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921.
Jesús Galindo-Zaldivar Francisco Gonzalez-Lodeiro Antonio Jabaloy 《Geodinamica Acta》2013,26(1):73-85
AbstractThe present contact caused by the superposition of the Alpujarride complex over that of the Nevado-Filabride in the western area of Sierra Nevada and Sierra de Filábres corresponds to a detachment. The deformation in the footwall associated with this contact, produced mylonitic fabrics with a significant stretching-lineation, over which brittle structures are superimposed. The deformation in the hanging wall associated with this contact is, on the other hand, essentially brittle. These deformations are subsequent to a series of syn-to post-metamorphic structures related to thrust phases.The micro- and meso-structures indicate that the hanging wall has moved towards the west-south-west.Other brittle structures, which began during the same extensional regime, are superimposed on the detachment and have continued to develop up to the present time. These structures were produced in an extensional regime with a non-coaxial deformation component and suggest the possibility of a tectonic evolution similar to that described for core complexes in the USA. 相似文献
922.
923.
Sara Villa Marco Vighi Valter Maggi Antonio Finizio Ezio Bolzacchini 《Journal of Atmospheric Chemistry》2003,46(3):295-311
The significance of persistent organic pollutants, such as organochlorine compounds, as global contaminants in cold regions has been recognised for a long time. In particular, there is a growing interest on the role of high mountains as `cold condensers' for these chemicals. In this paper, for the first time, organochlorine pesticides (DDTs, HCHs, HCB) are analysed in an ice core sampled on a `cold' glacier in the Alps. Several methods were applied to achieve accurate dating of the core layers. Historical trends of organochlorine pesticides from the 1950s up to the year 2000 are reconstructed, showing, for each individual chemical, the influence of long range transport, as well as of local transport patterns. The role of mountain glaciers as natural archives for studying the local and global transport of persistent organic pollutants is highlighted, though results can be biased by volatilisation losses. 相似文献
924.
The Atlas Mountains have been uplifted by two mechanisms: Cenozoic thickening of the crust and thinning of the mantle lithosphere due to a buoyant thermal anomaly, previously inferred by indirect criteria to have started some 15 Ma. Because crustal shortening‐related uplift and mantle‐related uplift affect the topography at different spatial scales, we use scattered direct surface evidence to clarify the palaeoelevation dynamics. Uplifted Messinian shallow marine sediments in the southern margin of the Saïss Basin and in the northern Middle Atlas, tilted Pliocene lacustrine deposits in the Saïss Basin and in the piedmont of the southern High Atlas and drainage‐network reorganization in the Saïss Basin underscore the long‐wavelength rock uplift of the Atlas domain of mantle origin. The low erosion of the aforementioned deposits indicates that such uplift is a true surface uplift that occurred in post‐Miocene times at a minimum rate ranging from 0.17 to 0.22 mm yr?1. 相似文献
925.
Antonio Hernández-Espriú J. Antonio Reyna-Gutiérrez Emilio Sánchez-León Enrique Cabral-Cano Jaime Carrera-Hernández Pedro Martínez-Santos Sergio Macías-Medrano Giacomo Falorni Davide Colombo 《Hydrogeology Journal》2014,22(6):1469-1485
Mexico City relies on groundwater for most of its domestic supply. Over the years, intensive pumping has led to significant drawdowns and, subsequently, to severe land subsidence. Tensile cracks have also developed or reactivated as a result. All such processes cause damage to urban infrastructure, increasing the risk of spills and favoring contaminant propagation into the aquifer. The effects of ground deformation are frequently ignored in groundwater vulnerability studies, but can be relevant in subsiding cities. This report presents an extension to the DRASTIC methodology, named DRASTIC-Sg, which focuses on evaluating groundwater vulnerability in urban aquifers affected by differential subsidence. A subsidence parameter is developed to represent the ground deformation gradient (Sg), and then used to depict areas where damage risk to urban infrastructure is higher due to fracture propagation. Space-geodetic SqueeSAR data and global positioning system (GPS) validation were used to evaluate subsidence rates and gradients, integrating hydrogeological and geomechanical variables into a GIS environment. Results show that classic DRASTIC approaches may underestimate groundwater vulnerability in settings such as the one at hand. Hence, it is concluded that the Sg parameter is a welcome contribution to develop reliable vulnerability assessments in subsiding basins. 相似文献
926.
