HR: 11:20h
AN: T32C-05    [Abstracts]
TI: Deconvoluting Himalayan Climate and Tectonics Based on Zada Basin Sediments, Southwestern Tibet
AU: * Saylor, J E
EM: jsaylor@geo.arizona.edu
AF: University of Arizona, Dept. of Geosciences, 1040 E. 4th St., Tucson, AZ 85721 United States
AU: DeCelles, P G
EM: DeCelles@geo.arizona.edu
AF: University of Arizona, Dept. of Geosciences, 1040 E. 4th St., Tucson, AZ 85721 United States
AU: Quade, J
EM: jquade@geo.arizona.edu
AF: University of Arizona, Dept. of Geosciences, 1040 E. 4th St., Tucson, AZ 85721 United States
AU: Kapp, P
EM: pkapp@geo.arizona.edu
AF: University of Arizona, Dept. of Geosciences, 1040 E. 4th St., Tucson, AZ 85721 United States
AB: The Zada basin of southwestern Tibet is the largest late Cenozoic basin on the Tibetan plateau. The basin developed above the Tethyan Himalayan sequence and is located between major detachment faults to the northwest and southeast, the Ayi Shan Mountains along the dextral Karakoram fault to the northeast, and a major newly recognized dextral strike slip fault to the southwest. However, Zada basin fill is presently flat-lying, buttressing paleotopography along its northern and southern margins and not spatially associated with the South Tibetan detachment system. The Zada basin records one major pulse of accommodation creation as indicated by basal debris flows and fluvial pebble conglomerates. Paleocurrent data show transverse flow along basin margins and axial NW-ward flow along the basin center. A period of lacustrine sedimentation followed, with deposition of multiple, upward coarsening calcareous clay - fine sand para-sequences within an overall progradational sequence. The sands display turbidites, oscillatory current ripples, mudcracks, hummocky cross-stratification and planar and trough cross-stratification. Fossils, primarily gastropods, ostracods, fish and rare large vertebrates, are found in both the lower fluvial and also lacustrine/fluvial units. An alluvial fan boulder conglomerate caps the basin fill. Subsequent incision by the Sutlej River following breaching of a structural dam in the western corner of the basin created spectacular bluffs and canyons. The basin contains a sedimentary record extending back to the late Miocene. As such, it records the regional C3 - C4 transition and associated climate change at 7 - 8 Ma. The extensive lacustrine deposits also provide an excellent source of paleoelevation data. Paleosol carbonates in the basal and capping conglomerates extend this data set to the onset of sedimentation in the basin. Finally, sedimentary provenance, basin subsidence history, and regional structure give insight into the causes of sediment accumulation and basin evolution. The combination of these techniques allows us to evaluate the influence of tectonics and climate on the topography of the Himalayas as uniquely recorded in the sediments of the Zada basin.
DE: 8108 Continental tectonics: compressional
DE: 8109 Continental tectonics: extensional (0905)
DE: 8169 Sedimentary basin processes
DE: 8175 Tectonics and landscape evolution
DE: 8177 Tectonics and climatic interactions
SC: Tectonophysics [T]
MN: Fall Meeting 2005