Decoupling of precipitation and temperature in North China across the Pliocene−Pleistocene transition

The intensity of the East Asian summer monsoon and associated rainfall changes in East Asia during the transition to cooler average global temperatures across the Pliocene−Pleistocene interval are widely debated. Here, we reconstruct monsoon evolution for the period of 3.85−2.20 million years ago using geochemistry, bulk sediment grain size, and organic matter content (OMC) from a lacustrine succession in the Sanmenxia Basin of North China. Chemical index of alteration (CIA) and OMC, both of which serve as indirect proxies for temperature, suggest that this region experienced two cooling events at ca. 2.9 Ma and ca. 2.7 Ma. Indirect precipitation proxies based on titanium (Ti), vanadium/chromium (V/Cr), vanadium/(vanadium + nickel) [V/(V + Ni)], V enrichment factor (V_EF), and grain size all suggest an increase in rainfall at ca. 2.8 Ma. Therefore, taken together, our results reveal a decoupling of precipitation from temperature trends in North China during the Pliocene−Pleistocene transition. This finding provides novel insights into the opposing responses of continental precipitation and temperature during the global cooling of the late Pliocene period.