http://www.sciencedirect.com/science/article/pii/S1674987113000613     

Yangfan Deng  Zhongjie Zhang  Weiming Fan  Marta Perez-Gussinye 《地学前缘(英文版)》2014,5(2):193-203

The effective elastic thickness （Te） represents the thickness of the elastic layer or the flexural rigidity of the lithosphere, the equivalent of which can be calculated from the spectral analysis of gravity and topographic data. Studies of Te have profound influence on intracontinental deformation, and coupling of the tectonic blocks. In this paper, we use the multitaper spectral estimation method to calculate the coherence between Bouguer gravity and topography data, and to obtain the Te map of South China. Through the process of correction, we discuss the relationships of Te versus heat flow, and Te versus seismicity. The results show that Te distribution of South China is affected by three factors：the original age, which controls the basic feature;the Mesozoic evolution, which affects the Te distribution;and the neotectonic movement, which shaped the final distribution. The crust age has a positive correlation with the first-order Te distribution;thus the Yangtze Craton has a relatively higher Te （about 50 km） whereas the Te in Cathaysia block is only 10e20 km. By analysis and comparison among the tectonic models of South China, the Te distribution can be well explained using the flat-subduction model. As is typical with neotectonics, the region with a higher heat flow is related with a lower Te. The seismicity does not have a clear relationship with Te, but the strong seismicity could cause a low Te. Seismogenic layer （Ts） has a similar trend as Te in the craton, whereas in other areas the relationship is complex.  相似文献   

Development of a User-Centred Web-Mapping Application for Ocean Modellers     

Marta Padilla-Ruiz  Emmanuel Stefanakis  Ian Church 《Marine Geodesy》2013,36(6):507-534

Abstract

This paper reports on the User-Centred Design and development of a web-mapping application from the Ocean Mapping Group (OMG) at the University of New Brunswick (UNB), to deliver ocean mapping data to ocean modellers. First, a work domain analysis was conducted to determine the required application functionality and content, consisting of an ocean modeller informal interview, a competitive analysis, and an online survey. Taking insight from the work domain analysis, a requirements document was prepared to support the development of the first application prototype. This prototype was then evaluated by eight target users, using a cognitive walkthrough and an online survey. The results from this evaluation led to a series of revisions to the functionality, content, and interface of the web-mapping application, establishing the revised prototype. The results showed a useful tool, end-user satisfaction, and stated a wide range of recommendations to enhance functionality for the next steps of the development.  相似文献   

Comparison and Combination of Coastal and Off-Shore Tide Gauge Measurements from Eivissa Island,Western Mediterranean     

Andreas Richter  Marta Marcos  Sebastià Monserrat  Damià Gomis  Simon Ruiz  Gunter Liebsch 《Marine Geodesy》2013,36(4):271-289

Two sea-level records, spanning eight months of simultaneous data in 2002, have been derived from pressure tide gauge measurements at Sant Antoni harbor (Eivissa Island, Western Mediterranean) and off Es Vedrà island, 15 km SW from Sant Antoni. The two time series are compared and used to characterize the sea-level variability in the Balearic Sea. The main forcings for the observed variations, astronomic tides, and meteorologic forcing by the inverse barometer effect are quantified. In a further step, an amplitude transfer function is determined, reflecting the frequency dependent amplification or damping of the nontidal sea-level residuals between both locations due to their local topography. The interpretation of the obtained transfer function indicates sea-level modulating topographic specifics not only for the coastal record at Sant Antoni, but also at the Es Vedrà site. In general, the application of such a transfer function allows the prediction of off-shore sea-level variations from coastal tide gauge measurements. In the present study, ellipsoidal sea-surface heights for Es Vedrà are inferred from Sant Antoni tide gauge data with an accuracy of about 1.5 cm by applying the determined transfer function and a geoid model.  相似文献   

Harpacticoid copepod response to epiphyte load variations in Posidonia oceanica (L.) Delile meadows     

