Foraminifera in surface sediments of the Bering and Chukchi Seas and their sedimentary environment     

Meng Yi  Chen Ronghu  Zheng Yulong 《海洋学报(英文版)》2002,21(1):67-76

Based on a quantitative analysis of foraminifera in 39 surface samples of the Bering andChukchi Seas, the nearly absence of planktonic foraminifera in the surface sediments can be related to the low surface primary productivity and strong carbonate dissolution in the study area. It has been revealed that the surface primary productivity, and carbonate dissolution and properties of water masses related to the water depth mainly control the distribution of benthic foraminifera. The shelf of the Chukchi Sea is dominated by the Elphidium spp. assemblage and Nonionella robusta assemblage with low foraminiferal abundance and diversity, which is controlled by the coastal water mass of the Arctic Ocean. The slope of the Bering Sea is dominated by the Uvigerina peregrina - Globobulimina affinis assemblage with abundant N. robusta, and relatively high foraminiferal abundance and diversity, which is controlled by the intermediate and deep water masses of the Pacific Ocean. However, the Bering Sea has relatively sha  相似文献   

Water masses in the Gulf of Aden     

Mohammed Ali Al Saafani  S. Satheesh Chandra Shenoi 《Journal of Oceanography》2007,63(1):1-14

Hydrographic data collected from Gulf of Aden since 1920 have been compiled to identify and refine the definitions of water masses in the Gulf of Aden (GA) and to describe their spatio-temporal variability. Four water masses have been identified based on their θ-S characteristics. The Red Sea Water (RSW) that flows from the Red Sea is the most prominent water in the GA; this occupies about 37% of the total volume of Gulf of Aden. The Gulf of Aden Surface Water (∼3%) forms as a mixture of local water and the water from western Arabian Sea during winter and Red Sea surface water during summer. The intermediate water, identified as Gulf of Aden Intermediate Water (GAIW), occupies about 9% of the total volume of GA; a characteristic salinity minimum is associated with it at σ_θ=26.50 kg m⁻³. The northward spread of sub-tropical subsurface water from the south appears to be the major source of GAIW. The bottom water, named Gulf of Aden Bottom Water, showed the least variability. It was formed due to the mixing of Red Sea Water and water of southern origin. Mixing triangles have been used to analyze the composition of water in the GA.  相似文献   

法向承力锚(VLA)--一种适用于深海工程的新型系泊基础   总被引：2，自引：0，他引：2  

刘海笑  杨晓亮 《海洋技术学报》2005,24(3):78-82,87

深水系泊基础是深水系泊系统的重要组成,随着海洋油气资源开发的加速发展,深水系泊系统的关键技术成为国际海洋油气资源开发的重要研究领域.法向承力锚（VLA）是一种崭新的适用于深海油气资源开发的系泊基础形式,论文对其应用、性能特点、工作原理、安装与回收以及计算分析方法等进行了全面介绍,以期对科研人员进一步认识深水系泊系统的关键技术有所帮助,并对国内深水系泊系统的研发起到一定的借鉴作用.  相似文献   

An investigation of the effects of important grouting and rock parameters on the grouting process     

Ali Mortazavi  Abbas Maadikhah 《Geomechanics and Geoengineering》2016,11(3):219-235

Today, grouting is used as an aid in ground improvement in most civil and mining engineering projects. Groutability and grout penetration depth are among the most important issues that are considered in grouting operation. Various parameters such as in-situ stress, pore water pressure, joint geometric and geomechanical characteristics, grout properties (viscosity and yield stress) and technical factors such as grouting pressure and flow rate affect the groutability and grout penetration depth in a jointed rock mass. Knowledge of the effect of these parameters has advantages in the prediction of grouting results. Typically, cement-based grout is used in jointed rock masses. Unlike water, stable cement-based grout usually acts as a Bingham fluid. In this study the effect of important parameters on grouting process in a jointed rock mass was investigated numerically using the DEM method. In the conducted study, the problem geometry represents a horizontal section in a regularly jointed rock mass with two joint sets. The analyses results show that the grout penetration depth and intake increase as joint aperture, normal stiffness and grouting pressure increase and in-situ stress and pore water pressure decrease. Increase in joint spacing does not have any effect on the grout penetration depth but decreases the grout intake. The effect of joint orientation on grouting process is strongly dependent on in-situ stress state. On the other hand, increase in grout yield stress decreases the grout penetration depth and intake, while grout viscosity does not have any effect on maximum grout penetration depth and intake. To further investigate the above mechanisms, the grouting process conducted in Gotvand dam-Iran was simulated numerically.  相似文献   

The high-supply,current-dominated continental margin of southeastern South America during the late Quaternary     

Hendrik Lantzsch  Till J.J. Hanebuth  Cristiano M. Chiessi  Tilmann Schwenk  Roberto A. Violante 《Quaternary Research》2014

