High resolution Late-Holocene biomarkers records in southern continental shelf of the Korean peninsula: Implications for climate variations in East Asian region over the last 4 kyr

Abstract

High-resolution records for carbon isotopes of organic matter and n-alkane compounds were investigated in two gravity cores (SJP15-2 and SJP15-4) taken from the southern continental shelf of the Korean peninsula to evaluate the influxes of terrestrial biomarkers and their linkage to paleoclimate and marine environmental changes since the last 4 kyr. The total organic carbon contents were <1%, and the carbon isotope ratio of organic matter (δ13Corg) ranged from approximately -21‰ to -22‰ and, they show gradual lighting trends toward surface in two cores. However, the vertical distributions of total terrestrial biomarkers, long-chain n-alkanes (nC25-35), and individual n-alkane compounds exhibited distinctive fluctuations. There are two switching points that discriminate patterns of excursion and distribution. Several n-alkane combined indices such as average chain length (ACL), carbon preference index (CPI), and paleovegetation index (Paq) were coincident with these switching points, implying that the supply of terrestrial biomarkers was strongly associated with environmental changes at the source area. Therefore, our high-resolution n-alkane data are very useful for reconstructing past climatic climatic condition, suggesting that paleoclimate system of the East Asian region may have influenced the sediment records of study area since the last 4 kyr.