应用河流阶地^(10)Be深度剖面计算千年至十万年尺度流域平均古侵蚀速率  

AVERAGE CATCHMENT-WIDE PALEOEROSION RATES OVER TIMESCALES OF 10~3~10~5 YEARS FROM^(10)Be DEPTH PROFILES IN RIVER TERRACES

作　　者：田晴映 张培震 梁浩 张逸鹏 李志刚 王伟涛 郑文俊 许斌斌 卢帮华[1,2] TIAN Qingying;ZHANG Peizhen;LIANG Hao;ZHANG Yipeng;LI Zhigang;WANG Weitao;ZHENG Wenjun;XU Binbin;LU Banghua(Guangdong Earthquake Administration,Guangzhou 510070,Guangdong;Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai 519082,Guangdong;Guangdong Provincial Key Laboratory of Geodynamics and Geohazards,School of Earth Sciences and Engineering,Sun Yat-Sen University,Zhuhai 519082,Guangdong)

机构地区：[1]广东省地震局,广东广州510070 [2]南方海洋科学与工程广东省实验室(珠海),广东珠海519082 [3]中山大学地球科学与工程学院,广东省地球动力作用与地质灾害重点实验室,广东珠海519082

出　　处：《第四纪研究》2022年第5期1247-1259,共13页Quaternary Sciences

基　　金：南方海洋科学与工程广东省实验室(珠海)创新团队建设项目(批准号:311021002);科技部第二次青藏高原综合科学考察研究项目(批准号:2019QZKK0901);国家自然科学基金项目(批准号:41872204、41802225和42172233)共同资助。

摘　　要：古侵蚀速率的时空变化规律是研究构造-气候-地表侵蚀之间耦合关系的重要线索。已有的研究多侧重于百万年(10~6)或百年(10~2)尺度上的侵蚀速率限定,但对千年至十万年(10~3~10~5)尺度上的侵蚀速率限定较少。河流阶地的发育能够延续千年至十万年,其沉积记录保留了大量流域侵蚀信号,为建立该时间尺度上的流域古侵蚀速率记录提供了理想的数据支撑。本研究介绍了一种千年至十万年尺度上的流域平均古侵蚀速率计算方法。基于河流阶地^(10)Be深度剖面,约束阶地表面沉积物的^(10)Be继承浓度和阶地面废弃年龄,进而计算出多期阶地发育期间的流域平均古侵蚀速率。随后,以青藏高原东北缘北祁连西段为例,基于山前6条河流(自西向东分别为石油河、白杨河、北大河、洪水坝河、丰乐河和马营河)已发表的16个阶地^(10)Be深度剖面数据(共81个^(10)Be样品)和7个现代河道沉积物的^(10)Be浓度数据,建立了北祁连西段约200 ka以来的流域平均侵蚀速率记录(共23个侵蚀速率值)。结果表明,北祁连西段千年至十万年尺度上的流域平均古侵蚀速率变化趋势与气候波动曲线之间存在较强的对应性,揭示了气候变化是引起流域地表侵蚀的关键因素。上述实例证明,应用河流阶地^(10)Be深度剖面可有效地计算千年至十万年尺度上的流域平均古侵蚀速率,并有助于深入剖析构造、气候和地表侵蚀过程三者之间的潜在关系,进而推动活动造山带地区定量地貌学研究的发展。Spatial and temporal variations in paleoerosion rate are important clues in understanding the interactions among tectonics,climate,and surface processes.Traditionally,the quantification of erosion rates over these timescales of millions of years or hundreds of years has been highlighted.For example,Low-temperature Thermochronology is used to determine erosion rates in uplifted areas such as orogenic belts,or sedimentation rates are used to be proxies of erosion rates in sedimentary basins.However,the calculation and determination of erosion rates over timescales of 10~3~10~5years are still relatively scarce.In recent years,the application of the cosmogenic nuclide^(10)Be to estimate the average erosion rate of a watershed has become an effective means.Fortunately,the development of river terraces can extend over millennia to 10~5 years,and their sedimentary deposits contain watershed erosion signals,which provide ideal evidence to evaluate paleoerosion rates over this period.In this paper,we briefly propose a method to evaluate the average catchment-wide paleoerosion rates from^(10)Be depth profiles of river deposits atop river terraces.Using^(10)Be depth profiles in terrace surfaces,^(10)Be inheritance concentrations and abandon ages of terraces can be inferred,both of which serve for yielding the average catchmentwide erosion rate records at various stages of terrace development.Subsequently,based on 16^(10)Be depth profiles(81^(10)Be individual samples)and 7 modern^(10)Be concentration samples from six seasonal rivers among the western segment of north Qilian Shan,23 determinations of erosion rates over the past 200 ka have been quantified.We find that the glacial-interglacial climate cycle has a direct influence on variations in erosion rate in the western segment of north Qilian Shan over the past 200 ka,as revealed by apparent increases in the catchment-wide erosion rates corresponding to these coldest phases of glacial periods.This pattern demonstrates the application of^(10)Be depth profiles in river terr

关 键 词：流域平均古侵蚀速率 千年至十万年 宇宙成因核素^(10)Be深度剖面 河流阶地 

分 类 号：P931.1[天文地球—自然地理学] P597.3