Cenozoic Left-Slip Motion along the Central Altyn Tagh Fault as Inferred from the Sedimentary Record

Several Cenozoic sedimentary basins are present along the central segment of the Cenozoic Altyn Tagh fault (ATF) that marks the northern boundary of the Tibetan Plateau. Field investigations reveal that basin sedimentation and subsequent deformation are controlled by left-slip motion along the Cenozoic ATF. In order to better understand the temporal and spatial interactions between the Altyn Tagh fault and the development of adjacent basins, we divided Cenozoic sedimentary sequences into three subunits based on lithologic variation and the presence of unconformities. From our own observations and regional correlations, we suggest that slip along the central ATF began in the Early Oligocene. Reconstruction of sedimentary relationships among the basin, slip along the fault, and offset topography suggests that the ATF experienced four stages of Cenozoic leftslip motion. The offset of a Late Miocene sequence and its possible correlation across the Altyn Tagh fault suggests 80-100 km left slip. This yields an average slip rate of 10-12.5 mm/yr assuming that the sequence was deposited at ~8 Ma.