The development and evolution of landform based on neotectonic movement: The Sancha river catchment in the southwestern China

摘要

Neotectonics has changed the coupled process of endogenic and exogenic geological dynamics, which mold the modern landform. Geomorphologic analysis is essential for identifying and understanding the tectonic activity and indicates the responsive mechanism of the landform to tectonic activity. At first, this research reconstructed the twisted Shanpen period planation surface, computed the valley floor width-to-height ratio of Sancha river and extracted the cross sections marking the river terraces to analyze the characteristics of the neotectonics. And then, the relation between neotectonic movement and landform development was analyzed by dividing the landform types. At last, the spatial variation of landform evolution was analyzed by extracting the Hypsometric Integral of sub-catchments. The Sancha river catchmenta??s neotectonic movement presents the tilt-lift of eartha??s crust from NW to SE, which is characterized by the posthumous activity of Yanshan tectonic deformation. The spatial distribution of river terraces indicates that Sancha river catchment has experienced at least four intermittent upliftsand the fault blocks at both the sides of Liuzhia??Zhijin basement fault have differentially uplifted since the late Pleistocene. As the resurgence of Liuzhia??Zhijin basement fault, the Sancha river catchment was broken into two relative independent landform units. The spatial variations of the landform types nearthe Sancha river and the sub-catchmentsa?? landform evolution are characterized by periodic replacement. The styles of geological structure have controlled the development of landform far away from the Sancha River and influenced the landform evolution. The posthumous activities of the secondary structurehave resulted in the spatial variation of sub-catchmentsa?? landform evolution, which presents periodic replacement with local exceptions. The present study suggests that spatial variations of the development and evolution of modern landform of Sancha River catchment owe their genesis to the interplay betweenthe hydrodynamic force and tectonic activity in the neotectonic period. Likewise, the application of geomorphic indicators also provides a new way to assess the regional crustal stability.