Monsoonal climate evolution in southern China since 1.2Â Ma: New constraints from Fe-oxide records in red earth sediments from the Shengli section, Chengdu Basin

Large fluctuations in major-element oxide concentrations and clay-mineral assemblages in the lower part of the section indicate climatic fluctuations between perennially humid and seasonally humid conditions in the mid-Pleistocene. Monsoonal climate evolution, as proxied by the hematite/(hematite + goethite) [Hm/(Hm + Gt)] ratio, shows a long-term but stepwise cooling and drying pattern in the Chengdu Basin with major transitions at ~ 1.0, 0.45, and 0.1 Ma. These transitions were probably triggered by episodes of tectonic uplift of the Tibetan Plateau and global climate change, with consequent effects on the Asian monsoons. The transitions in our paleoclimate proxy records for southern China match well with shifts in the marine oxygen and carbon isotope records since the mid-Quaternary, providing evidence of strong teleconnections between global and regional climates, terrestrial weathering, and the global carbon cycle.