Giant submarine landslide grooves in the Neoproterozoic/Lower Cambrian Phe Formation, northwest Himalaya: Mechanisms of formation and palaeogeographic implications     

E. Draganits  J. Schlaf  B. Grasemann  T. Argles 《Sedimentary Geology》2008,205(3-4):126-141

Giant groove casts have been found in the upper Proterozoic to Lower Cambrian Phe Formation (Haimanta Group), a siliciclastic sandstone/shale succession in the Tethyan Zone of the Higher Himalaya tectonic unit. The grooves are among the largest linear erosion structures related to submarine mass-movements observed in the geologic record. They are up to 4 m wide, about 0.2 m deep and can be traced for more than 35 m without changing their character. The grooves are straight, subparallel to cross-cutting striations with shallow semi-circular cross-sections and well-defined superimposed minor ridges and grooves. Groove casts exist on the soles of several sandstone beds within a 73 m thick logged section, commonly associated with flute casts. Their characteristics were compared with several other types of ancient and modern submarine linear erosion structures. A sand-rich, non-channelized basin floor depositional environment is inferred from the lithofacies, the combination of sedimentary structures, the lack of coarse-grained pebbly facies, the lateral continuity of beds, and the lack of channel structures. The grooves probably formed by laminar debris flows/concentrated density flows dragging blocks of already lithified sediment across the basin floor. When the bedding is structurally rotated back to horizontal, the groove casts show consistent North–South oriented palaeocurrent trends, with South-directed palaeocurrent directions indicated by flute casts. These palaeocurrent orientations contrast with previous palaeogeographic reconstructions of this area, which propose sediment delivery from the South. We therefore suggest a new “double provenance” model for the spatial relationship of late Proterozoic to Early Cambrian strata of the Himalaya, in which Lesser and Tethyan Himalayan age-equivalent sediment was deposited in a connected basin, where the former received detritus from the South, and the latter from a hitherto unknown source in the North. One possible candidate for this northern source is the South China Block and an associated Neoproterozoic volcanic arc.  相似文献   

Analysis of drivers governing temporal salinity and temperature variations in groundwater discharge from Altug Submarine Karst Cave (Kas-Turkey)     

N. Nur Ozyurt 《Environmental Geology》2008,54(4):731-736

Salinity and temperature variations in groundwater discharge from the Altug submarine karst cave have been observed at 28 m below sea level for every 10 min between November 2004 and August 2005 to determine the drivers that govern the salinization. Comparisons between temporal trends of salinity and temperature with those of precipitation, air pressure, sea level and wind velocity revealed an apparent dominance of precipitation regime on the salinity and temperature variations. Spectral analyses applied to observations showed that the air pressure and sea level oscillations are affected by sun and moon tides which do not have an appreciable impact on the salinity and temperature variations. Annual rate of salinization in Altug cave seems inversely related to the inland groundwater head so that the maximum and minimum fresh water contributions occur at mid-spring and late-summer, respectively.  相似文献   

Methodology of hydrogeological characterization of deep carbonate aquifers as potential reservoirs of groundwater. Case of study: the Jurassic aquifer of <Emphasis Type="Italic">El Maestrazgo</Emphasis> (Castellón,Spain)     

M. Mejías  J. Garcia-Orellana  J. L. Plata  M. Marina  E. Garcia-Solsona  B. Ballesteros  P. Masqué  J. López  C. Fernández-Arrojo 《Environmental Geology》2008,54(3):521-536

A methodology for the characterization of deep carbonate aquifers has been developed and applied to El Maestrazgo Jurassic aquifer in Castellón, Spain. Characterization of these aquifer formations, located at more than 300 m deep, consisted of a previous phase of compilation, analysis and synthesis of the existing information about the area, followed by a coordinated combination of different speciality studies: geology, stratigraphy, structural analysis, hydrogeology, hydrochemistry, geophysics and remote sensing. Geological studies included geological mapping, definition of stratigraphical units and facies and structural analysis. The aim of the hydrogeology study was to define aquifer formations, recharge area, aquifer points inventory and groundwater flow directions for the establishment of piezometric and water quality observation nets. Special techniques were applied, like thermal infrared aerial images and the evaluation of submarine groundwater discharge by means of natural radium isotopes. Hydrochemical techniques, including majority elements characterization and stable isotopes (¹⁸O, ²H and ³H) determination, allowed classifying hydrochemical facies and establishing a renewal pattern for water within the system. Geophysics was useful in determining the aquifer geometry, the features of the basement and the petrophysical characteristics of the geological formations. Preliminary results show an important tectonic complexity and the possibilities for groundwater uses in the area of study.  相似文献   

海底管道开沟机械的技术经济性能评定与选型   总被引：1，自引：0，他引：1  

张国光  顾林声 《海洋技术学报》1993,12(3):16-27

本文在对水下管道开沟机械的需求市场、实际应用和研制开发动向作深入调研的基础上，选择水下管道开沟机械特有的技术先进性、适用性、安全可靠性以及经济性评价指标，构造评价模型，对水下管道施工作业中广为应用的水力冲射开沟机械、海底管道犁、机械开沟机和土壤液化法埋管设备及其机型的技术经济性能作了较为详尽地分析对比及综合评价。在此基础上，笔者提出了水下管道开沟机械的一般选型原则和对我国海底管道开沟机械研究开发工  相似文献   

