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Re: causes of K-T ferns

In a message dated 5/24/01 7:36:23 AM Pacific Daylight Time, 
david.marjanovic@gmx.at writes:

Can someone remind me what a bentonite is? I forgot... :-]

       Bentonite is "fossilized" volcanic ash--turned into a clay. It's 
rather soapy in texture and is used as a drilling mud and a filler in candy 
bars and many other things. It's quite spectacular in the black Pierre Shale 
as it forms bands of yellowish white. They are used as horizon markers and 
sometimes have spectacular fossils spilling out of them. We found two 
mosasaurs almost swimming out of a band of bentonites in South Dakota. The 
Sharon Springs member of the Pierre Shale begins with the Ardmore Bentonite 
that, when figuring in compaction, must have been an ashfall of around 40 
feet in depth. And the Ardmore is far from the largest one. DV