崇左市预警信号发布现状及探讨     

卢炳夫  冷伟  梁永强 《气象研究与应用》2014,35(3):115-121

统计2008-2013年以来崇左市下辖江州区、扶绥县、天等县、大新县、宁明县、龙州县、凭祥市七县（市、区）,几种常用的气象灾害预警信号发布现状以及实际工作中遇到的问题展开谈论,探讨预警信号发布工作面临的新形势,并提出新形势下预警信号发布工作相应的对策和措施,从而更好的做好＂气象灾害预警信号＂的发布工作,减少气象灾害所带来的损失。  相似文献   

Multi-sourced depositional sequences in the Neogene to Quaternary succession of the Venice area (northern Italy)     

《Marine and Petroleum Geology》2014

The Plio-Pleistocene succession of the Venice area represents part of the infill of a foreland region located between three mountain chains: the Northern Apennines, the Southern Alps and the Dinarides. This structural setting favored the development of a complex stratigraphic architecture of the succession, mostly due to the conveying of sediments from the Southern Alps to the north and the Northern Apennines to the south, in particular since the activation of strong subsidence related to the NE-ward migration of the Apennine foredeep in the early Pleistocene. Accordingly, the studied succession is composed of five third-order sequences mostly controlled by tectonics, the most recent of which display complex patterns due to the interfingering of sedimentary bodies showing contrasting directions of progradation and pinch-out. Despite this, the sequence stratigraphic method still can be applied in the present context, allowing to recognize diagnostic stratal architectures and reconstruct the relative sea-level history of the region. Moreover, the recognized peculiar stratigraphic architecture of the basin fill may serve as an analogue that needs to be taken into account to predict the distribution of porous coarse-grained sedimentary units in similar contexts, aiding for a profitable exploration and production of reservoirs and source/sealing rocks.  相似文献   

Late Pleistocene–Holocene seismic stratigraphy of Nha Trang shelf,central Vietnam     

《Marine and Petroleum Geology》2014

The late Pleistocene–Holocene stratigraphic architecture on the steep and narrow shelf off Nha Trang, central Vietnam has been explored by high resolution seismic profiles integrated with sediment core data. Sequence stratigraphic results reveal five major seismic units and three bounding surfaces which are composed of two distinctive sequences. Those sequences are bounded by two regional unconformities (SB1, SB2) which have been formed in respond to different sea-level regimes. The revealed relict beach–ridge deposits at water depth of about ∼130 m below the present water depth indicate that the Last Glacial Lowstand (LGM) sea-level in this area was lower than in neighboring areas and it probably resulted from subsidence due to high sedimentation rate and/or neotectonic movements of the East Vietnam Fault System. The late Pleistocene high amplitude of sea-level change during a long fourth-order and superimposed by shorter fifth-order cycle is the principal factor in reorganizing the formation of the Nha Trang continental shelf sequence. Other local controlling factors as fluctuations in sediment supply, morphological variations of the LGM surface, subsidence rate and hydrodynamic conditions provided the distinctive features of the Nha Trang shelf sequence stratigraphic model in comparison with neighboring other areas.  相似文献   

莱州湾东岸三山岛段砂质海岸沉积物运移动力机制   总被引：1，自引：0，他引：1       下载免费PDF全文

刘世昊  丰爱平  杜军  夏东兴  胡维芬  李平 《海洋科学进展》2014,32(3)

通过对三山岛岸段冬夏重复的地形测量和表层沉积物的粒度分析,研究了其地貌特征与地形变化规律、沉积物类型、粒度特征、运移趋势,并探讨了沉积物运移的动力机制。结果表明:该岸段可根据1985黄海高程-1.2m(低潮水位)和-6.5m(闭合深度)平面划分为海滩、水下岸坡和浅海陆架三个地貌单元,各地貌单元表层沉积物分布规律与地形变化特征区别显著。其中水下岸坡和浅海陆架地貌单元主要受潮流作用,海滩地貌单元主要受波浪作用。在西向落潮流和西南向潮余流的作用下,水下岸坡地貌单元发育一个中等规模潮流通道-沙脊沉积系统。表层沉积物以向西运移的趋势为主,少数滞留于西部潮流沙脊处,与地形"东侵西淤"的变化规律相符,这些西向运移的沉积物最终离开研究区,补给莱州浅滩。  相似文献   

