汉江一级阶地抬升以来北亚热带风尘堆积、发育与东亚季风演变的耦合关系——以郧县段汉江上游谷地为例

风成黄土对东亚冬夏季风优势期转换及起迄时间起到良好指示作用，探究风尘黄土堆积、发育特征与东亚季风演变的耦合关系十分必要。本文通过研究汉江一级阶地上覆黄土-古土壤序列的构型、磁化率、烧失量、粒度、元素组成特征，分析汉江一级阶地抬升以来黄土-古土壤序列的成因及成壤特征，探究东亚冬夏季风的演化序列。结果表明：（1）汉江上游地区黄土-古土壤序列的地层构型为表层土（MS）-近代黄土（L₀）-古土壤（S₀）-过渡层（L_t）-马兰黄土（L₁），磁化率、粒度、烧失量、元素组成等特征指示各地层成壤强度特征为S₀>L₀/L_t>L₁。（2） 成壤强度指示18000 a BP以来，东亚冬夏季风演替特征为末次盛冰期冬季风强烈→全新世早期冬季风减弱→全新世中期夏季风主导→全新世晚期夏季风减弱~，冬季风强盛，其演变滞后于低纬太阳辐射变化2000~3000 a。（3）该风尘堆积物理化性质对6000~5000a BP的气候恶化期有所响应。总而言之，汉江上游一级阶地上覆黄土为风尘堆积物，指示18000a BP以来东亚季风的变迁规律及季风异常事件，能够体现北亚热带对全球气候变化及极端事件的响应。

The Coupling Relationship of Pathogenesis and East Asian Monsoon Variability since 18000 a BP in the Upper Reaches of Hanjiang River Valley of China

As the accumulation of dust storm, aeolian loess indicates the conversion of East Asian Summer Monsoon, which is necessary to explore the coupling relationship of the loess accumulation & pathogenesis characteristics and East Asian Monsoon variability. Pedogenic modification characteristics and the structure of soil profiles were observed in the field survey process in the Hanjiang River valley, and magnetic susceptibility,particle-size distribution, mineral assemblage, major elements trace and OSL age were analyzed in laboratory. The research tries to use loess-like as ancient inductor to induct the transformation of East Asian Monsoon. (1)The loess sediments profile structure is MS-L₀-S₀-L_t-L₁-AD in the Hanjiang River valley. The pathogenesis strength's sequence shows S₀>L₀ /L_t>L₁, the elements features (Al, Fe, Na, K, Si) are consistent with the Loess Plateau. (2)East Asian Monsoon and solar radiation exists a phase difference of 2000-3000.The East Asian Monsoon succession characteristic in northern subtropics was as following: strong winter wind(Last Glacial Maximum)→weak winter monsoon (early Holocene)→dominant summer monsoon (Mid-Holocene) →weak summer monsoon (the late Holocene) (3)Hanjiang River valley loess recorded cold and dry events happened during 5000-6000 a BP.