RE: Map

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Nick Pharris
>
> Quoting "Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>:
>
>
> > Just about the best site for modern reconstructions is that of Northern
> > Arizona Univ.'s Ron Blakey.  See:
> > http://jan.ucc.nau.edu/~rcb7/globaltext.html
>
> Personally, I'm fascinated by how stuff keeps sloughing off Gondwana and
> wandering northward across the Tethys/Indian Ocean to crash into Asia,
> culminating with India (and eventually to include Australia?).
> Is there some
> overarching explanation for this northward drift?

Don't know any overarching explanation per se, but the recognition of this
has suggested that the idea that new divergent boundaries are generated
primarily by big plumes forming in the centers of supercontinents due to the
build up of heat is... less important than previously thought.  (In other
words, Atlantic Ocean basins may not be the norm with regards to rifting).

> Also, what's the status of Rodinia (by which I mean the hypothesis that
> Australia and Antarctica were once joined to the west coast of
> North America)?

Funny you should ask that...  Today's issue of Science has an article on
Rodinia: the enhanced webversion is here:
http://www.sciencemag.org/cgi/content/full/300/5624/1379

Torsvik, T.H. 2003. GEOLOGY: The Rodinia Jigsaw Puzzle.  Science 300:
1379-1381.

The early Neoproterozoic supercontinent Rodinia is still restored with
Laurentia (North America + Greenland) in the middle, but the arrangement of
other cratons around it are different than earlier reconstructions.
Australia and East Antartica are still attached on the modern western side
of Laurentia.

Not discussed in this article is Pannotia, the proposed latest
Neoproterozoic-early Cambrian supercontinent (formed during the Pan-African
Orogeny).  The collisions that created Pannotia are the ones that generated
the land mass that would become Gondwana when Pannotia broke apart.

                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