Modern (<100 years) sedimentation in the Taiwan Strait: Rates and source-to-sink pathways elucidated from radionuclides and particle size distribution

A large number of sediment cores collected during 2005–2010 from the Taiwan Strait were analyzed for radionuclides (210Pb, 137Cs and 7Be) to elucidate sedimentation dynamics in this all-important gateway linking two largest marginal seas in the western Pacific (namely, the South China Sea and the East China Sea). Apparent sediment accumulation rates derived from 210Pb and 137Cs profiles vary from <0.1 to >2 cm/yr, averaging ∼0.4 cm/yr and showing a spatial pattern closely related to hydrodynamics and sediment source-to-sink pathways. Spatial-temporal variation of 7Be activity in surface sediments off Taiwan’s west coast indicates episodic deposition of flood layers and their mobility from river estuaries toward the north. In conjunction with particle size distribution in surface sediments and the structure of sediment strata revealed by sub-bottom echo images; the radionuclide data can be used to outline three different sediment source-to-sink dispersal systems. Based on sediment loads of surrounding rivers and the distribution of sediment accumulation rates, lateral transport is required to account for the budget and size distribution of sediments in the strait.

Research Highlights
► Modern (<100 years) sedimentation in the Taiwan Strait elucidated from radionuclides (7Be, 234Th, 210Pb and 137Cs) is a key to the sediment strata revealed by sub-bottom echo images.
► Transport pathways, accumulation rates and budget of sediments in the Taiwan Strait are derived from temporal–spatial distribution of radionuclides (7Be, 234Th, 210Pb and 137Cs) in a large number of sediment cores.
► Different shapes of sedimentary 137Cs profiles in two sides of the Taiwan Strait reflect rapid transport by mountainous rivers in Taiwan vs. long transit time of fluvial sediments from large drainage basins in China.
► In the Taiwan Strait, higher sediment accumulation rates correspond to small particle sizes found in areas with low tidal and current flows.