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Re: Mesozoic biosphere depth



I don't know if anyone has (yet) been able to determine the maximum depth
below the surface that any particular Mesozoic biozone could reach.  There
are, of course, complicating factors.  Paleosoils ("paleosols") are often
stacked on top of each other and the biologic activity in the later
paleosols may also effect the buried paleosols (sort of like a
cross-cutting relationship in structural geology).  It is none-the-less an
interesting question, and one that shouldn't be out of the realm of
possibility of addressing. IF fossil microorganisms can be identified in
hydrothermal vein minerals, AND if the emplacement age of the vein can be
determined, AND if the P/T (pressure/temperature) conditions of the
formation of the vein minerals can be determined, THEN the depth of the
fossil hydrothermal microorganisms below the paleo-surface of the earth
could be determined. A big project.  It is akin to the current study of
those funny-looking wormy thingies in that meteorite form Mars that McKay
et al. believe are tiny Martian hydrothermal critters.  And even THAT
debate isn't settled yet (although, presently, it doesn't look good for
the "Martian critter"-hold-outs). 

For insight into this problem, and how such a study may eventually be
borrowed and conducted back on Earth on dinosaur-age rocks, check out the
follwing web page: 

http://www.skypub.com/news/special/9904microbes.html 


As far as Mesozoic biozones closer to the surface, there is quite a bit of
literature on the subject. Here is only a smattering of stuff available
(if I were near my references this would have been more complete):

On Ancient soils:
Retallack, G.J. 1994.  A pedotype approach to latest Cretaceous and
earliest Tertiary Paleosols in eastern Montana. Geological Society of
America Bulletin 106(11).

On Paleo-plop:
Chin, K. 1996. Dinosaurs, dung beetles, and conifers: participants in a
Cretaceous food web. Palaios 11(3).

Web sites on fossil Mesozoic Termites:
http://www.usatoday.com/life/science/paleo/lsp015.htm
http://www.enn.com/enn-news-archive/1997/10/102497/10249707.asp

Also, do a web search on the following subject:
Morrison Formation Extinct Ecosystem Project


For more info on fossil Mesozoic bug nests, do a literature search on the
following people:

Timothy Demko
Stephen Hasiotis
Russel Dubiel

                      <pb>

--
"Gentlemen!  You can't fight in here!  This is the War Room!"
(from Dr. Strangelove)




On Sun, 2 Apr 2000, Larry Dunn wrote:

> Has it been possible to determine how "deep" the
> biosphere was during the Mesozoic, that is, how far
> under the earth's surface it "penetrated?"  
> 
> If so, was it substantially different than the present
> earth biosphere?  And if so, what impact would this
> have had on the animals occupying the surface?