共查询到19条相似文献，搜索用时 109 毫秒
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高密度采集福建前湖湾海岸剖面133个泥沙样品做粒度分析,其频率曲线显示多种粒度分布特征,预示多种沉积环境的变化。采集研究剖面周边海滩、河口浅滩、河口、滨海沼泽和海岸沙丘等已知环境的样品作为目标样本。将目标样本沉积参数平均粒径(Mz)、标准偏差(σ)、峰态(Kg)设为判别参数,利用Excel计算海岸剖面样品与目标样本参数的距离,筛选最小距离样品,归为已知目标样本的同类。据此,分析了海岸剖面蕴含的6个沉积环境变化阶段。利用剖面底部淤泥测年14C=(328 15±170)a BP,和剖面上部泥炭测年14C=(24 130±100)a BP,了解这一变化发生的年代。自(32 815±170)a BP以来,前湖湾经历了河口浅滩-河口、沙丘-河口-滨海沼泽-海滩-沙丘等海岸环境演变过程。 相似文献
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台湾浅滩沉积物和沉溺海滩岩的研究 总被引：2，自引：0，他引：2
台湾浅滩位于南海北部大陆架之东部,面积约8800km~2,由众多的沙丘组成,水深一般为20—40m,呈北东向展布(图1)。近半个世纪以来,中外许多学者进行了研究,认为这套砂质沉积是冰期残留沉积物。1979年,中国科学院南海海洋研究所在台湾浅滩进行调查,本文对这次调查中采集的沉积物样品和沉溺海滩岩作了研究,并对古地理、古气候及海平面变化进行了讨论。 相似文献
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对埕岛海域CBG4a孔岩芯进行粒度分析，划分出海滩、三角洲支流河口滨线、海滩附近沙丘、黄河三角洲河口沙坝、黄河三角洲水下三角洲前缘隆起、水下天然堤、河流等7种沉积环境。对样品进行Q型聚类分析，识别出分辨力及代表性更强的一组分类统计量：各粒组百分含量及相关的粒度参数（C，Md，Mφ，δ1，Sk，Kg，Q1，Q3）。Mφ-δ1，Kg-Sk等结构参数散点图与沉积环境有很好的相关性，河流、海滩、沙丘等沉积物有较明确的界线。粒度象图反映了沉积物分布总体特征，其中水下天然堤、三角洲支流河口滨线沉积、海滩及其附近沙丘沉积等亚相易于在F-M图中区分，而黄河水下三角洲前缘隆起沉积、黄河三角洲河口沙坝沉积、河流沉积等在L-M图和A-M图中均易于区分。 相似文献
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半遮蔽型海滩由于一侧海岬的差异作用而影响海滩的演变过程。本文以青岛石老人海水浴场海滩为例,基于对3条典型剖面连续11年现场监测的高程数据,利用经验正交函数(empirical orthogonalfunction,EOF)分析方法将该海滩各剖面高程数据组成的原始距平矩阵依次分解为相应的空间和时间特征函数,分析了石老人海滩的形态演化特征、蚀淤趋势及驱动因素,并采用方差总占比超过77%的前3个经验正交函数来反映此类海滩的基本演化情况,分别为:表征长时间尺度砂质海滩滩面最主要蚀淤变化趋势的第一模态、表征季节性蚀淤变化及其引起的滩肩剖面形成增长或削弱消亡的第二模态和表征人类活动、偶发因素或海岸地形等引起的具有随机性的不规律蚀淤变化的第三模态。结果表明:11年来石老人海滩经历了三个阶段,第一阶段为平稳期(2009年1月—2011年7月),第二阶段为突变期(2011年7月—2012年9月),该阶段之后至今,是第三阶段的平稳期(2012年9月—2019年12月)。海滩剖面在自然和人类活动影响下的高程变化范围在0.1—2.0m范围内。波浪是影响该海滩形态演化的最主要水动力因素,岬角对半遮蔽型海滩的差异庇护作用导致不同位置的剖面演化存在差异。高频率台风的影响、海平面阶段性升高并长期保持较高水平导致了远离岬角的开放岸段存在明显阶段性调整,剖面滩肩宽度减少约30m,岬湾内部剖面则相对稳定,目前海滩剖面形态在第二阶段突变期后达到了新的稳定状态。 相似文献
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海滩的演变特征是海岸地形动力学研究的一个重要内容。基于在海口湾假日海滩连续33d的地形剖面观测数据和台风前后表层沉积物粒度参数数据, 分析了海口湾中间岸段海滩剖面及沉积物变化特征。利用经验正交函数分析, 得出观测期间海口湾海滩有4个主要模态, 分别对应于涌浪对海滩的建设过程、当地风浪对海滩的侵蚀过程、台风对海滩的侵蚀过程和海滩特征地形的调整过程。研究结果表明: 涌浪和风浪对海滩剖面的作用受到了潮位调制的影响; 海口湾海滩显示出遮蔽型海滩变化特征; 沉积物粒度参数对海滩变化反应敏感, 可以提供丰富的海滩演变信息。 相似文献
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福建深沪湾潮间带沉积异质体及其成因初探 总被引：3，自引：0，他引：3
深沪湾潮间带并列着两种性质迥异的沉积异质体——沉溺古树林和牡蛎礁。其号观性质、形成年代和沉积特征都有显著差异。古树林主要树种有：油杉(Keteleeria)、桑树(Mouas)和皂荚(Gleditisia)等，属于亚热带常绿落叶阔叶混交林，^14C测量表明其生长于7000aBP前后；牡蛎礁造礁生物主要属种有：近江重蛎(Crassostrea riwlaris)，长重蛎(Crassostrea gigas Tunbers)等。属于河口贝类，^14C测量表明其生长于20000aBP左右。地貌调查和钻孔沉积物分析显示：牡蛎礁是晚更新世古河口的产物，古树林是全新世河道古土壤生长林，两者被埋藏后近代重现海滩。 相似文献
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为了探讨福建长乐东部海岸环境演变,运用探地雷达(GPR)探测了研究区海岸沙丘的沉积构造,初步得出以下结论:(1)研究区海岸沙丘沉积构造主要由海滩沉积和海岸沙丘沉积构成,其中下伏沉积为海滩波浪作用形成的波状交错层理,上覆沉积为风成大角度倾斜的交错层理以及局部的水平层理;(2)上部发育的倾向向背的大角度风成交错层理,反映了研究区丰富的沙源、宽阔的海滩、植被扩张的进积海岸特点;(3)从沉积序列分析,研究区海岸地貌环境演变经历了早期的滨岸浅海到晚期的海岸沙丘带两个阶段,反映了海岸向东的进积过程中,外力作用由波浪作用为主演变为风沙沉积作用为主。 相似文献
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晚玉木冰期台湾海峡的沉积环境 总被引：4，自引：1，他引：3
对台湾海峡西部海域及河口平原14个钻孔剖面经孢粉、14C年龄和古地磁测定确定为晚玉木冰期的沉积层(Q33)样品进行了硅藻、有孔虫分析.结果表明,该时期海域的沉积层均属海相沉积,而河口平原区的沉积层则由海相和陆相地层交互组成.据此,提出了台湾海峡在晚玉木冰期属于水深在30～50m的浅海沉积环境的观点;阐述了这一与全球性气候冷暖更替所引起的海平面升降不一致现象是由于晚玉木冰期台湾海峡的地壳运动正处于间歇性下降时期,从而保持了浅海环境. 相似文献
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John F. Bratton John Karl Böhlke David E. Krantz Craig R. Tobias 《Marine Chemistry》2009,113(1-2):78-92
