Editing Weaubleau structure (section)

{{Infobox terrestrial impact site
| name            = Weaubleau structure
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| photo           = Weaubleau Structure shaded relief.jpg
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| photo_caption   = The {{convert|12|mi|adj=on}} circular Weaubleau structure is discernible in the drainage patterns of this shaded-relief image.
| map             = United States#Missouri
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| confidence      = Probable
| diameter        = 
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| age             = 335 and 340 million years
| exposed         = 
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[[Image:Weaubleau Structure outline v2.svg|thumb|This diagram illustrates the large-scale structures interpreted in the shaded-relief image.]]

The '''Weaubleau structure''' is a probable [[meteorite]] [[Impact event|impact]] site in western [[Missouri]] near the towns of [[Gerster, Missouri|Gerster]], [[Iconium, Missouri|Iconium]], [[Osceola, Missouri|Osceola]], and [[Vista, Missouri|Vista]]. It is believed to have been caused by a {{convert|1200|ft|adj=on}} [[meteoroid]] between 335 and 340 million years ago<ref>Miller, J.F., Evans, K.R., Rovey, C.W., II, Ausich, W.L., Bolyard, S.E., Davis, G.H., Ethington, R.L., Sandberg, C.A., Thompson, T.L., and Waters, J.A., Mixed-age echinoderms, conodonts, and other fossils used to date a meteorite impact, and implications for missing strata in the type Osagean (Mississippian) in Missouri, USA. Echinoderm Paleobiology, 2008, 53p.</ref> during the middle [[Mississippian age|Mississippian Period]] (Latest Osagean to Earliest [[Meramecian]]).
It is listed by the [[Impact Field Studies Group]] as a "probable" impact structure.<ref>{{cite web
  | last = Rajmon
  | first = David
  | title = Impact database 2009.1
  | date = 2009-07-01
  | url = http://impacts.rajmon.cz
  | accessdate = 2009-08-25 }}
</ref>

The structure consists of an area of severe structural deformation and extensive [[breccia]]tion that was poorly understood and had been thought to be the result of either [[Thrust fault|thrusting]] over a [[Dome (geology)|dome]]<ref>Beveridge, T.R., 1949, The Geology of the Weaubleau quadrangle, Missouri [Ph.D. thesis]: Iowa City, State University of Iowa</ref> or a [[cryptoexplosion|cryptoexplosive]] event.<ref>Snyder, F.G., Gerdemann, P.E., Hendricks, H.E., Williams, J.H., Wallace, G., and Martin, J.A., 1965, Cryptoexplosive structures in Missouri: Guidebook, 1965 Annual Meeting of the Geological Society of America: Missouri Geological Survey and Water Resources, Report of Investigations No. 30, 73 p.</ref>  A {{convert|12|mi|adj=on}} circular structure was discovered by [[geologist]] Kevin R. Evans through examination of [[Digital elevation model|digital elevation data]].<ref name=Evans>Evans, Kevin R.; Mickus, Kevin L.; Rovey, Charles W. III; & Davis, George H. (2003). Field Trip I: The Weaubleau Structure: Evidence of a Mississippian Meteorite Impact in Southwestern Missouri. ''Association of Missouri Geologists Field Trip Guidebook, No. 26, 50th Annual Meeting'', pp.&nbsp;1-30. Missouri Department of Natural Resources. [http://courses.missouristate.edu/KevinEvans/RI-75(2003AMGguidebook).pdf PDF]</ref>  The structure was originally called the Weaubleau-Osceola structure after Weaubleau Creek and [[Osceola, Missouri|Osceola]]. It is now known as the Weaubleau structure.

Because the site was covered by later [[Pennsylvanian (geology)|Pennsylvanian Period]] sediments, and only partially exposed to erosion relatively recently, its structure is well preserved, and its age can be determined with fair accuracy. It is one of a series of known or suspected impact sites along the [[38th parallel north|38th parallel]] in the states of [[Illinois]], [[Missouri]], and [[Kansas]]. These [[38th parallel structures]] are thought to possibly be the result of a serial impact, similar to that of [[comet Shoemaker-Levy 9]] on [[Jupiter]], an extremely unlikely event on [[Earth]]. The argument for a serial strike would be greatly strengthened if the ages of the other 38th parallel structures could be constrained to the same period as the Weaubleau structure.<ref name="Dulin Elmore serial">{{cite journal | url=https://books.google.com/books?id=mLswN4OgQYEC&q=Weaubleau%20structure%2038th%20parallel&pg=PA63 | title=The Sedimentary Record of Meteorite Impacts | volume=437 | journal=Geological Society of America Special Paper | editor=Evans, Kevin R. | year=2008 | page=63 | author=Dulin, Shannon | author2=Elmore, R.D.| isbn=9780813724379 }}</ref>

The Weaubleau structure is one of the fifty largest known [[impact structure]]s on earth and the fourth largest in the United States. The three larger ones in the US either have been glaciated and buried ([[Manson crater]]), are under water ([[Chesapeake Bay impact crater|Chesapeake Bay crater]]), or have been subjected to [[orogeny]] ([[Beaverhead impact structure]]). Therefore, the Weaubleau structure is the largest exposed [[Tectonics|untectonized]] impact structure in the US.<ref name=Evans/>