Paleoclimate and paleoceanographic variations based on foraminiferal isotope study in shelf sediment of the East Sea (Japan Sea), Korea

Abstract

To understand the paleoclimate and paleoceanographic evolution in the western continental slope area of the East Sea, we conducted the planktonic and benthic foraminiferal isotope study as well as carbon and nitrogen isotope of organic matter. The oxygen isotopic compositions of the planktonic foraminifera show approximately 0‰, but it shows heavier trend toward core top entirely. Whereas oxygen isotope compositions in benthic foraminifea do not have significant variation, they remain constant throughout the core with an average of approximately 4‰. This difference of oxygen isotope values between planktonic and benthic foraminifera (about 4‰) was derived by the temperature difference between surface and bottom water. Biogenic carbonate content and carbon and nitrogen isotope of organic matter provide valuable information on biological productivity and related climatic variation including ocean environmental changes. Total organic carbon (TOC) content (%) increased during Holocene and decreased during glacial periods with small fluctuation. Also, carbonate content seem to clear variation between glacial and interglacial period; glacial increase and interglacial decrease. These two opposing trend of TOC and carbonate may be contributed by either biogenic productivity changes including ocean environmental change or climate variations. Carbon and nitrogen isotope values ranged from -21.75matter. The oxygen isotopic compositions of the planktonic foraminifera show approximately 0‰, but it shows heavier trend toward core top entirely. Whereas oxygen isotope compositions in benthic foraminifea do not have significant variation, they remain constant throughout the core with an average of approximately 4‰. This difference of oxygen isotope values between planktonic and benthic foraminifera (about 4‰) was derived by the temperature difference between surface and bottom water. Biogenic carbonate content and carbon and nitrogen iso