Climate-driven provenance variation and sedimentary system evolution at the Changjiang distal mud since the mid-Holocene

The Changjiang (i.e., Yangtze River) distal mud is a typical region for studying source-to-sink systems in the world. The coupling between climate change and the sedimentary system evolution of the Changjiang distal mud since the Holocene is widely debated. In this study, based on a 14C chronological framework, we investigated the sedimentary system evolution of the Changjiang distal mud since 8 ka. The provenance identification and climate conditions indicated that the climate oscillation largely determined the sediment source-to-sink processes. The sedimentary system was controlled by monsoon system oscillation from 8 to 3 ka. Specifically, during 8-5.4 ka, the prevailing Indian and east Asian summer monsoons increased the sediment flux to the Changjiang distal mud, and the proportion of the Changjiang sediments increased across the entire Changjiang distal mud. Notably, the southern regions were significantly influenced by western Taiwan rivers. Additionally, the prevailing east Asian winter monsoon enhanced the Zhejiang-Fujian coastal current, resulting in the deposition rates increased in south while declined in north. During 5.4-3.0 ka, the summer monsoon systems attenuated, causing decreased sediment discharges from the Changjiang and Taiwan, and the deposition rates declined across the entire Changjiang distal mud. In the southern regions, the intensified Taiwan warm current increased the proportion of Taiwan sediments. Since 3 ka, the monsoon system has become stable, and anthropogenic activities in south China have increased remarkably. The anthropogenic activities resulted in increased Changjiang sediments and rose deposition rates across the entire Changjiang distal mud. During 1.2-0 ka, the frequent floods in the Changjiang basins and typhoons in Taiwan, caused by increased El Nin similar to o-Southern Oscillation (ENSO) frequency, resulted in provenance fluctuation at the Changjiang distal mud. In addition, the attenuated east Asian winter monsoon caused a northward depocenter shift, which was reflected in spatially different deposition rates, i.e., retained high values in the north but declined in the south. Our findings emphasized the dominant roles of different climatic factors in different stages, and enhance our understanding of the east Asia land-ocean in-teractions and the relationships among the Earth's spheres since the mid-Holocene.

Automated summary

The study found that the sedimentary system evolution of the Changjiang distal mud since the Holocene is strongly influenced by climate change. The oscillation of monsoon systems plays a dominant role in the sediment source-to-sink processes, affecting the sediment flux and deposition rates. Additionally, anthropogenic activities in south China have contributed to increased sediment discharge and deposition rates. The findings enhance our understanding of the interactions between land and ocean in East Asia since the mid-Holocene.