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China University (2007)

Holocene Climate Variability Of Arid Central Asia Documented By Bosten Lake, Xinjiang, China

Huang X Z

Titre : Holocene Climate Variability Of Arid Central Asia Documented By Bosten Lake, Xinjiang, China

Auteur : X Z Huang

Grade : Doctoral Dissertation 2007

Université : China University

Résumé partiel
The arid central Asia is sensitive to global climate change. Bosten Lake, the largest inland freshwater lake in China, is strongly influenced by westerly and can document the model and process of the climatic variations of westerlies dominant area during the Holocene. Based on the age model constructed with 210Pb, 137Cs, AMS C-14 and OSL dating results, multiproxy analysis of core sediments and surface sediments, including pollen analysis, carbonates content, grain size, magnetic susceptibility, has been applied to reconstruct the regional climate variability since late glacial. The primary conclusions are as follows:1. Environmental significance of proxies and their modern process : A modern process within the Bosten Lake was investigated to understand the environmental significance of the proxies. Pollen analysis of the surface sediments suggested that the main difference of the pollen assemblages within the Bosten Lake was caused by the plants on the shore, and the pollen assemblage from the center of the lake could generally represent the regional vegetation scenery. On the other hand, it is also notable to consider the river induced influence on depositional process of the pollen grains, for example, as the dominant species, the spatial distributions of Chenopodiacea and Artemisia percentage had a zonal structure. The pollen A/C index can generally reflect the arid state of the area. Like other lakes, the pollen concentration is correlated to the water depth, having a higher concentration in the lake center than that of the shallow water area. The growth of Pediastrum algae is strongly correlated with water depth and its concentration increase rapidly when water depth exceeds around 10 meters. Because Pediastrum algae is a kind of freshwater algae, its concentration variations can generally reflect both water salinity and lake depth. The spatial distribution of other proxies of the surface sediments also showed...

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