Nina Larissa Arroyo  Inés Castejón  Marta Dominguez  Jorge Terrados 《Marine Ecology》2013,34(3):345-362

We conducted a field experiment to assess the response of phytal harpacticoids to nutrient‐driven increases of epiphyte load in Posidonia oceanica meadows. First, we evaluated differences in species richness, diversity and assemblage structure of phytal harpacticoids in P. oceanica meadows with differing epiphyte loads. Secondly, we conducted a field experiment where epiphyte load was increased through an in situ addition of nutrients to the water column and evaluated the responses of the harpacticoid assemblages. We predicted that there would be changes in the harpacticoid assemblages as a result of nutrient‐driven increases of epiphyte load, and that these changes would be of a larger magnitude in meadows of low epiphyte load. Our results show that the harpacticoid fauna (>500 μm) present in P. oceanica meadows in the Bay of Palma comprised taxa which are considered phytal and other less abundant ones previously described as sediment dwellers or commensal on other invertebrate species. Nutrient addition had an overall significant effect on epiphyte biomass and on harpacticoid abundance, diversity and assemblage structure, possibly as a response to the increased resources and habitat complexity provided by epiphytes. The abundance of dominant species at each location was favoured by nutrient addition and in some cases correlated with epiphytic biomass, although never strongly. This may indicate that structural complexity or diversity of the epiphytic cover might be more important than the actual epiphytic biomass for the harpacticoid species investigated. More species‐specific studies are necessary to ascertain this and clarify the relationships between harpacticoids and epiphytes in seagrass meadows. To our knowledge, this is the first account of harpacticoid species associated with P. oceanica leaves and the epiphytic community they harbour in the Mediterranean Sea.  相似文献   

Amphibole and phlogopite in “hybrid” metasomatic bands monitor trace element transfer at the interface between felsic and ultramafic rocks (Eastern Alps,Italy)     

Marta Marocchi  Jörg Hermann  Peter Tropper  Giuseppe Maria Bargossi  Volkmar Mair 《Lithos》2010,117(1-4):135-148

Ultramafic rocks in contact to gneisses in the Mt. Hochwart HP mélange (Eastern Italian Alps) preserve a series of metasomatic mineral zones. A phlogopitite with minor tremolite and accessory zircon and apatite forms close to the gneiss (Zone 1). Zone 2 consists of tremolite, phlogopite and anthophyllite followed by Zone 3 with anthophyllite plus minor chlorite and talc. Zone 3 grades into an amphibole–garnet peridotite lens. This reaction zone has been generated by infiltration of hydrous fluids at T of 660–700 °C and P < 1.2 GPa, which occurred during exhumation of coupled continental crust and mantle peridotites.The reaction zone between a trace element-rich (gneiss) and a trace element depleted reservoir (peridotite) allows assessment of local trace element mobility in aqueous fluids. We present the results of in situ LA-ICP-MS trace element analysis of minerals from the reaction zone. Phlogopite is the main host for Large Ion Lithophile Elements (LILE) and contributes significantly to the Li, Ti, Nb, Ta, Pb and Sc budget. Anthophyllite is the main host for Li whereas all other trace elements including Rare Earth Elements (REE) are preferentially incorporated into tremolite. Combined with the abundance of these minerals over the contact zone, the mineral trace element data suggests that the LILE and REE were mobile on a small scale of a few centimetres only. Limited mobility of Ta, which is generally regarded as barely mobile in fluids, is documented in elevated contents of Ta in anthophyllite coupled with low Nb/Ta. The high Li content in minerals throughout the reaction zone suggests that Li was the most mobile element.The studied metasomatic zones mirror geochemical processes occurring in subduction zones at the slab–mantle interface. Phlogopite crystallization at the slab–mantle interface is an efficient mechanism to filter LILE from the aqueous fluid. Thus, such reaction zones, forming at temperatures < 660–700 °C, likely prevents that the typical slab signature with enriched LILE is transported by aqueous fluids over long distances in the mantle wedge. However, if coupled to the downgoing slab, phlogopite- and tremolite-rich rocks from such reaction zones might be able to act as carriers of trace elements and water into deeper parts of the subduction zone.  相似文献   

