南海东沙海域末次冰期最盛期以来的沉积特征  

LITHOLOGIC FEATURES OF SEDIMENTS CHARACTERIZED BY HIGH SEDIMENTATION RATES SINCE THE LAST GLACIAL MAXIMUM FROM DONGSHA AREA OF THE SOUTH CHINA SEA

作　　者：陈芳[1] 苏新[2] D Nurnberg 陆红锋[1] 祝幼华[4] 刘坚[1] 廖志良[1] 

机构地区：[1]广州海洋地质调查局,广州510760 [2]中国地质大学,北京100083 [3]Leibniz Institute for Marine Science [4]中国科学院南京古生物研究所,南京210008

出　　处：《海洋地质与第四纪地质》2006年第6期9-17,共9页Marine Geology & Quaternary Geology

基　　金：中国地质调查局"天然气水合物资源评价及勘探开发战略研究"项目(GZH200200203-02-01);国家自然科学基金项目(40372005)

摘　　要：对采自南海东北部东沙海域不同海区的14个大型重力活塞样进行肉眼观察描述、沉积物涂片分析和粒度分析，并利用浮游有孔虫氧碳同位素、AMS^14C测年和碳酸盐地层学等方法对上述柱状样进行地层年代划分。有关沉积特征结果表明，末次冰期最盛期以来其沉积物组分、沉积特征、沉积速率存在较明显的时空差异，从区域上可划分成3个沉积区：Ⅰ区沉积物类型较单一，沉积连续，未见底栖生物扰动和非正常搬运沉积，钙质组分相对贫乏，CaCO3含量偏低，一般不超过10％，自生黄铁矿特别丰富。沉积速率偏离，全新世沉积速率最高达41．7cm／ka；Ⅱ区水深最大，超过3000m，位于深海盆区。该区以沉积搬运作用明显，岩性复杂多变、浊流沉积较发育为特征。沉积物粒度明显变粗，砂含量在3个海区中最高，陆源物质石英、长石和钙质生物群（主要是有孔虫）明显增加，其中石英、长石含量最高达83％，CaCO3含量最高达57％。全新世沉积速率最高达31.6cm／ka；Ⅲ区以正常深海沉积为主，为青灰色含硅质钙质生物黏土质粉砂，富含生物化石，CaCO3含量一般介于10％～30％之间，石英、长石含量偏低，全新世沉积速率最高达20cm／ka。造成上述差异的主要因素有水深、地理位置、陆源物质的稀释作用、沉积搬运和碳酸盐溶解作用等。A total of 14 piston cores, with lengths ranging from 658 to 937cm and with water depths from 1 616 to 3 426 m, were obtained by several exploration cruises for gas hydrate survey from 2001 to 2004 in the Dongsha area of the South China Sea. Ages of these sediment cores were determined by means of AMS ^14C dating and stable oxygen isotope stratigraphy of plankton foraminifera and CaCO3 stratigraphy. Results from visual core description, smear slide and grain size analyses indicate that sedimentary features of Holocene sediments, including sedimentary components and sedimentation rates are varing with time and location. Three sedimentary sub-areas with different sedimentary features were recognized. In Area Ⅰ , Holocene sediments are characterized by clayey silt, with rare biogenie components and low CaCO3 （less than 10M）, but with common authigenic pyrite and high sedimentation rates （41.7 cm/ka）. In Area Ⅱ, Holocene sediment sequences are dominated by clayey silt, interbedded with turbidite layers of sandy silt, silty sand and sand. Abundant turbidite layers were observed in cores HD77, HD133 and GC10. In addition, contents of feldspar and quartz and biogenic calcareous component （mainly foraminifers） in the sediments increase obviously. In this area, a sedimentation rate of 31.6 cm/ka was estimated for the Holoeene sediments. In Area Ⅲ, Holocene sediments contain abundant biogenic components and rare feldspar and quartz minerals, showing features that are commonly observed in deep-sea sediments. CaCO3 content varies from 10% to 30% and sedimentation rate of Holocene is 20 cm/ka.

关 键 词：沉积特征 沉积速率 末次冰期最盛期 南海东沙海域 

分 类 号：P736.21[天文地球—海洋地质]