台湾海峡西部柱状沉积物粘土矿物的分析   总被引：4，自引：0，他引：4  

游仲华  唐锦龙 《台湾海峡》1993,12(1):1-7

根据台湾海峡西部10个柱102个样品的X 射线衍射等分析,鉴定了该区粘土矿物组合与含量变化,分析了其与沉积环境的关系.结果表明,该区粘土矿物组合大多数站位以伊利石含量占首位,绿泥石和高岭石次之,且含少量蒙脱石;伊利石含量随距岸、水深的增加而递增,高岭石则反之;蒙脱石含量与火山活动密切相关,绿泥石含量呈斑块状分布;775和819号站有典型的陆相层,为早玉木冰期的“台湾陆桥”或“东山陆桥”提供有力证据.  相似文献   

Wave interaction with a submarine pipeline in clayey soil due to random waves     

A. Vijaya kumar  S. Neelamani 《Ocean Engineering》2005,32(13):1517-1538

The wave pressure and uplift force due to random waves on a submarine pipeline (resting on bed, partially buried and fully buried) in clayey soil are measured. The influence of various parameters viz., wave period, wave height, water depth, burial depth and consistency index of the soil on wave pressures around and uplift force on the submarine pipeline was investigated. The wave pressures were measured at three locations around the submarine pipeline (each at 120° to the adjacent one). It is found that the wave pressure and uplift force spectrum at high consistency index of the soil is smaller compared to that of low consistency index. Just burying the pipeline (e/D=1.0) in clayey soil reduces the uplift force to less than 60% of the force experienced by a pipeline resting on the seabed (e/D=0.0) for I_c=0.33.  相似文献   

GIS与遥感支持下的南黄海辐射沙脊群现代演变趋势分析   总被引：4，自引：1，他引：4  

李海宇  王颖 《海洋科学》2002,26(9):61-65

南黄海辐射沙脊群是世界罕见的大型水下泥沙堆积体，具有独特的动力地貌组合。利用1988-1995年的LANDSATTM遥感影像，ERS1SAR影像及1979年编绘地形资料，综合应用GIS与遥感方法，对这一区域在20世纪80-90年代的变化及演变趋势作出分析，其基本演变特征与趋势表现为；沙脊群枢纽地区处于不断的增长，扩张过程；南部区域堆积与侵蚀作用较弱，沿岸潮滩向海淤进；而北部区域变化较强烈，并继续脊槽相间的模式，所取得的结果与该区域动力地貌研究结果相吻合。  相似文献   

Plastic buckling of ring-stiffened conical shells under external hydrostatic pressure     

Carl T.F. Ross  Andrew P.F. Little  Kehinde A. Adeniyi 《Ocean Engineering》2005,32(1):753-36

The paper describes experimental tests carried out on three ring-stiffened cones that were tested to destruction under external hydrostatic pressure. The cones were carefully machined from EN1A Steel. All three cones failed by plastic non-symmetric bifurcation buckling in a mode commonly known as general instability. In this mode the entire ring-shell combination buckles bodily.The paper also provides a design chart using the results obtained from these three vessels, together with the results of six other vessels obtained from other tests. The design chart allows the possibility of obtaining a plastic knock down factor, so that the theoretical buckling pressures, based on elastic theory, can be divided by the plastic knockdown factor, to give the predicted buckling pressure. This method can also be used for the design of full-scale vessels.  相似文献   

基于ArcGIS Engine的水下间断等高线自动连接研究   总被引：1，自引：0，他引：1  

蒋淼  张琴 《现代测绘》2008,31(3)

本文利用ArcGIS提供的数据分析和数据管理功能对不连续的水下等高线自动连接问题进行了研究。ArcGIS Engine作为ESRI公司最新推出的面向开发的嵌入式组件,具有高效便捷的特点,由于其开发时完全脱离了ArcGIS桌面平台,因而为用户提供了一个可供选择的,有针对性的,低成本的GIS应用选择。本文对水下地形等高线的断线自动连接问题应用ArcGIS Engine进行了研究实验,阐述了使用该技术编程的具体过程,实验结果证明了本文方法的有效性和实用价值。  相似文献   

扬子东南大陆边缘晚前寒武纪古海洋演化的稀土元素记录   总被引：10，自引：1，他引：9  

伊海生  彭军 《沉积学报》1995,13(4):131-137

本文采用中子活化方法分析了晚震旦～早寒武纪１９件样品的稀土元素组成,发现硅质岩石ＲＥＥ配分形式有着复杂的变化,初步可以划分为五种类型,包括“台地型”、“红海型”、“海水型”及两种特殊的配分形式。剖面上Ｃｅ异常由小到大的演变反映了古海洋底层水由缺氧环境向氧化条件的逐渐转化。正Ｅｕ异常的出现代表了热水沉积事件的存在。  相似文献