Preparation and characterization of antibacterial silver/vermiculites and silver/montmorillonites   总被引：1，自引：0，他引：1  

Marta Valášková  Marianna Hundáková  Jana Seidlerová  Erich Pazdziora  Martin He?mánek  David Rafaja 《Geochimica et cosmochimica acta》2010,74(22):6287-6300

The reason for the preparation and characterization of the novel antibacterial silver/vermiculites (Ag/V) together with the silver/montmorillonites (Ag/M) was that the information on the vermiculite structure change and stability of Ag/V in water as well as its effect on bacteria are sporadic. The vermiculite (V), (Si_3.02Al_0.98)^IV (Mg_2.27Al_0.12Ti_0.07)^VI O₁₀(OH)₂ Ca_0.09Na_0.21K_0.50 from West China and montmorillonite (M), (Si_3.96Al_0.04)^IV (Al_1.20Mg_0.42Ti_0.02)^VI O₁₀ (OH)₂Ca_0.15Na_0.14K_0.08 from Ivan?ice (Czech Republic), fraction <0.4 μm were the starting clay materials for sample preparation. The samples V1 and M1 were prepared via reaction of the V and M with the 0.01 mol L⁻¹ AgNO₃ aqueous solution. The samples V2 and M2 were treated with the aqueous solution of AgNO₃ for two times. The cation exchange and reduced metallic silver on M1 and V1 evoked the specific surface area (SSA) diminution, the mean particle-size diameter extension and appearance of micropores with radius (<0.4 nm). Repeated silver cation exchange in M2 and V2 reduced particle size, increased slightly SSA and micropores with radius of 0.4-0.5 nm. Samples Ag/V and Ag/M showed higher content of pores with radius 0.5-1.0 nm than original V and M. The Ag concentration was found higher in Ag/V than in Ag/M and higher in repeatedly treated samples: 0.9 wt.% Ag in V1, 1.4 wt.% Ag in V2, 0.6 wt.% Ag in M1 and 1.0 wt.% Ag in M2. Vermiculite structure consisting of the hydrated interstratified phases and the mica-like phase changed to the cation-one-zero layer hydrate interstratification structure in V1 and to the random of two-one layer hydrate interstratifications in V2. Infrared and Mössbauer spectroscopy revealed no changes in the structure of the clay minerals that could be related directly to the sorption and crystallization of silver. Transmission electron microscopy showed that the silver nanoparticles size distribution was much narrower for the samples Ag/M than for Ag/V. The mean size of the Ag particles was between 40 and 50 nm. Although the Ag nanoparticles did not adhere sufficiently at the clay minerals surface and migrated moderately into water, all samples under study were approved to be effective inhibitors of the bacterial growth persisting for the whole testing period of 6 days. Silver/vermiculite was antimicrobial more efficient against Klebsiella pneumoniae and Pseudomonas aeruginosa than silver/montmorillonite.  相似文献   

Reconstructing the ancestral (Plio-Pleistocene) Rio Grande in its active tectonic setting, southern Rio Grande rift, New Mexico, USA     

