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Re: Chesapeake Bay Crater



The Chesapeake Bay impact is one of several major impacts that occurred
close together in time near the Eocene/Oligocene border. It has been
hypotesized that these could be related and due to a "comet swarm", which is
expected to occur occasionally when the Oort cloud is disturbed by e. g. a
passing star.
There certainly was a lot of extinction and a striking episode of faunal and
floral turnover (Stehlin's "Grande Coupure") at about this time. However it
is uncertain hof much of this (if any) was impact-related. There was a big
climatic shift from the Late Cretaceous/Early Tertiary "hothouse" climatic
regime to the Neogene/Quaternary "icehouse" climate at approximately the
same time and this may have driven the biotic changes. The climate shift
probably had paleogeographic causes, Australia became well separated from
Antarctica opening a circum-Antarctic ocean which climatologically isolated
Antarctica, probably causing the first widespread glaciation there. There
were other major geographic shifts att approximately the same time, for
example Europe which had long been an archipelago with connections with
North America earlier inthe Eocene became connected with Asia instead.
Tommy Tyrberg

>From www.space.com, a story about large impact at mouth of present day
Chesapeake Bay. Estimated date 35,000,000 B.C., or so. Havent heard of this
one on
>list, although strictly speaking is not Dino related. Any funky extinction
events correspond to it?