珠江三角洲花斑粘土磁学特征及其沉积环境实例研究  

A CASE STUDY OF MAGNETIC PROPERTIES AND SEDIMENTARY ENVIRONMENT OF THE SPOTTED CLAY IN THE PEARL RIVER DELTA

作　　者：贺辰戋 张桂华 梁定辉 李明坤 张俊岭 李结涛[5] 关燕萍 彭莎莎 丁盛昌 曾提 王云鹏 欧阳婷萍[2] 朱照宇[3,7] HE Chenjian;ZHANG Guihua;LIANG Dinghui;LI Mingkun;ZHANG Junling;LI Jietao;GUAN Yangping;PENG Shasha;DING Shengchang;ZENG Ti;WANG Yunpeng;OUYANG Tingping;ZHU Zhaoyu(State Key Laboratory of Organic Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong;School of Geography,South China Normal University,Guangzhou 510631,Guangdong;CAS Center for Excellence in Deep Earth Science,Guangzhou,510640,Guangdong;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049;Management Office of Xiqiao Mountain National Park of China,Foshan 528211,Guangdong;Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong;State Key Laboratory of Isotope Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong)

机构地区：[1]中国科学院广州地球化学研究所,有机地球化学国家重点实验室,广东广州510640 [2]华南师范大学地理科学学院,广东广州510631 [3]中国科学院深地科学卓越创新中心,广东广州510640 [4]中国科学院大学地球与行星科学学院,北京100049 [5]佛山市南海区西樵镇西樵山风景名胜区管理处办公室,广东佛山528211 [6]中国科学院广州地球化学研究所,矿物学与成矿学中国科学院重点实验室,广东广州510640 [7]中国科学院广州地球化学研究所,同位素地球化学国家重点实验室,广东广州510640

出　　处：《第四纪研究》2024年第5期1349-1361,共13页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:41977379);中国科学院广州地球化学研究所同位素地球化学国家重点实验室项目(批准号:SKLaBIGZC-21-01);广东省佛山市西樵山国家风景名胜区管委会科技项目共同资助。

摘　　要：华南地区珠江三角洲的形成和演变历史是国内外高度关注的重要科学问题,其中,全新世与更新世界线附近“花斑粘土”形成的沉积环境及气候条件是最有兴趣的问题之一。本研究利用珠江三角洲陆地西北部的广东省佛山市西樵山XQS-ZK7钻孔岩芯(全长16 m),对花斑粘土及其邻近6.1 m特定层位岩芯进行了AMS14C和OSL测年,同时进行了系统的环境磁学参数测量和粒度分析,并对代表性样品进行了岩石磁学参数测量。其中磁学参数主要包括χlf、χfd%、S_(-300)、HIRM、IRM、κ-T曲线等。将610 cm岩芯自下而上划分为4个层位,第一层年龄约67~60 ka B.P.,第二层年龄约60~59 ka B.P.,第三层(花斑粘土层)年龄约59~49 ka B.P.,这3层分别相当于深海氧同位素MIS 4后半期、MIS 4/MIS 3过渡期和MIS 3早期的沉积层;第四层年龄小于11 ka B.P.,对应于MIS 1早期。缺失MIS 3中后期至MIS 2时期的沉积物。研究结果显示:本地花斑粘土与其下伏沉积物具有一种自下而上从粗到细的“正粒序层理”沉积构造,花斑粘土层中夹有3层灰色砂、粉砂、粘土并含有贝壳碎片,其原始沉积为水成成因类型;从花斑粘土到下伏地层,沉积物颜色由红黄杂色→灰白色→青灰色逐渐变化,与经典的风化作用程度自上而下逐渐减弱的规律一致;花斑粘土层下伏第一层灰色沉积层中的磁性矿物以磁铁矿为主并含部分碎屑赤铁矿,而花斑粘土层则含有较多的成土作用新生成的赤铁矿和针铁矿以及超细磁铁矿;花斑粘土中的亚铁磁性超顺磁(SP)颗粒矿物与高矫顽力不完全反铁磁性矿物同时形成,即原始水成沉积在后期高温高湿环境下经历了强烈的化学风化作用而产生了磁性矿物的转变。据此认为:由于华南地区湿热气候导致的强烈风化成土作用,本地花斑粘土经历了多期水下沉积→暴露地表→差异风化的气候-沉积环境变化过程,其最终形成是�The formation and evolution of the Pearl River Delta in South China is an important scientific issue of great concern at both home and abroad,among which the sedimentary environment and climatic conditions of"the spotted clay"developed near the boundary of Pleistocene and Holocene is one of the most interesting issues.The Xiqiaoshan area of Foshan City,Guangdong Province is located in the northwest land part of the Pear River Delta.The XQS-ZK7 borehole investigated in this study is located in the delta plain area in the south of the Xiqiaoshan,about 100 km away from the coast of the South China Sea.Its geographical coordinates are 22°54'25.2″N,112°58'52.1″E,with an altitude of 2 m and core length of 16 m.In this study,AMS 14C and OSL dating have been performed for specific horizons and representative samples of the 610 cm long core of the spotted clay and its adjacent horizons(the borehole depth is 188~798 cm).The grain size of 142 groups of samples was analyzed.The environmental magnetic parameters of 321 groups of samples were tested systematically.The rock magnetic parameters of 19 representative samples were measured.The magnetic parameter mainly includeχlf,χfd%,S_(-300),HIRM,IRM,κ-T curve,etc.The XQS-ZK7 borehole is divided into four layers from bottom to top:the first layer,the interbedding of gray-black clay silt and red-gray fine sand,age about 67~60 ka B.P.;The second layer,gray silty clay layer,age about 60~59 ka B.P.;The third layer,spotted clay with some thin layers of black gray sand and silt,age about 59~49 ka B.P.;The fourth layer,dark black-yellowish-brown clay,is less than 11 ka B.P.The geological age from the first to the third strata is late Pleistocene,and the fourth strata is Holocene.Compared with the marine oxygen isotope stages,the sedimentary ages of each layer are equivalent to the latter half of MIS 4,the MIS 4/MIS 3 transition period,the early MIS 3 and the early MIS 1,respectively.The sediments from the mid-late MIS 3 to MIS 2 are missing.From the first layer to the third lay

关 键 词：磁学特征 沉积环境 气候变化 花斑粘土 珠江三角洲 

分 类 号：P534.631[天文地球—第四纪地质学] P318.4[天文地球—古生物学与地层学] P532[天文地球—地质学]