Segmented variations in tectonic geomorphology of Datong-Yangyuan fault zone, NW Beijing, China

Abstract

The Datong-Yangyuan fault zone (DYFZ) is the largest normal fault in the late Cainozoic Shanxi rift system. Heights of late-Quaternary fault scarps and their along-trending distribution pattern divide the fault zone into two segments, the southwestern segment (SWs) and the northeastern segment (NEs). Between these two segments there are significant variations in mountain front and piedmont slope tectonic geomorphology, mountain front sinuosity, valley width-depth relief ratio and stream gradient index, as well as in the sequence of the micro-physiographic stages, erosion - aggradation - erosion along the NEs and aggradation-erosion-aggradation along the SWs. Rate of faulting and downcutting, fault behaviour and segment boundary characteristics seem to be responsible for such contrast in tectonic geomorphology of the two segments of the fault zone. The boundary between the two segments is characterised by a fault overlap zone, along which a fault displacement deficit has occurred. Therefore, fault behaviour and the distribution of overlapping faults are conjointly responsible for the variations in geomorphology of the Datong-Yangyuan fault zone.