Late Quaternary terrestrial climatic variability recorded in deep-sea turbidites along the Toyama Deep-Sea Channel, central Japan Sea

Stratigraphic variations of coarse fraction, and frequency and thickness of turbidites in three cores collected along the Toyama Deep-Sea Channel (TDSC) in the central Japan Sea show consistent temporal trends with changes in terrestrial climatic records. These temporal changes in turbidite deposition may reflect climatic forcing in the sediment source areas for the last 70 ka. Comparison of temporal changes in turbidite deposition with paleoclimatic and paleoceanographic records in the central Japanese mainland and the Japan Sea revealed the following modes of climatic linkages; (1) During the stadials and interstadials of the last glacial period (70–22 ka) when the Tsushima Warm Current (TWC) periodically flowed into the Japan Sea, the Japanese mainland climate was cold and periodically wet, resulting in occasional glacial advances in adjacent mountains. Turbidite flux increased in the TDSC system during the major glacial advances because of the increased production of coarse debris by glacial processes and high transport potential due to high precipitation. (2) During the last glacial maximum (22–18 ka) when the Japan Sea was capped by cold, low-salinity surface water, the terrestrial climate was cold and dry due to low evaporation from the Japan Sea. As a result of low precipitation, less coarse debris was transported into deep basins, and so during this period, the turbidite flux along the TDSC was reduced. (3) During the last deglaciation (18–8 ka), precipitation in central Japan increased due to intensified summer monsoons. This resulted in destabilization of mountain slopes and increased transport of detritus to the lowlands and also to the TDSC system. (4) After the TWC flowed into the Japan Sea, the land climate became warm, wet, and stable. Enhanced vegetation and re-stabilized mountain slopes have reduced sediment input to the TDSC system since 8 ka.