湖北郧县辽瓦店黄土剖面风化特征及其对气候变化的响应

Pedogenic Characteristics of Liaowadian Holocene Loess Profile in the Upper Hanjiang River Valley of China and Its Response to Climate Change

对湖北郧县辽瓦店剖面的沉积学特征及磁化率、粒度、Rb、Sr含量等理化指标进行了研究。结果表明:辽瓦店剖面自下而上具有马兰黄土(L1)-过渡层(Lt)-古土壤(S0)-全新世黄土(L0)-表土(TS)地层序列;不同地层单元的风化成壤差异明显,其成壤强弱顺序为古土壤S0成壤最强、全新世黄土L0和过渡层Lt次之、马兰黄土L1最弱。成壤强弱的变化揭示出该区晚更新世末期(11 500aBP以前)气候干冷,全新世早期(11 500~8 500aBP)气候处于晚更新世干冷向全新世中期暖湿的过渡阶段,全新世中期(8 500~3 100aBP)气候最为温暖湿润,全新世晚期(3 100aBP以来)气候转为干冷且逐渐恶化的变化过程。

The Liaowadian(LWD)profile in Yunxian,Hubei of China was surveyed in details.Investigations into this soil profile,including pedo-stratigraphy,chronology,were carried over the first river terrace of the upper Hanjiang River valley.Magnetic susceptibility,particle-size distribution,the contents of Rb and Sr were analyzed in laboratory.The result shows that LWD profile recorded the environment features and evolution with the stratigraphic series TS-L0-S0-Lt-L1.Different degree of weathering intensity in different stratigraphic units is paleosol S0>Holocene loess L0>modern TS>transitional loess layer Lt>Malan loess layer L1.The climate was dry and cold before 11 500 aBP and dust falls led to the formation of Malan loess layer L1.And between 11 500 aBP and 8 500 aBP,the climate got warmer,and was characterized by dry and wet,and dust falls led to the formation of Transitional loess layer Lt.During8 500 aBP to 3 100 aBP,Yunxian basin experienced its warmest period with a warm and humid climate during Holocene,and dust falls led to the formation of S0.During the late Holocene,namely 3 100 aBP,the climate was deteriorating very quickly.It turned from warm to cold,and precipitation began to decline.