HR: 10:35h
AN: T32C-02    [Abstracts]
TI: Paleoaltimetry of the Tibetan Plateau based on stable isotopes from the Oiyug, Lunpola and Fenghuoshan basins, Tibet
AU: * Currie, B S
EM: curriebs@muohio.edu
AF: Miami University, Department of Geology 114 Shideler Hall, Oxford, OH 45056 United States
AU: Rowley, D B
EM: drowley@uchicago.edu
AF: The University of Chicago, Department of the Geophysical Sciences 5734 S. Ellis Avenue, Chicago, IL 60637 United States
AU: Cyr, A J
EM: ajcyr@purdue.edu
AF: Purdue University, Dept. of Earth and Atmospheric Sciences 550 Stadium Mall Drive, West Layfayette, IN 47907 United States
AB: The elevation history of the Tibetan Plateau provides direct insight into the tectonic processes associated with continent-continent collisions. Oxygen-isotope based estimates of the paleo-altimetry from Oiyug, Lunpola and Fenghuoshan basins, of Miocene, Late Eocene to Miocene, and Late Eocene to Oligocene age provide data on the paleo-elevation evolution of the Tibetan Plateau. Paleosol and lacustrine carbonates of the Oiyug and Lunpola basins are characterized by quite depleted oxygen isotopic compositions. Estimated Δ(δ¹⁸O), the difference in isotopic compositions of high elevation samples and low elevation starting compositions, for Oiyug are <caron>"14.5<caron>± 2.1 ‰, and from Lunpola are for "9.2 ± 2.0‰, for Late Eocene middle Niubao lacustrine carbonates, "12.6 ±1.2‰ for Late Eocene to Oligocene upper Niubao paleosol carbonates, and -10.0 ±2.0‰ for Late Miocene Dingqing Formatin lacustrine carbonates. Using the Rowley et al. (2001, EPSL, 188, 253-268) model these correspond with best estimates of the hypsometric mean paleo-elevations of the drainage basins providing surface waters into these of about ~5200 m +340/-405 for Oiyug, 4050 m +510/-620 m for the middle Niubao, 4850m +380/-460m for upper Niubao, and 4260 m +475/-575m for the Dingqing. Fenghuoshan lacustrine limestones are less depleted with estimated Δ(δ¹⁸O) of less than -6 ±2.0‰ suggesting elevations of northern Tibet were less than about 2 km in late Eocene to early Oligocene. These data are consistent with essentially constant elevation within uncertainty of the southern and central part of Tibetan Plateau for at least the last 35 million years. Retrodictions based on scaling using thermo-mechanical model results of Beaumont et al. (2004, JGR, 109, doi 10:1029/2003JB002809) of crustal, but not mantle, thickening combined with plate kinematic solutions of the India-Asia convergence history are compatible with existing paleo-elevation estimates across the Tibetan Plateau that suggest that the N-S dimension of the Himalaya-Tibet Plateau increased by an average of 28 km/my over the since 50 Ma.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 8011 Kinematics of crustal and mantle deformation
DE: 8102 Continental contractional orogenic belts and inversion tectonics
DE: 8157 Plate motions: past (3040)
SC: Tectonophysics [T]
MN: Fall Meeting 2005