A combined geochemistry study of late Pliocene Red Clay deposits from southern Chinese Loess Plateau and their paleoclimate implications

Abstract

<p>Pliocene warmth has been used as one of the best analogues for future anthropogenic warming. How East Asian hydroclimate respond to the increased temperature during the Pliocene is still elusive. Here, we present a combined element and isotopic geochemistry study of a Red Clay and loess-paleosol sequence covering the period 4-2 Ma on the southern Chinese Loess Plateau (CLP). The Na/K ratio and CIA values indicate increased weathering intensity during the late Pliocene. Meanwhile, the stable carbon isotopic compositions of pedogenic carbonate (δ<sup>13</sup>Ccarb) show relatively negative values which are explained as enhanced soil respiration flux (SRF) along with increased vegetation density. We propose that the increased East Asian Summer Monsoon (EASM) precipitation is a primary control of increased weathering intensity and vegetation density during the late Pliocene. An overall higher SRF across the CLP during the mid-Pliocene, compared with the Holocene and the Last Glacial Maximum, suggests there was a northwestward shift of the EASM rain belt and vegetation under warmer climate. In combination of modeling result from CESM 2, we support the hypothesis that global warming has driven the increasing of the EASM-derived rainfall, through the north migration of the intertropical convergence zone (ITCZ) and the monsoon precipitation belt during the Pliocene warmth.</p>