北部湾东部沉积物结构和碳酸盐含量变化对末次海侵和环流作用的响应  

The Response of Sedimentary Records in Eastern Beibu Gulf to the Last Postglacial Transgression and Circulation

作　　者：许冬[1,2,3] 李家彪[2] 初凤友[2] 龙江平[2] 叶黎明[2] 韩喜彬[2] 

机构地区：[1]中国科学院海洋研究所,山东青岛266071 [2]国家海洋局第二海洋研究所国家海洋局海底科学重点实验室,浙江杭州310012 [3]中国科学院大学,北京100049

出　　处：《地球科学（中国地质大学学报）》2013年第S1期70-82,共13页Earth Science-Journal of China University of Geosciences

基　　金：国家自然科学基金(No.41106046);海洋公益性行业科研专项(No.201105003);国家海洋局第二海洋研究所基本科研业务费专项(Nos.JG1109;JT1002);国家海洋局青年海洋科学基金(No.2011333)

摘　　要：为了揭示末次冰消期以来北部湾东部沉积环境的整体变化,深入认识环流对北部湾沉积的控制作用,对位于北部湾东部的15只柱样进行了粒度、碳酸盐含量和C/N分析,并测定了其中11只柱样的AMS14 C年代.结果表明,在末次冰消期随海平面上升,北部湾沉积环境由陆向海转变,沉积物碳酸盐含量总体递增,而C/N值则递减,其间伴随发生于全新世早期的碳酸盐低值事件,在北部湾深水区的柱样中也有记录.全新世中期海平面基本稳定以后,稳定的C/N数值表示有机质来源趋于稳定,而碳酸盐含量受钙质生物生产力不同(南高北低)和陆源输入的区域性差异影响出现不同变化.与C/N分析结合,碳酸盐含量曲线可用于地层划分与对比.北部湾环流可能形成于7ka BP左右,影响了沉积物的输运与沉积.全新世中晚期沉积厚度存在区域差异,海南岛西侧大于2.0m,湾顶多介于0.8~2.0m,而涠洲岛西南海域厚度相对最小,可能与湾北物质难以向南输运,而湾南物质主要在琼州海峡西口外卸载有关.To reveal the general change of sedimentary environment of eastern Beibu Gulf since Last Deglaciation,and to understand the influence of circulation to sedimentation in Beibu Gulf,granularity,calcium carbonate content and C/N of 15cores were analyzed,and 11cores were dated by AMS14 C.The results show that with the sea level rising during Last Deglaciation,the sedimentary environment of Beibu Gulf changed from oceanic to terrestrial,and the calcium carbonate content of sediment increased by degrees but C/N decreased by degrees.The signal of low calcium carbonate event in early Holocene is recorded in cores in deeper water in Beibu Gulf.Since the sea level being stable in middle Holocene,C/N stayed steady but the calcium carbonate content fluctuated with the productivity of calcareous organisms and the terrestrial input.Together with C/N,the calcium carbonate content curve can be used in comparison and division of strata.The transport and aggradation of sediment were controlled by the circulation in Beibu Gulf which probably formed at about 7ka BP.The depositional thickness of middle and late of Holocene was spatially differential,which was more than 2meters in west off Hainan Island,mainly 0.8-2.0meters in northern gulf and minimum in southwest off Weizhou Island,probably due to the difficulty of north to south transport of sediment and the aggradation of south coming sediment mainly took place in west off Qiongzhou Strait.

关 键 词：北部湾 沉积记录 碳酸盐含量 环流 末次冰消期 海洋地质 沉积学 

分 类 号：P736.21[天文地球—海洋地质]