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渤海西南岸贝壳滩脊发育典型,贝壳含量高、规模大,不仅作为古岸线标志,还是抵御风暴潮的天然屏障。作者通过对鲁北贝壳滩脊的沉积结构,发育环境分析,将贝壳滩脊分为堤梗和堤内充填两个亚相。前者以贝壳和贝壳碎块为主,具有平行层理和高角度斜层理,后者以贝壳细碎屑为主,亦含细粉沙,具有向陆倾的平行层理。贝壳滩脊的形成和发育受多种因素的控制,其中贝壳物质的大量富集、较强的暴风浪、风的吹积作用及入海河流的改道效应等均与其有密切关系。当黄河从鲁北入海时,潮滩快速加积,贝壳贫乏,当黄河远离本区时,鲁北岸滩相对侵蚀,利于贝壳滩脊的发育。 相似文献
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海南岛海岸环境特征 总被引：8，自引：0，他引：8
海南岛虱热带季风岛屿型气候，为南海大陆架岛屿，中央为山地，临海为多种类型海岸，以处于动态平衡的海蚀-海积型海岸为主。海南岛主要是基岩岬湾海岸，潮汐属日潮型，东部与南部为不规则日潮混合潮。海岸构造运动与气候变化的双重影响，更新世初期，海岸属基岩港湾型，晚更新世构造运动频敏，使不少海湾底部抬升为阶地。构造抬升运动持续到全新世，使一些珊瑚抬升为高出海面数米的阶地。海岸类型按其成因与形态可分为两大类：基岩港湾海岸与砂砾质平原海岸。基岩港湾海岸分布于山地与丘陵临海处，砂砾质平原海岸（或为三解洲平原海岸）其表现形式多为沙坝与泻湖海岸，沙坝上叠置发育着海滩、沙堤或沙丘，随着海岸加积展宽或地壳上升，老的沙坝可抬高成为海积阶地。潮流作用对洪湾众多的海南岛的发育演变以及开发利用亦有重要作用。潮汐汊道港湾规模较大，水域面积达数十平方公理。 相似文献
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根据2011年在海阳万米海滩岸段与威海国际海水浴场岸段调查获得的夏、冬两季海岸实测地形剖面与沉积物粒度数据,并收集相关水文资料,对南北两海岸地貌与沉积差异性进行分析,探讨了半岛东部南北岸典型砂质海岸动力环境的差异。研究结果表明,南部海岸宽广平缓,发育滩脊、滩肩、沙波纹等地貌,沉积物在水下岸坡上段以中粗砂、中细砂为主,水下岸坡以下段以粉砂、黏土质粉砂为主;北部海岸地形陡,发育滩肩陡坎、水下沙坝等地貌,沉积物以砾质砂为主。导致这些差异的动力为风、波浪、潮汐及沿岸流堆积。 相似文献
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本文从沉积结构、构造、贝壳组分与停积方式、沙体的几何形态以及垂向地层层序等方面,阐述长江三角洲南部古沙堤(冈身)的沉积特征,并据此确认古沙堤(冈身)属盐沼滩脊类型,而由各条冈身和其间泥质平原构成的整个冈身地带则是古代盐沼滩脊平源,这种滩脊与盐沼相间排列的格局,系历史时期三角洲海岸前展与后退嬗替的结果。同时,本文还以18个贝壳样品的14C测年为依据,探讨了古沙堤形成的年代分别距今6800—6000、5800—5500、4200—4000和3200年前。 相似文献
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冰后期海侵,海岸必然遭受改造。东海海岸砂源与海侵时期陆架均夷过程密切相关。现代堆积海岸的物质多具陆源性,但主要通过沉积物的再搬运和再沉积所形成。宽缓陆架及其大量松散物质的储备,有利于海侵时期东海陆架的细粒沉积物,在潮流作用下往复搬运和向岸迁移、加积。 相似文献
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第四纪加积型红土与下蜀黄土理化特征比较 总被引：2，自引：0，他引：2
加积型红土和下蜀黄土是我国亚热带地区常见的第四纪沉积物。测试了加积型红土的粒度、矿物与石英砂表面特征、磁化率、常量元素和稀土元素等理化指标,并与下蜀黄土进行了对比分析,结果表明,加积型红土与下蜀黄土在理化特征上具有整体相似性,显示风成特性,但较下蜀黄土经历了更为强烈的化学风化作用。同一剖面自下而上为加积型红土至棕黄色下蜀土的沉积序列,揭示了中更新世至晚更新世风化成壤强度减弱、气候由湿热向干凉转变的趋势;北亚热带和中亚热带沉积年代相当的下蜀土风化特征差异反映了古环境变化的纬度效应。 相似文献
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古代黄河三角洲海岸的现代特征——黄河三角洲潮滩时空谱系研究Ⅰ 总被引：6，自引：3，他引：6
从冀鲁交界的大口河口向东至顺江沟为蜿蜒120km的粉沙淤泥质海岸。作者先后于1987、1992和2000年对该海岸进行了多次实施考察，并应用80年代至90年代末以来的航空和卫星遥感等资料对其进行了综合分析。公元11－1128年，黄河尾阎在此摆动入海，开成河口滩型海岸。1128年以后，黄河自此迁走，在海洋动力作用下，由河口滩型海岸逐渐演变成为典型的潮滩型海岸。该岸段海岸发育了广阔平坦的、相带十分明显的潮滩地带。在潮滩上同时发育了岛链状贝壳堤、残留冲积岛和巨大的多级分叉贯通性的潮水沟网络，构成了独具特色的海岸地貌环境体系，即黄河三角洲潮滩海岸时空谱系中的古代典河三角洲海岸。 相似文献
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从冀鲁交界的大口河口向东至顺江沟为蜿蜒120 km的粉沙淤泥质海岸。作者先后于1987、1992和2000年对该海岸进行了多次实地考察，并应用80年代至90年代末以来的航空和卫星遥感等资料对其进行了综合分析。公元11～1128年，黄河尾闾在此摆动入海，形成河口滩型海岸。1128年以后，黄河自此迁走，在海洋动力作用下，由河口滩型海岸逐渐演变成为典型的潮滩型海岸。该岸段海岸发育了广阔平坦的、相带十分明显的潮滩地带。在潮滩上同时发育了岛链状贝壳堤、残留冲积岛和巨大的多级分叉贯通性的潮水沟网络，构成了独具特色的海岸地貌环境体系，即黄河三角洲潮滩海岸时空谱系中的古代黄河三角洲海岸。 相似文献
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青岛港湾海岸区第四纪地下卤水生存环境与富集条件 总被引：1，自引：0，他引：1
青岛港湾海岸区发现可利用卤水资源是中国北方沿海第四纪滨海相地下卤水研究的又一次重要进展。青岛港湾海岸区只有全新世海侵期，具备成卤古海水来源。虽然海岸平原狭小，第四系沉积层浅薄，却有封闭环境优良的湾中湾和堰坝式沉积盆地提供聚卤场所。又有滨海第四纪沉积盆地地质基础以及入海径流贫乏的水文条件，为地下卤水形成和富集创造了有利环境。港湾海岸区海岸地貌特点控制了卤水分布区呈斑块状散布，局部岸段可形成小型矿带。青岛胶州湾沿岸含卤岩系结构特征在中国北方沿海具有典型性，故命名为“胶州湾型” 相似文献
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海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。 相似文献
