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Re: patterns in extinction, etc.



> From: JohnE37179@aol.com
>
> If there were a nuclear winter, which may have lasted fifty years - cerainly
> long enough to devastate many forms of life - would it show up in the
> geologic record?  If it does show up, how would you find it.   What would you
> look for? certainly global cooling for fifty years might include severe short
> term climatic changes that might not be represented in the geologic record.
>  Presumable the climate both before and after such a short event would be
> very nearly identicle on this time scale.  I don't think anyone has suggested
> that a catacysmic impact had long term climatic impact - only wide spread -
> short time change of significant magnitude - then it was back to business as
> usual.
>

As the dust that caused the nuclear winter settled out of the
atmosphere, it would create a thin layer of clay where it fell into
reasonably quiet water. Because a significant portion of the dust came
from the bolide, it would have an unusual chemical or isotopic
constitution, a composition one might call "unearthly". The clay layer
would mark a noticable transition in flora and fauna above and below
it.

It's just such a layer observed at the K-T boundary at several sites
around the world that led the Alvarezes to postulate the bolide
extinction theory.

The Dennis Miller disclaimer may apply...

Andrew Robinson