丹江一级阶地沉积地层光释光测年研究

王蕾彬+周亚利+庞奖励+黄春长+査小春+高鹏坤

摘 要：通过对丹江一级阶地进行广泛细致的野外考察，丹凤县茶房村的典型黄土-古土壤沉积序列从上到下依次为：表土层（TS）-黄土层（L0）-弱古土壤层（S0上）-黄土层（Lx）-古土壤层（S0下）-过渡性黄土层（Lt）-马兰黄土层（L1）-河漫滩相砂砾石层（T1-al）。应用光释光（OSL）测年技术的单片再生剂量法（SAR）选取粒径90～125 μm 的石英矿物颗粒进行了地层年龄测定，得到此剖面从下到上沉积序列为：上限为6.16±0.12 ka的古土壤，5.86±0.14 ka的黄土层，（4.83±0.12）～（2.51±0.17） ka的弱古土壤，1.94±0.07 ka以来的黄土层。结合理化数据分析，全新世大暖期（6.16 ka）时秦岭南坡气候温暖湿润，土壤发育良好，植被繁茂;在5.86±0.14 ka时，气候变得冷干，发育典型黄土沉积;4.83～2.48 ka时段气候再次变得较为暖湿，发育弱古土壤;1.94 ka以来发育黄土层，气候较为冷干。古土壤层沉积发育持续到距今2.5 ka左右，较黄土高原全新世大暖期结束时限3 ka稍晚;5.86 ka的冷事件是全新世大暖期中的一次气候快速变冷事件，是气候波动的区域响应。

关键词：丹江;一级阶地;光释光年龄;气候变化

中图分类号：P533  文献标识号：A  文章编号：1001-4942（2015）06-0075-08

Study on OSL Dating of Sediment Stratigraphy on the First

River Terrace in Danjiang River Valley

Wang Leibin，Zhou Yali*，Pang Jiangli，Huang Chunchang，Zha Xiaochun，Gao Pengkun

（College of Tourism and Environment， Shaanxi Normal University， Xian 710062， China）

Abstract The extensive and careful fieldwork was carried out on the first river terrace in Danjiang River valley. The typical loess-paleosol sedimentary sequence in Chafang Village of Danfeng County from top to bottom was as follows： surface soil layer （TS）-loess layer （L0）- weak paleosol layer （S0-upper）-loess layer （Lx）-paleosol layer （S0-lower）- transitional loess layer （Lt）-Malan loess layer （L1）-alluvial flat facies sand gravel layer （T1-al）. The quartz grains of 90～125 μm was choosed to detect the stratigraphic age by single aliquot regeneration （SAR） of OSL dating technique. The sedimentary sequences from bottom to top were as follow. The upper limit was S0-lower of 6.16±0.12 ka， Lx of 5.86±0.14 ka， S0-lower of 4.83±0.12～2.51±0.17 ka， L0 of 1.94±0.07 ka. Combined with the physical and chemical data， the analysis results showed that at Holocene Megathermal period （6.16 ka）， the climate was warm and moist with good developement soil and density vegetation in the south of Qinling Moutain. Around 5.86±0.14 ka， the climate was arid and cold and the typical loess was developed. At 4.83±0.12 ka， the climate was warm and moist and the weak paleosol was developed. From 1.94 ka， the climate was arid and cold and the loess was developed. The paleosol layer developed about 2.5 ka， which was later than the ending deadline of Holocene Megathermal period of around 3 ka in the Loess Plateau. The cold event of 5.86 ka was one of the rapid cooling climate event and regional response of climate fluctuate.

Key words Danjiang River;First terrace; OSL age; Climatic changeendprint