2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 40
Presentation Time: 8:00 AM-4:45 PM

Cenozoic Basin Evolution in the Central and Northern Tibetan Plateau as Constrained by Sandstone Petrology, U-Pb Detrital Zircon Dating, and Fission-Track Thermochronology

MCRIVETTE, Michael W.1, YIN, An1, CHEN, Xuanhua2 and GEHRELS, G.E.3, (1)Department of Earth & Space Sciences, University of California, Los Angeles, 595 Charles Young Drive East, 3806 Geology Building, Los Angeles, CA 90095-1567, (2)Institute of Geomechanics, Chinese Academy of Geol Sciences, Beijing, 10081, China, (3)Department of Geosciences, University of Arizona, Gould-Simpson Building #77, 1040 E 4th St, Tucson, AZ 85721, mmcrivet@ucla.edu

The Early Eocene-Miocene Hoh Xil basin in central Tibet and the Paleocene-Quaternary Qaidam basin in northern Tibet together cover approximately one-third of the total area of the Tibetan plateau. The extensive spatial and temporal ranges of these basins suggest that they preserve important records of plateau growth history since the onset of Indo-Asian continental collision. While evolution of each basin has been separately investigated previously, the relationship between them has not been addressed due to the prevailing view that topographic growth of the plateau has progressed either continuously or discretely from south to north. This interpretation implies independent development and evolution of the two intra-plateau basins. Alternatively, initiation of contraction at the onset of the Indo-Asian collision in northern Tibet raises the possibility that Hoh Xil and Qaidam basins were parts of a contiguous Paleogene basin partitioned later by Miocene uplift of the Eastern Kunlun Range. We test the above model by integrating sedimentology, sandstone petrology, U-Pb detrital zircon geochronology, and apatite and zircon fission-track thermochronology across central and northern Tibet. Our results indicate that the Paleogene sediments in the Hoh Xil and Qaidam basins were derived from a similar source, while the Neogene sediments have a distinctively different source provenance. Modeled cooling histories constrained by fission-track data indicate that rapid uplift of the Eastern Kunlun Range started in the Miocene, late in the developmental history of the basins. The Miocene uplift of the Eastern Kunlun Range explains the development of a large Miocene lake in Hoh Xil basin and supports the hypothesis that Hoh Xil and Qaidam basins were parts of a single basin between the Qilian Shan and Fenghuo Shan orogenic belts, much like the Tarim basin today between the Tian Shan and Tibet.