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RE: Response II



Also consider the development of the Emperor Sea Mounts which began in the
late Cretaceous starting under the Russia Pennisula. The upwelling of
magma beneath the crust at the hot spot could have easily pushed the
plate(s) in that area up above the late Cretaceous sea level.

The Bering strait may not have been above sea level but it is possible
that a "land bridge" existed just south amoungst the now Aleutian island
chain.

Something to consider.
John Schneiderman

On Mon, 11 Jun 2001, Thomas R. Holtz, Jr. wrote:

> > 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
>