Los domos graníticos de la Cuenca del Ridaura (Girona)

[Resumen] Se describen los domos graníticos de la cuenca del rio Ridaura. Sus características geométricas se relacionan estrechamente con la disposición de las fracturas. Su génesis deriva de una fase subsuperficial, bajo un manto de alteración, presumiblemente desarrollada durante el Plioceno, y una fase de exhumación torrencial, que comprende desde el Plioceno terminal hasta la actualidad.[Abstract] This paper deals with the bornhardts of the Ridaura river area. Their geometrical characteristics are tightly related to the fracture system. These bornhardts evolve in two different stages: the first occurs under a regolith bed and develops during the Pliocene, and the later is an torrential stripping that extends from the latest Pliocene to the present

Características geológicas y geotécnicas de los lodos de flotación de la Sierra Minera de Cartagena-La Unión (SE España)

En el trabajo se presentan los resultados de la caracterización geológico-geotécnica de los lodos de flotación (LF) de la Sierra Minera Cartagena-La Unión. Se han estudiado los LF almacenados en ocho presas, en las que se ha realizado la toma y caracterización de 42 muestras. Se han efectuado ensayos granulométricos, medida del peso especifico de las partículas sólidas, determinación del índice de plasticidad, medidas de permeabilidad in situ y de laboratorio, corte directo y humedad. Los LF según los análisis granulométricos se clasifican como limos arenosos. Presentan un índice de plasticidad medio, bajo a nulo. El ángulo de fricción interna varía entre 25 y 42 grados. La cohesión es nula o baja entre 0 y 2,2 t/m2. El peso específico de las partículas sólidas tiene un amplio rango de variación entre 1,8 y 4 g/cm3. La conductividad hidráulica saturada oscila entre 1,3x10-5 y 3,2x10-9 m/s. Las determinaciones in situ de humedad muestran que el grado de saturación permanece relativamente elevado, a pesar de las bajas precipitaciones y las elevadas tasas de vaporación. Varias presas de residuos han fallado. Las principales causas de fallos ó rotura de las presas son: 1) deslizamiento del talud, 2) sobrepaso de agua, 3) erosión del dique, 4) subsidencias o colapso del terreno. El principal problema que favorece el proceso de fallo o rotura de la presas es la existencia de un alto grado de saturación en los LF almacenados y el almacenamiento de agua en la laguna de decantación.We present the results of a geological and geotechnical characterization of the metallurgic waste from the Sierra Minera de Cartagena-La Union. We have studied eight tailings dams from which we collected and analysed 42 samples of metallurgic waste. We measured grainsize distribution, the specific gravity of solid particles, plasticity index, permeability, both in situ and in the laboratory, direct shear characteristics and moisture content. According to size distribution the tailings can be classified as sandy silt. Their plasticity index ranges from medium to nil. The internal friction angle varies between 28 and 42 degrees. Cohesion is between 0 and 2.2 t/m2. The specific gravity of the solid particles ranges widely from 1.8 to 4 g/cm3. The saturated hydraulic conductivity values vary between 1.3x 10-5 and 3.2x 10-9 m/s. The water content measured in situ shows that the degree of saturation remains relatively high despite low rainfall and high evaporation rates. Several tailings dams have failed. The leading causes of tailings-dam failure are: 1) slope instability; 2) overflow; 3) erosion; and 4) subsidence or collapse. The main factor leading to dam failure is that the tailings stored in the ponds are highly saturated

Petrological characterization of flint from Montmaneu's Limestones Formation (Eastern sector of the Ebro Basin)

[EN] Flint from Montmaneu's Limestones Formation of Rupelian age (Oligocene) is being here characterized. The analysis of the compositional texture, mineralogy and geochemical features has revealed this flint is highly pure and of microcrystalline texture, with a significant content of moganite. This flint is product of an early diagenetic replacement of limestone from littoral lacustrine facies. This flint was exploited by human populations in a regional range, especially in the early stages of the Neolithic.[ES] Se caracteriza el sílex de la Formación calizas de Montmaneu, de edad Rupeliense (Oligoceno). El análisis textural, mineralógico y de sus rasgos geoquímicos indica que se trata de un sílex microcristalino, bastante puro, con una proporción significativa de moganita. Es producto del reemplazamiento diagenético temprano de calizas de facies lacustres litorales. Este sílex fue objeto de una explotación regional, especialmente en los primeros momentos del Neolítico.Este trabajo forma parte del proyecto de constitución de una litoteca de rocas silíceas del NE peninsular (LITOcat). Los estudios sobre la explotación prehistórica del sílex de Montmaneu se llevan a cabo en el marco del proyecto "Aprofitament prehistòric i històric del sílex a Catalunya: contextos extractius i de primera transformació". Ambos proyectos son financiados por el CSIC-IMF y el Departamento de Cultura de la Generalitat de Catalunya.Peer reviewe

