ABSTRACT
The tectonic mechanisms by which the convergence between India and
Asia has been accommodated have varied considerably in both time
and space over the past 40 million years. This dissertation
concerns rocks from three distinct areas, southern Tibet, central
Nepal, and the southern Bengal Fan, and relates geochronologic
data from these rocks to the tectonic history of the India-Asia
collision in southern Tibet and the eastern Himalaya.
Cooling histories of several plutons of the Gangdese batholith as
well as ages of detrital minerals from the southern Bay of Bengal
indicate the southern Tibetan plateau and eastern Himalaya have
been a significant topographic feature since the begining of the
Miocene and that the uplift and erosion of this area has been
markedly variable in both space and time.
U-Pb dating of a granite near Mt. Everest suggest a closure
temperature of Pb in monazite of -720-750°C, significantly
higher than previous estimates. Thermochronologic data from the
Nyainqentanghla range in southern Tibet suggest that the southern
Tibetan plateau achieved an elevation and crustal thickness
similar to its present day values by the end of the Miocene.
A profound thermal disturbance was centered on the Main Central
Thrust, central Nepal, at the end of the Miocene. This disturbance
is interpreted to be the result of the passage of hot fluids
through the MCT zone at about this time for a period of less than
1 million years. The fluids are thought to be a result of
thrusting of hot hanging wall rocks of the Main Boundary Thrust
over colder footwall rocks, inducing dehydration. The data
presented here do not favor tectonic models for the Tibetan
plateau in which the uplift proceeds at an even pace nor those in
which most of the uplift takes place in the past 5 million years.
The available data do permit models in which much of the
convergence in the Oligocene is acccommodated by continental
escape, the Miocene is dominated by crustal thickening of the
Tibetan plateau (distributed shortening), and the past 5 million
years have alternated between E-W extension, continental escape,
crustal thickening, and incipient plate reorganization.
Copeland, P.C., 1990. Cenozoic tectonic history of the southern
Tibetan Plateau and eastern Himalaya: evidence from 40Ar/39Ar
dating. Unpublished PhD dissertation, State University of New York
at Albany. 397pp., +xiii
University at Albany Science Library call number: SCIENCE
MIC Film QE 40 Z899 1990 C66
Copies of this PhD dissertation can be ordered
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Front matter (title,
table of contents, abstract, acknowledgements) - 0.5MB pdf
file
Photo pages in dissertation
(colour
photos with captions): - 0.9MB pdf file
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