Geochemical Characterization and Paleoclimatic Significance of the Xiaganchaigou Formation–Xiayoushashan Formation in the Youquanzi Area, Qaidam Basin

Abstract

Since the Cenozoic, the Earth’s climate has experienced significant transformations, transitioning from a “greenhouse” to the current “icehouse,” where ice sheets presently cover both Antarctica and the Arctic. The thick sediments deposited in the Cenozoic stratigraphy of the Qaidam Basin hold immense significance in unraveling the uplift of the Tibetan Plateau and the paleoclimate evolution of northwestern China. To understand the process of Cenozoic paleoclimate changes in the western Qaidam Basin, the paleoclimate of the Shangganchaigou Formation, Xiaganchaigou Formation, and the Xiayoushashan Formation was reconstructed by analyzing 114 mudstone samples of the Y3 well in the Yauchazi area for major elements and n-alkanes. The results indicate that the Younanshan area of the Qaidam Basin experienced two climatic transitions of wet-dry-relatively wet during the Eocene–Miocene period. The paleoclimatic changes indicated by the results of the correlation indexes of major elements and n-alkanes are consistent and well coupled with global climate change, East Asian monsoon, uplift of the Tibetan Plateau, and the Paratethys retreat event, suggesting that the paleoclimatic environmental changes during the Eocene–Miocene period may have been affected by the combined influence of these several factors.