Research on the critical conditions for clay particle release during saline aquifer freshening process     

Xilai Zheng  Ran Chen 《中国海洋大学学报(英文版)》2014,13(4):628-636

Water sensitivity phenomenon occurs during saline aquifer freshening process in seawater intrusion area, and clay particles released in the phenomenon can damage the infiltration capacity of the aquifer. In order to find out the factors and mechanisms for clay particle release, laboratory column infiltration experiments simulating saline aquifer freshening process were designed to measure the critical conditions(critical flow velocity, critical salt concentration and critical ionic strength) and force analysis for clay particle according to DLVO electric double layer theory was employed to illustrate the mechanisms for particle release. The research results showed that critical flow velocity for clay particle release is influenced by salt concentration of injecting solution. When salt concentration of injecting solution is very high, clay particles are not released, indicating that there does not exist a critical flow velocity in this situation. As salt concentration of injecting solution decreases, particles start to be released. The critical salt concentration for clay particle release is 0.052 mol L-1 in our work, which was determined by a constant-flux experiment for stepwise displacement of high concentration Na Cl solution. The critical ionic strength for clay particle release decreases as Ca2+ molar content percentage of the mixed solution of Na Cl and Ca Cl2 increases following the first-order exponential decay equation y = 0.0391e-0.266 x + 0.0015.  相似文献   

贵州晴隆中二叠统大厂层砾岩成因研究   总被引：1，自引：0，他引：1  

陈军  杨瑞东  郑禄林  高军波  魏怀瑞 《地质论评》2014,60(6):1309-1322

贵州晴隆中二叠统大厂层中—上部产出一套呈囊状、透镜状分布的砾岩层。对大厂层砾岩沉积序列、结构、构造特征和矿物组合进行研究,结果表明:沉积序列为"反粒序",砾岩成分单一,基本为玄武质,是由峨眉山玄武岩直接改造而成,未发育河道相沉积特征;大厂层砾石具特殊的"泥化边"构造,是玄武岩在海水中大量水解的直接证据,填隙物中的青磐岩化矿物组合表明砾岩遭受了低温热液的改造。填隙物具有接近凝灰岩的Zr/Hf(30.7~43.4,均值38.0),揭示玄武岩在改造形成砾石的过程中有火山碎屑(火山灰)参与成岩;砾石和填隙物相对玄武岩贫Na(Na2O)富K(K2O),三者具有相似的稀土配分模式,其中∑REE呈规律性变化(玄武岩最高,砾石次之,填隙物中最低)。沉积背景分析认为,峨眉地幔柱作用使地壳发生了差异抬升,抬升一侧暴露遭受剥蚀形成不整合面,相对沉降一侧继续接受沉积,大厂层正是峨眉山玄武岩前锋带在局限海盆边缘(沉降侧),于茅口灰岩之上继续沉积的产物。大厂层砾岩形成机制是:炽热玄武岩流在海水中急剧爆裂,同时火山碎屑参与沉积,形成的玄武岩前积层(淬碎熔岩角砾)及凝灰岩,沉积在茅口组灰岩之上;在后期的演化过程中,炽热玄武岩冷凝收缩,柱状节理发育,在潮汐流和沿岸流的相互作用下不断磨蚀形成大厂层砾岩。  相似文献   

长江河口拦门沙河床淤积和泥沙再悬浮过程   总被引：23，自引：1，他引：22  

李九发  何青  张琛 《海洋与湖沼》2000,31(1):101-109

利用近２０年来长江河口所观测的地形、水文、悬沙和河床沉积物资料,着重对１９８８、１９８９、１９９６和１９９７年最新观测资料进行计算分析。结果表明,长江河口航道拦门沙河段来水沙量大,潮流作用强,潮波变形明显,水流挟沙力强。该河段潮流速随时间和空间变化,又处在盐淡水交换地带,流域和海域来沙在此河率时淤时冲,悬沙与床沙交换频繁,表现在涨急、落急时可床淤积层泥沙再次起动悬浮,憩流时只河床,在一个潮周期中含  相似文献   

