北冰洋中部阿尔法脊晚第四纪介形虫化石群与古海洋环境变迁

基于北冰洋中部阿尔法脊ARC3-B84A岩芯（水深2280 m）中的介形虫化石群记录,重建了MIS 13期以来该海域的古海洋环境变迁。从该岩芯获取的介形虫壳瓣逾7000枚,包含8属11种。由介形虫丰度所代表的底栖生物古生产力在MIS 13–10期很低,进入MIS 9期之后显著升高。海冰指示种Acetabulastoma arcticum显示常年海冰很可能是在MIS 9期之后出现的。在所有属种中,北冰洋中层水（AIW）指示种Polycope spp.和北冰洋深层水（AODW）指示种Cytheropteron sedovi的个体数量最多,二者在岩芯中的百分含量呈负相关,它们与其他属种(Microcythere medistriatum, Pseudocythere caudata, Pedicythere spp., Cytheropteron scoresbyi, Cytheropteron higashikawai, Henryhowella asperrima)一起,揭示该岩芯站位经历了如下的水团变迁历史：最初处于AODW上部（MIS 13–12）,之后被上涌的AODW下部所取代（MIS 11–10）;尔后,上方的AIW大幅下潜,取代了AODW（MIS 9期–MIS 5早期）;在MIS 5中–晚期,AODW下部快速上涌,取代了AIW;最终在MIS 4之后,水团定格在AODW上部。     

Comparison of airsea fluxes of CO2 in the Southern Ocean and the western Arctic Ocean

The data were collected during Chinese Arctic and Antarctic Expeditions in the western Arctic Ocean and the marginal sea ice zone (MSIZ) of the Southern Ocean, respectively in the boreal summer from July to September of 1999 and in the austral summer from December of 1999 to January of 2000. The concentrations of CO2 in surface water of the survey regions would mostly present lower than those in the atmosphere. A significant biological driving force could also been observed in summer waters in both of the above oceans. Air to sea CO2 fluxes were also calculated to compare oceanic uptake capacity of CO2 in both oceans with the world oceans using Liss, Wanninkhof, and Jacobs‘s methods. The averaged CO2 fluxes of air to sea in the western Arctic Ocean or in the MSIZ of the Southern Ocean doubled that in the world oceans.     

西北冰洋表层沉积物黏土矿物分布特征及物质来源

西北冰洋表层沉积物黏土矿物分析结果显示其黏土矿物组成的区域分布和变化具有明显的规律性:从楚科奇海到北冰洋深水区,随着水深的增加,蒙皂石和高岭石含量增高,绿泥石和伊利石含量降低。自西往东,伊利石结晶度值降低,化学指数升高。根据Q型聚类分析获得的黏土矿物组合特征,结合周缘陆地的地质背景、河流及洋流情况,对研究区进行了黏土矿物组合分区,讨论了其黏土矿物来源。楚科奇海表层沉积物黏土矿物组合在靠近阿拉斯加一侧海域以Ⅰ类为主,靠东西伯利亚海一侧主要有Ⅱ类、Ⅲ类和Ⅳ类,中部主要为Ⅵ类,主要是西伯利亚和阿拉斯加的火山岩、变质岩以及一些含高岭石的沉积物以及古土壤等,经风化、河流搬运入海,在北太平洋的3股洋流及西伯利亚沿岸流的作用下沉积形成的。西北冰洋深水区表层沉积物的黏土矿物组合以Ⅰ类和Ⅴ类为主,表明其沉积物来源为欧亚陆架和加拿大北极群岛周缘海域的海冰沉积和大西洋水体的搬运以及加拿大马更些河的河流物质输入。     