Sedimentological and palaeohydrological characterization of Late Pleistocene and Holocene tufa mound palaeolakes using trenching methods in the Spanish Pyrenees

Lakes developed in the inner depressions of tufa mounds are rare geomorphic features and still poorly understood. Sedimentation in this unusual type of endorheic lake with a very restricted catchment area is highly sensitive to environmental and hydrological changes. The Isona tufa mound complex, north-eastern Iberian Peninsula, is associated with the discharge zone of a confined artesian aquifer and comprises 11 tufa mounds consisting of an annular rimstone enclosing a central depression filled with lake deposits. Data gathered from trenches excavated in four palaeolakes located within three different morphostratigraphic units permitted a precise analysis of the geometrical characteristics and stratigraphic relationships of the deposits and provided a sedimentation model for the Late Quaternary infilling of the spring-fed lakes. The work illustrates that trenches allow a precise characterization of the stratigraphic arrangements, lateral facies changes and deformation structures, which are not apparent in studies relying solely on borehole records, and facilitate sampling for dating and geochemical analyses. The five sedimentary facies described represent different evolutionary stages of the lakes, including: (i) carbonate-rich palustrine deposits probably related to periods with strong hydrological seasonality; (ii) massive highly bioturbated organic ooze; (iii) banded organic carbonate-rich facies associated with an increase in the regional effective moisture; (iv) finegrained quartz-rich aeolian/slope-wash sediments; and (v) colluvial facies deposited following the desiccation of the lakes located at higher altitudes. Geochemical and sedimentological analyses of the lacustrine sequences provided information on the palaeohydrological evolution of the Isona tufa mound complex and the palaeoenvironmental conditions of the area over the last 28 ka. Radiometric dating suggests that deposition occurred simultaneously at ca 22 ka in palaeolakes situated at different elevations. A drop in the piezometric level prompted by the opening of springs at lower altitudes probably caused the deactivation of the upper springs and the desiccation of the lakes. Arid conditions prevailed in the area during the Late Glacial and the early Holocene (28·0 to 8·5 ka BP). More humid conditions recorded from 8·5 to 4·2 ka and again since 1·7 ka are in accordance with palaeoenvironmental reconstructions available in the Western Mediterranean since the Last Glacial Maximum

Identifying the boundaries of sinkholes and subsidence areas via trenching and establishing setback distances

One of the most effective mitigation strategies in sinkhole areas is the exclusion of sinkholes and their vicinity to construction. The application of this preventive measure requires precise mapping of the boundaries of the areas affected by subsidence and the establishment of adequate setback distances, which is an important policy issue with significant economic implications. Through the investigation of several buried sinkholes in the mantled evaporite karst of the Ebro Valley by trenching, this work illustrates that the actual extent of the subsidence areas may be much larger than that inferred from surface mapping and geophysical surveys. The objective and accurate subsurface information acquired from trenches on the outer edge of the deformed ground revealed sinkhole radii 2–3 times larger than initially estimated, increasing one order of magnitude the sinkhole area. Trenches can therefore help to reduce mapping uncertainties and the size of setbacks. Moreover, the trenching technique, in combination with geochronological data and retrodeformation analyses, provides critical information on the subsidence phenomena and the characteristics of the sinkholes relevant to hazard assessment. Since recommended setback distances found in the existing literature are highly variable and rather arbitrary, we include a discussion here on the main factors that should be considered when defining setback zones for sinkholes

Sinkholes in hypogene versus epigene karst systems, illustrated with the hypogene gypsum karst of the Sant Miquel de Campmajor Valley, NE Spain

The Garrotxa-Banyoles artesian aquifer system in NE Spain includes zones with epigene and hypogene evaporite karst and sinkhole development. The sinkhole fields related to hypogene evaporite dissolution are associated with the discharge zones of the aquifer, where groundwater from a confined limestone rises traversing an overlying gypsum formation capped by thick marls. This work analyses the sinkhole field developed in the Sant Miquel de Campmajor Valley (SMCV), a discharge area of the aquifer, where a cartographic inventory including 94 sinkholes has been produced. Sinkholes in this hypogene gypsum karst are mainly large caprock-collapse sinkholes rooted in deep-seated cavities generated by interstratal hypogene karstification, as corroborated by an electrical resistivity imaging (ERI) survey. They show a non-clustered distribution within the sinkhole field and the variations in size and density across the area are mainly controlled by the thickness of the marl caprock. The magnitude and frequency relationships of the sinkholes can be modelled with a high goodness of fit with a log-normal function, like in other regions of the world. However, in this deep-seated hypogene system the depressions show much larger dimensions. Potential differences between the sinkholes developed in hypogene and epigene karst environments are discussed, including their distribution with respect to the groundwater flow system, their spatial patterns and dimensions

