Spatial heterogeneity of Cenozoic provenance in the Nima and Lunpola basins of China: Implications for the origin of the low-relief topography in central Tibet Plateau

Abstract

The central Tibet Plateau is characterised by low-relief topography of high elevation; however, the origin of this surface flatness is uncertain because of a lack of reliable evidence from palaeogeography and palaeodrainage. In this study, we conduct sedimentological and provenance analysis of the Nima Basin, one of several terrestrial basins developed along the Bangong–Nujiang suture zone since the middle Eocene. Our data show that the Dingqinghu Formation in the Nima Basin was deposited in fan delta, braided river and lacustrine environments in the late Eocene after 37 Ma. It received sediment consisting mainly of recycled detritus, including orbitolinid-bearing limestone with volcanic fragments from the Lhasa Terrane in the south. Comparison of the stratigraphic sections in the Nima Basin with those of the adjacent Lunpola Basin suggests that these regions are characterised by local but similar provenance signals. We suggest that a source-to-sink system once existed from the shallower Nima Basin eastward to the deeper and bigger Lunpola Basin. We hypothesise that the Oligocene–early Miocene source-to-sink system from the Nima to Lunpola may have played a role in the surface flattening of the central Tibet Plateau.