Thermochronology of the modern Indus River bedload: New insight into the controls on the marine stratigraphic record
Table T2A gives analytical results and age calculations for analyses performed on batches of 10 biotite crystals. (70.80Kb)
Table T2B gives analytical results and age calculations for analyses performed on single black biotite grains. (36.59Kb)
Table T2C gives analytical results and age calculations for analyses performed on single brown biotite. (34.37Kb)
Table T2D gives analytical results and age calculations for analyses performed on single muscovite crystals. (68.03Kb)
Clift, Peter D.
Campbell, Ian H.
Pringle, Malcolm S.
Hodges, Kip V.
Khan, Ali Athar
Allen, Charlotte M.
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The Indus River is the only major drainage in the western Himalaya and delivers a long geological record of continental erosion to the Arabian Sea, which may be deciphered and used to reconstruct orogenic growth if the modern bedload can be related to the mountains. In this study we collected thermochronologic data from river sediment collected near the modern delta. U-Pb ages of zircons spanning 3 Gyr show that only ~5% of the eroding crust has been generated since India-Asia collision. The Greater Himalaya are the major source of zircons, with additional contributions from the Karakoram and Lesser Himalaya. The 39Ar/40Ar dating of muscovites gives ages that cluster between 10 and 25 Ma, differing from those recorded in the Bengal Fan. Biotite ages are generally younger, ranging 0–15 Ma. Modern average exhumation rates are estimated at ~0.6 km/m.y. or less, and have slowed progressively since the early Miocene (~20 Ma), although fission track (FT) dating of apatites may indicate a recent moderate acceleration in rates since the Pliocene (~1.0 km/m.y.) driven by climate change. The 39Ar/40Ar and FT techniques emphasize the dominance of high topography in controlling the erosional flux to the ocean. Localized regions of tectonically driven, very rapid exhumation (e.g., Nanga Parbat, S. Karakoram metamorphic domes) do not dominate the erosional record.
Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Tectonics 23 (2004): TC5013, doi:10.1029/2003TC001559.
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