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Shale (was Re: AMPHIBIOUS MOSASAURS?)



At 01:33 PM 3/2/99 EST, Dan Varner wrote:

>  If I'm not mistaken, I don't believe shale is a kind of aquatic coal, ...or
>is it? Is there a geologist in the house? Help!

Shale is a mudstone: its just lithified clay.  (Technically, it is fissile
claystone: that is, claystone which tends to break along bedding surfaces).
Some shales DO have a high content of organic carbon, but this is different
from coal (which is basically "distilled" plant material: buried plant
matter in which many of the volatiles (water, oxygen, etc.) are lost through
low grade metamorphism).

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:tholtz@geol.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661