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1.
An inherent tension exists between legal approaches to nature conservation and fisheries management in the European Union, as the former remains the remit of Member States while the latter is under the exclusive legislative jurisdiction of the European Community (EC). This tension is of particular importance when addressing the conservation of habitats or species that are under threat from fishing activities. This article examines recent developments in offshore marine conservation in the North-East Atlantic in light of the legislative developments and political frameworks that are currently evolving. By analysing the emergency closure of the Darwin Mounds area of cold-water corals and the UK pair-trawl ban, it becomes evident that the precautionary principle is a key factor in the tension between fisheries management and marine nature conservation, and is not always taken into account. 相似文献
2.
J. Acosta E. Uchupi A. Muñoz P. Herranz C. Palomo M. Ballesteros 《Marine Geophysical Researches》2003,24(1-2):41-57
Circular to elliptical mounds in the Canary Channel with reliefs of 75 to 375 m and diameters of 4 to 8 km partially surrounded by moats with reliefs of 25 to 75 m, were formed by piercement of the seafloor by Mesozoic evaporites. Several long gullies, < 1km wide, with abrupt terminations and pockmarks associated with these mounds were probably eroded by dense brine and hydrocarbon seeps. The salt brines that eroded the gullies were formed where salt diapirs intersect the seafloor, or in the subsurface by circulating ground water heated by igneous activity along the Canary Ridge. If the brines originated in the subsurface they reached the seafloor along faults. Displacement of the surficial sediments by sliding and creep is probably the result of the expulsion of hydrocarbons and/or vertical motion of the Mesozoic evaporites. Microtopographic features along or near the east flank of the Canary Ridge are the creation of uplift of the ridge, hydrothermal activity, mass wasting processes and turbidity currents. 相似文献
3.
Small mounds of peat rise several metres above the level of the water‐table at Melaleuca Inlet and Louisa Plains on the buttongrass plains in southwest Tasmania. Possible origins of the peat mounds have been explored by pollen analysis and radiocarbon dating of a set of samples taken from a vertical section of one peat mound at Melaleuca. The peat accumulation is entirely of Holocene age although the mound is underlain by sapric peats preserving a cold climate palynoflora of probable Late Pleistocene age. Peats at and near the base of the mound accumulated under a heath sedgeland during the earliest Holocene while after about 7630 a BP the peat‐forming vegetation was shrub‐dominated. The radiocarbon data indicate two main phases of overall peat accumulation, between 7630 and 5340 a BP (Middle Holocene) and between 4450 and 450 a BP (Late Holocene), that were interrupted by a wildfire which burnt into the surface peats. The maintenance of high surface and internal levels of moisture almost certainly was the critical factor behind the low incidence of in situ fires burning into the surface peats on the mound. The perennial influx of groundwater below the mound is a possible origin that fits well with our observations, although the expansion and contraction of soils cannot be discounted as an initiating factor. Enhanced nutrient input from birds may have helped promote growth in the peat‐forming communities. The data do not support the mounds being eroded remnants of a former blanket peat cover or being due to periglacial activity. The peat mounds of southwest Tasmania deserve maximum protection because of their rarity in the Australian landscape and, it seems, elsewhere. 相似文献
4.
A. Foubert D. Van Rooij D. Blamart J.-P. Henriet 《International Journal of Earth Sciences》2007,96(1):141-158
Three provinces, characterized by the presence of carbonate mounds interpreted as cold-water coral banks have been reported
in Porcupine Seabight, SW of Ireland and were recently subjected to many detailed studies. This contribution discusses the
use of X-ray imagery and physical properties in deciphering palaeoceanographic, sedimentological and biological processes.
