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RE: Response II



> From: Dinogeorge@aol.com [mailto:Dinogeorge@aol.com]
>
> In a message dated 6/3/01 12:33:21 PM EST, david.marjanovic@gmx.at writes:
>
> << OOC, what happens if I write "there's no evidence that this
> was not the
> case
>  either"? Are e. g. marine sediments from the relevant parts of
> Alaska and/or
>  eastern Siberia known? >>
>
> Considering that much of North America was flooded at the time,
> and likewise
> much of Asia, I can't see how the Bering land bridge escaped
> being flooded as
> well. But who knows. The region is pretty inaccessible, and I
> haven't been
> able to find any geological studies of the area in the literature
> yet (though
> I haven't searched very assiduously, either).

Okay, this is WAY late, as I am just back from vacation.

However, in breif: the geography of what we now call Alaska and Siberia was
RADICALLY transformed throughtout the late Mesozoic and Cenozoic.  It is a
patchwork of little microplates all smushed (and still smushing) together: a
very actively tectonic region.

Incidentally, the tectonic edge of the North American Plate is NOT within
the confines of current North America as the geographers set the boundary.
Instead, a large section of northeastern Asia, including parts of Siberia,
Korea, and northern Japan are (from a tectonic standpoint) part of the North
American Plate.

This is by far one of the most troubling areas to reconstruct in
paleogeography.  (Phylogenetic comparision: this is a ten-or-more branch
polytomy...).  ANY reconstruction you see for this area is more guesswork
than not.

In any case, the Cretaceous "Bering Land Bridge" and its morphology had very
little bearing (;-) on the true late Cenozoic Bering Land Bridge, which
includes terranes which during the Cretaceous were in some other part of the
world.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796