To better understand large-scale interactions between fresh and saline groundwater beneath an Atlantic coastal estuary, an offshore drilling and sampling study was performed in a large barrier-bounded lagoon, Chincoteague Bay, Maryland, USA. Groundwater that was significantly fresher than overlying bay water was found in shallow plumes up to 8 m thick extending more than 1700 m offshore. Groundwater saltier than bay surface water was found locally beneath the lagoon and the barrier island, indicating recharge by saline water concentrated by evaporation prior to infiltration. Steep salinity and nutrient gradients occur within a few meters of the sediment surface in most locations studied, with buried peats and estuarine muds acting as confining units. Groundwater ages were generally more than 50 years in both fresh and brackish waters as deep as 23 m below the bay bottom. Water chemistry and isotopic data indicate that freshened plumes beneath the estuary are mixtures of water originally recharged on land and varying amounts of estuarine surface water that circulated through the bay floor, possibly at some distance from the sampling location. Ammonium is the dominant fixed nitrogen species in saline groundwater beneath the estuary at the locations sampled. Isotopic and dissolved-gas data from one location indicate that denitrification within the subsurface flow system removed terrestrial nitrate from fresh groundwater prior to discharge along the western side of the estuary. Similar situations, with one or more shallow semi-confined flow systems where groundwater geochemistry is strongly influenced by circulation of surface estuary water through organic-rich sediments, may be common on the Atlantic margin and elsewhere. 相似文献
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Estuarine environmental assessment by sub-individual responses is important in order to understand contaminant effects and to find suitable estuarine biomonitor species. Our study aimed to analyze oxidative stress responses, including glutathione-S-transferase (GST) activity, total antioxidant capacity (ACAP) and lipid peroxidation levels (TBARS) in estuarine crabs Hemigrapsus crenulatus from a high anthropogenically-impacted estuary (Lenga) compared to low and non-polluted estuaries (Tubul and Raqui), in a seasonal scale (winter–summer), tissue specific (hepatopancreas and gills) and sex related responses. Results showed that hepatopancreas in male crabs better reflected inter-estuary differences. Morpho-condition traits as Cephalothorax hepatopancreas index (CHI) could be used as an indicator of physiological status of estuarine crabs. Discriminant analysis also showed that GST and TBARS levels in summer are more suitable endpoints for establishing differences between polluted and non-polluted sites. These results suggest the importance of seasonality, target tissue, sex and physiological status of brachyuran crabs for estuarine biomonitoring assessment. 相似文献
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Climate variability and planktonic communities: The effect of an extreme event (severe drought) in a southern European estuary 总被引：1，自引：2，他引：1
Snia Cotrim Marques Ulisses Miranda Azeiteiro Filipe Martinho Miguel ngelo Pardal 《Estuarine, Coastal and Shelf Science》2007,73(3-4):725-734
