Long-chain alkenones in sul-fate lakes and its paleoclimatic implications

Abstract

The proxy of U37K′ index is widely applied to reconstructing paleotemperature in the marine environment. However, the long-chain alkenones (LCAs) research is rarely reported in the liminic system. In this paper, we studied LCAs in the surface sediments (0–10 cm) of nine sulfate lakes in the Inner Mongolia Autonomous Region, Xinjiang Uygur Autonomous Region and Qinghai Province, China. LCAs are detected in eight of the nine lakes, except a dry salt lake — Lake Lop. The result shows that LCAs might be universal in the sulfate lakes. In most of the surface samples, the sequence of the abundance of the long-chain alkenones is C37>C38C39>C40· And C37:4 methyl ketone is a predominant compound in the C37 alkenone homologue. Based on regression analysis of U37K′ -ratios and the average annual, seasonal (spring, summer, autumn, winter) temperatures, the linear relativity of U37K′ -ratios and mean annual temperatures is superior to the others, and the correlation coefficient is 0.88 (r2= 0.88). The linear relationship of U37K′ and the average annual temperature in different water chemistry environments suggests that the mechanisms controlling U37K′ index in the saline lakes might be the same as those in the ocean environment. The alkenone unsaturation could become an important paleotemperature proxy in the lacustrine environment.