The Holocene Yangtze River sediment derived mud wedge that deposits along the Zhejiang-Fujian coast, inner shelf East China Sea, has attracted considerable research attention; however, there is still controversy over the redistribution flux of Yangtze River sediment after it enters the sea. There are many bays along Zhejiang and Fujian coasts, but the role of these bays in the source-sink process of Yangtze River sediment is less well documented owing to limited data. As the second largest bay in Zhejiang Province, Sanmen Bay is an important sink of Yangtze River sediments, according to the newly obtained shallow seismic profiles and boreholes. The characteristic of clay minerals indicate that the fine grained sediments in Sanmen Bay are mainly derived from Yangtze River sediments. The thickness of Holocene deposits in Sanmen Bay ranges from 8.2 to 32 m, with an average of 23.4m and a total sediment of 5.06×10⁴ Mt, accounting for 1% of the sediment of the Yangtze River in Holocene. The Bayesian age-depth model based on borehole AMS¹⁴C dating shows that the high sedimentary rate occurred in the early and late Holocene, but decreased significantly in the Middle Holocene, which is similar with that on the inner shelf of East China Sea. The variation of the Holocene sedimentary rate in Sanmen Bay is related to the southward transport process and mechanism of Yangtze River sediments. The research has enriched and developed the scientific connotation of the source-sink process of sediment in large rivers.

Sanmen Bay, Holocene, Yangtze River, Seismic profiles, Sediment budget