长江口外扬子浅滩YZ05孔沉积序列及晚更新世以来的环境演化  

Sedimentary facies and environmental evolution of the Yangtze shoal,eastern China Sea shelf since Late Pleistocene:Evidence from core YZ05

作　　者：徐岱璐 殷勇[1] 时连强 林文荣 王爱华[4] 郑禹君 XU Dailu;YIN Yong;SHI Lianqiang;LIN Wenrong;WANG Aihua;ZHENG Yujun(School of Geography and Oceanography Science,Nanjing University,Key Laboratory of Coast and Island Development of MOE of China,Nanjing 210023,China;State Research Center for Island Exploitation and Management,Second Institute of Oceanography,MNR,Hangzhou 310012,China;Qingdao Institute of Marine Geology,China Geological Survey,Qingdao 266071,China;Nanjing Geological Survey Center,China Geological Survey,Nanjing 210016,China)

机构地区：[1]南京大学地理与海洋科学学院,海岸与海岛开发教育部重点实验室(南京大学),南京210023 [2]自然资源部第二海洋研究所,国家海岛开发与管理研究中心,杭州310012 [3]中国地质调查局青岛海洋地质研究所,青岛266071 [4]中国地质调查局南京地质调查中心,南京210016

出　　处：《海洋地质与第四纪地质》2020年第6期22-38,共17页Marine Geology & Quaternary Geology

基　　金：国家自然科学基金项目“晚第四纪苏北南黄海辐射沙脊区强制海退与潮流沙脊沉积体系”(40776032);国家科技部重大科学研究计划项目“扬子大三角洲演化与陆海交互作用过程及效应研究”(2013CB956501)。

摘　　要：2014年在东海陆架扬子浅滩水深41.5 m处钻获进尺80 m的YZ05孔,该孔沉积相方面的研究成果虽然已经发表过,但略显简单,结合新获得的有孔虫鉴定结果和指示海陆环境变化的Sr/Ba比值,仍有必要对沉积相进行更为精细的研究。根据沉积物颜色、粒度、沉积结构和构造、接触关系和所含化石,共识别出河道-边滩相(F1)、河漫滩相(F2)、泥质潮滩相(F3)、河口湾前缘相(F4)、潮流沙脊相(F5)、脊间潮道相(F6)、分流河道沙坝相(F7)、分流河道相(F8)、远端三角洲前缘相(F9)以及前三角洲相(F10)十种类型。通过相组合与相序列分析,并辅以选择性提取方法获得的可交换态Sr/Ba比值,识别出退积型的河口湾序列和进积型的三角洲序列,它们与冰后期长江三角洲具有相似的沉积层序。AMS14C测年和光释光测年数据指示YZ05孔属于晚更新世以来的沉积。扬子浅滩的物质基础是晚更新世的三角洲堆积体,在全新世早期海面快速上升背景下,堆积成潮流沙脊,改造后形成潮流沙席。A 80 m long core,i.e.the Core YZ05,taking from the Yangtze shoal at the inner shelf of Eastern China Sea,is carefully studied by this paper.Although some preliminary results have been published before,it is still necessary to reexamine the interpretation concerning sedimentary facies and the previous models with the newly acquired information.Based on color,grain size,sedimentary texture and structure,contact relationship and fossils,the Late Pleistocene and Holocene succession of the core YZ05 can be classified into ten environmentally significant facies,which include fluvial channel-point bar(F1),overbank(F2),muddy tidal flat(F3),estuary front(F4),tidal sandy ridge(F5),inter-ridge channel(F6),distributary channel bar(F7),distributary channel(F8),distal delta front(F9)and prodelta(F10).Through the analysis of facies association and facies sequences,with the support of Sr/Ba ratios,a retrogradational estuary sequence and a progradational detaic sequence are recognized,which are similar to the post glacial sequences in the Yangtze River delta.AMS14C and OSL dating suggest that the deposits penetrated by Hole YZ05 are younger than Late Pleistocene.Then the Yangtze Shoal is sourced from the Late Pleistocene deltaic deposits reworked by tidal current.

关 键 词：沉积相 古三角洲 古河口湾 Sr/Ba比值 扬子浅滩 

分 类 号：P736.2[天文地球—海洋地质]