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 (delta C-13(org)) and long-chain n-alkanes, which are terrestrial plant biomarkers, and their compound-specific carbon isotope ratios (delta C-13(ALK)) were investigated in the sediment of the Jeongok-ri Paleolithic Site in central Korea to interpret changes in paleovegetation and paleoclimate. The delta C-13(org) ranged between approximately -24 parts per thousand and -27 parts per thousand, suggesting different organic matter sources. Relatively lighter delta C-13(org) occurred in lower part and the occurrence of heavier delta C-13(org) in upper part may indicate terrestrial C-3 plant dominance and/or a mixture of C-3 and C-4 plants, respectively. The patterns of n-alkane distribution were characterized by a continuous predominance of odd-numbered n-alkanes, particularly nC(29) and nC(31), 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 delta C-13(org). Individual n-alkane isotopes, delta C-13(ALK), ranged between -18.64 parts per thousand and -38.09 parts per thousand, suggesting different sources of n-alkanes. Although some petrogenic sources of n-alkanes were possible, the distribution of n-alkanes and their delta C-13(ALK) support paleovegetation and paleoclimatic variations in Jeongok-ri Paleolithic site, Korea for the last 300 ka. (C) 2015 Elsevier Ltd and INQUA. All rights reserved.