Framework of environmental changes in East Asia during the past 20 ka

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In order to clarify the framework of environmental changes during the past 20 ka, in Yangtze Delta, middle Yangtze area, lowest reaches of Heihe, Tarim Basin and Jungar Basin, China, and Kanto Plain, Saga Plain, Kagoshima Bay, and south Hokkaido, Japan.a. MIS2In the inland China, where alternation of wet or dry conditions is the most important, 17-18 ka and 13-12 ka were the stage of high sand and mud supply, at the same time that of active dune and dust formation, corresponding to dust peaks in Antarctic ice cores (Petit et al.,1999).b. Younger DryasIn Kanto and south Hokkaido, Japan, basal gravelly layer (HBG) of the Holocene will be relevant to the Younger Dryas event.c. HypsithermalIn Japan and east China, quick warming and sea level rising starts around 10 ka, corresponding to early phase of the Hypsithermal. This stage of rapid sea level rising is subdivided into two by the interruption of short lowering of sea level about 8.0 to 8.4 ka, nearly 8.2 ka event by Alley et al.(1997). It is necessary to understand whole Hypsithermal from 10 to 5.5 ka.d. Medieval Warm Period to Little Ice AgeIn the Medieval Warm Period, it is much drier and warmer in China, but in the latest Medieval Period and earliest phase of the Little Ice Age, river water level of Yangtze River increased suddenly in the middle reaches of the river. In the lowest reaches of Heihe, old channels were abandoned and new channels supplied water into new lakes.To grasp the timing of such important events in various part of the earth, especially in terrestrial areas, including inland and marginal areas of the continent, will contribute to make clear the unsolved problems in environmental changes, its mechanism, migration, magnitude and so on.