Marta Perez-Arlucea  Greg Mack  & Mike Leeder 《Sedimentology》2000,47(3):701-720

Deposits of the ancestral Rio Grande (aRG) belonging to the Camp Rice Formation are preserved and exposed in the uplifted southern portion of the Robledo Mountains horst of the southern Rio Grande rift. The sediments are dated palaeomagnetically to the Gauss chron (upper Pliocene). The lower part of the succession lies in a newly discovered palaeocanyon cut into underlying Eocene rocks whose margins are progressively onlapped by the upper part. Detailed sedimentological studies reveal the presence of numerous river channel and floodplain lithofacies, indicative of varied deposition in channel bar complexes of low‐sinuosity, pebbly sandbed channels that traversed generally dryland floodplains and shifted in and out of the study area five times over the 1 Myr or so recorded by the succession. Notable discoveries in the deposits are: (1) complexes of initial avulsion breakout channels at the base of major sandstone storeys; (2) common low‐angle bedsets ascribed to deposition over low‐angle dunes in active channels; (3) palaeocanyon floodplain environments with evidence of fluctuating near‐surface water tables. Sand‐body architecture is generally multistorey, with palaeocurrents indicative of funnelling of initial avulsive and main fluvial discharge from the neighbouring Mesilla basin through a narrow topographic gap into the palaeocanyon and out over the study area. An avulsion node was evidently located at the stationary southern tip to the East Robledo fault during Gauss times, with aRG channels to the north flowing close to the fault and preventing fan progradation. Subsequent Matuyama growth of the fault caused (1) deposition to cease as the whole succession was uplifted in its footwall, (2) development of a thick petrocalcic horizon, and (3) fan progradation into the Mesilla basin. Parameters for the whole aRG fluvial system are estimated as: active single channels 2 m deep and 25 m wide; valley slope 0·24–0·065°; maximum mean aggradation rate 0·05 mm year^–1; major channel belt avulsion interval 200 ky; individual channel recurrence interval 100 ky; minimum bankfull mean flow velocity 1·54 m s^–1, minimum single‐channel discharge 77 m³ s^–1, bed shear stress 22·3 N m^–2; and stream power 34·3 W m^–2.  相似文献   

Sediment characteristics and internal architecture of offshore sand ridges on a tideless continental shelf (western Mediterranean)     

Ruth Durán  Jorge Guillén  Marta Ribó  Gonzalo Simarro  Araceli Muñoz  Albert Palanques  Pere Puig 《地球表面变化过程与地形》2020,45(14):3592-3606

An integrated approach combining swath bathymetry, an extensive dataset of vibrocores and high-resolution seismic reflection data was used to assess the origin and evolution of offshore sand ridges on a tideless continental shelf (Gulf of Valencia, western Mediterranean). The sand ridges are located in the mid-outer shelf at 55–85 m water depth, obliquely oriented to the shoreline. They are 1.5 to 7 m high, with a wavelength between 600 and 1,100 m and a mean height-to-wavelength ratio of 0.004. The sand ridges are composed of well-sorted medium sand and are partially covered by a mud layer, evidencing a moribund stage. They overlie an erosion surface that locally crops out at the seafloor and is interpreted as the Holocene wave-ravinement surface. In the sediment cores, this surface corresponds to an erosional lag composed of coarse sand and gravel with pebbles. Small topographic irregularities on this surface are interpreted as shoreline-associated features that may act as the precursor for ridge development. Their preservation within the sand ridges could be related to the hardness of these features. Internally, the sand ridges display high-angle dipping reflections, indicating ridge migration towards the southeast in the direction of the present-day sediment transport direction. The presence of interbedded mud layers, associated with these reflections, indicates intermittent episodes of mud deposition when active. The internal architecture of some small ridges also provides new insights into their transition from an active to moribund state, as evidenced by a change in the geometry of the internal units from progradational to aggradational, finally being overlain by onlapping finer deposits over the flanks and in the troughs. The Gulf of Valencia sand ridge field constitutes a valuable potential sand resource of 22 million m³ of well-sorted medium and coarse sand with limited mud content, which must be preserved as a strategic sand reservoir. © 2020 John Wiley & Sons, Ltd.  相似文献   

Seasonal trend analysis (STA) of MODIS vegetation index time series for the mangrove canopy of the Teacapan-Agua Brava lagoon system,Mexico     

César Alejandro Berlanga-Robles  Arturo Ruiz-Luna  Marta Rocío Nepita Villanueva 《地理信息系统科学与遥感》2019,56(3):338-361

