Comprehensive Analysis of Lake Sediments in Yanchi Lake of Hexi Corridor since the Late Glacial
详细信息
- 责任者：Li Yu (Center for Hydrologic Cycle and Water Resources in Arid Region ; College of Earth and Environmental Sciences ; Lanzhou University ; Lanzhou 730000 ; China) ; Wang Nai’ang
- 刊名：Acta Geographica Sinica
- 出版年：2013
- 卷期：68(7)
- 关键词：冰川沉积作用 ; glacial sedimentation ; 全新世 ; Holocene ; 河西走廊 ; Hexi Corridor
- 页码：p.933-944
- 图表：7 illus., 2 tables, 41 refs.
- 分类号：1400
- issnNo：ISSN0375-5444
- isbnNo：CN11-1856/P
摘要
Yanchi Lake is located in the northern Qilian Mountains and the central Hexi Corridor,which is a key research area for the long-term northern boundary changes of the Asian summer monsoon.Modern climate research shows that the Asian summer monsoon moisture transport is limited to the eastern part of Qilian Mountains.On the Holocene millennial-scale,whether the northwest boundary of the summer monsoon varies according to climate change is a key scientific issue.Paleoclimatic data,including AMS 14 C dates of pollen concentrates,lithology,grain-size,mineral composition and geochemical proxies were acquired from lake sediments of Yanchi Lake.The chronological results show that the lower part of the lacustrine section is formed mainly in the late glacial and early Holocene period,while the proxies’ data indicate that the lake expansion is associated with high contents of mineral salts.The middle part of this section is formed during the transition period of the early and middle Holocene.The AMS 14 C ages of pollen concentrates from the middle part of the section are generally older than those from the lower part.Proxy data indicate that the lake began to retreat since the transition period of the early and middle Holocene.When the lake level is relatively low,the location of the lacustrine section is near the lake edge.Reworking effects of lake sediments are strong on the lake edge;therefore,the ages are relatively old.Since the mid-Holocene,Yanchi Lake retreated significantly and the deposition rate dropped obviously.The Yanchi Lake record is consistent with the late glacial lake records on the Qinghai-Tibet Plateau and in the typical monsoon domain,which shows the late glacial and early Holocene lake expansion and the strong Asian summer monsoon.The long-term monsoonal pattern is different from that of the lake evolution in Central Asia on the Holocene millennial-scale.This study suggests that the monsoon has impacts on the northwest margin of the summer monsoon,and also proves the fact that the northern boundary changes of the summer monsoon are related to millennial-scale climate change.
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