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

摘要

A large number of sediment cores collected during 2005-2010 from the Taiwan Strait were analyzed for radionuclides (~(210)Pb, ~(137)Cs 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 ~(210)Pb and ~(137)Cs profiles vary from <0.1 to >2cm/yr, averaging ~0.4cm/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.