Late Cenozoic Left-Slip Faulting Process of the East Kunlun-Qinling Fault System in West Qinling Region and Its Eastward Propagation
西秦岭地区东昆仑-秦岭断裂系晚新生代左旋走滑历史及其向东扩展

Based on TM imagery interpretation and field observations, this paper has described the distribution and morphostructural features of main active faults in East Kunlun, analyzed tectono-sedimentary characteristics of the Neogene pull-apart basins in West Qinling region, and proposed a 3-stage evolutionary model for the East Kunlun-Qinling fault system in Late Cenozoic. It is pointed out that the East Kunlun-Qinling fault system behaved as transtensional strike-slip faulting from Late Miocene to Early Pliocene, with the development of pull-apart basins and ultrabasic volcanic activities along the fault zones. The onset of this faulting stage was concomitant with the change in the direction of extension from NE-SW to NW-SE in Weihe graben. Beginning from Late Pliocene (about 3.4 Ma ago), the kinematics of the East Kunlun-Qinling fault system changed into transpressional strike-slip faulting, which caused gentle deformation of the Neogene pull-part basins. This deformation stage lasted till Early Pleistocene. Its eastward propagation caused widespread effect of crustal deformation, which included the initiation and development of the N-S trending Minshan uplift in the eastern margin of Tibetan plateau, the Fen-Wei graben system in North China and the right-lateral strike-slip motion along the Tan-Lu fault zone. During Middle and Late Pleistocene, the fault system was active left-laterally with a normal slip component, mostly localized along the three bifurcated fault zones in East Kunlun.