Carbon and oxygen isotopic records from Lake Tuosu over the last 120 years in the Qaidam Basin, Northwestern China: The implications for paleoenvironmental reconstruction

Isotopic compositions of total organic carbon (TOC) and authigenic carbonate in lakes have been widely used to reconstruct paleoclimatic changes and the depositional environments of lake sediments. However, since these proxies are often controlled by multiple environmental factors, detailed examinations of modern environmental processes is necessary before further applying them into paleoclimatic studies, especially in arid/semi-arid northwestern China. Here we generate High -resolution multi-proxy sedimentary records from Lake Tuosu, a hydrologically closed, saline and alkaline lake located at the north margin of the Qaidam Basin, through analysis of carbon isotope of TOC, and delta O-18 and delta C-13 values of ostracods over the last 120 years. Together with the meteorological data (precipitation and temperature), lake area record, and other tree-ring evidence, we examine how these sedimentary indices respond to changes in hydrologic balance and climate at interannual to decadal timescales. We found that sedimentary delta(13)Corg values resemble the variation of lake areas of Lake Tuosu over the last 40 years, suggesting that delta(13)Corg values would be an ideal indicator of lake area/level fluctuations and thus effective moisture variations (precipitation vs. evaporation). However, ostracod delta O-18, which was previously used as proxies of effective precipitation, is not well correlated with delta(13)Corg values in Lake Tuosu. Therefore, the changes of ostracod delta O-18 values cannot be straightforwardly explained as the effective precipitation. Instead, the isotopic composition of carbonate would be additionally controlled by other factors including isotopic compositions of input water and drainage pattern. (C) 2016 Elsevier B.V. All rights reserved.