Sedimentary signals of the upwelling along the Zhejiang coast, China

The muddy deposits of the Zhe-Min coastal area have attracted much recent research interest. However, the sedimentary processes that dominate along the Zhejiang coast remain controversial. Determining sedimentation rates is important for understanding sedimentary processes and depositional patterns. In the present study, 23 vibrocores were collected from the muddy area along the Zhejiang coast to analyse their sediment accumulation rates over the past 100 years using Pb-210 geochronology. Three types of typical excess Pb-210 profiles were identified in the sediment vibrocores. The spatial distribution of the sedimentation rates derived from the 23 vibrocores, as well as previously published data, demonstrated that the middle part of the study area around 29 degrees N experienced relatively high sedimentation rates, and that the rate of deposition gradually decreased landwards and seawards. The location of high sedimentation rates is approximately consistent with that of the Holocene maximum thickness deposition, finest surface sediments and high concentration of chlorophyll, resulting from the existence of upwelling along the Zhejiang coast besides the fluvial inputs.