후기 제4기 동해 한국대지의 고기후 진화

Abstract

Sedimentary, geochemical study and stable oxygen isotope of planktic foraminifera were conducted in order to assess paleoclimate evolution in two core taken from the Korea Plateau, East Sea (Sea of Japan). Cyclic variation of oxygen isotopic signal with two negative spikes, which imply freshwater input is a significant characteristic in 96EBP-4. Based on the comparative study with published data, these two negative oxygen isotope signal correspond to ages about 15ka and 130 ka. Therefore the age of 96EBP-4 probably go back to, at least, marine isotope stage (MIS) stage 6. Sedimentological data; thin laminated layer, which is usually formed under anoxic condition between glacial to interglacial period, is well matched with other cores from the other part of the East Sea. M04-PC1A, taken from the near top of the Korea Plateau, holds drastic sedimentological changes, composed of two distinctive sedimentary units, upper and lower. Especially lower unit is mostly composed by shallow dwelling shell fragment. However sediment of the upper part is compared with nearby core 96EBP-4, it contains thin laminated mud layer and drastic TOC variation. Assuming that the site is tectonically submerged in past geological events, than this core probably holds climatic evolution since Miocene even though age dating is not conducted. Gradual decrease of benthic foraminifera occurred in lower part of sediment column probably implies that gradual sinking history followed by abrupt tectonic movement. More detailed studies are necessary to understand these paleoclimatic evolutions in the East Sea.