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Sedimentary process and its impact on diatom record in the Lake Basomtso (SE Tibetan Plateau) over the past 200 years

Glacial lakes distribute widely in the alpine mountains on the southeastern Tibet Plateau. Lake sedimentary process in this region is synthetically controlled by regional climate change, hydrological and geological conditions in the catchment, and lake morphological feature. To gain a more comprehensive understanding of lake sedimentary process, a 480 cm long core BSCW⁃1 was collected from the deepest part (120 m in depth) of the Lake Basomtso on October, 2012. The top 90 cm was used in this study to reveal the sedimentary process over the past 200 years. The chronology was constructed based on Pb / Cs measurements from the upper 60 cm and one AMS C result at 90 cm depth. Physical (grain size, sorting coefficient) and chemical data ( TOC, TN, C / N) were measured and analyzed. These data reveal a remarkable transition in sedimentary process between the late 18th and 19th centuries, showing abrupt decrease in sedimentation rate. By comparing tree⁃ring⁃based climate reconstructions ( temperature, precipitation and relative humidity) and records of palaeoglacial investigation, we suggested that regional climate change and glacier distribution in the catchment together influenced the sedimentary process in Lake Basomtso. Given that glacier had extended to lower altitude during the late 18th