Extendiendo transformaciones MDA con metamodelo de patrones de diseño

Object Management Group (OMG) ha producido un importante paso hacia el modelado del Proceso de Desarrollo de Software (PDS), el enfoque Model Driven Architecture (MDA). Sin embargo, no ha tenido el impacto esperado en la calidad de las instancias del modelo ni en los productos resultantes. La principal razón radica en el nivel de abstracción alejado de los dominios para los cuales deben generarse dichas instancias. En el caso de Diseño de Software (DS), no incluye abstracciones del proceso como tal y mucho menos de la actividad principal, la toma de decisiones. Presentamos aquí una línea de investigación que propone extender el modelo de transformaciones MDA con abstracciones inherentes a la actividad de síntesis y evaluación de alternativas para la toma de decisiones. Proponemos utilizar Patrones de Diseño de Software como el estándar de representación este tipo de conocimiento e incluir un metamodelo del mismo, para posibilitar su inyección en transformaciones MDA. Estas extensiones permitirán la generación de instancias del PDS, más cercanas a los dominios tecnológicos y de aplicación direccionados por los patrones, incrementando así el perfil ingenieril de la actividad.Eje: Ingeniería de Software.Red de Universidades con Carreras en Informática (RedUNCI

As and S speciation in a submarine sulfide mine tailings deposit and its environmental significance: The study case of Portmán Bay (SE Spain)

The dumping of an estimated amount of 57 million tons of hazardous sulfide mine waste from 1957 to 1990 into Portmán's Bay (SE Spain) caused one of the most severe cases of persistent anthropogenic impact in Europe's costal and marine environments. The resulting mine tailings deposit completely infilled Portmán's Bay and extended seawards on the continental shelf, bearing high levels of metals and As. The present work, where Synchrotron XAS, XRF core scanner and other data are combined, reveals the simultaneous presence of arsenopyrite (FeAsS), scorodite (FeAsO₄·2H₂O), orpiment (As2S3) and realgar (AsS) in the submarine extension of the mine tailings deposit. In addition to arsenopyrite weathering and scorodite formation, the, the presence of realgar and orpiment is discussed, considering both potential sourcing from the exploited ores and in situ precipitation from a combination of inorganic and biologically mediated geochemical processes. Whereas the formation of scorodite relates to the oxidation of arsenopyrite, we hypothesize that the presence of orpiment and realgar is associated to scorodite dissolution and subsequent precipitation of these two minerals within the mine tailings deposit under moderately reducing conditions. The occurrence of organic debris and reduced organic sulfur compounds evidences the activity of sulfate-reducing bacteria (SRB) and provides a plausible explanation to the reactions leading to the formation of authigenic realgar and orpiment. The precipitation of these two minerals in the mine tailings, according to our hypothesis, has important consequences for As mobility since this process would reduce the release of As into the surrounding environment. Our work provides for the first time valuable hints on As speciation in a massive submarine sulfide mine tailings deposit, which is highly relevant for similar situations worldwide

Extendiendo transformaciones MDA con metamodelo de patrones de diseño

Object Management Group (OMG) ha producido un importante paso hacia el modelado del Proceso de Desarrollo de Software (PDS), el enfoque Model Driven Architecture (MDA). Sin embargo, no ha tenido el impacto esperado en la calidad de las instancias del modelo ni en los productos resultantes. La principal razón radica en el nivel de abstracción alejado de los dominios para los cuales deben generarse dichas instancias. En el caso de Diseño de Software (DS), no incluye abstracciones del proceso como tal y mucho menos de la actividad principal, la toma de decisiones. Presentamos aquí una línea de investigación que propone extender el modelo de transformaciones MDA con abstracciones inherentes a la actividad de síntesis y evaluación de alternativas para la toma de decisiones. Proponemos utilizar Patrones de Diseño de Software como el estándar de representación este tipo de conocimiento e incluir un metamodelo del mismo, para posibilitar su inyección en transformaciones MDA. Estas extensiones permitirán la generación de instancias del PDS, más cercanas a los dominios tecnológicos y de aplicación direccionados por los patrones, incrementando así el perfil ingenieril de la actividad.Eje: Ingeniería de Software.Red de Universidades con Carreras en Informática (RedUNCI