Links Between Orbital Forcing, Antarctic Ice Volume, and the East Asian Hydrological Cycle Over the Pliocene

Abstract

AbstractRevealing the evolution of monsoonal intensity through the Pliocene on orbital timescales is of potential utility for providing insights into the response of Asian monsoons to future high pCO2 scenarios. Here, we report a continuous Pliocene cyclostratigraphic record from lake deposits of the Xinding Basin, Shanxi Graben, North China, and reconstruct the regional hydrological cycle from this location during ∼5.2 to 2.56 Ma. Our results show that regional hydrological cycling was consistently dominated by long‐and short‐eccentricity (405‐and 100‐kyr) forcing over the Pliocene. Gamma‐ray (GR) data (reflecting hydrodynamic changes) show strengthened 100‐kyr eccentricity power after ∼3.5 Ma, whereas 100‐kyr eccentricity power preserved in magnetic susceptibility (MS; interpreted as a proxy of pedogenesis and magnetic mineral dissolution) slightly weakened after ∼3.5 Ma. This orbital power transition at the 100‐kyr eccentricity scale may link to expansion of Antarctic ice volume after ∼3.5 Ma, which enhanced East Asian summer monsoon intensity and thus increased summer rainfall in North China, resulting in changes to hydrological cycling and the expression of eccentricity climate forcing in East Asian basins. In addition, our results demonstrate that the orbital configuration at ∼4.2–4.4 Ma could have been a contributory factor in strengthening the intensity of the East Asian summer monsoon at this time.