Physical property core logging and X-ray imagery are used to identify and describe sedimentation regimes and so their respective
palaeoceanographic and palaeoclimatological settings in two mound provinces, respectively the Belgica mound province and the
Magellan mound province. Both provinces show at present time clear differences in the hydrodynamic environment. This study
confirms that also during the past the oceanographic and sedimentological environment of both provinces differ clearly. Impacts
of glacial–interglacial variations and locally derived ice rafting events (IRE), comparable with the North Atlantic Heinrich
events (HE) have been recognized in both provinces. Moreover, the combination of X-ray imagery, magnetic susceptibility, gamma
density and P-wave velocity makes it possible to estimate the coral content and coral distribution in unopened cores localized
on top of carbonate mounds. A comparison between on-mound and off-mound cores in both provinces allowed revealing some mechanisms
of mound evolution and coral growth versus time. 相似文献
5.
The possibility of recrystallization is a long‐standing barrier to deciphering the genetic origin of dolomites. There is often uncertainty regarding whether or not characteristics of ancient dolomites are primary or the consequence of later recrystallization unrelated to the original dolomitization event. Results from 65 new high‐temperature dolomite synthesis experiments (1 m , 1·0 Mg/Ca ratio solutions at 218°C) demonstrate dolomite recrystallization affecting stoichiometry, cation ordering and nanometre‐scale surface texture. The data support a model of dolomitization that proceeds by a series of four unique phases of replacement and recrystallization, which occur by various dissolution–precipitation reactions. During the first phase (induction period), no dolomite forms despite favourable conditions. The second phase (replacement period) occurs when Ca‐rich dolomite products, with a low degree of cation ordering, rapidly replace calcite reactants. During the replacement period, dolomite stoichiometry and the degree of cation ordering remain constant, and all dolomite crystal surfaces are covered by nanometre‐scale growth mounds. The third phase (primary recrystallization period), which occurs in the experiments between 97% and 100% dolomite, is characterized by a reduced replacement rate but concurrent increases in dolomite stoichiometry and cation ordering. The end of the primary recrystallization period is marked by dolomite crystal growth surfaces that are covered by flat, laterally extensive layers. The fourth phase of the reaction (secondary recrystallization period) occurs when all calcite is consumed and is characterized by stoichiometric dolomite with layers as well as a continued increase in the degree of cation ordering with time. Inferences of recrystallization, in natural dolomite, based on cation order or stoichiometry of dolomite, usually depend on assumptions about the precursor dolomite subjected to recrystallization. If it is assumed that the experimental evidence presented here is applicable to natural, low‐temperature dolomites, then the presence of mounds is direct evidence of a lack of recrystallization and the presence of layers is direct evidence of recrystallization. 相似文献
6.
基于对川北米仓山西部旺苍县鼓城乡唐家河下寒武统仙女洞组露头剖面的观察与镜下分析发现,仙女洞组下段由生物碎屑泥晶灰岩(L)、粉砂质泥岩(M)、似瘤状砾屑灰岩(L')、角砾灰岩(R)、藻凝块灰岩(A)和含生屑钙质砂岩(S)组合而成,其以角砾灰岩、似瘤状砾屑灰岩和藻凝块灰岩为特征,且发育异地岩块和滑塌变形构造。进一步分析认为:L-M岩石组合为正常的斜坡环境低能沉积;L'-R岩石组合中的角砾灰岩为上斜坡生物灰泥丘崩坍滑动至下部而形成的,似瘤状砾屑灰岩可能是由于L-M岩石组合快速沉积导致沉积物失稳滑动变形、上斜坡生物灰泥丘崩落角砾致使的差异压实和滑动、以及后期物质成分差异引起的压溶作用等共同作用的结果,从而使灰质层发生破碎并被泥质包围形成断续的砾屑状,甚至轻微的位移,进而形成条带特征不明显的杂乱变形构造;微生物岩(Mb)组合为上斜坡的灰泥丘沉积;S-M岩石组合为斜坡上部的浊流沉积。根据上述分析结果建立米仓山西部仙女洞组碳酸盐岩台缘斜坡沉积模式,表明仙女洞组沉积早期米仓山西部存在台缘斜坡相沉积。 相似文献
7.
