Aquatic species dominate organic matter in Qinghai Lake during the Holocene: Evidence from eolian deposits around the lake

Abstract

Total organic carbon (TOC) in lake sediments and its stable carbon isotope (δ13Corg) are widely applied to investigate paleoenvironmental changes even though their implications are complicated and multi-explanatory. Organic geochemistry studies of lake sediments from Qinghai Lake have been investigated, but some interpretations are controversial. In this study, TOC of one Holocene eolian section and δ13Corg of three eolian sections were studied around Qinghai Lake. Results indicate that the TOC content in eolian deposits was low during the Early Holocene, and gradually increased to high values during the Middle and Late Holocene. The variation in TOC content of eolian deposits is different from that in the lacustrine sequence from Qinghai Lake during the Holocene. The δ13Corg values in the eolian sections were relatively stable, with oscillation amplitudes of ~4‰ (ranging from -25.8‰ to -22.1‰), in contrast to ~10‰ variations in δ13Corg values (varying from -30‰ to -20‰) in lacustrine sediments. Through comparison of TOC and δ13Corg values between eolian deposits and lacustrine sediments, we can confirm indications that the organic matter in Qinghai Lake sediments during the Holocene was primarily a contribution of the aquatic species in the lake. This is significant for understanding the origin of organic matter in lake sediments on the northeastern Qinghai-Tibetan Plateau and for paleoenvironmental inferences using such proxies.