印度洋钙质软泥和硅质软泥稀土元素组成和富集机制

本文针对采自印度洋深海中最常见的两类生物成因沉积物——钙质软泥和硅质软泥,开展了全岩样和不同粒级组分中常微量元素、稀土元素和Y（REY）含量的系统分析,探讨了两类沉积物中REY的组成特征、物质来源和富集机制。研究表明,钙质软泥以富含CaO和Sr为主要特征,硅质软泥则富集SiO₂、Al₂O₃、Fe₂O₃等。钙质软泥中∑REY平均含量为40.56×10-6,轻稀土元素（LREE）略有富集,REY有向细粒沉积物中富集的特征,PAAS标准化后全岩样和不同粒级组分均表现为Ce负异常、Eu和Y正异常;REY以自生来源为主,继承了海水的组成特征,同时也受到了热液流体物质和洋底玄武岩风化产物的影响。硅质软泥中∑REY的含量为248.54×10-6,LREE相对富集,REY在4φ以细的沉积物中富集;研究站位沉积物中∑REY含量处于边界品位附近,但在细粒级沉积物中重稀土元素（HREY）含量则达到了工业品位;该类沉积物细粒组分中REY主要来自陆源或火山碎屑组分中黏土矿物和铁锰氧化物吸附作用,粗粒组分中REY来源则主要与生物作用相关;硅质软泥中REY的富集与沉积物中磷灰石等矿物相关,部分不同来源的REY可能是在沉积之后的成岩过程中再次分配向磷灰石、钙十字沸石等矿物中富集。     

2003年夏季西北冰洋浮游动物群落结构和地理分布研究

根据西北冰洋43个调查站位的浮游动物种类组成和数量资料,分析了浮游动物的群落结构和地理分布特征,探讨了浮游动物群落与环境因子的关系.结果表明,在调查区域存在三种不同的浮游动物群落类型:楚科奇海台和加拿大海盆地区的高纬度深海群落;楚科奇海中部的陆架群落;阿拉斯加沿岸和楚科奇海北部的沿岸过渡群落.深海群落浮游动物数量较少,...     

庙岛群岛西部海域表层沉积物常量和稀土元素的分布特征及其物源指示意义

通过对庙岛群岛西部海域表层沉积物常量、稀土元素的系统研究,探讨了表层沉积物元素地球化学特征、控制因素及其物质来源。结果表明,庙岛群岛西部海域表层沉积物常量元素以SiO₂和A1₂O₃为主,SiO₂含量随着沉积物粒径变粗逐渐增大,Al₂O₃含量随着沉积物粒径变细逐渐增大。稀土元素(Rare Earth Element,REE)呈现轻稀土元素(Light Rare Earth Element,LREE)富集、重稀土元素(Heavy Rare Earth Element,HREE)平坦以及中等程度的Eu负异常等特征,轻重稀土分异明显,稀土元素球粒陨石配分曲线与黄河沉积物类似。通过因子分析和相关性分析发现研究区沉积物的元素含量主要取决于陆源碎屑,海洋生物沉积和化学作用对沉积物元素含量有一定的影响,元素含量基本服从粒度控制规律。物源判别结果显示,庙岛群岛西部海域沉积物主要来源于黄河物质和辽河物质,并且从南到北辽河物质的混合比例逐渐升高,黄河物质的混合比例逐渐降低。     

Evaluation and modelling of Tertiary source rocks in the central Arctic Ocean

With the recently recovered organic-rich sediments of early Tertiary age from the Lomonosov Ridge by the Integrated Ocean Drilling Program (IODP) Expedition 302, the first data collection directly from source rocks of the central basins of the Arctic Ocean is now available. Using the results of seismic interpretations and published sedimentological and organic geochemical data from Expedition 302, the framework for the first quantitative assessment of source-rock quality and distribution of the Palaeogene sediments was modelled in the central Arctic Ocean. The modelling results suggest that an approximately 100-m-thick Early to Middle Eocene sedimentary sequence of good to very good source rocks exists along a 75 km long transect across the Lomonosov Ridge. In-situ generation of hydrocarbons is unlikely because the overburden (200–250 m) and consequently the thermal maturity are too low. Burial history and thermal modelling reveal that an additional overburden of at least 1000 m is necessary to start hydrocarbon generation along the ridge. However, source-rock modelling results show that good source-rock potential may exist in correlative units in the adjacent Amundsen Basin. Simulated organic carbon contents of 1.5–5%, coupled with an overburden of 1000–1200 m, and heat flow anomalies (117 and 100 mW m⁻²) due to the vicinity to the Gakkel Ridge spreading centre indicate that necessary conditions for hydrocarbon expulsion are already reached, and point to viability of a potential petroleum system. Our results support the hypothesis that deposition of a potentially good hydrocarbon source rock occurred across the entire Arctic Basin and adjacent margins during the early Tertiary.     

