Enverionment Evalution Of Lacustrine Sediments In A Floodplain Lake Of The Lower Yellow River Area During The Historical

The lower reaches of the Yellow River area is located in north-central China, belongs to the typical east Asian monsoon region, the response is sensitive to climate change. Historical period of the lower reaches of the Yellow River more than 140 lakes and marshes, as today’s number of lakes in the Yangtze river basin, but in the context of global climate change, due to the Yellow River diversion frequently change and the influence of human activity intensifies, the vast majority of the lakes and marshes is dead. The area of the lake sediments contain rich information environment evolution and human activities, to restore the area on the study of lake sediments of ancient environment, understand the river change history and response to human activities is of great significance. Paper ancient cold ditch short core in the lower reaches of the Yellow River area as the research object, through the high precision of the AMA-14 C dating in combination with particle size, TOC, C/N, elements, such as climate/environment of the region history since 2500, the paper obtained the following results:(1)Based on accurate AMA-14 C dating framework, combined with particle size, WC, TOC index shows that, since 2500 cold ditch sedimentary environment stage can be roughly divided into the following several characteristics: During 2500~1700 cal yr BP, for lakeshore facies or impact plain facies sedimentary environment; during 1700~1000 cal yr BP, for shallow lake facies sedimentary environment; after 1000 cal yr BP, translate into fluvial facies or alluvial plain facies sedimentary environment.(2) Based on the above verification results and dating, use more environmental proxies comprehensive analysis reconstruction for nearly 2500 years since the lower reaches of the Yellow River region environment evolution information. Results show that the 2500~1700 cal yr BP, the climate is warm wet, cold, late and lower the intensity of human activities, affected by the river lake is frequent, sedimentary environment for the flood plain facies and shallow lake facies; 1700~1000 cal yr BP, give priority to with warm wet climate, with extreme weather, dry and cold climate change frequently, for shallow lake facies sedimentary environment still water lake facies sedimentary deposits or relatively stable; Finally evolved into flood plain facies and shallow lake facies; After 1000 cal yr BP, depositional enverionment evolved into fluvial facies or alluvial plain facies, human activities influence gradually strengthen, climate is warmer, and showed a trend of rise, this period of time, lakes for later development, has a tendency to down the decline.(3) Comprehensive comparison of the northern hemisphere polar ice core, and the plateau monsoon region, show that in the lower Yellow River River aere environmental evolution sequence and stalagmites, regional climate change is synchronous, there are specific characteristics and their evolution. Through the study we found the regional environmental changes may be controlled by the diversion of the Yellow River and earth system complex internal ocean atmosphere land coupled process.