基于XRF岩心扫描证据的福建木兰溪河口全新世沉积环境演化重建  

Holocene Depositional Environment Evolution at Mulanxi Estuary in Fujian Province:Evidences from XRF Core Scanning

作　　者：宋震 李亚龙 赵云 高建华[4] 印萍[5] 杨守业[1] Song Zhen;Li Yalong;Zhao Yun;Gao Jianhua;Yin Ping;Yang Shouye(State Key Laboratory of Marine Geology,Tongji University,Shanghai 200092,China;School of Environmental and Geographical Sciences,Shanghai Normal University,Shanghai 200234,China;School of Oceanography,Shanghai Jiaotong University,Shanghai 200240,China;School of Geographic and Oceanographic Sciences,Nanjing University,Nanjing 210023,China;Qingdao Institute of Marine Geology,China Geological Survey,Qingdao 266237,China)

机构地区：[1]同济大学海洋地质国家重点实验室,上海200092 [2]上海师范大学环境与地理科学学院,上海200234 [3]上海交通大学海洋学院,上海200240 [4]南京大学地理与海洋科学学院,江苏南京210023 [5]中国地质调查局青岛海洋地质研究所,山东青岛266237

出　　处：《地球科学》2024年第6期2213-2226,共14页Earth Science

基　　金：国家重点研发计划(No.2022YFF0800504);国家自然科学基金项目(Nos.42230410,41991324)。

摘　　要：为精确刻画和揭示强潮控山溪性河流河口全新世的沉积环境演化特征和控制因素,本研究选取福建中部潮控型山溪性河流——木兰溪河口的钻孔(MLX-S)为研究对象,在运用放射性14C和光释光建立沉积年代框架基础上,开展了沉积物粒度、XRF岩心扫描及ICP-OES元素分析.研究发现,全新世木兰溪河口相继发育河流相、滨岸沼泽相、浅海相到潮控河口相,沉积环境演变主要受控于研究区的相对海平面变化.福建中部沿岸的相对海平面高度在9.0 ka左右,约为-20 m;此后海侵不断扩大,至5.8 ka左右海平面达到最大高度,随后缓慢下降至今.岩心高分辨率XRF扫描的元素相对强度数据校正后可指示沉积物的物源及古环境变化.钻孔的K/Ti比值表明,约8.8 ka以来,木兰溪河口沉积物主要为流域剥蚀产物和口外长江源细粒物质的混合;岩心Fe/Ti比值在约3.6 ka、4.3 ka、5.4 ka和6.0 ka 4个东亚冬季风较强时期均达到峰值且与东海内陆架泥质沉积记录一致,指示浙闽沿岸流强度的影响.揭示了我国东南沿海潮控型山溪性河口的河海相互作用特征,以及全新世季风-海平面变化驱动下的长江源细粒沉积物在陆架海复杂的源汇沉积过程,也拓展了XRF岩心扫描方法在海陆相互作用强烈的大陆边缘地区应用潜力.To investigate the depositional environment evolution and controlling factors of a mountainous river estuary during the Holocene,in this study it selected a drilling core(MLX-S)from the river mouth of Mulanxi,a tidal-controlled mountainous river in central Fujian Province,China.The core was subjected to radiocarbon dating,optically stimulated luminescence dating,grain size analysis,XRF core scanning,and ICP-OES elemental measurements.During the Holocene,the Mulanxi estuary experienced a transition from fluvial facies to riparian marsh facies,shallow marine facies,and finally to tide-controlled estuarine facies.The sedimentary environment evolution was primarily influenced by relative sea-level changes in the study area.The relative sea level along the coast of central Fujian is around 9.0 ka and about-20 m.Subsequently,the marine transgression reached the strongest and the maximum sea level occurred around 5.8 ka,followed by a slow decline till the present.High-resolution XRF core scanning data,after calibration of element relative intensities,can indicate sediment provenance and paleoenvironmental changes.The downcore variation of K/Ti ratio suggests that since 8.8 ka,the sediments in the Mulanxi Estuary were mainly derived from a mixture source of local basin erosion and fine offshore material from the Changjiang(Yangtze River).The core Fe/Ti ratio reached its peak in four strong East Asian winter monsoon periods of about 3.6 ka,4.3 ka,5.4 ka and 6.0 ka,corresponding to periods of strong East Asian winter monsoon,which is consistent with the sedimentary records on the East China Sea inner shelf and tightly related to the changes of Min-Zhe coastal current intensity.This study reveals the typical river-sea interaction in the tide-controlled mountainous estuaries along the southeastern coast of China,and suggests the complex source-sink transport processes of Changjiang-derived fine sediments on the continental shelf driven by the Holocene monsoon and sea level changes.This study also promotes the potential appli

关 键 词：木兰溪 全新世 XRF岩心扫描 沉积环境 海平面变化 东亚冬季风 海洋地质 

分 类 号：P736[天文地球—海洋地质]