中印度洋海盆南部中新世以来碳酸盐补偿深度的演变:来自微体化石组合和元素地球化学的证据  

CCD evolution since the Miocene:Evidence from nannofossils assemblage and element geochemistry in the south part of Central Indian Ocean Basin

作　　者：刘振尤 葛晨东[1,2] 石学法 邹欣庆[1,2] 纪振强 鲍洋 黄牧 Liu Zhenyou;Ge Chendong;Shi Xuefa;Zou Xinqing;Ji Zhenqiang;Bao Yang;Huang Mu(School of Geography and Ocean Science,Nanjing University,Nanjing,210023,China;Key Laboratory of Coast and Island Development,Ministry of Education,Nanjing University,Nanjing,210023,China;The First Institute of Oceanography,Ministry of Natural Resources,Qingdao,266061,China;Key Laboratory of Marine Geology and Mineralization,Ministry of Natural Resources,Qingdao,266061,China;Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology,Qingdao,266061,China)

机构地区：[1]南京大学地理与海洋科学学院,南京210023 [2]南京大学海岸与海岛开发教育部重点实验室,南京210023 [3]自然资源部第一海洋研究所,青岛266061 [4]自然资源部海洋地质与成矿作用重点实验室,青岛266061 [5]青岛海洋科学与技术国家实验室海洋地质过程与环境功能实验室,青岛266061

出　　处：《南京大学学报（自然科学版）》2020年第5期702-709,共8页Journal of Nanjing University（Natural Science）

基　　金：国家重点研究发展计划(2017YFC0602305);国际海域资源调查与开发“十三五”规划(DY135-R2-1-01);国家自然科学基金(41706061)。

摘　　要：通过对中印度洋海盆GC18孔沉积物元素地球化学特征和微体化石组合进行分析,恢复了该区域碳酸盐补偿深度(Carbonate Compensation Depth,CCD)的演变及环境演化历史.结果表明,GC18孔从上到下可分为五段.第Ⅰ段(0~30 cm)CaO含量和总无机碳(Total Inorganic Carbon,TIC)从表层向下呈显著下降趋势,SiO2呈显著上升趋势,微体化石主要是有孔虫碎屑,还含有少量钙质超微化石Calcidiscus leptoporus(弱脐钙盘藻)和Ceratolithus cristatus(具冠毛角石藻),沉积时代为第四纪.第Ⅲ段(150~280 cm)CaO和TIC含量少于第Ⅰ段,两者从上到下经历了上升-稳定-下降的过程,SiO2变化趋势相反,含钙质超微化石,主要为Discoaster deflandrei(德佛兰盘星石藻),沉积时代为中中新世晚期或更早.第Ⅴ段(300~415 cm)沉积物组分波动相对较大,CaO和TIC平均含量达到最高,SiO2含量较低,钙质超微化石非常丰富,以Umbilicosphaera Jafari(贾法脐球藻),Umbilicosphaera rotula(轮形脐球藻)和Discoaster deflandrei为主,沉积时代为中中新世-早中新世.第Ⅱ段(30~150 cm)和第Ⅳ段(280~300 cm)相似,均呈现低CaO和高SiO2特征且相对稳定,TIC含量很低,未发现微体化石,主要是深海黏土.第Ⅰ,Ⅲ和Ⅴ段CaO含量较高,钙质超微化石均有保存,反映当时沉积均处于CCD以上.第Ⅱ,Ⅳ段CaO含量低,SiO2含量高,钙质超微化石没有保存,反映当时沉积处于CCD以下.从第Ⅴ段到第Ⅱ段(中中新世-晚中新世),CCD整体逐渐变浅,这与全球CCD在此期间的变化特征一致.中印度洋海盆CCD自中新世以来经历了深-浅-深-浅-深的变化历史.Based on analysis of the element geochemistry and nannofossils assemblage in the sediments of core GC18 in Central Indian Ocean Basin(CIOB),the evolutionary history of sedimentary environment in this area is discussed. The results show that the sediments in this core can be divided into five sections downwards. In section Ⅰ(0~30 cm), CaO and total inorganic carbon(TIC) display a decreasing trend while SiO2 increases. Nannofossils are mainly foraminifer detritus and a small quantity of calcareous nannofossils are found as well,such as Calcidiscus leptoporus and Ceratolithus cristatus. The age of this section is Quaternary. Section Ⅲ(150~280 cm) shows a significant shift in the CaO and TIC compared with sectionⅠ,which both experiences an up-stable-down process with the depth. However,the trend of SiO2 is opposite to CaO and TIC. Calcareous nannofossils are found,which mainly are Discoaster deflandrei. The age of this section is late Miocene. In section Ⅴ(300~415 cm),sediment components fluctuate frequently. The increases of CaO and TIC are coeval with lower values of SiO2. A high relative abundance of calcareous nannofossils are found in section Ⅴ, mainly composed of Umbilicosphaera jafari,Umbilicosphaera rotula and Discoaster deflandrei. The age of this section is late Miocene to early Miocene. Section Ⅱ(30~150 cm) is similar to section Ⅳ(280~300 cm). They are all relatively stable and characterized by low CaO and high SiO2. TIC is also very low with no nannofossils co-existed. Sediments are mainly deep-sea clay.Calcareous nannofossils were preserved in section Ⅰ,Ⅲ and Ⅴ with high CaO and TIC,reflecting that the sediments were all above carbonate compensation depth(CCD) at those times. Calcareous nannofossils were not found in section Ⅱ and Ⅳ with low CaO & TIC and high SiO2, indicating that the sediments were all below CCD. Overall, CCD gradually became shallower from section Ⅴ to section Ⅱ(middle Miocene to late Miocene). It was consistent with the global CCD evolution trend in this t

关 键 词：超微化石组合 碳酸盐补偿深度变化 中新世 中印度洋海盆 

分 类 号：P76[天文地球—海洋科学]