Constraints of clay mineral assemblages on the provenance of sediments in the northern East China Sea with implications for the tectonic activities

Abstract

The Zhe-Min Uplift (ZMU) has significantly impacted the geomorphology of eastern China. Due to the geographic barrier created by the ZMU, the transport pathway of sediments from the paleo-Yangtze River to the East China Sea remains unclear. This study presents a high-resolution clay mineralogy analysis of a borehole (ECS-DZ1, 153.6 m) within the ZMU to investigate sediment provenance and paleoenvironmental changes in the northern East China Sea. In the Early Pleistocene, the clay minerals of marine sediments were predominantly illite, with notable contents of smectite (24 %) and kaolinite (12 %), primarily sourced from proximal sources such as the Bailonggang basalt and the Qiantang River. However, with ongoing tectonic subsidence, sediments from the paleo-Yangtze River began to influence the study area during the Early-Middle Pleistocene, leading to a decrease in kaolinite content (6 %). In the terrestrial deposits of core ECS-DZ1, illite is the dominant mineral (68 %), with relatively high kaolinite (12 %) and the absence of smectite, indicating that sediments were primarily derived from the Qiantang River. During the Holocene sea-level highstand, over 50 m of marine sediments accumulated in the Yangtze River estuary, with clay mineral assemblages from this period matching those of the Yangtze River, confirming it as the primary source. The sediment provenance of the East China Sea continental shelf is influenced by the complex interplay of global sea-level fluctuations and tectonic activity.