The Cenozoic tectonic evolution of the faulted basins in the northern margin of the Eastern Qinling Mountains, Central China: Constraints from fault kinematic analysis

摘要

A series of NE and NW-trending Cenozoic faulted basins, located at the north margin of the Eastern Qinling Mountains, document Cenozoic intracontinental extension process in Central China. Based on fault kinematic analysis of the faulted basins, coupling with the stratigraphic sequence, we rebuilt a tectonic stress sequence of the faulted basins since the Cenozoic era. Combined with the previous chronological data, we define the Cenozoic faulted basin formation process including two stages of tectonic evolution. The first stage largely presents the NW-SE extensional rifting in a long period from the Paleocene to the Middle-Late Miocene due to northwestward subduction of the Pacific plate. It is marked by the basin occurrence along the north margin of the Eastern Qinling Mountains (e.g., the Sanmenxia, Lushi, Shangluo, and Weihe Basins) in the Paleocene to the Early-Middle Miocene in accordance with a NW-SE extension, and regional basin inversion in the Middle Miocene as the result of a NW-SE compression. The second stage is featured by the three-episode extension since the Middle-Late Miocene, which is probably affected by the combination of the northeastward growth of the Tibetan Plateau and the northwestward subduction of the Pacific Plate. The earliest episode of NW-SE extension caused by regional NE-SW compression in the Late Miocene to Early Pleistocene, which leads to the formation of the Yuncheng Basin. A gentle NE-SW extension subsequently dominated here in the Late Pleistocene, as represented by the widespread appearance of paleo-lakes in the basins. Then the youngest tectonic regime controlled this region, characteristic of a tectonic transpression (ENE-SWS compression and NNW-SSE extension), causing evidently strike-slip activities on the primary faults in the basins.