Evaluation of the sources and seasonal production of brGDGTs in lake Sihailongwan (N.E. China) and application to reconstruct paleo-temperatures over the period 60–8 ka BP

Abstract Paleotemperature changes during the Late Quaternary are mainly derived from marine and ice core records. However, there are relatively few temperature reconstructions from the East Asian Monsoon region, which has hindered our mechanistic understanding so far. To address this issue, a new time series of paleo-temperature was developed, based on the analysis of branched glycerol dialkyl glycerol tetraethers (brGDGTs) from the well-dated sedimentary record of Sihailongwan maar lake (Lake SHL). This was achieved in two steps. Firstly, the sources and timing of seasonal production of brGDGTs were evaluated in the modern settings of Lake SHL. Secondly, using this information, we attempted to correct the temperature bias from soil derived brGDGTs using a binary mixing model, and a quantitative reconstruction of the paleo-temperature was derived from the Lake SHL brGDGTs sequence for the period of ∼60-8 ka BP. The results show that brGDGTs in Lake SHL are produced predominantly in summer and autumn (June–November). The sediment record reveals several important points: 1) the summer-autumn temperatures over the period ∼60–8 ka BP varied between ∼7 °C and ∼12.5 °C and the coldest period occurred during ∼25-21 ka BP when the mean summer-autumn temperature was ∼8.2 °C, 2) the summer-autumn temperature in Northeast China began to increase at ∼21 ka BP, and gradually warmed until the early Holocene in agreement with what has been recorded in southern China, most likely forced by summer insolation at 65°N.