A new age model for the sediment cores from Academician ridge (Lake Baikal) based on high-time-resolution AMS C-14 data sets over the last 30 kyr: Paleoclimatic and environmental implications

摘要

We constructed a new age model based on high-time-resolution C-14 data sets from three sediment cores from Academician ridge, Lake Baikal, for reconstruction of environmental and biological changes in southern Siberia during the last ca. 30 kyr. We used C-14 ages of total organic carbon (TOC) for the model, because terrestrial plant residues and biogenic carbonate were not observed in the sediments. For accurate dating and age models based on C-14 ages of TOC, the freshwater C-14 reservoir effect and the effect of dead carbon from land-derived organic materials must be estimated. In this study, we estimated the correction factor for these effects to be 2100 +/- 90 yr, on the basis of a key layer, the "C-14 plateau", caused by changes in the atmospheric C-14 concentration during the Younger Dryas (YD) cooling event. The new age scale, along with the TOC mass accumulation rate (MAR(TOC)) and stable carbon isotope ratio in the sediment cores, clearly indicate a rapid decrease in lake productivity and reduced influx of terrestrial organic materials into the lake during the YD (12.8-11.6 cal ka BP). Productivity was high (MAR(TOC), up to 19.7 mg/cm(2).kyr) in and around Lake Baikal during 9.3-6.4 cal ka BP (Holocene climate optimum). Moreover, paleoproductivity changes during the last ca. 30 kyr in and around the Lake Baikal were clearly associated with fluctuations in the East Asian monsoon intensity, as inferred from the delta O-18 record from Sanbao and Hulu caves, China, during the late Quaternary (Wang et al., 2008. Nature 451, 1090-1093).