中国南海北部陆架区更新世晚期沉积物年代学及古环境研究——以DG钻孔为例  

THE CHRONOLOGICAL AND PALEOCLIMATIC STUDY OF THE LATE PLEISTOCENE CONTINENTAL SHELF SEDIMENTS,NORTHERN SOUTH CHINA SEA:USING CORE DG AS AN EXAMPLE

作　　者：张志亮 刘金瑞 张浩博 张中保 哈广浩 闵伟[1] 聂军胜 任治坤[1] ZHANG Zhi-liang;LIU Jin-rui;ZHANG Hao-bo;ZHANG Zhong-bao;HA Guang-hao;MIN Wei;NIE Jun-sheng;REN Zhi-kun(Key Laboratory of Seismic and Volcanic Hazards,Institute of Geology,China Earthquake Administration,Beijing 100029,China;College of Earth and Environmental Sciences,Lanzhou University,Lanzhou 730000,China)

机构地区：[1]中国地震局地质研究所,地震与火山灾害重点实验室,北京100029 [2]兰州大学资源环境学院,兰州730000

出　　处：《地震地质》2021年第6期1351-1367,共17页Seismology and Geology

基　　金：国家重点研发计划项目(2017YFC1500401)资助。

摘　　要：大陆架作为海陆相互作用的关键地区,对于研究大陆的构造演化、海陆变迁、海平面升降以及气候变化具有重要意义。然而由于不同研究方法的局限性,目前对大陆架沉积物年代学及其蕴含地质信息的认识仍然不足。南海是西太平洋最大的边缘海,是全球海洋沉积作用最为活跃的地区之一,也是海陆相互作用最为典型的区域。作为东亚大陆物质的主要沉积区,南海已经受到了学术界越来越多的关注。然而,目前的研究工作主要集中于沉积连续、信号记录稳定但沉积速率较慢、总体分辨率较低的深海区沉积物。相对而言,沉积速率较快、分辨率较高的浅海大陆架沉积为高分辨率年代学和古环境的研究提供了重要的地质材料,但由于大陆架沉积环境动荡导致沉积信号记录不稳定甚至缺失。针对南海大陆架沉积,尤其是对钻孔沉积物高分辨率年代学研究仍相对较少,限制了对南海构造与气候演化过程的认识。为了更好地限定南海北部陆架区更新世晚期沉积物的年代,研究其中蕴含的古环境信息,探讨东亚地区气候变化的驱动机制问题,同时为南海海域活动构造研究提供年代学框架,文中以南海北部DG钻孔为研究对象,在微体古生物化石和碳同位素年龄(;C)数据的基础上,利用大陆架沉积物磁化率与深海氧同位素的对比对其沉积物年代学进行了系统研究。基于此,结合色度和孢粉结果,对其古气候意义进行了初步探讨。结果表明,该钻孔沉积物的磁化率可对应于深海氧同位素的阶段1—阶段9(MIS 1—MIS 9),底部年龄约为300ka,磁化率低值区间对应于冰期,高值区间对应于间冰期。这与该钻孔沉积物中的孢粉和色度所记录的古环境信息相吻合。冰期时气候较为寒冷,水体变浅,沉积物搬运距离相对增大,矿物以氧化作用为主,主要形成弱磁性的磁性矿物(如赤铁矿),导致磁化率较�As the key area of interaction between land and sea,continental shelf is important for the tectonic evolution of continent,sea-land change,sea level eustacy and climate change.Due to the limits of different methods,the understanding of the chronology and potential geological information of the sediments on the continental shelf is not enough.The South China Sea,as the largest marginal sea of the West Pacific,is not only one of the most active areas of marine sedimentation in the world,but also the typical region of the interaction between land and sea.As the main sedimentary area of the East Asia,the South China Sea has received increasing academic research attention.At present,the researches mostly focus on the deep-sea sediments because they are continuous and can record stable signals,even though the relative slow deposition and low resolution.Comparatively,the shallow continental shelf deposits with faster sedimentary rate and higher resolution can provide important geological materials for studying the high-resolution chronology and paleoenvironment.However,the sedimentary signals recorded by the continental shelf sediments are unstable and even missing due to the turbulence of the sedimentary environment of the continental shelf.There are relatively few studies on the continental shelf sediments of the South China Sea,especially the high-resolution chronology of cores,thus limiting the understanding of tectonic and climate evolution of the South China Sea.In order to better constrain the geological chronology of the Late Pleistocene continental shelf sediments in northern South China Sea,study the paleoenvironmental signals in the continental shelf sediments and discuss the driving mechanism of the climate changes in East Asia and provide the chronological framework for the study of marine active tectonics in the South China Sea,the comparison between magnetic susceptibility and Marine Oxygen Isotope based on microscopic paleonotological fossils and carbon isotopic age(;C)was studied on the Core DG in this

关 键 词：中国南海 大陆架 更新世晚期 磁化率 古环境 

分 类 号：P597.3[天文地球—地球化学]