Monthly time series, from 2001 to 2016, of the Normalized Difference Vegetation Index (NDVI) and the Enhanced Vegetation Index (EVI) from MOD13Q1 products were analyzed with Seasonal Trend Analysis (STA), assessing seasonal and long-term changes in the mangrove canopy of the Teacapan-Agua Brava lagoon system, the largest mangrove ecosystem in the Mexican Pacific coast. Profiles from both vegetation indices described similar phenological trends, but the EVI was more sensitive in detecting intra-annual changes. We identified a seasonal cycle dominated by Laguncularia racemosa and Rhizophora mangle mixed patches, with the more closed canopy occurring in the early autumn, and the maximum opening in the dry season. Mangrove patches dominated by Avicennia germinans displayed seasonal peaks in the winter. Curves fitted for the seasonal vegetation indices were better correlated with accumulated precipitation and solar radiation among the assessed climate variables (Pearson’s correlation coefficients, estimated for most of the variables, were r ≥ 0.58 p < 0.0001), driving seasonality for tidal basins with mangroves dominated by L. racemosa and R. mangle. For tidal basins dominated by A. germinans, the maximum and minimum temperatures and monthly precipitation fit better seasonally with the vegetation indices (r ≥ 0.58, p < 0.0001). Significant mangrove canopy reductions were identified in all the analyzed tidal basins (z values for the Mann-Kendall test ≤ ?1.96), but positive change trends were recorded in four of the basins, while most of the mangrove canopy (approximately 87%) displayed only seasonal canopy changes or canopy recovery (z > ?1.96). The most resilient mangrove forests were distributed in tidal basins dominated by L. racemosa and R. mangle (Mann-Kendal Tau t ≥ 0.4, p ≤ 0.03), while basins dominated by A. germinans showed the most evidence of disturbance.  相似文献   

A description of chloride cell and kidney tubule alterations in the flatfish Solea senegalensis exposed to moderately contaminated sediments from the Sado estuary (Portugal)     

Pedro M. Costa  Sandra Caeiro  Mrio S. Diniz  Jorge Lobo  Marta Martins  Ana M. Ferreira  Miguel Caetano  Carlos Vale  T. ngel DelValls  M. Helena Costa 《Journal of Sea Research》2010,64(4):465-472

The effects of sediment-bound contaminants on kidney and gill chloride cells were surveyed in juvenile Solea senegalensis exposed to fresh sediments collected from three distinct sites of the Sado Estuary (Portugal) in a 28-day laboratorial assay. Sediments were analyzed for metallic contaminants, polycyclic aromatic hydrocarbons and organochlorines as well as for total organic matter, redox potential and fine fraction. The potential for causing adverse biological effects of each surveyed sediment was assessed by comparison of contaminant levels to available guidelines for coastal sediments, namely the Threshold Effects Level (TEL) and the Probable Effects Level (PEL). The Sediment Quality Guideline Quotient indices (SQGQ) were calculated to compare the overall contamination levels of the three stations. A qualitative approach was employed to analyze the histo/cytopathological traits in gill chloride cells and body kidney of fish exposed to each tested sediment for 0, 14 and 28 days. The results showed that sediment contamination can be considered low to moderate and that the least contaminated sediment (from a reference site, with the lowest SQGQ) caused lesser changes in the surveyed organs. However, the most contaminated sediment (by both metallic and organic xenobiotics, with highest SQGQ) was neither responsible for the highest mortality nor for the most pronounced lesions. Exposure to the sediment presenting an intermediate SQGQ, essentially contaminated by organic compounds, caused the highest mortality (48%) and the most severe damage to kidneys, up to full renal necrosis. Chloride cell alterations were similar in fish exposed to the two most contaminated sediments and consisted of a pronounced cellular hypertrophy, likely involving fluid retention and loss of mitochondria. It can be concluded that sediment contamination considered to be low or moderate may be responsible for severe injury to cells and parenchyma involved in the maintenance of osmotic balance, contributing for the high mortality levels observed. The results suggest that sediment-bound organic contaminants such as PAHs (polycyclic aromatic hydrocarbons) and PCBs (polychlorinated biphenyls) may be very toxic to the analyzed organs, especially the kidney, even when present in low-risk concentrations.  相似文献