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Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans 总被引：1，自引：0，他引：1
A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level. 相似文献
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Sediment properties, such as water content and density, have been used to estimate the dry and wet weights, as well as the volume of sediment recovered and discharged, during benthic impact experiments conducted in the Pacific and Indian Oceans. The estimates show that the weights of dry (355-1332 t) and wet sediment (1651-4888 t) recovered during the experiments, are not only a function of the total duration and distance covered during the experiment, but also depend on water content and density of the sediment. Estimation of dry sediment and its volumetric ratio in the discharge, are key parameters for calculating the discharged volume. The estimated volume of wet sediment recovered (1427-4049 m 3 ) as well as discharged (2693-6951 m 3 ) during the experiments, provide important inputs to evaluate the sediment resettlement and migration. Using these estimates, the average depth of excavation on the seafloor, can also been calculated. However, the stages of sediment recovery and discharge are expressed differently in some of the experiments. In order to standardize these, different stages have been identified, and definitions of certain terms have been suggested, for use in the future. The methods of calculating different properties, as well as weight and volume of discharged sediment are described in the paper for use in other applications concerning deep-sea discharges. 相似文献
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A vertically integrated model has been used to study the tidal circulation and currents in the Gulf of Kachchh along the west coast of India. The model is fully nonlinear and uses a semiexplicit finite difference scheme to solve the basic hydrodynamic equations on a staggered grid. The model is forced by prescribing the tides along the open boundary of the model domain. The flow is simulated both with and without the presence of the proposed tidal barrage across the Hansthal Creek in the Gulf of Kachchh. The results show a considerable change in the behavior of the tidal flow in the presence of the barrage. 相似文献
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利用中国GF-3卫星SAR和HY-2A卫星微波散射计的首次台风联合定量观测 总被引：4，自引：0，他引：4
<正>The typhoon,as a mature tropical cyclone that develops in the western part of the North Pacific Ocean with high wind speed and heavy rainfall,is one of the most lethal and costly of natural disasters for the densely populated countries of East Asia.It can be easily detected by space-borne sensors operated at microwave,visible or infrared bands(Liu et al.,2014).Synthetic Aperture Radar(SAR)is 相似文献
