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Re: Fossils in igneous rocks
On Wed, 10 Apr 2002 08:05:45
Thomas R. Holtz, Jr. wrote:
>As for fossils in granite: extraordinarily unlikely, at least as geologists
>use the term "granite" (there is an industrial definition of the term, which
>is any hard rock (where almost every soft rock is "marble"), but that is
>beside the point). Granites cool from molten masses which were entirely
>underneath the surface of the Earth; they form under temperature conditions
>which would obliterate organic tissue, and are molten for up to millions of
>years (extreme cases: more generally ten-to-hundreds of thousands). Hence
>they do not form in environments where living things are present.
>
>(One possibility, though, is that the native rock into which the granitic
>magma intruded was a sedimentary rock possessing fossils. A section of the
>native rock could break off and be suspended in the magma as a xenolith.
>That way you could have a fossil in a sedimentary rock in a granite).
Yep, this shocked me for many of the same reasons (I wish I could find the
ref...). The above possibility that Dr. Holtz mentions is plausible. Or,
perhaps:
1) The granite "fossils" weren't fossils at all, but something akin to the
"Martian fossils."
2) Instead of bona fide granite, the author may have been referring to
something like basalt.
3) The author had no idea what he or she was writing.
Interesting ideas. Thanks for the short, but thorough, reply!
Steve
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