N-alkane-based reconstruction of late Holocene lake-level changes at Lake Qinghai

Abstract

In previous studies, several kinds of methods have been used to do researches of the paleo-environment of Lake Qinghai or adjacent regions. Here, n-alkanes are used to reconstruct late Holocene lake level changes at Lake Qinghai. Sediments were extracted in the eastern lake shore area, where the biomarker would be sensitive to lake level changes. Five major stages have been divided according to the fluctuating values of four proxies, namely average chain length (ACL), carbon preference index (CPI), proportion of aquatic macrophyte (Paq) and concentration of C31 n-alkanes in the sum of C18 - C33 (C31%) during the late Holocene. These five stages are 3000-2500 yr BP (high and rising lake level), 2500-1500 yr BP (decreasing lake level from high to low), 1500-700 yr BP (low lake level), 700-0 yr BP (decreasing lake level), and after AD 1950 (from a low lake level to an intermediate stage). However, only a qualitative trend can be worked out, which is slightly different from previous quantitative study. The reason still needs further researches.