Late Miocene to Quaternary Development of the Jiujing Basin, Southern Beishan Block, China: Implications for the Kinematics and Timing of Crustal Reactivation North of Tibet

Abstract

We present results from a multidisciplinary investigation of the Jiujing fault (JJF) system and adjacent Jiujing Basin in the southern Beishan block, western China. Structural and geomorphological fieldwork involving fault and landform investigations, remote sensing analysis of satellite and drone imagery, analysis of drill-core data, paleoseismological trench studies, and Quaternary dating of alluvial sediments suggest the JJF is a late Pleistocene to Holocene oblique sinistral-slip normal fault. Satellite image analysis indicates that the JJF is a connecting structure between two regional E-W-trending Quaternary left-lateral fault systems. The Jiujing Basin is the largest and best developed of three parallel NE-striking transtensional basins within an evolving sinistral transtensional duplex. Sinistral transtension is compatible with the orientation of inherited basement strike belts, NE-directed SHmax, and the modern E-NE-directed geodetic velocity field. Cosmogenic 26Al/10Be burial dating of the deepest sediments in the Jiujing Basin indicates that the basin began to form at ~5.5Ma. Our study reveals a previously unreported actively deforming domain of transtensional deformation 100 km north of Tibet in a sector of the Beishan previously considered tectonically quiescent. Recognition of latest Miocene-Recent crustal reactivation in the Jiujing region has important implications for earthquake hazards in the Beishan and western Hexi Corridor/North Tibetan foreland sectors of the Silk Road Economic Belt. Additionally, we compare the timing of latest Miocene-Recent crustal reactivation in the southern Beishan with the documented onset of reactivation in other deforming regions north of Tibet.