Dian

Continuous lacustrine records of the Indian Summer Monsoon that span the Pleistocene-Holocene transition to the present are relatively rare, yet crucial to providing context to future changes in hydroclimate. We summarize here a 17,000 year continuous multi-proxy record of hydroclimate and primary productivity from Lake Dian in the central Yunnan Province of China. Analysis of sediment composition, opal, carbon to nitrogen ratios, carbon and nitrogen stable isotope ratios, and magnetic susceptibility (MS) are used to identify four distinct lithologic units in the sediment record. Unit I sediments from 17,000 to 11,500 years BP are characterized by high MS and uniformly low organic and opal content interupted by a decrease in MS during the Bølling-Allerød indicating the influence of the North Atlantic on the Indian Monsoon. We interpret this to reflect cold, dry, and windy conditions during the transition out of the Last Glacial Maximum. Unit II from 11,500 to 5,000 years BP is marked by a pronounced decrease in MS, increase in opal, and decrease in 13Corg of organic carbon driven by peak warmth and wet conditions increasing productivity. Unit III from 5,000 to 1,800 years BP shows further increases in primary productivity, marked by lower carbon to nitrogen ratios and carbonate precipitation, possibly driven by a drop in lake level. A period of aridity is in wide agreement with a number of other records from the region. Unit IV from 1,800 years BP to present is dominated by anthropogenic impacts and hallmark signs of catchment soil erosion and cultural eutrophication. Our interpretations of the Dian sediment record agree well with previous palynological work and add a new dimension to our understanding of lake hydrology and productivity over the past 17,000 years.

连续的印度夏季季风湖泊记录，涵盖从更新世-全新世过渡至今的时期，虽相对罕见，但对揭示未来水文气候变化的背景至关重要。本文总结了我国云南省中部滇池17,000年连续的多代理水文气候和初级生产力记录。通过对沉积物组成、蛋白石、碳氮比、碳氮稳定同位素比以及磁化率（MS）的分析，识别出沉积记录中的四个不同的岩性单元。I单元（17,000至11,500年前）的沉积物以高MS值和均匀的低有机质及蛋白石含量为特征，期间Bølling-Allerød期间MS值的下降表明了北大西洋对印度季风的影响，我们将其解释为最后冰期最大冰消期之后的寒冷、干燥和风大条件。II单元（11,500至5,000年前）以MS值的显著下降、蛋白石含量增加以及有机碳δ13Corg的降低为标志，这些变化是由峰值温暖和湿润条件以及生产力增加所驱动的。III单元（5,000至1,800年前）初级生产力进一步增加，表现为碳氮比降低和碳酸盐沉淀，这可能是由于湖面下降所引起的。与该区域其他多个记录相一致的是，一个干旱时期被广泛记录。IV单元（1,800年前至现在）以人为影响为主，并呈现出流域土壤侵蚀和文化富营养化的典型迹象。我们对滇池沉积记录的解释与之前的孢粉学研究结果相符，并为我们过去17,000年来对湖泊水文学和生产力理解增添了新的维度。