Geomorphic Index Analysis Along The Yumu Shan And Its Implications For Tectonic Activities

The Yumushan Mountain is located at the front of the actively growing mountain range of the Qilianshan Mountain, which is trending NWW-SEE for more than1000km at the northeastern margin of the Tibetan Plateau. The Yumu Shan is the topographic expression of the actively growing fault-propagation fold developed in the hanging walls of the reverse fault along the NE margin of the Qilian Shan. The fault is a system of mostly northeast-vergent buried reverse faults which has not yet broken the Quaternary surface. The Yumu Shan block is tectonically active since the Cenozoic, and the acitivity successivly becomes younger from south to north, and the magnitude gradually weaken from south to north.We calculated stream-length gradient (SL), hypsometric curve (HI) and asymmetry factor (AF) along the Yumu Shan, and found that there are significant differences with these indexes between the north and south flanks of the Yumu Shan. SLk analysis shows a strong correlation between the abnormal Z-score and fault distribution. The contrary distribution of AF in northern and southern Yumu Shan probably correspond to growing of the Yumu Shan anticline, whose formation is related to the buried reverse faults along the northern margin of the Qilian Shan. Hypsometric curve analysis and HI values show differences between northern and southern mountain ranges, probably due to tectonic activity intensity and lithologic differences. The tectonic activity in northern flank is stronger than in southern, but the erosion intensity is weaker than in northern. The geomorphic index analysis along Yumu Shan demonstrate that the landform characteristics can effectively indicates the characteristics of regional tectonic activity in the region of slow tectonic deformation rate.