마지막 빙하기~홀로세 동안 동해에서 산출되는 규조류의 안정동위원소 성분: 고해양학적 응용

Abstract

The piston core M04-PC3A was obtained from the Ulleung Basin, East Sea. Core sediments consist of two lithologic units: the upper unit dominated by bioturbated mud, and the lower unit consisting of alternating layers of crudely laminated mud and homogeneous mud. Age control is provided by four AMS radiocarbon dates for organic matter in core sediments. Oxygen isotopes of planktonic foraminifera (G. bulloides) and diatoms are analyzed. The δ18O record of record of planktonic foraminifera shows that a strong depleted values during 15~21 kyr BP reflect surface water freshening. The δ18O record of diatoms fluctuated between 33~39‰ (SMOW) and depleted values during 8~21 kyr BP. The differences of the δ18O record between planktonic foraminifera and diatoms during the LGM and transitional periods may reflect the different dwelling depths of these plankton groups. Diatoms generally dwell in surface waters where they conduct photosynthesis, whereas planktonic foraminifera can change their dwelling depths in accordance to surface environments. The timings and values for these two planktonic forms suggest that surface water was still freshened until 8 kyr BP. A freshwater pool appears to have covered a wide area of the southern East Sea from 21 to 8 kyr BP.