Modern Rainfall and Paleoclimate Across NE Tibet: Climate Consequences of the Growth of the Tibetan Plateau

Carmala N. Garzione
University of Rochester, Rochester, New York ([email protected])

Abstract

The NE Tibetan plateau consists of sedimentary basins at elevations between ~2 to 3 km and intervening mountain ranges that reach elevations 1 to 2 km higher than the basin floors. The stable isotopic composition of modern rainfall across NE Tibet shows patterns associated with the topography across the region. The patterns in precipitation amount and isotopic composition across NE Tibet are compared with paleoprecipitation composition derived from sedimentary carbonates to understand the development of late Cenozoic topography across the region. Based on paleoflow patterns and the Sr and stable isotopic compositions of lacustrine carbonates, individual sub-basins in NE Tibet appear to have been segmented early in their history (by ~20 to 10 Ma). Similar to modern isotopic patterns since ~8 Ma across the region suggest that individual ranges formed significant topographic barriers by that time. These data, as well as (U-Th)/He cooling histories from basin-bounding ranges, indicate that NE Tibet experienced a long term growth history that established the major topographic features that bound individual basins between ~45 and 8 Ma. Since ~10 to 8 Ma, outward growth of the Tibetan plateau has accommodated deformation on the distal margins, including the northern Qilian Shan along the northern margin and the Liupan Shan along the northeastern margin.

AAPG Search and Discovery Article #90086 © 2008 AAPG Foundation Distinguished Lecturer Series 2008-2009