The collision between India and Asia has forcefully raised the Tibetan plateau, the most extensive region of elevated topography and thick crust on the Earth's surface. The uplift of the plateau may also have played a major role in controlling global climate during Cenozic time. Understanding the uplift history of the Tibetan plateau is one of the main challenges in earth sciences today. Despite more than three decades of active research, there is little consensus regarding the timing of plateau uplift and the tectonic processes by which the plateau was raised. In this collaborative study, researchers from the University of California at Santa Cruz and Indiana University are carrying out an integrated research program combining paleomagnetism (magnetostratigraphy and tectonics), sedimentology (facies descriptions, and paleocurrent and provenance studies), isotopoic dating, and paleoaltimetry (basalt vesicularity and oxygen isotopes) in a series of three latitudinally spaced basins in North-Central Tibet. The primary goals are to reconstruct the Paleogene tectonic history of north central Tibet, assess the relative contribution of upper crustal processes to plateau growth and maintenance, and assess the relative roles of tectonic models that predict early (e.g., approximately 40 million years ago) gradual uplift and those that predict more recent (less than 15 million years ago) abrupt uplift. To achieve these goals, lithostratigraphy and depositional environments in each basin are being compared using standard basin-analysis techniques to characterize the tectonic setting of sedimentation. The detailed new magnetostratigraphic results and radiometric dates will clarify the age of and correlation between these basins. The new paleomagnetic results will also provide pole positions and paleolatitudes to constrain the calculation for the Indo-Asian convergence rate and the amount and timing of tectonic rotation between tectonic blocks in the region. Times series of oxygen isotopes from these basins will provide quantitative information on their topographic development and climatic history. Comparison with vesicularity paleoaltimetry of the lavas may provide an independent check on elevation and remove ambiguity as to whether low oxygen-isotope values signal high paleoelevation of the basins themselves or of regions downwind along the vapor transport path. This research will improve understanding of the tectonic processes of intracontinental deformation related to the India-Asia collision. A definitive uplift history of northern Tibet is important for understanding climate change during Cenozoic time and will place fundamental constraints on the mechanism(s) of plateau formation, which interests a broad scientific community. This project forms the basis for two graduate students' PhD studies, and parts of the project are suitable for undergraduate research theses.
