Long-chain alkenones in the Shimosa Group reveal palaeotemperatures of the Pleistocene interglacial Palaeo-Tokyo Bays

Abstract The Shimosa Group, a Middle- to Late-Pleistocene sedimentary succession, has been the focus of stratigraphic attention because it lies beneath Tokyo metropolitan area central Japan. It is also palaeoclimatic significance contains important interglacial marine strata past 450,000 years. Because Group were formed in shallow inner bay known as Palaeo-Tokyo Bay, rare occurrences planktonic foraminifera make difficult quantitatively reconstruct palaeo-sea surface temperatures (SSTs). Here, we extracted long-chain alkenones (LCAs) from core GS-UR-1 penetrating Marine Isotope Stage (MIS) 11. We found that alkenone unsaturation ratio appears reflect SST Bay during peaks MISs 5e, 7e, 9, and 11, which was consistent with inflowing water mass changes inferred benthic foraminiferal assemblages. palaeo-SSTs each period 2–3 °C higher than pre-industrial levels seemed reach level similar Holocene thermal maximum. findings this study demonstrate LCA-based proxy, not before utilised studies on strong potential provide palaeoceanic information.