High-resolution clay mineral assemblages in the inner shelf mud wedge of the East China Sea during the Holocene: Implications for the East Asian Monsoon evolution

The inner shelf mud wedge of the East China Sea (ECS) is a high-sedimentation-rate fine-grained sediment unit that has preserved a continuous environmental evolution history since the last deglaciation. We present a high-resolution clay mineralogical study from Core MD06-3040 to semi-quantitatively evaluate terrigenous sediment contributions from various potential provenances throughout the Holocene. The results showed that the clay mineral assemblage is composed of dominant illite (34-49%), moderate smectite (16-41%) and chlorite (15-28%), and minor kaolinite (5-12%). Provenance analysis suggested that most fine-grained terrigenous sediments originated from the Yangtze River, with minor sediments derived from Taiwan island and negligible sediments from nearby Zhejiang and Fujian provinces. Time series variation in the contribution of the Yangtze source fluctuated in the range of 38-80%, whereas that of Taiwan island had a converse variation pattern from similar to 10% to similar to 55%, and the contribution of Fujian was relatively stable in the range of 7-11% throughout the Holocene. The fluctuations of clay mineral assemblages and variations of clay mineral contributions from different provenances of Core MD06-3040 were controlled by the variability of precipitation in the Yangtze drainage associated with periodic fluctuations in the East Asian monsoonal circulation.