Timing and Kinematics of Cenozoic E-W Extension in central Tibet - Transition in the Strain Field of the Tibetan Plateau Stockli, D.F., Lin, D., Dewane, T.J., Hager, C. 
Cenozoic extension within
the Tibetan Plateau is expressed as a series of prominent N-S trending rift valleys.
Recent GPS studies show that these graben systems and associated conjugate strike-slip
systems accommodate a significant portion of internal N-S shortening and E-W expansion
of the Tibetan Plateau. The development of these structures represents a significant
shift in deformational style and marks the transition to a constrictional strain
field within the Tibetan crust. Determining the timing of the formation of these
structures is an important step in understanding the evolution of the plateau.In order to test existing hypotheses proposed to explain these N-S trending rifts and associated strike-slip fault systems and to understand the geodynamic significance of Cenozoic E-W extension in Tibet, we need to answer two fundamental questions. (1) What is the timing of initiation and spatial distribution of E-W extension throughout Tibet? (2) What is the temporal and kinematic interplay between conjugate strike-slip deformation and E-W extension within central Tibet? A regionally synchronous versus diachronous onset of rifting or progressive migration of fault initiation from E to W has very different implications for the evolution of the intraplate strain field and the driving forces responsible for rift formation. Currently, the different geodynamic models for the Cenozoic evolution of Tibet are difficult to evaluate due to the lack of sufficient temporal constraints on the onset of rifting. Once we understand the history of extensional and associated strike- slip faulting in northern and southern Tibet, we will be able to address the larger issue of how strain has been distributed in time and space across Tibet. This question has far-reaching implications for our understanding of how the lithosphere behaves during continent-continent collision. We propose to use an integrated approach, combining apatite (U-Th)/He and fission track dating with structural mapping, to elucidate the timing and magnitude of faulting associated with the Cenozoic strain pattern across Tibet. Thermochronological methods directly dating the cooling of rocks in exhumed fault blocks will complement field-based kinematic analysis of the rift systems and should help resolve outstanding questions regarding the timing and geodynamic significance of the Tibetan rifts. Collaborators Ding Lin - Academia Sinica Students T.J. Dewane - University of Kansas Chris Hager - University of Kansas |
