Travel time of accreted igneous assemblages in western Pacific orogenic belts and their associated sedimentary rocks     

Costas Xenophontos  Soichi Osozawa   《Tectonophysics》2004,393(1-4):241

Accreted igneous assemblages in orogenic belts maybe divided into three types depending on whether they derive from seamounts, ocean ridges or subduction-related ophiolites. Seamount type basalts are associated with shallow water sediments—mostly reefoidal limestones. Ocean ridge type basalts are generally overlain by pelagic cherts. Subduction-related ophiolitic eruptives, often underlain by gabbroic and ultramafic rocks, are associated with hemipelagic mudstones. The age of such diverse eruptive lithologic assemblages reflects the time taken for them to have traveled from their locus of generation to their place of accretion at a continental margin. This relationship has been established for each type of accretionary complex, examples being taken mostly from Japan and the western Pacific rim in order to represent evolutionary processes at a typical active plate margin. In general, the seamount types are older, ridge types are of intermediate age, and the ophiolitic types are by far the youngest, usually close to zero age. Seamount type basalts are accreted by shallower scraping of the seamount's sediment apron together with fragments of seamount basalt, ridge type, by peeling due to permeability contrast, and the ophiolitic types by deeper scraping as a consequence of an inflected temperature gradient. Accordingly, it is concluded that the ophiolitic rocks are generated close to the trench and may be accreted as a result of ridge subduction.  相似文献   

Generation of overtides and compound tides in Amazon estuary     

Marcos Nicolás Gallo  Susana Beatriz Vinzon 《Ocean Dynamics》2005,55(5-6):441-448

Tidal propagation in estuaries is affected by friction and fresh water discharge, besides changes in the depth and morphology of the channel. Main distortions imply variations in the mean water level and asymmetry. Tidal asymmetry can be important as a mechanism for sediment accumulation and turbidity maximum formation in estuaries, while mean water level changes can affect navigation depths. Data from several gauges stations from the Amazon estuary and the adjacent coast were analyzed and a 2DH hydrodynamic model was configured in a domain covering the continental shelf up to the last section of the river where the tidal signature is observed. Based on data, theoretical and numerical results, the various influences in the generation of estuarine harmonics are presented, including that of fresh water discharge. It is shown that the main overtide, M₄, derived from the most important astronomic component in the Amazon estuary, M₂, is responsible for the tidal wave asymmetry. This harmonic has its maximum amplitude at the mouth, where minimum depths are found, and then decreases while tide propagates inside the estuary. Also, the numerical results show that the discharge does not affect water level asymmetry; however, the Amazon river discharge plays an important role in the behavior of the horizontal tide. The main compound tide in Amazon estuary, Msf, generated from the combination of the M₂ and S₂, can be strong enough to provoke neap low waters lower than spring ones. The results show this component increasing while going upstream in the estuary, reaching a maximum and then slightly decaying.  相似文献   

Conodont colour alteration indices (CAI) of Upper Ordovician limestones from the Iberian Peninsula     

Sarmiento  Graciela N.  García-lópez  Susana  Bastida  Fernando 《Geologie en Mijnbouw》1998,77(1):77-91

Conodont colour alteration index (CAI) data in Upper Ordovician rocks from several areas of the Variscan domain in the Iberian Peninsula indicate conditions ranging from diagenesis to low-grade metamorphism. In most of the areas, where studies using other indicators, such as illite crystallinity (IC) or where vitrinite reflectance are lacking, the CAI method has permitted a preliminary estimation of the metamorphic grade. In the Almadén syncline (Central-Iberian Zone), where IC studies are available, the thermal conditions inferred from CAI data agree with those obtained by the IC method. In the Puertollano–Almuradiel syncline, the thermal interval obtained primarily from fluid inclusions (270–370°C) overlaps considerably with that obtained from CAI data (180–340°C). In general, cleavage in rocks is present in anchizonal or epizonal conditions, whereas in diagenetic conditions with CAI 2.5, cleavage is scarce. The conodont texture changes with increasing metamorphism, and apatite recrystallisation appears in general with CAI 5. Variation of CAI values within a single sample and/or within short stratigraphic distances observed at several localities is due to hydrothermal activity.  相似文献   

Seismic hazard impact of the Lower Tagus Valley Fault Zone (SW Iberia)   总被引：5，自引：1，他引：5  

Susana P. Vilanova  Joao F.B.D. Fonseca 《Journal of Seismology》2004,8(3):331-345

The seismic hazard of SW Iberia is composed of two contributions: offshore, large to very large events on the plate boundary between Africa and Eurasia such as the Lisbon earthquake of 1755 or the Gorringe Bank earthquake of 1969; and onshore, moderate to strong intraplate earthquakes on inherited crustal fractures. One of these zones of crustal weakness is the Lower Tagus Valley (LTV) fault zone, which displays the highest level of seismic hazard in Western Iberia. In this paper we review the active tectonics and seismicity of the LTV, integrating previous geophysical data with recent results of paleoseismological investigations, and discuss its impact on the seismic hazard of SW Iberia. We conclude that the seismic zonation for hazard assessment currently in force in the building code is biased towards the scenario of distant offshore rupture, and does not take adequately into account the LTV seismic source.  相似文献   

Effect of isolation temperature on the characteristics of extracellular proteases produced by Antarctic bacteria   总被引：1，自引：0，他引：1  

