[meteorite-list] Crow Creek Member of Pierre Shale is Impact Tsunami Generated

[Paul]

In “December Media Highlights: Geology and GSA Today” at:
http://www.geosociety.org/news/pr/07-68.htm , there is:

Weber, R. D., and D. K. Watkins, 2007, Evidence from 
the Crow Creek Member (Pierre Shale) for an impact-
induced resuspension event in the late Cretaceous 
Western Interior Seaway. . Vol. 35, no. 12, 
pp. 1119-1122.

http://www.gsajournals.org/perlserv/?request=get-abstract&doi=10.1130%2FG24209A.1

The press release stated:

The Crow Creek Member, a unique rock unit in the Upper 
Cretaceous Pierre Shale in South Dakota and Nebraska, 
has been thought to represent sea-level rise along 
the eastern margin of the Western Interior Seaway. 
However, Weber et al. show that the presence of impact 
ejecta from the Manson Impact Structure, found within 
the Member, suggests an impact-induced genesis. 
Current investigation of a reworked nannofossil 
assemblage occurring within the Crow Creek Member is 
consistent with an origin involving gravitational 
settling rather than sea-level rise. Additionally, 
the reworked assemblage decreases in abundance with 
increased distances from the Manson Impact Structure. 
These observations support the hypothesis that Manson 
Impact may have caused a resuspension event in the 
Western Interior Seaway, resulting in Crow Creek 
deposition.”

Yours,

Paul H.





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