Jorge M. Gaspar-Escribano Manuel Navarro Belén Benito Antonio García-Jerez Francisco Vidal 《Bulletin of Earthquake Engineering》2010,8(6):1547-1567
An approach that relates results from a regional seismic hazard assessment study with local-scale site-effect characterizations
in an area of low-to-moderate seismic activity such as Andalusia (southern Spain), is presented. Results of a previous probabilistic
seismic hazard analysis of Andalusia on rock conditions are disaggregated to infer hazard controlling earthquakes for different
target motions. A collection of controlling magnitude-distance pairs and the corresponding site-specific response spectra
at main capital cities of the region are obtained. These spectra are first-order approximations to expected seismic actions
required in local earthquake risk assessments. In addition, results of independent, local-scale studies developed in Almeria
City (SE Andalusia) are used to derive an updated seismic zonation of the city. These include predominant soil period estimates
and shear-wave velocity profiles at different locations. If a local seismic risk assessment study or an earthquake-resistant
structural design is to be developed, it may be recommended the use of different seismic actions on sites characterized by
distinct response to seismic shaking (as derived from the seismic zonation). The seismic action related to worst-case scenarios
may be modeled through a hazard-consistent response spectrum, obtained by hazard disaggregation at the spectral acceleration
with period matching the prevailing resonant period of the target site or structure. 相似文献
927.
Alessia Viero Sandro Furlanis Cristina Squarzoni Giordano Teza Antonio Galgaro Piero Gianolla 《Landslides》2013,10(4):393-408
On October 12th, 2007 about 40,000 m3 of dolomitic rock detached from the northern wall of the peak known as “Cima Una” (Val Fiscalina, Sesto Dolomites, Bolzano, Italy), and fell 900 m to Fiscalina Valley below. The event generated a dense dust cloud, which traveled up to 4 km from the source area. The failure surface was formed by two near-vertical surfaces, almost perpendicular to each other. The orientation of these surfaces is consistent with two of the main regional tectonic sets. Only a small portion of the fallen material appeared to be preserved as blocks deposited at the base of the rock wall. About a fifth of the fallen mass was deposited on a colluvial cone. The missing mass, estimated to be about 80 %, may be represented by highly fragmented rock in part deposited as sand on the valley floor and in part dispersed as a dense dust cloud generated during the rockfall. There appears to be a deficit of deposited material, which could lead underestimation in the calculation of rock–cliff recession rates. The dynamics of the rockfall, strongly conditioned by the local topography, partially explains the intense rock breakage and the generation of the dust cloud. The rockfall was not caused by an external trigger, such as an earthquake or heavy rainfall; the failure was most likely progressive due to mechanical and physical degradation along highly stressed failure surfaces, possibly promoted by permafrost degradation and freeze and thaw processes. 相似文献
928.
Jose Oteros Herminia García-Mozo Roser Botey Antonio Mestre Carmen Galán 《Climatic change》2015,132(4):545-558
Over recent years, the Iberian Peninsula has witnessed an increase both in temperature and in rainfall intensity, especially in the Mediterranean climate area. Plant phenology is modulated by climate, and closely governed by water availability and air temperature. Over the period 1986–2012, the effects of climate change on phenology were analyzed in five crops at 26 sites growing in Spain (southern Europe): oats, wheat, rye, barley and maize. The phenophases studied were: sowing date, emergence, flag leaf sheath swollen, flowering, seed ripening and harvest. Trends in phenological response over time were detected using linear regression. Trends in air temperature and rainfall over the period prior to each phenophase were also charted. Correlations between phenological features, biogeographical area and weather trends were examined using a Generalized Lineal Mixed Model approach. A generalized advance in most winter-cereal phenophases was observed, mainly during the spring. Trend patterns differed between species and phenophases. The most noticeable advance in spring phenology was recorded for wheat and oats, the “Flag leaf sheath swollen” and “Flowering date” phenophases being brought forward by around 3 days/year and 1 day/year, respectively. Temperature changes during the period prior to phenophase onset were identified as the cause of these phenological trends. Climate changes are clearly prompting variations in cereal crop phenology; their consequences could be even more marked if climate change persists into the next century. Changes in phenology could in turn impact crop yield; fortunately, human intervention in crop systems is likely to minimize the negative impact. 相似文献
929.
