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Scientists find evidence of Iowa meteor crater

The U.S. Geological Survey said it has confirmed a 470 million year old meteorite crater in Iowa.
The USGS said it conducted airborne geophysical surveys near Decorah to get a better look at the crater, which is concealed beneath bedrock and sediments.
 
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Crater found in Iowa points to asteroid break-up 470 million years ago

An asteroid as big as a city block smashed into what is now northern Iowa about 470 million years ago, says a Smithsonian geologist, supporting a theory that a giant space rock broke up and bombarded Earth just as early life began flourishing in the oceans.
The impact dug a crater nearly four miles wide that now lies beneath the town of Decorah, said Bevan French, one of the world's foremost crater hunters and an adjunct scientist at the National Museum of Natural History.

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Decorahb.jpg
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 Latitude: 43°17'57.19"N, Longitude:  91°47'44.88"W



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Meteorite impact shapes Decorah's geological structure

Robert McKay, geologist for the Iowa Department of Natural Resources, will speak Thursday, Nov. 10, at Luther College about a meteorite strike that shaped the geological formation of the rock substrata that underlies the City if Decorah.
McKay's lecture is 7 p.m. in Room 262 of the Valders Science Hall. The event is open to the public with no charge for admission.

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Ordovician Winneshiek Shale
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Title: Preservation of the middle Ordovician Winneshiek Shale in a probable impact crater
Authors: MCKAY, Robert1, LIU, Huaibao1, WITZKE, Brian J.2, FRENCH, Bevan M.3, and BRIGGS, Derek E.G.4, (1) Iowa Geological & Water Survey, Iowa Department of Natural Resources, 109 Trowbridge Hall, Iowa City, IA 52242, robert.mckay@dnr.iowa.gov, (2) Department of Geoscience, University of Iowa, 121 Trowbridge Hall, Iowa City, IA 52242, (3) Meteorite Impact Crater Studies, Dept. of Paleobiology, Smithsonian Institution, PO Box 37012, NMNH, Room E-310, MRC 0121, Washington, DC 20013-7012, (4) Dept. of Geology and Geophysics & Peabody Museum of Natural History, Yale University, 210 Whitney Avenue, P.O. Box 208109, New Haven, CT 06520

The Winneshiek Shale, an 18 m to 27 m thick Ordovician Lagerstätte-bearing shale, is restricted to and fills the upper portion of a 5.5 km diameter circular basin/crater of probable meteorite impact origin at Decorah, Iowa. Primary data sources available for study are water well samples, two cores, driller logs, and two exposures. The predominantly subsurface structure truncates and disrupts Lower Ordovician and Cambrian strata to a depth of at least 200 m below the base of the widespread St. Peter Sandstone.

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