Marine deposition and sea surface temperature changes during the last and present interglacials in the west coast of Taiwan Strait

In order to reconstruct the environmental and climatic conditions of the last and present interglacials, this study has examined a 52 m-long core obtained from a coastal embayment (Chang-Le) on the west coast of Taiwan Strait. The analyses of particle size distributions, total carbon content, organic carbon isotope ratios, n-alkane indices and alkenones from the core reveal two periods of marine transgression. Together with the radiocarbon and optically simulated luminescence dating analyses, the environmental proxies indicate that the older marine sequence (M1) was deposited during the period of rising sea level in the early-to-middle part of MIS5e. The younger marine sequence (M2) was confirmed as a deposit formed during the stable sea level of the latter part of the present interglacial. The shallow marine facies and the abundant alkenones from M2 suggest a deeper water environment under full marine conditions during the last interglacial. The sub-tidal to intertidal facies and weak appearance of alkenones in M1 imply a shallow water environment under weak marine influence. Because the site was close to upland landscape, high input of terrigenous material for both periods is evident. The alkenone-based sea surface temperature (SST) reconstructions indicate that the SST during MIS5e fluctuated slightly around 28.1 °C, which is about one degree higher than that of MIS1, consistent with records from the northern coast of the South China Sea. The depositional conditions and the burial depths of the two marine sequences also provide hints for the local tectonic movements.