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中国沙漠 ›› 2013, Vol. 33 ›› Issue (6): 1678-1683.DOI: 10.7522/j.issn.1000-694X.2013.00233

• 古气候与环境演变 • 上一篇    下一篇

汉江上游谷地归仙河口剖面风化成壤特征及其记录的气候变化事件

毛沛妮, 庞奖励, 黄春长, 查小春, 虎亚伟, 郑树伟   

  1. 陕西师范大学 旅游与环境学院, 陕西 西安 710062
  • 收稿日期:2012-10-07 修回日期:2012-11-14 出版日期:2013-11-20 发布日期:2012-11-14

Pedogenensis Characteristics and Its Environmental Information Interpretation of Guixianhekou Profile in the Upper Hanjiang River Valley, China

MAO Pei-ni, PANG Jiang-li, HUANG Chun-chang, ZHA Xiao-chun, ZHOU Ya-li, HU Ya-wei, ZHENG Shu-wei   

  1. College of Tourism and Environment, Shaanxi Normal University, Xian 710062, China
  • Received:2012-10-07 Revised:2012-11-14 Online:2013-11-20 Published:2012-11-14

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(Lt)→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地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>Lt>L1。归仙河口剖面风化成壤强度的变化表明:18 000~11 500 a BP,气候干冷,风尘大量堆积,成壤微弱,其中在12 500~12 400 a BP出现特大洪水事件;11 500~8 500 a BP,气候逐渐向暖湿方向转变,成壤作用有所增强;8 500~3 000 a BP,气候最为温暖湿润,成壤作用非常强烈,而在7 500~7 000 a BP汉江流域频繁发生特大洪水;距今3 000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3 100~3 000 a BP和1 000~900 a BP出现特大洪水事件。

关键词: 黄土, 风化成壤, 气候变化, 归仙河口, 汉江上游谷地

Abstract:

The Guixianhekou profile in the Upper Hanjiang River Valley were surveyed in detail and then sampled systematically. The stratigraphic and sedimentological characteristics, pedogenic modification characteristics and the profile structure were observed in the field. Magnetic susceptibility, particle-size distribution, 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-Lt-L1-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 S0>Holocene loess layer L0>Transitional loess layer Lt>Malan loess layer L1. (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 L1,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 S0. 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.

Key words: loess, pedogenesis, climate change, Guixianhekou, Upper Hanjiang River Valley

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