摘要
在江苏固城湖湖心采集了连续岩芯,进行了137Cs,210Pb,14C和光释光分析以研究全新世以来固城湖湖泊沉积年代序列,同时进行了粒度、有机质、总氮以及元素的分析,以辅助研究固城湖的沉积模式。137Cs和210Pb的分析表明,固城湖百年来的沉积是持续的,近20年平均沉积速率约在0.066cm/a。从0.5m深度到1.78m深度的AMS14C的树轮校正年龄在8000～6500BC之间,而光释光数据表明同等深度其绝对年龄在7～8ka之间。AMS14C的校正年龄与光释光年龄结果有较好的一致性。从多环境代用指标的剖面来看,在钻孔30cm深度出现了大的转折。结合现代沉积物平均沉积速率及对比历史文献得出上部30cm岩芯代表了约450年以来的沉积,这与公元1556年下坝的建成使得固城湖彻底与太湖隔绝时间相符。因此,固城湖地区可能的沉积模式是固城湖彻底与太湖隔绝后才出现持续沉积,在此之前一段时间内沉积物由于侵蚀或者人类活动如围垦导致缺失,而在约6～8ka之间沉积速率比较高。
The Gucheng Lake is a relatively small and shallow water body located in Nanjing, Jiangsu Province; China. The lake is on the lower reach of the Yangtze Valley. Historically, the Gucheng Lake was linked to or isolated from the Taihu Lake due to human activities such as establishment or destruction of dams. This area has also experienced frequent reclamation work since 500BC. The total surface area of the Gucheng Lake was about 65km^2 in the early 1960s, but the subsequent reclamation work held in the 1960＇s and 1970＇s around the lake caused a continual shrinkage, to only 24.5km^2 in 1979. In order to understand the sediment deposition pattern and human activities, sedimentary cores were collected from the lake in 2005. ^210Pb, ^137Cs, ^14C, and OSL were analyzed to study chronology of Gucheng Lake during Holocene. The total organic carbon （TOC）, total nitrogen （TN）, elements and particle size were also analyzed. Results of ^210Pb, ^137Cs reveals an average sedimentation rate of nearly 0. 066cm/a in the past twenty years. The age is between 8000 -6500BC based on AMS ^14C results from depth 0.50m to 1.78m, which is comparable with OSL age of 7 -8ka from corresponding depth. Sharp transition of index including TOC, TN, elements and grain size emerged at depth of 0.3m representing about 450 years based on sedimentation rates mentioned above. The age was consistent with 1556A. D. when the lake was isolated from the Taihu Lake due to the establishment of the dam Xiaba. It was inferred that continual deposition might occur after the isolation, while sediments deposited before that time might have been eliminated due to erosion or human impact such as cultivation. During 6 - 8ka high accumulation of sediment might have occurred.
出处
《第四纪研究》
CAS
CSCD
北大核心
2007年第3期365-370,共6页
Quaternary Sciences
基金
国家自然科学基金项目(批准号:40472085)资助
关键词
江苏固城湖
沉积模式
光释光
the Gucheng Lake, deposition pattern, OSL
