丹江一級階地沉積地層光釋光測年研究

王蕾彬+周亞利+龐獎勵+黃春長+査小春+高鵬坤

摘 要：通過對丹江一級階地進(jìn)行廣泛細(xì)致的野外考察，丹鳳縣茶房村的典型黃土-古土壤沉積序列從上到下依次為：表土層（TS）-黃土層（L0）-弱古土壤層（S0上）-黃土層（Lx）-古土壤層（S0下）-過渡性黃土層（Lt）-馬蘭黃土層（L1）-河漫灘相砂礫石層（T1-al）。應(yīng)用光釋光（OSL）測年技術(shù)的單片再生劑量法（SAR）選取粒徑90～125 μm 的石英礦物顆粒進(jìn)行了地層年齡測定，得到此剖面從下到上沉積序列為：上限為6.16±0.12 ka的古土壤，5.86±0.14 ka的黃土層，（4.83±0.12）～（2.51±0.17） ka的弱古土壤，1.94±0.07 ka以來的黃土層。結(jié)合理化數(shù)據(jù)分析，全新世大暖期（6.16 ka）時(shí)秦嶺南坡氣候溫暖濕潤，土壤發(fā)育良好，植被繁茂;在5.86±0.14 ka時(shí)，氣候變得冷干，發(fā)育典型黃土沉積;4.83～2.48 ka時(shí)段氣候再次變得較為暖濕，發(fā)育弱古土壤;1.94 ka以來發(fā)育黃土層，氣候較為冷干。古土壤層沉積發(fā)育持續(xù)到距今2.5 ka左右，較黃土高原全新世大暖期結(jié)束時(shí)限3 ka稍晚;5.86 ka的冷事件是全新世大暖期中的一次氣候快速變冷事件，是氣候波動的區(qū)域響應(yīng)。

關(guān)鍵詞：丹江;一級階地;光釋光年齡;氣候變化

中圖分類號：P533 ?文獻(xiàn)標(biāo)識號：A ?文章編號：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