Cenozoic tectonic history of the southern Tibetan Plateau and eastern Himalaya: evidence from 40Ar/39Ar dating
Peter Copeland 1990
A dissertation submitted to the State University of New York at Albany in partial fufillment of the requirements for the degree of Doctor of Philosophy
College of Sciences and Mathematics, Department of Geological Sciences
Advisors: T.M. Harrison and W.S.F. Kidd

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 from Proquest UMI

        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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