汉江上游Ⅰ级河流阶地形成及对东亚季风变化的响应  

Formation of the First River Terraces of Hanjiang River and Its Response to the East Asian Monsoon Change

作　　者：庞奖励[1] 黄春长[1] 周亚利[1] 查小春[1] 乔晶[1] 张玉柱[1] 周亮[1] 

机构地区：[1]陕西师范大学旅游与环境学院,西安710062

出　　处：《地质论评》2014年第5期1076-1084,共9页Geological Review

基　　金：国家自然科学基金资助项目(编号41271108;41030637);中央高校基本科研费(编号GK201301003)的成果

摘　　要：对郧县—白河段汉江Ⅰ级河流阶地上风成黄土的沉积学、理化性质、地球化学和年代学进行了系统研究.结果表明,汉江Ⅰ河流阶的形成不晚于25 ka BP;黄土具有马兰黄土（L1）→过渡黄土（L1）→古土壤（S0）→全新世黄土（L0）→表土（TS）的地层序列,与渭河谷地的黄土地层序列完全可比;25 ～ 11.5 kaBP,冬季风强盛,气候冷干,从11.5 ka BP开始,冬季风逐渐减弱,气候开始向暖湿方向逐步转化,从8.5 ka BP开始,夏季风达到了末次冰期结束后的鼎盛时期,3.1 ka BP前后,东亚季风格局发生变化,夏季风减弱,重新进入一个相对干冷的时期,而人类活动对地表的影响形成了表土;汉江上游谷地黄土记录的末次冰期后季风逐渐加强、中全新世季风强盛、随后季风衰退和气候变干的夏季风演变模式与渭河谷地黄土的记录高度一致,与邻区石笋和泥炭记录的季风变化趋势也有良好的可比性,但与石笋/泥炭记录的夏季风强盛期的起始时间（9.3 ～ 4.2 kaBP）并不完全一致.Qianfangcun profile at the first river terraces of the upper reaches of the Hanjiang River valley were surveyed in detail and then sampled systematically.The profile structure and characteristics were observed in the field.Magnetic susceptibility,particle-size distribution,geochemical characteristics and OSL age was analyzed in laboratory.Stratigraphy age was dated using OSL method.An integration of the results show that the first level river terraces of the Hanjiang River was formed 25 ka BP.The Qianfangcun profile in turn divided into following stratigraphic sequences from the lower to the upper：Malan loess （L1） → transitional loess （Lt） → paleosol （So） → Holocene loess （L0） → Modern soil （MS）,which is completely consistent with the loess stratigraphic sequences in the Weihe River valley.Bottom boundary age of Malan loess L1 is 25 ka BP and the top boundary age is 11.5 ka BP.Bottom boundary age of paleosol S0 is 0.85 ka BP and the top boundary age is O.31 ka BP.During 25 ～ 11.5 ka BP it was cold and dry glacial climatic characteristics,with the winter strong monsoon,and dust storms frequently occurred to form Malan loess layer L1 on the first level river terraces of the Hanjiang River.From the beginning of the 11.5 ka BP,the winter monsoon gradually weakened,the climate began to gradually transform to the warm and wet,and appear weak pedogenesis to form a transition loess layer （Lt）.During the Mid-Holocene （8.5 ～ 3.1 ka BP） various environmental indicators from the paleosol S0 is maximum or minimum value in whole Qianfangcu profile,it reflects strongly pedogenic modification and an optimum water and heat period and indicate summer monsoon reached its peak period after the last glacial period.About 3.1 ka BP,the East Asian monsoon recession leads to the weakening of summer monsoon,climate reentered a relatively cold period,and dust storm were obviously enhanced to from Holocene loess L0.At the same time,modern soil （MS） is formed on the surface by the farming activit

关 键 词：黄土 OSL年龄 季风 Ⅰ级阶地 汉江上游 

分 类 号：P53[天文地球—古生物学与地层学]