Sedimentation processes and accumulation rates on continental shelves of South China Sea and Andaman Sea – insights from 210Pb and 137Cs

Prof. Dr. Witold Szczuciński

Gamma spectrometry is a commonly used tool to measure the activities of natural and artificial radioisotopes in sediments. The most common application is related to geochronology applying 210Pb and 137Cs techniques, which are complementary methods to date sediments back in time to over 100 years ago, providing a key tool for the stratigraphy of the Anthropocene. However, the vertical and spatial distribution of these radioisotopes in sediments may provide also insights into the style of sedimentation, variability in sediment accumulation rates, sediment transport, as well as post-depositional processes (mixing). The present paper focuses on new data for marginal seas of SE Asia, namely  the high accumulation rate area off Mekong River (continental shelf of South China Sea) and continental shelf of Andaman Sea (offshore Thailand) affected by catastrophic cyclones and tsunami. It is underlined that the gamma spectrometry analyses of sediments provide more opportunities than age dating, e.g.,  tracers for qualitative and quantitative assessment of sediment transport and sedimentation. They can provide information about erosion and deposition events (e.g., tsunami and cyclones), sedimentation processes, areas of sediment bypassing, and sediment sinks, as well as their sediment provenance.

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