As a consequence of climate change, flood and drought events are increasing in frequency throughout the world. Nevertheless, knowledge of the effects on zooplankton estuarine communities is still scarce. The present study aimed to examine zooplankton ecology over two contrasting environmental conditions: regular years and extreme dry years, in a shallow temperate southern European estuary, the Mondego Estuary (Portugal). Monthly samples were carried out during three consecutive years: 2003 characterized as a regular temperate year concerning precipitation and river flow, and an extremely dry period during 2004–2005. The spatial and temporal structure of the biological data was evaluated by a three-mode principal component analysis (PCA), which allowed us to distinguish three distinct ecological areas based on their biological composition and their relationship with hydrologic parameters. The severe drought in 2004–2005 was responsible for spatial shifts in the estuary regarding zooplankton community and interannual variability, with an increase in abundance and diversity during the period of low freshwater flow. This freshwater flow regime influenced the composition of the zooplankton community at the most upstream section of Mondego estuary (zone 3), with a replacement of the freshwater community by one predominantly dominated by estuarine organisms. The occurrence of such estuarine community contributed to the increase in zooplankton abundance which is ascribed to the estuarine species Acartia tonsa. The comparison with previous data obtained for this estuarine ecosystem, demonstrated the occurrence of a different scenario at times of high freshwater flow, being defined the existence of two sub-estuarine systems, the north and south arm, presenting the south one the highest values of abundance. 相似文献
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滨海湿地是介于陆地生态系统和水生生态系统之间的特殊生态系统，是珍贵的湿地资源，具有重要的生态系统功能。掌握滨海湿地的分布状况对于我国滨海湿地自然资源的保护和管理意义重大。文章基于2018—2019年“哨兵2号”卫星10 m分辨率多光谱影像，完成广东、广西和海南滨海湿地的遥感制图；对岩石海岸、砂石海滩、淤泥质海滩、潮间盐水沼泽、红树林、河口水域、河口三角洲/沙洲/沙岛、海岸性咸水湖、海岸性淡水湖、浅海水域共10个亚类建立解译标志，通过目视解译，对滨海湿地进行分类和统计。研究结果显示：广东、广西和海南滨海湿地面积共计1 377 140 hm2，各地滨海湿地面积与岸线长度基本呈正相关，海岸线越长，滨海湿地面积越大，各地典型滨海湿地的类型也不相同。 相似文献
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The concentrations of rare earth elements in the dissolved, acid-soluble and residual phases in surface waters of the Changjiang
Estuary were determined using ICP-MS. The main purposes of the study are to understand the estuarine geochemistry of rare
earth elements and to explore water-particle interactions in the Changjiang estuarine mixing zone. The results show that there
are two distinct processes operating on dissolved rare earth elements in the estuary: large scale removal at low salinities
due to salt-induced coagulation and remarkable release at mid to high salinities. These processes result in modification of
the effective river water flux and the systematical fractionation of the dissolved rare earth elements toward the East China
Sea. The increase in concentration of dissolved rare earth elements in the mid to high salinity waters of the Changjiang Estuary
suggests a sediment source in the mixing zone of the estuary, which is located over a shallow, broad shelf where there is
