From a proximal-deposition-dominated basin sink to a significant sediment source to the Chinese Loess Plateau: Insight from the quantitative provenance analysis on the Cenozoic sediments in the Qaidam basin, northern Tibetan Plateau

Abstract

A better understanding of the Cenozoic source to sink relationship between the Qaidam Basin and the surrounding regions allows us to reveal the topographic evolution of the northern edge of Tibetan Plateau in response to the India-Asian collision and the Asian aridification process. However, the depositional history and provenance of Paleogene strata in the southwestern/northeastern Qaidam Basin and the genetic linkage between the Qaidam Basin and Cenozoic Chinese Loess Plateau is still debated. Here we compile ca. 12,000 U-Pb zircon analyses from the Qaidam Basin, Chinese Loess Plateau and the surrounding regions, and conduct quantitative provenance analysis using a MATLAB-based Inverse Monte Carlo simulation technique. When integrated with variations in stratigraphic thickness and lithology across the basin, our analysis suggests the minor topographic relief separating the Qaidam Basin from the Hoh Xil Basin to the south, served as the major source for the sediments deposited in the SW Qaidam Basin since the Paleogene. The Qilian Shan to the north, the underlying Mesozoic strata and the local paleo-reliefs to the southwest within the basin shed materials into the NE Qaidam Basin during the Paleogene. This finding exemplifies the fact that detrital zircon geochronology alone would lead to an incorrect interpretation if independent sedimentary evidence is not considered. Based on U-Pb detrital zircon geochronology data from Pliocene-Quaternary and loess samples collected from various locations in both the Qaidam Basin and Chinese Loess Plateau, our quantitative estimate shows that approximately 30% of materials in the Chinese Loess Plateau are derived from the sediments in the Qaidam Basin, twice the previous estimate. This higher proportion of the Qaidam Basin source for the Chinese Loess Plateau highlights that using a spatially limited sample set from the Qaidam Basin would result in underrating its contribution to the sediments preserved in the Chinese Loess Plateau.