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The role of erosion and extension in unroofing the Indian Plate thrust stack, Pakistan Himalaya

Published online by Cambridge University Press:  01 May 2009

Peter J. Treloar
Affiliation:
Dept of Geology, Imperial College, London, SW7 2BP, UK.
David C. Rex
Affiliation:
Dept of Earth Sciences, Leeds University, Leeds, LS2 9JT, UK.
Matthew P. Williams
Affiliation:
Dept of Geology, Imperial College, London, SW7 2BP, UK.

Abstract

In north Pakistan cooling history data show that metamorphism within the Indian Plate predated 40 Ma, and that the post-metamorphic thrust stack developed within the crystalline internal zones had cooled to less than 100 °C by c. 18 Ma. Much of this cooling occurred during late Oligocene to early Miocene time and can be equated to substantial unroofing of the metamorphic pile. This unroofing was by a combination of erosion, recorded in Lower Miocene molasse deposits within the foreland basins, and by large scale hinterland (northward) directed extensional normal faults developed within the upper parts of the Indian Plate and within the Kohistan–India suture zone and operative as late as 20 Ma. As up to 20 km of material was removed during exhumation, substantial uplift must have been synchronous with exhumation. Part of this may be accounted for by isostatic rebound of the thickened Indian Plate, and part by uplift in the hanging wall of major south-verging thrusts developed at the base of the crystalline pile.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1991

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Footnotes

School of Geological Sciences, Kingston Polytechnic, Kingston-upon-Thames, KT1 2EE, U.K.

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