【作者】 陈志华；

【导师】 杨作升；

【作者基本信息】 中国海洋大学 ， 海洋地质， 2004， 博士

【摘要】 中国第一次（1999年）和第二次（2003年）的北极科学考察区——楚科奇海及其北部海域，是了解北冰洋现代和过去海洋环境变化的关键地带。本论文以楚科奇海及邻近北冰洋深水区的60个表层沉积物样品和M03岩心为研究对象，以元素和稳定碳／氮同位素为主要研究手段，结合颜色反射率分析、粒度分析和粘土矿物分析，重点探讨了研究区表层沉积物来源与现代沉积环境，以及楚科奇海北部边缘地带的古海洋学演变。 通过对表层沉积物的研究，获得如下几点结论：（1）受水动力和海冰的双重制约，研究区沉积物总体较粗，分选较差，结构成熟度较低。（2）海底沉积物的化学成熟度低，带有明显的源区母岩信息；富K的伊利石，富Mg、Ca、Na、Zn的蒙皂石，以及富Mn、Fe的绿泥石等使得粘土矿物与粘土级组分的化学元素之间的耦合关系十分明显；常量元素Al、K、Mg、Fe、Ti和微量元素Li、V、Sc、La、Zn、Y、Cu、Ni等主要富集在细粒沉积物中，前者是粘土矿物伊利石、绿泥石、高岭石和蒙皂石的构成元素，后者多与粘土矿物等细粒物质的吸附或者结合有关。（3）陆源碎屑物质的分布受海区环流结构所制约：来自加拿大马更些河与阿拉斯加北部的物质富含高岭石和伊利石，富K、富Al，受顺时针方向流动的波弗特涡流影响，对研究区东北部和北部沉积物的影响大；来自阿拉斯加西北部河流和海岸带的物质富含绿泥石，高岭石含量变化大，SiO₂含量高，多富Zr，对阿拉斯加西北部近海沉积物影响明显；来自西伯利亚的物质富含绿泥石，富Na、Sr，富Zr，对研究区西部沉积物的影响较为明显；携带大量育空河物质的太平洋水自白令海峡进入研究区后，横穿楚科奇海陆架向北扩散，导致楚科奇海中部沉积物富含蒙皂石，富Na、Mg、Ca、Zn、Sr等。（4）稀土元素趋向于在细粒沉积物中富集，在粗粒沉积物中亏损，页岩标准化配分模式大部分较为平坦，说明楚科奇海表层沉积物主要来源于周边大陆，且陆源碎屑物质的化学风比作用较弱。（5）过渡金属：元素Mn、Co、Ni、Cu等共生，在氧化环境中富集，自生Mn和自生Ni的分布说明北冰洋深水区海水-沉积物界面为氧化环境，楚科奇海多表现为缺氧还原沉积环境；楚科奇海台前缘因太平洋水、大西洋水的活动，表层水生产力高，底层水含氧量高，有利于自生Mn的富集和微结核的形成。（6）沉积物中生物成因SiO₂的含量和有机质δ¹³C和δ¹⁵N值反映了海区生产力与陆源有机质的供应状况，并受控于海区环流结构和营养盐结构。太平洋水自白令海峡进入研究区后，分化成营养盐含量不同的三支分海流横穿楚科奇海陆架向北扩散，导致研究区水体的营养盐和生产力出现分异。研究区中西部海域受太平洋富营养盐海水的影响，海洋生产力高，6’3c和6’SN值的陆源信号较弱;在阿拉斯加西北部近海，海水的营养盐含量低，水体的生产力低，海岸带物质输入使陆源有机质信号增强。在研究区北部和东北部的楚科奇高地和加拿大海盆，海域冰封时间长，营养盐供应少，海洋生产力低，来自马更些河和阿拉斯加北部的陆源有机质增多，沉积物中生物成因510:含量小于5%，海源有机质比重小于40%。由于亚北极太平洋水通过研究区向北冰洋中央海盆输送，研究区营养盐池实际上可视为一个典型的开放系统，6’SN/Sio:比值说明研究区中西部海水的营养盐供应充足但利用率较低，东部和东北部海水营养盐含量低，利用率高，营养盐供应不足成为制约生产力的瓶颈。 通过对楚科奇海北部边缘地带M03岩心的粒度、颜色反射率和元素地球化学分析，获得如下几点结论:（1）M03岩心沉积物颜色的韵律变化明显，大致可划分出7个褐色层（BI一B7）和7个灰色层（GI一G7）;褐色层BI、BZ、B3、B4、BS、B6、B7的年龄分别与氧同位素l、3、5、7、9、11、13期相对应，GI、GZ、‘33、G4、GS、G6、G7的年龄大致与氧同位素2、4、6、8、10、12、14期相对应;]过03岩心底部年龄可能在530 ka BP左右，属中更新世沉积。（2）在氧同位素l、3、二;、7、9、11、13期，总的来说是沉积物粒度较粗，A12o3、FeZo3、TioZ、跳。、se、V、Li、Y含量低，沉积物呈褐色，富Mn，富C。，海底处于氧化环境。在氧同位素2、4、6、8、10、12、14期，总的来说是沉积物粒度较细，A12o3、FeZo3、TioZ、及。、sc、v、Li、Y含量高，沉积物呈灰色或浅黄灰色，贫Mn，贫CO，海底处于还原环境。冰筏碎屑含量在冰期（灰色层）低，在间冰期（褐色层）较高，在冰期和间冰期的转变阶段往往很高。在间冰期最盛期，气候温暖，大体与现代差不多，北冰洋大部分海区可能发育季节性海冰，陆源冰的输入少，冰体筏运的碎屑物质不多。在冰期的最盛期，海冰厚度大，覆盖度大，甚至可能形成巨厚的冰盖，冰的活动受到很大抑制，筏运的碎屑很少;同时，冰盛期气候干冷，河流的径流量小，输沙量降低，北冰洋深水区沉积作用以海水中细粒悬浮物质的缓慢沉降为特征，沉积速率低。在氧同位素1、3、5、7、9、11、13期，MgO、CaO的含量较高;在氧同位素2、4、〔、8、10、12、14期，Zr/AI比值较大;前者多与碳酸盐岩冰筏碎屑有关，反映间冰期波弗特涡流可能增强;后者多与硅酸盐冰筏碎屑有关，反映冰期来自西伯利亚及其陆架的物质更多还原