疏浚物中镉释放的影响条件   总被引：4，自引：0，他引：4  

廖文卓 《台湾海峡》2000,19(2):170-176

本文模拟研究了疏浚沉积物中Ｃd的释放行为和影响条件。结果表明介质的盐度、pＨ、氧化还原状态等环境条件和疏浚沉积物的污染程度、粒度大小、有机质含量等理化特征对Ｃd的 释放有明显的影响。Ｃd从疏浚物中释放,其释放速率较快,释放率在４０％～９６％之间。疏物的海上倾弃可能引起Ｃd的污染和对部分生态环境的危害。同时还讨论了Ｃd的释放所遵循的动力学规律。  相似文献   

表层系列采泥器生产过程中的工艺设计和工艺保障     

黎广燕  李力平  闫金彪 《海洋技术学报》2000,19(4):58-63

本文主要介绍了三种系列采泥器在加工生产过程中的工艺设计及工艺保障。  相似文献   

Molluscan assemblages of seagrass-covered and bare intertidal flats on the Banc d'Arguin, Mauritania, in relation to characteristics of sediment and organic matter     

Pieter J.C. Honkoop  Eilke M. Berghuis  Sander Holthuijsen  Marc S.S. Lavaleye  Theunis Piersma   《Journal of Sea Research》2008,60(4):255-263

The Banc d'Arguin, a non-estuarine area of shallows and intertidal flats off the tropical Saharan coast of Mauritania, is characterised by extensive intertidal and subtidal seagrass beds. We examined the characteristics of intertidal seagrass (Zostera noltii) meadows and bare areas in terms of the presence and abundance of molluscs (gastropods and bivalves). To explain observed differences between molluscan assemblages in seagrass and bare patches, some aspects of the feeding habitat (top-5 mm of the sediment) and of food (organic materials) of molluscs were examined. The novelty of this study is that phytopigments were measured and identified to assess source and level of decay (freshness) of organic material in the sediment and to study their importance as an explanatory variable for the distribution of molluscs. Over an area of 36 km² of intertidal flats, at 12 sites, paired comparisons were made between seagrass-covered and nearby bare patches. Within seagrass meadows, dry mass of living seagrass was large and amounted to 180 ±10 g AFDM m^− 2 (range 75–240). Containing twice the amount of silt per unit dry sediment mass, seagrass sediments were muddier than bare areas; the relative amount of organic material was also larger. The total number of species of bivalves and gastropods amounted to 27, 14 of which were found only in seagrass areas, 4 only in bare and 9 in both types of habitat. Among the three numerically most abundant species, the bivalves Anadara senilis, Dosinia hepatica and Loripes lacteus, the first was numerically most abundant in bare and the other two in seagrass-covered areas. Bare intertidal areas had greater mean total biomass of molluscs (80.5 g AFDM m^− 2) than seagrass meadows (30.0 g AFDM m^− 2). In both habitats, the bulk of the biomass was made up by A. senilis. Excluding this species, bare mudflats contained on average only 3.1 g AFDM m^− 2 and seagrass meadows 6.9 g AFDM m^− 2. As compared to previous surveys in 1980–1986, the biomass of A. senilis had increased almost 10-fold and D. hepatica, previously found in very small numbers, had become the most numerous species. However, the total biomass excluding that of A. senilis was similar. Concentrations of phytopigments were similar to those observed at temperate mudflats, indicating that the Banc d'Arguin might not be as oligotrophic as previously thought. Per unit of dry sediment mass, smaller amounts of phytopigments were found in bare than in seagrass areas. Per unit of dry organic material, bare sediments contained most (fresh) phytopigments. This suggests that in seagrass-covered meadows the organic material is more degraded than in bare sediments. Overall, the composition of phytopigments, quite surprisingly, indicated a benthic-diatom-dominated trophic system. Multivariate statistics revealed that patterns of zoobenthic assemblages were correlated with patterns of a combination of four environmental parameters: grain size of the sediment, amount of fresh phytopigments and amounts of leaves and roots of seagrass.  相似文献