The episodic geomorphological-sedimentary evolution of different basins in the Fenwei Graben and its tectonic implication

Abstract

There are a series of basins in the Fenwei Graben. Field survey found that there took place several paleolake regressions or intensive stream down-incisions in all basins during the Mid-Late Quaternary. The lowest and oldest paleosol/loess units overlying three of the lacustrine terraces or alluvial ones and some paleomagenetism data from the lacustrine sediment indicate that the onset times of three paleolake regressions or intensive stream down-incisions are synchronous with the formation of L9, L6 and L2 respectively in the Weihe Basin, S8, S5 and S1 respectively in the Linfen-Taiyuan-Xingding Basins, and L8, L5 and L1 respectively in the Datong Basin. The difference in the onset time of each lake regressions or intensive stream down-incision in different basins reveals that the farther the basin is from the Tibetan Plateau, the later it took place. Taking these field facts and the former research results in terms of the regional tectonic movement into account, it is inferred that the tectonic movement of the Tibetan Plateau most probably controlled such geomorphologicalsedimentary evolution in the graben.