Cenozoic sediment flux in the Qaidam Basin, northern Tibetan Plateau, and implications with regional tectonics and climate

Abstract

As the largest Mesozoic-Cenozoic terrestrial intermountain basin in the northern Tibetan Plateau, the Qaidam Basin is an ideal basin to examine the influences of regional tectonics and climate on sediment flux. Research conducted over the last two decades has provided abundant information about paleoclimatology and tectonic histories. In this study, we used the restoration of seven balanced cross-sections and compiled thickness data of ten outcrop sections and four boreholes to reconstruct the basin boundaries, develop isopach maps, and calculate the sediment flux in the Qaidam Basin. Our results show that the sediment flux in the Qaidam Basin increased gradually between 53.5 and 35.5Ma, decreased to its lowest value from 35.5 to 22Ma, increased between 22 and 2.5Ma, and then increased dramatically after 2.5Ma. By comparing the changes in the sediment flux with our reconstructed shortening rate in the Qaidam Basin, and the records of regional tectonic events and regional and global climate changes, we suggest that the gradual increase in the sediment flux from 53.5 to 40.5Ma was controlled by both the tectonic uplift of the Tibetan Plateau and the relatively warm and humid climate, and that the high sediment flux from 40.5 to 35.5Ma was mainly controlled by tectonics. The low sediment flux from 35.5 to 22Ma was a response to the relatively cold and arid climate in a stable tectonic setting. The relatively high sediment flux between 22 and 15.3Ma was related to tectonic activity and the warm and humid climate. The intense tectonic uplift of the northern Tibetan Plateau and the frequent climate oscillations after 15.3Ma, particularly the glacial-interglacial cycles after 2.5Ma, caused the high sediment flux after 15.3Ma and the dramatic increase after 2.5Ma, respectively.