Variation and paleoclimatic significance of organic carbon isotopes of Ili loess in arid Central Asia

As an indicator for terrestrial paleovegetation, the stable isotopic composition of total organic matter (δ13Corg) in loess sediments has been widely used for paleoclimatic reconstruction in western Europe, the Great Plains of North America and the Chinese Loess Plateau (CLP). However, little is known about the variation and paleoclimatic significance of the loess δ13Corg in arid Central Asia (ACA). We report δ13Corg data from an Axike (AXK) loess/paleosol profile from the eastern Ili Basin, eastern Central Asia. Along the profile, the δ13Corg values were more negative in the paleosol layers observed in the field and were confirmed by environmental magnetic proxies and a higher concentration of total organic carbon (TOC), consistent with results for western Europe and the northwestern CLP. Our results demonstrate that the loess δ13Corg in this region documents mainly the response of δ13C of locally predominant C3 plants to paleoclimatic variation, especially paleoprecipitation. Our results also suggest that the loess δ13Corg values in the area have the potential for quantitative paleoprecipitation reconstruction on the basis of detailed δ13Corg results from modern plants and surface soils in the future.