Discovery of a Buried Wood Piece and its 14C Date in the Esaoman-Tottabetsu Valley, Hidaka Mountains, Hokkaido, Japan

A buried wood piece was discovered in alluvial cone sediments in the Esaoman-Tottabetsu Valley, Hidaka Mountains, Hokkaido, Japan.The buried wood was identified as Pinus subgen. Haploxylon sp., and it should most probably be Pinus pumila. The AMS age of 12.3cal ka of the wood indicates that the alluvial cone might have been deposited during the Younger Dryas (YD), a globally recognized distinct cold climate phase of about 11-13cal ka during the last deglaciation. During the same period, distribution of cold flora was also recognized in the lowland area of Hokkaido, and this cold period is called the Kenbuchi Stadial. The sediments containing the wood are considered to be slope failure deposits which overlie a diamicton that might be subglacial till formed by the last glaciations. Thus, the identification and dating of the buried wood piece in the Esaoman-Tottabetsu Valley provide valuable and fundamental information to evaluate the alpine environments in Hokkaido, in relation to the significant rapid climate change of YD, in the course of global warming of the late-/postglacial periods.