extensive physical contact between bottom sediment and estuarine waters. Acid-soluble rare earth elements, the concentrations
of which also dropped sharply in the low salinity region, appear to be controlled by salt-induced coagulation process and
intense deposition of suspended particulate matter in the low salinity region. In the mid to high salinities, all acid-soluble
rare earth element concentrations increase slightly with increasing salinity, suggesting that resuspension of sediments occurred.
In contrast, the residual rare earth element concentrations are relatively constant with salinity variation in the Changjiang
estuarine surface waters. 相似文献
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Patterns in community structure and functioning of motile epibenthic fauna were investigated in shallow (0–1 m) sediment habitats along the Skagerrak–Baltic estuarine gradient (salinity range from 4 to 34). The study area was divided into five regions, reflecting different sea-basins along the 1260 km coastline, and fauna was collected at six sites within each region. Ten replicate samples of motile epibenthic fauna were taken randomly at each site with a portable drop trap (bottom area 1 m2) in June and September in 2004. 相似文献
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Chun-Ming Lin Yan-Li Li Hong-Chun Zhuo George W. Shurr Jennie L. Ridgley Zhi-Ping Zhang Tao Xue 《Marine and Petroleum Geology》2010,27(4):909-922
Late Quaternary shallow biogenic gas reservoirs have been discovered and exploited in the Qiantang River (QR) estuary area, eastern China. The fall of global sea level during the Last Glacial Maximum resulted in the formation of the QR incised valley. From bottom to top, the incised valley successions can be grouped into four sedimentary facies: river channel facies, floodplain–estuarine facies, estuarine-shallow marine facies, and estuarine sand bar facies.All commercial biogenic gas pools occur in floodplain–estuarine sand bodies of the QR incised valley and its branches. The deeply incised valleys provided favorable conditions for the generation and accumulation of shallow biogenic gas.The clay beds that serve as the direct cap beds of the gas pools are mostly restricted within the QR incised valley, with burial depths ranging from 30 to 80 m, remnant thicknesses of 10–30 m, and porosities of 42.2–62.6%. In contrast, the mud beds cover the whole incised valley and occur as indirect cap beds, with burial depths varying from 5 to 35 m, thicknesses of 10–20 m, and porosities of 50.6–53.9%. The pore-water pressures of clay and mud beds are higher than that of sand bodies, and the difference can be as much as 0.48 MPa. The pore-water pressures of clay or mud beds can exceed the total pore-water pressure and gas pressure of underlying sand reservoirs. Shallow biogenic gas can be completely sealed by the clay and mud beds, which have higher pore-water pressure. The direct cap beds have better sealing ability than the indirect cap beds.Generally, the pore-water pressure dissipation time of clay and mud beds is conspicuously longer than that of sand beds. This indicates that the clay and mud beds have worse permeability and better sealing ability than the sand beds. However, once the gas enters the sand lenses, the pore-water pressure cannot release efficiently. 相似文献