Geomorphologic Characteristics and Genesis of Linear Image Belt in the Southwest of Longlin and Its Relationship with Youjiang Fault Zone

ZHANG Peiquan; ZUO Tianhui; ZOU Yan; MI Yuanwei; PAN Yueyi; ZHONG Dewei

doi:10.13512/j.hndz.2023.04.02

Abstract：In order to explore the genesis of a linear image belt in the southwest of Longlin,Guangxi,and analyze its tectonic relationship with Youjiang fault zone,the methods of satellite remote sensing,UAV tilt photogrammetry and field geological and geomorphological survey are used to carry out this work.In the sentinel satellite image,a clear NWW linear image belt appears between Nongsangtun and Longneitun,with a length of 5 km and an angle of 17°-20°with Dagucheng fault valley that controls the synchronous turning of the water system.The field investigation shows that the linear image passes over the southern slope of the Longnei fault valley,and it is shown as a southward-dipping reverse slope steep cliff.A normal fault dipping south-west can be seen in the direction of eastward extension of the cliff.Near the turning point of the Nongsang River in the west,there are normal faults inclined to NNE or NE on the linear image belt.With the support of UAV tilt photogrammetry technology,there are nickpoints on the longitudinal section of the river at the upstream reach of the turning point of the Nongsang River,with a drop of about 78 m.There are normal faults exposed in the upstream and downstream of the nickpoint reach.It is considered that the fault controlling the linear image belt is a normal fault(Nongsang-Longnei fault)trending NWW.This normal fault,the Dagucheng fault,which controls the synchronous left turning of the water system,and the Jiuzhou-Zetun section of the Youjiang fault zone constitute a left-lateral strike-slip Riedel shear system,which are respectively T-fracture,R-fracture and Y-main shear fracture in this shear system.This Riedel shear system has been active for a long time at least during the Himalayan period.