Rafael Prez-Lpez Antonio M. lvarez-Valero Jos Miguel Nieto Reinaldo Sez Joo X. Matos 《Applied Geochemistry》2008,23(12):3452-3463
São Domingos is one of the most emblematic Portuguese mining districts in the Iberian Pyrite Belt (IPB). The beginning of mining exploitation in the area has been dated back to pre-Roman times, remaining in activity until 1966 when it was definitely halted. The intense mining labours are reflected in the presence of a huge amount of sulphide-mining wastes and downstream production of acid mine drainage (AMD). The mining wastes in the area are highly heterogeneous, and numerous different types may be recognized, including slags, iron oxides, smelting ashes, brittle and blocks of pyrite, leaching tank refuses, industrial landfill and other residues coming from ore extraction (gossan wastes and country rocks). The chemical speciation of potentially toxic elements (As, Cd, Cr, Cu, Fe, Mn, Pb, S, Sb and Zn) in all mine wastes from São Domingos was determined by modified BCR-sequential extraction procedure (European Community Bureau of Reference) and combined with the mass/volume proportions of each waste to quantify the potential risk of this mining district at regional scale. Analytical recoveries by sequential extraction, with respect to a pseudo-total metal content digestion, were generally acceptable (100 ± 17%). The oxidizable fraction corresponds with metals bound to sulphides and released easily under oxidizing conditions in AMD production processes. This is the most polluting fraction for the environment in this type of residues. Part of this fraction is retained by precipitation of soluble secondary minerals in warm periods, moving to the bio-available fraction that is dissolved in rainy periods. Just considering the bio-available fraction, all mine wastes from São Domingos may leach up to 172514 ton of Fe, 10564 ton of S, 6644 ton of Pb, 2610 ton of Zn, 1126 ton of Mn, 1032 ton of Cu, 183 ton of Cr, 109 ton of As, 34 ton of Sb and 0.9 ton of Cd. The process of precipitation and re-dissolution of efflorescent salts formed directly by oxidation of the oxidizable fraction is seasonally repeated, which causes an annual self-feeding and releasing of the bio-available fraction. Thus, the present study shows the pollutant potential of this IPB mining district and explains the spoiled state of the fluvial courses in the region. 相似文献
930.
Ismar de Souza Carvalho Antonio de Celso Arruda Campos Pedro Henrique Nobre 《Gondwana Research》2005,8(1):11-30
Baurusuchus salgadoensis is a new baurusuchid crocodylomorph from Bauru Basin (Cretaceous), Brazil, partially preserved through a complete skull. The fossil comes from a fine sandstone sequence of Adamantina Formation, General Salgado County, São Paulo State. The sedimentary sequence where it was found, located in Fazenda Buriti, is considered Turonian-Santonian in age. The described species _Baurusuchus salgadoensis sp. nov. _ is a baurusuchid with an antorbital fenestra, double external nares with a bony septum, two well-fused supraorbitals, the supratemporal fenestrae larger than the orbits and a quadrangular-shaped laterotemporal fenestra. The position of the external nares, located on anterior and terminal portion of the rostrum together with the theropod-like lateral compression of the snout and teeth are indicators that Baurusuchus salgadoensis was a terrestrial crocodyliform. This was a carnivorous species and the lateral compression of the rostrum could be interpreted as a mechanism to increase the skull resistance forces during biting. The pointed, conical teeth, some with crenulated borders, could be used to perforate and to carve the prey. The geological context of Baurusuchus salgadoensis indicates that it probably lived in a hot and arid climate. 相似文献