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Geological Society of America Bulletin

Article: pp. 142–155 | Full Text | PDF (1.09M)

Coupling of rock uplift and river incision in the Namche Barwa–Gyala Peri massif, Tibet

Noah J. Finnegan1, Bernard Hallet1, David R. Montgomery1, Peter K. Zeitler2, John O. Stone3, Alison M. Anders4, and Liu Yuping5

1. Department of Earth and Space Sciences and Quaternary Research Center, University of Washington, P.O. Box 351310, Seattle, Washington 98195, USA, 2. Department of Earth and Environmental Sciences, Lehigh University, 31 Williams Drive, Bethlehem, Pennsylvania 18015, USA, 3. Department of Earth and Space Sciences and Quaternary Research Center, University of Washington, P.O. Box 351310, Seattle, Washington 98195, USA, 4. Department of Geology, University of Illinois at Urbana-Champaign, 245 Natural History Building, 1301 West Green Street, Urbana, Illinois 61801, USA, 5. Chengdu Institute of Geology and Mineral Resources, 2 Beisanduan, Yihuanlu, Chengdu 610081, Sichuan Province, China

Geodynamic modeling demonstrates the strong potential for erosion to influence the pattern and style of deformation in active mountain belts, but field studies yield conflicting views on the importance of erosion in influencing orogenesis. Here we compare patterns in river power, inferred excess fluvial-transport capacity, topographic relief, precipitation, and mineral-cooling ages to assess the coupling between surface erosion and rock uplift within the vicinity of the Namche Barwa–Gyala Peri massif, an active antiformal structure within the eastern Himalayan syntaxis. Our rich and dense data set reveals a tight spatial correspondence of fluvial incision potential, high relief, and young cooling ages. The spatial coincidence is most easily explained by a sustained balance between rock uplift and denudation driven by river incision over at least the last ∼1 m.y. The Yarlung Tsangpo–Brahmaputra River is the largest and most powerful river in the Himalaya, and two lines of evidence point to its active role in the dynamic interaction of local erosion, rock uplift, thermal weakening of the lithosphere, and deformation: (1) Whereas along the rest of the Himalayan front, high relief and high rock uplift rates are essentially continuous, the high relief and rapid exhumation in the syntaxis is restricted to a “bull's-eye” pattern exactly where the largest river in the Himalaya, the Yarlung Tsangpo–Brahmaputra, has the most energy per unit area available to erode its channel and transport sediment. (2) The location of rapid incision on the Yarlung Tsangpo–Brahmaputra has been pinned for at least 1 m.y., and without compensatory uplift of the Namche Barwa–Gyala Peri massif during this time the river would have eroded headward rapidly, incising deeply into Tibet.

Keywords: river incision, rock uplift, climate, tectonics, landscape evolution, eastern Himalayan syntaxis, Namche Barwa

Received: 13 MARCH 2007; Revised: 3 SEPTEMBER 2007; Accepted: 5 SEPTEMBER 2007

DOI: 10.1130/B26224.1

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