汉江上游二级阶地光释光测年研究  

OPTICAL LUMINESCENCE DATING RESEARCH OF THE SECOND TERRACE IN THE UPPER HANJIANG RIVER

作　　者：朱燕燕 周亚利 羊俊敏 贾彬彬 庞奖励 崔颖颖 闫雪娇 孙晓巍 张岳敏 ZHU Yanyan;ZHOU Yali;YANG Junmin;JIA Binbin;PANG Jiangli;CUI Yingying;YAN Xuejiao;SUN Xiaowei;ZHANG Yuemin(School of Geography and Tourism,Shaanxi Normal University,Xi'an 710062,Shaanxi)

机构地区：[1]陕西师范大学地理科学与旅游学院,陕西西安710119

出　　处：《第四纪研究》2022年第5期1260-1276,共17页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:42071112、41371209、42171092和41971116)资助。

摘　　要：汉江上游地处亚热带季风气候区北部边缘地带,对气候变化非常敏感,该地区发育有多级河流阶地,其上堆积有厚层黄土,是研究阶地形成年代及气候演化的良好材料。以往对汉江上游阶地形成年代的研究主要集中于一级阶地,二级阶地形成年代框架还未系统建立,其主要原因是受限于测年技术和合适的地质载体。文章通过对汉江上游汉中盆地、安康盆地、郧县盆地二级阶地上覆黄土-古土壤层、河漫滩相砂层样品的光释光测年,利用常规SAR法、 TT-OSL法对石英矿物进行等效剂量的测定。结果表明:汉江上游二级阶地上覆黄土-古土壤的地层序列自下而上依次为黄土L→古土壤S→黄土L。汉中盆地、安康盆地、郧县盆地二级阶地河漫滩相砂层顶部石英TT-OSL测年得到的年龄分别为206.17±18.04 ka、 215.14±9.99 ka和212.04±8.68 ka,河漫滩相砂层之上的砂黄土层/黄土层底部年龄分别为184.16±12.78 ka、 198.09±9.65 ka和178.18±9.48 ka。结合地层的光释光年龄数据及相邻区域同一时期的气候变化和构造活动,确定汉江上游二级阶地在距今220 ka左右开始出现,最晚于180 ka左右形成,在随后的构造稳定时段(180~46 ka),阶地面上堆积厚层风成黄土,是构造运动和气候变化共同作用的结果。The upper reaches of the Hanjiang River is located in the northern edge of the subtropical monsoon climate zone and is very sensitive to climate change. There are multi-stage river terraces coverd with thick layers of loess,which is a good material for studying the age of terraces formation and the region climate evolution. Previous studies,is mainly focused on the formantion age of the first-level terraces in the upper reaches of the Hanjiang River. However,the chronological framework of the second terrace has not been systematically established,which is mainly due to the limitation of dating techniques and suitable geological carriers. Three representative secondary terrace profiles were selected in Hanzhong Basin,Ankang Basin and Yunxian Basin in this study. SAR method and TT-OSL methods were combined to determine the dating sequence of secondary terrace sedimentary strata and reveal the age of secondary terrace formation. Baoshanzhuanchang( BSZC)( 33. 12°N,107. 20°E) in Hanzhong Basin is located on the secondary river terrace( accumulation terrace) on the left bank. The thickness of BSZC profile is21. 5 m. The river floodplain binary structure is covered with wind into accumulation,There are one layer of sand loess,four layers of loess,three layer of paleosol and one layer of weak paleosol;Zhoutaicun( ZTC)( 32. 43°N,109. 01°E) in the Ankang Basin is located on the secondary river terrace( accumulation terrace) on the left bank.The thickness of ZTC section is 5. 4 m,two layers of loess and one layer of paleosol sequence is accumulated above the binary structure of floodplain facies. Tuojiazhou( TJZ)( 32. 50°N,110. 23°E) in Yunxian Basin is located on the secondary river terrace( base terrace) on the right bank of the Hanjiang River. The profile is about 8. 15 m thick.The river floodplain dual structure sediments and the eolian loess-paleosol sequence are accumulated above the bedrock. From bottom to top the stratigraphic units can be divided into river floodplain dual structure sediments,sand and sandy l

关 键 词：汉江上游 河流阶地 OSL测年 风成黄土 

分 类 号：P597.3[天文地球—地球化学] P931.1[天文地球—地质学]