Multi-proxy stratigraphy and paleoceanographic variations in sediment from the Korea Plateau, East Sea (Japan Sea), over the last 500 kyr

Abstract

High-resolution geochemical measurements were performed on core E09-08, which was taken from the top flat area of the Korea Plateau in the East Sea (Japan Sea). Based on analyses of sedimentary lamination, high-resolution oxygen isotopes, alkenone sea surface temperature (SST) variations, and comparison with previous results from the eastern part of the East Sea, a detailed multi-proxy-based stratigraphy was reconstructed. The results demonstrated that the core bottom dates approximately 500 kyr in the late marine isotope stage (MIS) 13, and provides high-resolution data on the paleoceanographic regime in the study area. Biogenic components of total organic carbon (TOC), carbon and nitrogen isotopes of organic matter (δ13Corg and δ15Norg), and alkenone concentrations indicate a paleoceanographic regime shift within the last 500 kyr. The excursion of proxies of δ18O, δ13Corg and δ15Norg and alkenone-based SST indicate two modes of oceanographic conditions: strong negative coupled mode (SNCM) during MIS 2, 10, and 12, and normal oceanographic decoupled mode (NODM) during other MIS. These two modes were interpreted as the terrestrial organic matter source domain and high-productivity oceanographic domain, respectively. The SNCM is characterized by relatively low δ13Corg and δ15Norg, and a high C/N ratio (> 12), whereas the NODM is characterized by relatively high δ13Corg and high δ15Norg, implying that larger amounts of terrestrial material were supplied during MIS 2, 10 and 12, with enhanced productivity during other MIS. The SNCM and NODM mode are also strongly associated with eustatic sea-level changes. The δ13Corg and δ15Norg values and alkenone-based SST excursions over glacial-interglacial periods were generally consistent with global-scale paleoclimate variation, as well as local paleoclimate. This study employed multi-proxy-based stratigraphy to demonstrate dramatic oceanographic variations since MIS 13, indicating that the local oceanographic setting was superimposed on global glacial-interglacial variations.