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学术报告通知:Cosmogenic 10Be constraints on Little Ice Age glacial advances in the eastern Tian Shan, China——李亚楠 博士
2016-06-29 15:59:30  发布者:张泉  来源:  评论:0 点击:


报告题目:Cosmogenic 10Be constraints on Little Ice Age glacial advances in the eastern Tian Shan, China(小冰期冰川东进范围与时序分析:以东天山山脉为例)
报告内容:Presumed Little Ice Age (LIA) glacial advances, represented by a set of fresh, sharp-crested, boulder covered and compact moraines a few hundred meters downstream from modern glaciers, have been widely recognized in the Central Asian highlands. However, few studies have constrained the formation ages of these moraines. We report 31 10Be exposure ages from presumed LIA moraines in six glacial valleys in the Urumqi River headwater area and the Haxilegen Pass area of the eastern Tian Shan, China. Our results reveal that the maximum LIA glacial extent occurred mainly around 430±100 yr, a cold and wet period as indicated by proxy data from ice cores, tree rings, and lake sediments in Central Asia. We also dated a later glacial advance to 270±55 yr. However, 10Be exposure ages on several presumed LIA moraines in front of small, thin glaciers are widely scattered and much older than the globally recognized timing of the LIA. Historical topographic maps indicate that most glaciers were more extensive in the early 1960s, and two of our 10Be sample sites were located close to the ice front at that time. Boulders transported by these small and thin glaciers may be reworked from deposits originally formed prior to the LIA glacial advances, producing apparently old and widely scattered exposure ages due to varied nuclide inheritance. Other published ages indicated an earlier LIA advance around 790±300 yr in the easternmost Tian Shan, but in our study area the more extensive advance around 430±100 yr likely reworked or covered deposits from this earlier event.
报告人简介:李亚楠博士,美国南达科他州立大学地理系助理教授。2008年本科毕业于北京师范大学地理学与遥感科学学院;硕士与博士学位来自美国田纳西大学地理系。研究方向包括冰川地貌,古气候重建,地形分析等。硕士专业方向是利用树轮信息重建过去几百年美国东南部气候及大气涛动;博士研究侧重地貌学与地形分析,博士论文研究中国中东部天山小冰期冰进的时序与范围。李亚楠曾获得Robert Long杰出研究生奖、田纳西科学联合会奖、美国国家地理青年探险家奖、美国国家自然科学基金博士论文奖等。目前发表SCI论文八篇,期刊包含Quaternary Science Reviews(第四纪科学综述), Annals of Glaciology(冰川学年鉴), 和 Annals of American Association of Geographers(美国地理学会年鉴).

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