Uplift-enhanced Neogene silicate weathering intensity over the northern East Asian summer monsoon region

Abstract

The Neogene evolution of the Asian monsoon and East Asian silicate weathering remains debated. Previous reconstructions of the silicate weathering intensity (SWI) from the Asian interior and the South China Sea have shown a notable long-term decrease since the mid-Miocene, which has been attributed primarily to global cooling. However, considerable geologic evidence indicates that uplift of the northern Tibetan Plateau occurred mainly during the Neogene, and modelling studies suggest that this uplift intensified the monsoon precipitation in East Asia, which should have increased the SWI. It is therefore difficult to explain the absence of the impact of tectonic uplift on Neogene SWI evolution. Here, we present 23–5 Ma weathering records from the northern East Asian monsoon region (EAM). Our results revealed a long-term increase in the SWI since the mid-Miocene, in contrast to the decrease in the SWI in the South China Sea and the Asian interior. We speculate that the interplay between tectonic uplift and Neogene cooling has created a contrasting pattern of silicate weathering in East Asia. The increase in the SWI in the northern EAM was largely due to the uplift-intensified East Asian summer monsoon in North China, while the decrease in the SWI in the southern EAM was due to global cooling, with both cooling and uplift driving the decrease in the SWI in the Asian interior. The proposed pattern of SWI evolution in East Asia reconciles the discrepancies among regional weathering reconstructions, offering new insights into the interactions among plateau uplift, global cooling, and continental weathering.