제4기후기동안 동해 남한국대지에서 발견되는 암니층의 천년단위의 고해양학적 변화

Abstract

A piston core (05GCRP21), collected from the South Korea Plateau in the East Sea, is characterized by the preservation of a series of dark mud layers. The chronostratigraphy of core 05GCRP21 was established by comparison of L* values between core 05GCRP21 and well-dated core MD01-2407 which was collected in the Oki Ridge. Age of this core was judged to span about 190-kyr. Biogenic opal concentrations are high during Marine Isotope Stage (MIS) 1 and MIS 5.5 and low during the glacial period, suggesting the enhanced diatom production during the warm period. In contrast, glacial opal paleoproductivity appears to be depressed, probably because of insufficient nutrient availability, resulting from limited vertical ventilation. Overall TOC contents follow the orbital variations. However, high-resolution TOC fluctuations are independent of opal concentration, which may be attributed more to the preservation of organic matter rather than to the surface-water production. The low peaks of L* value of core 05GCRP21 define the dark mud layers, among which during the last glacial correlate with Dansgaard-Oeschger (DO) interstadial events. The formation of individual dark layer seems to be largely controlled by the position of sea level and degree of current influx through the Korea Strait, which brings the nutrient-rich, lower salinity East China Sea Coastal Water, strength of summer/winter monsoon etc. Thus, the paleoenvironment in the East Sea is sensitive to the global climate changes associated with not only orbital-scale glacial-interglacial variations but also millennial-scale stadial-interstadial variations.