Palaeoenvironmental evolution of the Northeastern Tibetan Plateau and its response to global temperature change during the Late Miocene: Geochemical and clay mineralogical evidence from the Jianzha Basin

Abstract

Aeolian deposits on the northeastern Tibetan Plateau (NETP) are valuable archives of the interaction between plateau uplift and climate change. We used the clay mineral assemblages and geochemistry of aeolian red clay in the Jianzha Basin, on the NETP, to reconstruct its paleoenvironmental evolution during the Late Miocene. We compared these data with those for surrounding basins and with global temperature changes sheds light on the relationship between regional tectonic-climatic processes and global changes on the NETP. Geochemical proxies of provenance change (Th/Sc, Zr/Sc, Eu/Eu*, La_N/Yb_N, and Zr/Cr) indicate a significant tectonic uplift event at ∼8.5 Ma on the NETP. Chemical weathering proxies (Rb/Sr, Li/Sr, and Ba/Sr) of bulk samples may be affected by sedimentary sorting. Hence, we used clay mineral (It = illite, Ch = chlorite, I/S = illite/smectite mixed layers, and Kao = kaolinite) and their assemblages ([S + I/S + Kao]/(It + Ch), (S + I/S)/(It + Ch), and (S + I/S)/It) to show that the climate of the Jianzha Basin tended towards aridity before ∼8.5 Ma and after ∼7.2 Ma. Conversely, during ∼8.5–7.2 Ma, the relatively humid environment in the Jianzha Basin was affected by both tectonic uplift and the intensification of the East Asian summer monsoon precipitation. Our study suggests that global temperature change controlled the climate of the NETP during the Late Miocene, and regional tectonism reinforcing this effect as a secondary controlling factors.