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RE: Western U.S. (Part Deux)



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Rob Gay
>
> First of all, I would like to thank everyone who pointed me in
> the direction
> of resources for my talk. Thank you very much. I have been quite
> busy with
> work, so I haven't had to time to go out and get them yet, but I
> should be
> able to on Monday. Anyways, your help has been much appreciated.
> However, another question comes up while reading Renyolds and Jenney's
> paper. On one map of the Western U.S., they show a chunk of continent
> labeled "Cordilleran Miogeocline." I am at a loss for if this is
> a submerged
> or above-water level feature. In their explaination of the
> drawing, they do
> not mention anything about it's origins. So, I was wondering if
> anyone could
> give me some help here. Thanks again!

Didn't know people were still using that word: it is originally from
geosynclinal theory (the main pre-Plate Tectonics model of orogenesis, at
least among North American geologists).

If memory serves, the miogeocline was the shallow-water portion of the
trough, with well sorted sandstones, limestones, etc. (as opposed to the
eugeocline, which had turbidites and deep sea seds and volcanics).

I suppose that one might still use "miogeocline" for passive margin
continental shelves, in which case the Cordilleran miogeocline would be
(speculation here) the stable passive margin continental shelf off of the
west coast of Laurentia (aka North America) (note that the west coast at the
time would be considerably closer to the middle of the continent than now,
and depending on the time period might be facing a different direction than
West!!).  So, that would be between the break up of the Proterozoic
supercontinent Rodinia and the first batch of microplates accreting to the
Cordilleran margin of Laurentia (the Late Devonian Antler Orogeny).

On the other hand, memory may not serve and/or I could be entirely wrong.
Hopefully your library work (and perhaps some webwork) will help turn up the
answer.

                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): 301-314-7843


> -----Original Message-----
> Peace,
> Rob
> Student of Geology
> Northern Arizona University
> AIM: TarryAGoat
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