[meteorite-list] Geologists Suggest Asteroid Created Coal-Rich Williston Basin
From: David Freeman <dfreeman_at_meteoritecentral.com>
Date: Mon Nov 29 00:18:26 2004 Message-ID: <41AAB122.6040708_at_fascination.com> Rather boggy Creek/Frassian in nature? DF Ron Baalke wrote: > >http://www.billingsgazette.com/index.php?id=1&display=rednews/2004/11/28/build/state/60-asteroid-basin.inc > >Geologists suggest asteroid created coal-rich Williston Basin >Associated Press >November 28, 2004 > >KALISPELL - The asteroid thought to have killed the dinosaurs when it >slammed into Earth 65 million years ago may also have created the >coal-rich Williston Basin, a group of geologists suggest. > >The basin underlies most of northeastern Montana and western North >Dakota. It contains one of the largest lignite coal deposits in the >world at about 540 billion tons, according to U.S. Geological Survey >estimates. > >The asteroid killed off most major predators, meaning plants in the >basin would have grown and died unimpeded for years, a team of >geologists from the University of Wisconsin-Milwaukee, the Milwaukee >Public Museum and the University of Rhode Island say in their research. > >The uninhibited plant growth created substantial peat mires that >eventually turned into the coal fields that pepper the basin today, said >Peter Sheehan, curator of geology at the Milwaukee Public Museum. > >The boundary between pre-impact and post-impact rock formations in the >basin is obvious, researchers said, with darker floodplain deposits >replaced by distinctive layers of lighter-colored sediments. > >Just above the boundary, the first thin coal seam appears. > >"We're suggesting that the impact caused these changes," Sheehan said. >"If not for that and the associated change in vegetation and animal >life, there would not have been a continuation of the (pre-impact) >formation." > >Other theories on coal formation abound, however, and some colleagues >are already disputing the group's suggestion. > >Kirk Johnson, chief curator at the Denver Museum of Nature and Science, >said the resurgence of a major inland sea may also have played a role in >coal. > >"We think the coal formation could be related to the Cannonball Sea," he >said. "As sea levels rose, it may have raised groundwater levels and >created swamps." > >The Cannonball Sea split off from a much larger waterway about 2 million >years before the asteroid impact, running from the Gulf of Mexico to >present-day North Dakota. > >Johnson was somewhat skeptical of Sheehan's theory, saying he wanted to >see more data. More recent research shows that coal started forming in >the basin before the asteroid impact, he said. > >"That's the real question for Peter," Johnson said. "Where's the data?" > >Sheehan, who has studied the dinosaur extinction and other mass >extinctions for more than 20 years, said he knows proving the new theory >will be difficult. > >"This is just a first attempt," he said. "We need to look at how fast >some of these changes occurred, and we need to look at the distribution >of the coal seams in relation to when herbivores returned. At this >point, what we're really saying is that this type of 'extraterrestrial' >event is something we need to be considering." > > >______________________________________________ >Meteorite-list mailing list >Meteorite-list_at_meteoritecentral.com >http://six.pairlist.net/mailman/listinfo/meteorite-list > > Received on Mon 29 Nov 2004 12:18:26 AM PST |
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