摘要
对汉江上游谷地归仙河口剖面的地层学、沉积学特征以及磁化率、粒度组成、Rb／Sr比值等理化指标进行了研究。结果显示：归仙河口剖面地层完整，具有表土（MS）-全新世黄土（L0）-古土壤（S0）-过渡性黄土（L1）-马兰黄土（L1）-河流相沉积物（AD）的地层序列，它记录了汉江第一级阶抬升以来东亚季风的变化信息。不同地层单元的风化成壤差异明显，其成壤强弱序列为：S0〉L0〉L1〉L1。归仙河口剖面风化成壤强度的变化表明：1800O～11500aBP，气候干冷，风尘大量堆积，成壤微弱，其中在12500～12400aBP出现特大洪水事件；11500～8500aBP，气候逐渐向暖湿方向转变，成壤作用有所增强；8500～3000aBP，气候最为温暖湿润，成壤作用非常强烈，而在7500-7000aBP？汉江流域频繁发生特大洪水；距今3000年开始，气候重新进入一个相对干旱少雨时期，期间气候并不稳定，其中在3100～3000aBP和1ooo～900aBP出现特大洪7k事件．
The Guixianhekou profile in the Upper Hanjiang River Valley were surveyed in detail and then sampled systematically. The stratigraphic and sedimentological characteristics, pedogenic modification char acteristics and the profile structure were observed in the field. Magnetic susceptibility, particle-size distri- bution, geochemical characteristics, Rb/Sr ratio and OSL age were analyzed in laboratory. Results are shown as follows： （1） The loess profile at Guixianhekou recorded the East Asian monsoon change with the stratigraphic series MS-L0-S0-L-L-AD, and indicated that the first level terraces of Hanjiang River was formed in 18 000 a BP. （2） The aeolian sediments went through different degrees of pedogenic modification in different periods, with the sequence paleosol So ~Holocene loess layer L0 Transitional loess layer Lt Malan loess layer LI. （3） The climate was dry and cold between 18 000 to 11 500 a BP and dust deposition led to the formation of Malan loess layer L, and a flood event, occurred between 12 500 to 12 400 a BP, suggested the climate was instable. It was a climate shifting phase from dry-cold to warm-humid between 11 500 to 8 500 a BP and the dust storms was significantly reduced to form a transitional loess layer Lt. It was the most warm and humid between 8 500 to 3 000 a BP and dust storm deposits were strongly modified to form paleosol So. A flood event, occurred between 7 500 to 7 000 a BP, indicated the climate was not very stable. The East Asian level style changed and the climate reentered a period of relative drought since 3 000 a BP, leading to the formation of Holocene loess L0. But the two inserted slack water deposit layers （3 100--3 000 a BP and 1 000--900 a BP） suggested that the climate was not stable and changeful.
出处
《中国沙漠》
CSCD
北大核心
2013年第6期1678-1683,共6页
Journal of Desert Research
基金
国家自然科学基金项目(41271108
41030637)
教育部博士点基金优先发展领域项目(20110202130002)
中央高校基本科研业务费专项资金项目(GK201301003)资助
关键词
黄土
风化成壤
气候变化
归仙河口
汉江上游谷地
loess
pedogenesis
climate change
Guixianhekou
Upper Hanjiang River Valley
