巢湖早中全新世气候事件的高分辨率湖泊沉积记录研究

The Chaohu Lake in Anhui is a semi-enclosed lake, which located in the northern subtropical and warm-temperate transition belt in East China. The continuous lacustrine record from the Chaohu Lake provides good information on its past climate and regional environmental evolution. Previous studies have focused on the late Holocene climate change, human activity response and modern sedimentary records of eutriphication, but little in climatic events during the early-middle Holocene and their regional response mechanism. In this project, the lacustrine deposits from the Chaohu Lake are chosen as study materials through high-resolution multi-proxy records in priority of carbon and nitrogen geochemistry assisted of grain-size, magnetic susceptibility, and other sedimentary analysis. AMS14C dating is used to establish exact age frame assisted of other dating. Then, the high-resolution climate change sequence during the early-middle Holocene is reconstructed in Chaohu, and the chronology, changing process, environmental features and regional characteristics of main climatic events during the early-middle Holocene are also identified. At last, the above results are contrasted to other high-resolution records, environmental archaeology and simulation results to probe into mechanism of climatic events and environmental fluctuations during the early-middle Holocene in Chaohu, and their response to global changes, which can provide scientific basis to climate prediction, environmental protection and sustainable development of Chaohu area.

安徽巢湖是位于中国东部北亚热带和暖温带湿润季风气候区过渡地带的半封闭湖泊，湖泊沉积连续且记录了区域环境演化信息。以往的研究侧重于对其晚全新世气候变化、人类活动响应和近现代富营养化的沉积记录研究，很少开展早中全新世气候事件及其区域响应机制的探讨。本项目拟以巢湖湖泊沉积为主要研究材料，利用AMS14C等测年方法建立高精度年代框架；在沉积学分析基础上，以湖泊沉积物碳氮地球化学记录为主，粒度和磁化率等记录为辅综合分析，重建巢湖早中全新世高分辨率气候环境演变序列，辨识并重点探讨巢湖早中全新世主要气候事件的年代、变化过程、环境特征及其区域性特点；与其它高分辨率沉积记录、环境考古和气候模拟结果对比分析，探讨巢湖早中全新世气候事件与环境波动的区域响应机制，为我国东部季风区全球变化区域响应的湖泊沉积记录研究、气候趋势预测以及巢湖生态环境的保护、改善与可持续发展提供科学依据。

通过对巢湖西岸BZK1孔和湖心CH-1孔湖泊沉积岩芯的AMS14C测年、粒度、磁化率、磁组构、孢粉、炭屑及元素地球化学等的高分辨率多指标耦合记录的综合研究，重建了巢湖流域末次冰消期至全新世时期气候事件及环境演化史。结果表明：①末次冰消期以来，15.6-14.8 cal. ka BP，湖水逐渐变深，气候向温凉转变；14.8-12.8 cal. ka BP，气候环境已经过渡到相对温湿期，湖面为末次冰消期最大时期；12.8-11.7 cal. ka BP阶段气候环境急剧过渡到干冷期，该时期湖面缩小至末次冰消期最小时期；11.7-10.7 cal. ka BP阶段气候环境开始向相对温湿转变；10.7-10.5 cal. ka BP阶段气候环境又突然进入干冷期。②全新世早期，气候由寒冷干旱向温暖湿润过渡，但仍较为干旱，炭屑浓度也相对略高，火活动比较频繁，地方性和区域性火时有发生；全新世中期是最温暖湿润的适宜期，炭屑浓度出现全新世以来的低值，火活动微弱，但在文化兴盛时期炭屑浓度出现峰值，则归因于人类活动的影响；全新世晚期，在气候趋于凉干的环境背景下，人类活动的增强更加剧了火活动的频率和强度，炭屑浓度大幅增加；近200 a炭屑浓度的降低可能与湖区附近已没有足够生物量引起火灾有关。③巢湖湖泊沉积清晰记录了Bølling/Allerød暖期、YD事件及全新世早期发生在10.7-10.5 cal. ka BP和8.2-7.7 cal. ka BP的气候干冷事件，可与邻近区域葫芦洞石笋、低纬度的董哥洞石笋和天才湖孢粉，中纬度的海原剖面和硝沟剖面孢粉，以及格陵兰冰芯等形成鲜明对比，表明中国东部湖泊沉积记录的气候变化对全球变化有着积极的响应。