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Re: [dinosaur] Manson crater and the Campanian extinction



Except for localized killing, there has been no evidence of an extinction event 
or even so much as a species turnover.  The effect of the impact, the "killing 
ring" goes out about 650 mile radius from the epicenter which means most of the 
destruction to the west of the impact was absorbed in the KWIS and is recorded 
within the Pierre Shale (Crow Creek member). This member is not extensive and 
most likely represents the eject material laid down immediately after the 
impact (about 100 miles radius, the remaining member made up of ripe-up 
material adding to another 50 miles of radius as seen in drill cores in 
northeastern Nebraska and southeastern South Dakota)   Western equivalent 
formations: Bearpaw Shale, Mancos Shale and the Lewis Shale, show no 
disturbance or sign of the impact episode. Formations east of the impact site 
(Appalachia) unfortunately have been scraped away by recent glacial activity. 
(Pleistocene ice age) and formations in southern Appalachia also show no sign 
of the impacts effect. Although the Manson Impact was the largest impact in 
North America during the late Cretaceous its effects were short term and played 
no role in fauna or flora changes given the fossil record available.


---- Poekilopleuron <dinosaurtom2015@seznam.cz> wrote: 
> Good day,
> 
> I would like to ask if anyone has already evaluate the (literal) impact of
> the Manson crater impact on the late Campanian Appalachian and Laramidian 
> biota? Given its age (about 73.8 mya) there was very rich dinosaur fauna at
> least on the Laramidia. It was estimated that this impact was capable of 
> killing any surface-dwelling animal up to about 1050 km from its epicentre.
> 
> Did anyone looked for the evidence of some extinction patterns in the
> sediments of the same age in e. g. Montana and South Dakota, which were 
> relatively near areas? Was this regional catastrophic event cabable of
> making some significant changes in the course of evolution of Laramidean 
> dinosaur populations? Thank you in advance, Tom