Kinematics of Late Quaternary Slip Along the Qishan-Mazhao Fault: Implications for Tectonic Deformation on the Southwestern Ordos, China

摘要

The northwest striking Qishan-Mazhao fault (QMF) accommodates complex deformation in the Tibet-Ordos transition zone. We studied the geologic and geomorphic expression of the QMF using interpretations of high-resolution satellite images and structure-from-motion models combined with detailed field investigations. Displaced loess tablelands, stream channels, and fluvial terraces show that the QMF is predominately a left-lateral strike-slip fault with a minor normal component. The magnetic susceptibility and optically stimulated luminescence ages of offset fluvial terraces yield left-lateral slip rates ranging from 0.5 to 1.0mm/year. Regionally, the QMF and the Haiyuan fault (HYF) form a large right step, in which the Liupanshan Mountains are located. The QMF shares a similar orientation and sense of motion to the HYF, suggesting that the left-lateral slip of the HYF is not completely absorbed as crustal shortening across the Liupanshan Mountains but is partially transferred to slip along the QMF.