Research papers Modern ( o100 years) sedimentation in the Taiwan Strait: Rates and source-to-sink pathways elucidated from radionuclides and particle size distribution Chih-An Huh a,n , Weifang Chen a , Feng-Hsin Hsu a , Chih-Chieh Su b , Jui-Kun Chiu c , Saulwood Lin b , Char-Shine Liu b , Bor-Jiun Huang a a Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan b Institute of Oceanography, National Taiwan University, Taipei, Taiwan c Taiwan Ocean Research Institute, National Applied Research Laboratories, Taipei, Taiwan article info Article history: Received 23 June 2010 Received in revised form 6 September 2010 Accepted 5 November 2010 Available online 18 November 2010 Keywords: Taiwan Strait Sediment accumulation rate Source-to-sink transport 210 Pb 137 Cs 7 Be abstract A large number of sediment cores collected during 2005–2010 from the Taiwan Strait were analyzed for radionuclides ( 210 Pb, 137 Cs and 7 Be) 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 o0.1 to 42 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 7 Be 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. & 2010 Elsevier Ltd. All rights reserved. 1. Introduction The Taiwan Strait (TS) is bounded by Taiwan, mainland China, the South China Sea (SCS) and the East China Sea (ECS) on its east, west, south and north, respectively (Fig. 1). About 350 km in length, 180 km in average width and 60 m in average depth, the strait connects two largest marginal seas in the western Pacific and receives sediments from the largest continent and a high-standing mountainous island known to have the highest erosion rate in the world (Li, 1976; Dadson et al., 2003; Huh et al., 2009a). Hydro- dynamics and sedimentation processes in such a crucial setting are conceivably complex and play important roles in regulating the transport of water as well as sediments through it. While circulation patterns in the TS have been fairly well studied and documented in the past 1–2 decades (see next section), sedimentation dynamics in the strait remains poorly understood by comparison. There is no doubt that 210 Pb is the most commonly used and almost indispensable tool to date nearshore sediments. However, such data are virtually not available for the northern TS. Although a fairly comprehensive dataset has been established off southwestern Taiwan around the Gaoping submarine canyon recently (Huh et al., 2009a, b), there is as yet no report in the open literature of 210 Pb-based sediment accumulation rates to the north of the Penghu Channel. Published sediment accumulation rates in the TS were largely based on 14 C dating of suitable carbon-bearing material found in sediment cores (Chen and Covey, 1983; Xu et al., 1989, 1990; Lan et al., 1993) plus estimates based on paleomagnetism (Chien and Leu, 1984) and a two-component (terrigenous vs. pelagic) 10 Be mixing model (Lee et al., 1993). Rates from these methods are generally more than one order of magnitude lower than 210 Pb- and 137 Cs-based rates obtained in this work. As will be discussed later, such a discrepancy can be ascribed to the vastly different timescales involved in various methods and associated changes in environmental and sedimentation conditions with time. The purpose of this work is to elucidate the sources, pathways and accumulation rates of sediments in the TS from seasonal to centennial timescales. Radionuclides ( 7 Be, 137 Cs, 210 Pb and 234 Th) with different source functions and half-lives were used as tracers toward reaching this goal. Grain-size distribution in surface sediments was used to provide an additional constraint on sediment transport under the influence of hydrodynamic processes. Radionuclide and Grain-size data were integrated with sub-bottom echo images of relevant Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/csr Continental Shelf Research 0278-4343/$ - see front matter & 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.csr.2010.11.002 n Corresponding author. Tel.: + 886 2 27839910x607; fax: + 886 2 27839871 E-mail addresses: huh@earth.sinica.edu.tw (C.-A. Huh), henwf@earth.sinica.edu.tw (W. Chen), fenghsin@earth.sinica.edu.tw (F.-H. Hsu), donccsu@ntu.edu.tw (C.-C. Su), jkchiu@narl.org.tw (J.-K. Chiu), swlin@ntu.edu.tw (S. Lin), csliu@ntu.edu.tw (C.-S. Liu), jiun24@earth.sinica.edu.tw (B.-J. Huang). Continental Shelf Research 31 (2011) 47–63