Reconstruction of Chemical Weathering Intensity and Asian Summer Monsoon Evolution in the Red River Basin Over the Past 36 kyr

Abstract

AbstractThe Red River is located at the intersection of the Indian and East Asian monsoons. Understanding the evolution history of the monsoon in the Red River basin helps to comprehend the evolution of Asian Summer Monsoon. Herein, we present the high‐resolution major elements and Sr‐Nd isotopic ratios of the terrigenous sediment component for a well‐dated core retrieved from the northern South China Sea slope, aiming to identify the sediment provenance and reconstruct the silicate chemical weathering intensity since the past 36 kyr. The Red River was confirmed as the major sediment source through Sr‐Nd isotopic ratios. The silicate chemical weathering was affected by the rapid changes of sea level and monsoon, and thus it is difficult to indicate the regional paleoenvironment by the weathering degree. The principal component 1 composed of TFe2O3, Al2O3, K2O and MgO was shown to represent the fine‐grained sediment discharge, and employed as a proxy for the summer monsoon rainfall. Global cooling events/stages were identified through the proxies, including the Last Glacial Maximum, Heinrich events, Younger Dryas, and 8.2 ka, as well as the enhanced summer monsoon stages, including the Bølling/Allerød and early Holocene. Based on the comparison with the neighboring paleoclimate indicators, the region summer monsoon of the Red River basin was found to be governed by the Indian summer monsoon, and the summer insolation at low latitudes might be the primary forcing force on the orbital scale.