日本海東縁コアMD179-3296, 3304の後期更新世以降の明度変動

抄録

Lightness of two long (over 30 m) piston core sediment (MD179-3329 and -3304) obtained at the Umitaka Spur off Joetsu of Japan Sea, was measured at 2 cm interval by MINOLTA SPAD 503 spectrometer. Umitaka Spur, about 900 m below sea level, is closed to Japan Alps and characterized by high sedimentation rates of about 0.4 mm/y, along with dozens of distinctive marker tephras. MD 179-3296 and -3304 sites show similarities and record Dansgaard/Oeschger (D/O) type oscillations as the lightness change of the sediment during the late Pleistocene. The two marine cores also suggest that there are somewhat similar oscillations during Holocene. The symmetrical lightness changes of the marine cores resemble those of stalagmites record from caves in China rather than the asymmetrical changes of temperature proxy record from Greenland ice cores, ie rapid temperature rise and gradual decline. This implies the lightness of the marine sediments reflects terrestrial sediment flux depending on the precipitation controlled by summer Asian monsoon activity. Thus, the lightness change has a potential to reconstruct paleoenvironmental changes with high resolution of decennial timescale in the marginal areas of the Japan Sea with high sedimentation rates.