Cenozoic growth of the Eastern Kunlun Range (northern Tibetan Plateau): evidence from sedimentary records in the southwest Qaidam Basin

The Cenozoic sedimentary infill of the Qaidam Basin in the northern Tibetan Plateau provide significant insights into the uplift history and the tectonic evolution of the basin-bounding mountain ranges. Along the SW basin margin, a continuous record is preserved in the ~3000-m-thick Cenozoic succession at the Changweitai area. An up-section switch from marginal and deep lacustrine sedimentation to lacustrine delta-alluvial fan deposition indicates progradation and increasingly basinward advance of sediment transportation systems. Provenance data from sandstone petrology, palaeocurrent analysis and zircon U-Pb geochronology suggest that the Eastern Kunlun Range has been consistently providing material to the SW Qaidam basin since the deposition of the upper Xiaganchaigou Formation, indicating its latest uplift episode prior to the Late Eocene (before 35.5 Ma). However, variation in depositional systems indicates a clear shift in sediment provenance between the deposition of the Xiayoushashan Formation and the Shangyoushashan Formation. We propose that the Cenozoic Eastern Kunlun Range experienced a northward encroachment of shortening into the Qaidam Basin. During the Early Miocene, extensive topographic growth of the Altyn Tagh Range caused by reactivation of the Altyn Tagh strike-slip fault, provided the main source of sediment for the western Qaidam basin. Subsequently, a new source for the basin was provided by the uplifting Qimen Tagh subrange since ~15 Ma.