Northward transport of pacific summer water along the Northwind Ridge in the Western Arctic Ocean

The recent sea-ice reduction in the Arctic Ocean is not spatially uniform, but is disproportionally large around the Northwind Ridge and Chukchi Plateau compared to elsewhere in the Canada Basin. In the Northwind Ridge region, Pacific Summer Water (PSW) delivered from the Bering Sea occupies the subsurface layer. The spatial distribution of warm PSW shows a quite similar pattern to the recent ice retreat, suggesting the influence of PSW on the sea-ice reduction. To understand the regionality of the recent ice retreat, we examine the dynamics and timing of the delivery of the PSW into this region. Here, we adopt a two-layer linearized potential vorticity equation to investigate the behavior of Rossby waves in the presence of a topographic discontinuity in the high latitude ocean. The analytical results show a quite different structure from those of mid-latitude basins due to the small value of β. Incident barotropic waves excited by the sea-ice motion with large annual variation can be scattered into both barotropic and baroclinic modes at the discontinuity. Since the scattered baroclinic Rossby wave with annual frequency cannot propagate freely, a strong baroclinic current near the topographic discontinuity is established. The seasonal variation of current near the topographic discontinuity would cause a kind of selective switching system for shelf water transport into the basin. In our simple analytical model, the enhanced northward transport of summer water and reduced northward transport of winter water are well demonstrated. The present study indicates that these basic dynamics imply that a strengthening of the surface forcing during winter in the Canada Basin could cause sea-ice reduction in the Western Arctic through the changes of underlying Pacific Summer Water.     

白令海及西北冰洋有机质来源与新鲜程度的脂肪酸指示

白令海、西北冰洋等高生产力海域在北冰洋"生物泵"中起到重要作用;海水升温、海冰消退等北极快速变化,将强烈影响该海域"生物泵"的结构与规模,并在沉积物中有机质的来源与新鲜程度上有所体现,可用脂肪酸加以指征。对第五次、第六次中国北极科学考察在以上海域采集的表层沉积物进行脂肪酸含量(以沉积物干重计)及组成分析,结果显示楚科奇海陆架总脂肪酸含量非常高((97.15±55.31)μg/g),白令海盆最低((15.00±1.30)μg/g),加拿大海盆、楚科奇海陆坡、白令海陆架居中(分别为(88.65±3.52)μg/g,(70.35±11.32)μg/g与(38.28±14.89)μg/g)。海源脂肪酸占总脂肪酸比例最高(86.82%±7.08%),陆源次之(8.45%±6.62%),细菌最低(4.63%±2.24%);硅藻指数(16:1ω9/16:0)在楚科奇海陆架(> 0.82)、白令海陆架边缘(> 0.65)较高,其他区域均较低。脂肪酸结果表明:(1)该海域沉积有机质主要来自海源,陆源贡献小;在北部、南部楚科奇海陆架、白令海陆架边缘,硅藻生物量占主要优势;细菌脂肪酸比例显著低于...     

北冰洋西部沉积物黏土的Sm-Nd同位素特征及物源指示意义

通过对北冰洋西部(楚科奇海及北部边缘地带、加拿大海盆)34个表层沉积物样品中黏土组分的Sm-Nd同位素分析,结果表明:(1)黏土组分的Sm-Nd同位素分异明显,可将沉积物划分为北部、西部、南部和东部等多个同位素物源区;(2)在楚科奇海,太平洋入流的向北输运自西向东形成了3个不同的同位素物源区,沉积物的c(147Sm)/c(144Nd)比值、ε_Nd(0)值和T_DM年龄自西向东呈递减趋势;(3)在研究区北部,顺时针方向流动的波弗特涡流将马更些河物质向西搬运至加拿大海盆和楚科奇高地,使该区沉积物ε_Nd(0)值明显偏低,T_DM偏大;(4)在楚科奇海北部外陆架、海台和陆坡区,太平洋水、大西洋水和波弗特涡流的相互作用使该区沉积物T_DM年龄的标准偏差大,同时出现了南-北源和西-南源等同位素混合类型。