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Soil core samples fromRhizophora mangleL. andAvicennia schauerianaStapf & Leech forests from south-eastern Brazil were analysed for their total organic matter content and their sugars, amino acid and amino sugars composition. Organic carbon and nitrogen contents were higher inAvicenniathan inRhizophorasoils. The contribution of sugars and amino acids to the total organic carbon pool was constant with depth inRhizophorasoils whereas inAvicenniasoils it increased. Spectral distribution of sugars and amino acids showed a dominance of Ca-affine monomers, particularly acidic amino acids, and the sugar arabinose. Biogeochemical indicators derived from ratios of individual sugar and amino acid monomers confirm previous studies which showed that organic matter in both soils is mainly of mangrove origin. The results further suggest accumulation of organic matter inRhizophorasoils and a continuing degradation of organic matter inAvicenniasoils. The latter may thus release more nutrients to adjacent ecosystems thanRhizophorasoils. 相似文献
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《African Journal of Marine Science》2013,35(1):181-203
Orange roughy Hoplostethus atlanticus are unusual fish. They form dense aggregations that have fuelled lucrative fisheries at great depths (600–1 400 m), especially off Namibia, New Zealand and Australia. They are thought to be very long-lived (>100 years, maturity at 22 – 40 years), and to have exceptionally low natural mortality (M = 0.045–0.064 year?1) and slow growth rates (K = 0.055–0.070 year?1). In addition, they spawn large eggs and have low fecundity. These factors combine to make orange roughy highly susceptible to overfishing; most stocks are below 30% of pristine levels. Assessments are obtained from indices of catch rate and trawl, acoustic and egg surveys. Acoustic estimates are the most direct, but are confounded by the species' low target strength (?50 to ?53 dB)–attributable to the wax-filled swim bladder. Extracellular wax esters are stored in abundance and comprise mostly mono-unsaturated fatty acids, with low concentrations of the ω-3 fatty acid family. This unusual composition (resultant from the species' diet) ensures neutral buoyancy. Stock separation has been inferred mainly from biological studies, but genetic studies have also found differences among stocks within New Zealand and Australia. Deep-water habitat may be damaged by trawling operations and may take many years to recover, so in some quarters there is a call for a portion of suitable habitat to be set aside for preservation. Although Namibian orange roughy are shallower, smaller and younger than those in other stocks, the Namibian fishery sustained high catches for only a few years before quotas were reduced, from 12 000 to 1 875 tons. Three management lessons are suggested for developing orange roughy fisheries based on the Namibian experience: (1) imposition of catch limits during exploratory fishing; (2) starting the acoustic surveys earlier in the fishery, if possible; (3) greater reliance on trends in catch rate until a survey series has been established. 相似文献