RE: Ancient mountains

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

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> FlxLandry@aol.com

> Hullo!
>
> On a totally unrelated topic, I  have a little question (ah, yes, like in the
> old times; oh, I just should go to  sleep :-). Do we have any knowledge about
> ancient mountain ranges (let's say  mesozoic ones, just not to be off topic)?
> Things like localization and  orientation, local climate, fauna and flora?
> Can we estimate ancient mountain  heights? Any ref (pdf???) on this topic?

Ancient mountains can be inferred by all sorts of methods:
*Distribution of broad regions of metamorphic produced by burial, or igneous 
intrusions produced within volcanic ranges, that are
now exposed on the surface. (For example, what is now the bedrock of much of 
eastern North America was once the deep roots of the
mountain range produced by the collisions of North America and western Europe, 
and then Euramerica and  Gondwana. The modern
Appalachians are just the eroded "foothills" of this range, whose peaks would 
have been over places like Baltimore).

*Distributions of the erosional remnants of mountains, in the forms of great 
depths of terrestrial sedimentary rocks. (For example,
the presence of the Ancestral Rockies is inferred in part by vast layers of 
sediments shed into basins nearby).

*Various patterns of structural deformation.

Height of ancient mountains can be inferred in part by the degree of 
metamorphism of the exposed mountain roots. However, a caveat:
mountains are ephemeral, dynamic things from a geological point of view: they 
rise and fall, bounce up and down, get eroded, etc. So
a peak at a particular time will not be the same 1 million years later.

Search "orogenesis" for information on this topic. (Note, asking for refs on 
this is like asking for "ref on the anatomy of
dinosaurs": there's a lot out there, but not all the information is at one 
spot).

Now, as for paleo-montane floras and faunas: forget it. Mountains are regions 
of erosion, not deposition. So essentially all the
information of what lived in ancient mountains was destroyed, to be made into 
sediment so we can find out what lived in the
lowlands. (For example, erosion of the Nevadan orogeny of the American 
Cordillera keeps us from knowing what Late Jurassic mountain
dinos looked like, but all that eroded sediment is pretty damn useful for 
telling us about the dinosaurs of the lowland. That eroded
sediment, incidentally, is what we call the "Morrison Formation".)

My favorite paleogeography site is 
http://jan.ucc.nau.edu/~rcb7/globaltext.html. However, it doesn't go into great 
depth on HOW the
geography was reconstructed, which was your question.

However, this site: http://jan.ucc.nau.edu/~rcb7/paleogeogwus.html
gives a least a look into how the process works.

Hope this helps,

                Thomas R. Holtz, Jr.
        Senior Lecturer, Vertebrate Paleontology
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
        Mailing Address:
                Building 237, Room 1117
                College Park, MD  20742

http://www.geol.umd.edu/~tholtz/
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
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