Susana C. Vazquez  Walter P. Mac Cormack 《Polar research》2002,21(1):63-71

Protease-producing psychrotolerant bacteria were isolated from Antarctic biotopes on casein agar plates using different incubation temperatures. Most of the isolates were non-spore-forming Gram-negative motile rods with catalase activity, 30% were pigmented and none of them were glucose fermenters. All the strains were grown in liquid cultures at 20°C and protease secretion was tested using the azocasein method. Despite their capacity for production of a clear zone of hydrolysis in agar plates, some strains did not produce detectable levels of proteolytic activity in liquid cultures. The lowest apparent optimum temperature for protease activity found in culture supernatants was 40°C. Almost all the strains showed activation energy values about 10-20 kJ-mol⁻¹ lower than that observed for a mesophilic Subtilisin. Most of the proteases showed optimal activity at neutral or alkaline pH values and developed a multiple-band profile on gelatine-SDS-PAGE. It was observed that the lower the strain isolation temperature was, the more stongly cold-adapted–in terms of optimal temperature and activation energy–were the proteases produced by them. This dependence of the characteristics of the proteases on the isolation temperature is an important factor to take into account in the design of screening programmes directed towards the isolation of psychrotolerant bacteria able to produce proteases strongly or weakly adapted to work in the cold. The Antarctic area explored proved to be a promising source of proteolytic bacteria with potential use in industrial processes to be carried out at low or moderate temperatures.  相似文献   

The impact of sediment burial and erosion on seagrasses: A review   总被引：1，自引：0，他引：1  

Susana Cabao  Rui Santos  Carlos M. Duarte 《Estuarine, Coastal and Shelf Science》2008,79(3):354-366

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Comments on the development of new macroalgal indices to assess water quality within the Mediterranean Sea: A reply     

Enric Ballesteros  Susana Pinedo  Raquel Arévalo 《Marine pollution bulletin》2007,54(5):628-630

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Quadrant analysis of the scalar and momentum fluxes in the stable marine atmospheric surface layer     

George D. Katsouvas  Costas G. Helmis  Qing Wang 《Boundary-Layer Meteorology》2007,124(3):335-360

The quadrant technique, a conditional sampling approach that allocates Reynolds stresses into four different types of events (ejections or bursts, sweeps, inward interactions and outward interactions), is applied to stable marine atmospheric boundary-layer data, collected in the framework of the Coupled Boundary Layer Air—Sea Transfer, Low wind component experiment at Nantucket Island, Massachusetts, USA. The general properties of both scalar and momentum transport are analyzed under the scope of quadrant analysis experimentally and theoretically. It is shown that the third-order Gram–Charlier series is necessary and even sufficient in most of the cases, in describing the experimental time and flux contributions of each quadrant to the total transfer, for both scalar and momentum transport, while the ability of the Gaussian distribution is limited to outlining the general pattern of these quantities. Moreover, a threshold value is applied to the conditional analysis, separating the most important events from the less significant ones and the sensitivity of the flux and especially the time fraction of each quadrant on the choice of this value is presented and discussed. Also, a set of numerically extracted equations, completing the analytical relations, is derived, enabling the prediction of the time and flux fractions of each quadrant, for a wide range of correlation coefficient and threshold values. Finally, the sensitivity of the analysis to the atmospheric stability and the Reynolds averaging scales showed that correlated and uncorrelated motions tend to balance for increasingly stable conditions and/or for large time scales.  相似文献   

Tsunami Simulations for Regional Sources in the South China and Adjoining Seas     

Emile A. Okal  Costas E. Synolakis  Nikos Kalligeris 《Pure and Applied Geophysics》2011,168(6-7):1153-1173

We present 14 scenarios of potential tsunamis in the South China Sea and its adjoining basins, the Sulu and Sulawezi Seas. The sources consist of earthquake dislocations inspired by the the study of historical events, either recorded (since 1900) or described in historical documents going back to 1604. We consider worst-case scenarios, where the size of the earthquake is not limited by the largest known event, but merely by the dimension of the basin over which a coherent fault may propagate. While such scenarios are arguably improbable, they may not be impossible, and as such must be examined. For each scenario, we present a simulation of the tsunami??s propagation in the marine basin, exclusive of its interaction with the coastline. Our results show that the South China, Sulu and Sulawezi Seas make up three largely independent basins where tsunamis generated in one basin do not leak into another. Similarly, the Sunda arc provides an efficient barrier to tsunamis originating in the Indian Ocean. Furthermore, the shallow continental shelves in the Java Sea, the Gulf of Thailand and the western part of the South China Sea significantly dampen the amplitude of the waves. The eastern shores of the Malay Peninsula are threatened only by the greatest??and most improbable??of our sources, a mega-earthquake rupturing all of the Luzon Trench. We also consider two models of underwater landslides (which can be triggered by smaller events, even in an intraplate setting). These sources, for which there is both historical and geological evidence, could pose a significant threat to all shorelines in the region, including the Malay Peninsula.  相似文献   

A review of indicator minerals and sample processing methods for geochemical exploration     

Malcolm Gent  Mario MenendezJavier Toraño  Susana Torno 《Journal of Geochemical Exploration》2011

Geochemical exploration based on the analysis of indicator minerals (IMs) is becoming increasingly used as an effective method for mineral exploration for many types of mineral deposits. The types of IMs used or recommended for exploration for different types of deposits, their properties suitable for concentrating them, as well as those of other common minerals from which they must be separated are listed.  相似文献