical evaluation of the enigmatic Bedout basement high, offshore northwest Australia. Earth and Planetary Science Letters 237, 265-284.</ref>

== See also ==
{{portal|Geology}}
* [[List of possible impact structures on Earth]]

== References ==
{{reflist}}

== External links ==
* [http://records.viu.ca/~earles/bedout-jun04.htm Stephen Earle, "Double jeopardy at the end of the Permian - new evidence for a large impact"] {{Webarchive|url=https://web.archive.org/web/20160303231658/http://records.viu.ca/~earles/bedout-jun04.htm |date=2016-03-03 }}

[[Category:Possible impact craters on Earth]]
[[Category:Impact craters of Western Australia]]
[[Category:Permian impact craters]]
[[Category:Triassic impact craters]]
[[Category:Permian Australia]]
[[Category:Triassic Australia]]
[[Category:Geography of the Indian Ocean]]
[[Category:Permian–Triassic extinction event]]