Response of sediment grain size to sea-level rise during the middle Holocene on the west coast of the Gulf of Thailand

Siliciclastic grain size in lake sediments is an important proxy for studying the local paleoenvironmental conditions. Here, we report on temporal variations in siliciclastic grain size coupled with carbonate content of Core TLN-CP5 retrieved from Thale Noi Lake on the west coast of the Gulf of Thailand. The grain-size distribution coupled with sensitive component analysis in the studied core suggests that the 1.88–4.03 μm (Sensitive component: S2) and 9.86–24.1 μm (S3) grain-size populations responded to changes in the local sedimentary conditions of the area. A prominent feature is a sharp increase in the S2/S3 ratio after around 7.92 ± 0.12 cal ka BP, indicating the rapid sea-level rise during the middle Holocene on the west coast of the Gulf of Thailand. Moreover, our results reveal a change in the sediment processes of the lake, which could be caused by the trapping of fine-grained sediments in a low-energy environment when mangrove forests were established during the sea-level rise. These findings highlight that the variability of siliciclastic grain size in a coastal lake is closely correlated to sea-level change, which greatly increases our understanding of the effects of sea-level rise on the sediment dynamic processes in the lake on the west coast of the Gulf of Thailand.