Northwestern Chinese record of Cenozoic global events

• Published in: Catena (Giessen) Vol. 239; p. 107892
• Main Authors: Guo, Xuelian, Retallack, Gregory J., He, Lusheng, Li, Zaijun, Liu, Jinhao, Wang, Ronghua, Liu, Xiuming, Wang, Weibin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.04.2024
• Subjects: Cenozoic; Elemental geochemistry; Paleoclimate events; Paleosol; Paleosol; Paleoclimate events; Cenozoic; Elemental geochemistry
• ISSN: 0341-8162; 1872-6887
• DOI: 10.1016/j.catena.2024.107892

•Different paleosol types record past climate and vegetation change in the Lanzhou Basin, Gansu.•Persistent arid to semi-arid climate from Eocene to Miocene was interrupted by warm-humid spikes.•Lanzhou basin paleosols recorded a variety of Cenozoic global paleoclimatic events.•The rain shadow from Tibetan Plateau uplift maintained arid to subhumid eolian deposition. Global cooling over the past 45 million years has been well established from deep sea isotopic records, and one explanation has been the cooling effect of uplift of the Tibetan Plateau. Other explanations for cooling are initiation of circum-Antarctic circulation, and carbon sequestration by newly evolved grasslands. The Lanzhou Basin is located at the intersection of the Tibetan Plateau, eastern monsoon region, and northwestern arid region of China, so well placed to evaluate Tibetan Plateau effects. This paper infers paleoclimatic changes from a long sequence of Cenozoic paleosols within the Xiliugou, Yehucheng and Xianshuihe Formations, in the Lanzhou Basin of Gansu. Eleven distinct kinds of paleosols (pedotypes) were recognized in the field from root traces, soil horizons and soil structures. These pedotypes were then intepreted as soils by R-mode factor analysis and molecular weathering ratios of major element geochemical composition. Supporting data from compaction-corrected depth to carbonate in the paleosols show that paleoclimate was persistently arid to semi-arid from the middle Eocene to the middle Miocene, but interrupted by transient climatic warm-wet events, which correlate with marine oxygen-isotopic events and large igneous province basaltic eruptions. At 42, 34, 22, 18, 17 and 16 Ma, spikes of mean annual temperature (MAT) and mean annual precipitation (MAP) are evident from the paleosols, at times also recognized in global marine isotopic and stomatal index carbon dioxide records. At 37, 33 and 23 Ma, low MAP and MAT estimated from paleosols of the Lanzhou Basin coincide with glacial advances, and marine oxygen isotopic spikes and low CO2. Paleosols of the Lanzhou Basin record global paleoclimate events during the middle Eocene to the middle Miocene, rather than variation in Tibetan Plateau uplift. The rain shadow from Tibetan Plateau maintained generally arid to subhumid eolian deposition in Gansu for the past 50 million years.