Paleovegetation and paleoclimate changes based on terrestrial n-alkanes and their carbon isotopes in sediment from the Jeongok-ri Paleolithic Site, Korea

Abstract

Carbon isotope of total organic carbon (d13Corg) and long-chain n-alkanes, which are terrestrial plant biomarkers, and their compound-specific carbon isotope ratios (d13CALK) were investigated in the sediment of the Jeongok-ri Paleolithic Site in central Korea to interpret changes in paleovegetation and paleoclimate. The d13Corg ranged between approximately 24‰ and 27‰, suggesting different organic matter sources. Relatively lighter d13Corg occurred in lower part and the occurrence of heavier d13Corg in upper part may indicate terrestrial C3 plant dominance and/or a mixture of C3 and C4 plants, respectively. The patterns of n-alkane distribution were characterized by a continuous predominance of oddnumbered n-alkanes, particularly nC29 and nC31, and by variation in the distribution of evennumbered n-alkanes. Total concentration of n-alkanes and distributions of each number of n-alkanes are quite different over time, suggesting paleovegetation changes. The average chain length (ACL) and carbon preferences index (CPI) showed gradual variations with distinctive switching points at about 160 ka. This variation reflecting changes in paleovegetation type, is coincident with those of the d13Corg. Individual n-alkane isotopes, d13CALK, ranged between 18.64‰ and 38.09‰, suggesting different sources of n-alkanes. Although some petrogenic sources of n-alkanes were possible, the distribution of nalkanes and their d13CALK support paleovegetation and paleoclimatic variations in Jeongok-ri Paleolithic site, Korea for the last 300 ka.