Pedoja Kevin 《中国科学D辑(英文版)》2005,48(11):1900-1912
The importance of calcimicrobes and microbialite in carbonate platform and reefal environments has been stressed in recent literature. Burne and Moore[1] introduced the term microbialite to describe the clotted, laminated and undifferentiated fabrics formed by mi-crobial communities. Microbialites are organosedi-mentary deposits that have accreted as a result of ben-thic (prokaryotic or eukaryotic) communities, trapping and binding detrital sediment[1]. Microbial organisms and microbialite are… 相似文献
8.
François Bétard 《地球表面变化过程与地形》2021,46(1):89-109
Insects are the largest and most diverse group of living organisms on Earth, playing a critical but underestimated role as agents of geomorphic change. Burrowing insects create micro-scale landforms such as subterranean tunnels and surface mounds and, by this way, exert an influence on hydrology, soil erosion and sediment transfer at a wider landscape scale. However, social insects represented by ants and termites were the main taxa studied as geomorphic agents and ecosystem engineers. This article proposes an extended and critical literature review of insects as zoogeomorphic agents, with reference to various taxonomic orders and families of insects having a burrowing behaviour. It provides a large overview of their primary and secondary impacts on Earth surface systems, both supported by naturalistic evidence and available quantitative data. Some evolutionary insights are discussed based on fossil evidence of geomorphic work by insects and, at finer temporal scale, on recent advances in radiometric and luminescence dating of insect mounds. Finally, this article explores the fruitful links between geomorphology and entomology, and suggests several research perspectives in order to develop an integrated understanding of the importance of insects in Earth surface processes and landforms. © 2020 John Wiley & Sons, Ltd. 相似文献
9.
《Basin Research》2018,30(5):942-964
Mass wasting is triggered on many continental slopes by a number of mechanisms, including seismic shaking, high sedimentation rates, the presence of weak geological units and gas hydrate dissociation. In this study, the morphology of a Late Miocene–Early Pliocene mass‐transport complex (MTC) on the Utgard High is unravelled and discussed in relation to possible trigger mechanisms. The approach used here includes 3D seismic interpretation and the analysis of variance attribute maps. The interpreted MTC is located on the crest and flanks of the Utgard High and is composed of three mass‐transport deposits with seismic characters varying from transparent and chaotic seismic facies at the base to slightly deformed layers composed of mounds and rafted blocks in the middle and chaotic to transparent reflections at the top. Lithologically, the MTC consists predominantly of claystone with high gamma ray and low density and resistivity values, demonstrating that the associated mounds represent remobilized ooze sediments. A vertical stack of six magmatic sills emplaced from 55.6 to 56.3 Ma into the Upper Cretaceous shales is interpreted at depths of 3,000–5,500 ms two‐way travel time (TWTT). In association with these magmatic sills are several hydrothermal vent complexes that interacted with the top MTC horizon, signifying that episodic and secondary fluid‐venting events might be the principal mechanism facilitating mass wasting in the study area. In addition, the remobilization of ooze sediments into mounds is hypothesized to be dependent on fluids and clayey layers. As a corollary of this work, the importance of relict and recurrent episodes of fluid flow in the Vøring Basin and their influence on the geotechnical integrity of the overburden and later mass wasting is established. 相似文献
10.
A group of islands of varying size on the floodplain of the Okavango alluvial fan, were studied to establish the processes which lead to the initiation and growth of islands. It was found that islands are initiated by the mound-building activities of the termite Macrotermes michaelseni. These termites import fine grained materials to use as a mortar for the construction of epigeal mounds. Their activities create a topographic feature, raised above the level of seasonal flooding, and also change the physical properties and nutrient status of the mound soil. Shrubs and trees are able to colonize these mounds, which results in increased transpiration. As a result, precipitation of calcite and silica from the shallow ground water occurs preferentially beneath the mounds, resulting in vertical and especially lateral growth, causing island expansion. © 1998 John Wiley & Sons, Ltd. 相似文献