The continental margin off the La Plata Estuary (SE South America) is characterized by high fluvial sediment supply and strong ocean currents. High-resolution sediment-acoustic data combined with sedimentary facies analysis, AMS-¹⁴C ages, and neodymium isotopic data allowed us to reconstruct late Quaternary sedimentary dynamics in relation to the two major sediment sources, the La Plata Estuary and the Argentine margin. Sediments from these two provinces show completely different dispersal patterns. We show that the northward-trending La Plata paleo-valley was the sole transit path for the huge volumes of fluvial material during lower sea levels. In contrast, material from the Argentine margin sector was transported northwards by the strong current system. Despite the large sediment volumes supplied by both sources, wide parts of the shelf were characterized by either persistent non-deposition or local short-term depocenter formation. The location and formation history of these depocenters were primarily controlled by the interplay of sea level with current strength and local morphology. The high sediment supply was of secondary importance to the stratigraphic construction, though locally resulting in high sedimentation rates. Thus, the shelf system off the La Plata Estuary can be considered as a hydrodynamic-controlled end-member.  相似文献   

Efficiency of heavy mass technology in traffic vibration reduction: Experimental and numerical investigation     

《Computers and Geotechnics》2014

Vibrations induced by traffic and construction activities cause serious environmental problems. The reduction of the impact of these vibrations on the nearby environment constitutes an important challenge, mainly in urban area. This paper presents both experimental investigation and 3D numerical modeling of the performance of heavy masses technology for scattering the ground vibrations. The efficiency of this method is compared to that of the trench barriers, largely studied in the literature. Analyses show that the heavy mass constitutes an efficient technology for the attenuation of the traffic induced vibrations. The performance of this method depends mainly on the mass weight. An amplitude reduction ratio up to 70% can be reached using this technology.  相似文献   

Oxygen isotopic composition and its application to the study of tracing oceanographical process in Bering Sea and Chukchi Sea     

尹明端  曾宪章  曾文义  吴世炎  施纯坦 《极地研究(英文版)》2002,13(1)

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Sedimentation styles and depositional processes in a Middle to Late Jurassic slope environment, Bowser Basin, northwestern British Columbia, Canada     

Jean-François Gagnon  John W.F. Waldron 《Marine and Petroleum Geology》2011,28(3):698-715

The Middle to Upper Jurassic Todagin assemblage in northwestern British Columbia, Canada, was deposited in the Bowser Basin above arc-related rocks of the Stikine terrane. Sedimentary structures indicate that a variety of gravity flow processes were involved in transport and deposition in deep-water slope environments. At Mount Dilworth, laterally continuous and channelized turbidites are interbedded with and overlain by mass-transport deposits in which sedimentary clasts are supported in a mudstone matrix. More than 50% of the succession consists of mass-transport deposits, indicating significant slope instability. A 300 m thick mass-transport complex exposed near the top of the succession is interpreted to result from tectonic activity, which triggered a major change in sediment supply from a local source area. At Todagin Mountain, a channel complex displays three successive channel-fills with associated overbank sedimentation units. Mass-transport deposits are rare, and confined to channel axes. Channels 1 and 2 are characterized by 40-50 m thick, ungraded pebble clast-supported conglomerate while the uppermost Channel 3 contains graded beds and occasional traction structures. The gradual change from erosive and amalgamated channel deposits at the base, to more aggradational channels at the top, is related to elevation of the equilibrium profile. Creation of accommodation favored aggradation on the mud-dominated slope succession and construction of well-developed channel-levee systems. The vertical succession exposed at Todagin Mountain is consistent with normal progradation of the slope under high sedimentation rates. In the Mount Dilworth area, extensional faulting associated with development of the restricted Eskay rift in the early Middle Jurassic produced a dissected basement above which the Todagin assemblage was deposited. These structures were inverted during collision of the Stikine and Cache Creek terranes, and likely played a major role in the stratigraphic evolution of the deep-water architectures.  相似文献   

白令海峡水团来源的镭同位素示踪   总被引：4，自引：3，他引：1       下载免费PDF全文

陈敏  李艳平  邱雨生  杨俊鸿 《海洋学报》2011,33(2):69-76

对白令海峡64.3°N纬向断面镭同位素的研究表明,水体中226Ra比活度、228Ra比活度和228Ra/226Ra)A.R.存在明显的纬向变化,反映出太平洋与北冰洋水体交换的多种路径.根据温度、盐度和镭同位素的水平与垂直分布,太平洋水进入北冰洋的路径可能主要有3支,分别为白令海峡西侧的阿拉德水、白令海峡东侧的阿拉斯加沿...  相似文献   

Topographically constrained deep-water flows in the Baltic Sea   总被引：2，自引：0，他引：2  

Janek Laanearu  Peter Lundberg 《Journal of Sea Research》2003,49(4):257

Density-driven currents have a significant impact on the deep-water characteristics of the Baltic Sea since they account for the water exchange between the deeper parts of neighbouring basins. The essential quantitative problem is to determine the flow rates in relation to a set of external parameters such as the strait topography, the stratification, and the internal circulation of the upstream basin. Using hydraulic theory it is possible to accomplish this by analysing the dynamical constraints that limit the deep-water flux between adjacent basins. On the basis of these results, the deep-water flows through the Bornholm Channel and the Irbe Strait are compared.  相似文献