【Abstract】 The Arctic Ocean plays an important role in the late Cenozoic evolution of the Earth’s environmental s ystem, includin g modern climatic changes. The Chukchi Sea, together with its northern borderland, is the key area to understand modern and past oceanographic changes of the Arctic Ocean. 60 surface sediment samples and Core M03 were selected and analyzed major and minor elements, stable carbon and nitrogen isotopes, and other sedimentologic parameters, with the objectives for understanding sediment sources, spatial and temporal changes of sedimentary environments in the area.Based on numerous studies of surface sediments, several conclusions are summarized as follows: (1) Controlled by hydrodynamics and ice, surface sediments in the study area are relatively coarse and have bad sorting and low structure maturity. (2) Sediments also have relatively low chemical maturity and remain clear fingerprints of their sources. K-rich illite. Mg-, Ca-, Na-, Zn-rich smectite, Mn- and Fe-rich chlorite produce a clear coupling relationship between clay minerals and chemical compositions of clay fraction. Major elements Al, K, Mg, Fe, Ti and minor elements Li, V, Sc, La, Z,n, Y, Cu, Ni are enriched in fine-grained sediments, the former are main components to form clay minerals and the latter are generally related to adsorption and integration of fine-grained materials. (3) The dispersals of terrigenous components in the study area are controlled mainly by marine circulation. Kaolinite-, illite-, K- and Al-rich sediments in the northeast and the north of the study area are derived mainly from Canadian Mackenzie River due to the transport of i:he clockwise Beaufort Gyre. Sediments in the nearshore of Northwest Alaska enrich chlorite, and have variable kaolinite and high SiO2 contents, indicating a large fraction of sediments from the Northwest Alaskan coasts and riven;. Sediments off Wrangel Island in the west of the study area enrich chlorite, Na, Sr and Zr, indicating an elevated influences from Siberian continent and shelves. The Pacific waters entering from the Bering Strait entrain a large amount of the Yukon River materials; its northward dispersal possibly cause sediments in the central part of the Chukchi Sea to enrich smectite and elements Na, Mg, Ca, Zn, Sr etc. (4) REEs are relatively rich in fine-grainedsediments and deplete in coarse-grained sediments, and exhibit flat shale- normalized REEpattern in the Chukchi Sea, indicating surface sediments are composed dominantly ofterrigenous components with weak chemical weathering from Alaska and Siberia. (5)Transitional metals Mn, Co, Ni, Cu coexist and their enrichments denote oxidizingenvironments. The distributions of authigenic Mn and Ni indicate the northern deep seahas an oxidizing seabed environment while the Chukchi Sea has a reducing sedimentaryenvironment. (6) Biogenic SiO2 contents, organic 513C and 515N values in surfacesediments reflect surface water productivity and supply of terrigenous organic materials,which are controlled by marine circulation and seawater nutrient structure. After enteringthe study area, the Pacific waters disperse northward cross the Chukchi shelf as threebranches with different nutrients, and cause differentiations in nutrient and surface waterproductivity in the study area. Due to the influence of the nutrient-rich waters, themidwest of the study area have high surface water productivity, and weak signals ofterrigenous organic 513C and 515N; The nearshore of Northwest Alaska has the lessnutrient-rich seawater, and so has decreasing surface water productivity and enhancedsignals of terrigenous organic 6I3C and 615N. The Chukchi Plateau and the Canadian Basinin the northeast and the north of the study area have relatively long duration of ice coverand the least nutrient-rich seawater, so they have the lowest surface water productivity andthe highest terrigenous organic component, the latter is derived mainly from CanadianMackenzie River due to the transport of the clockwise Beaufort Gyre. For th更多还原