Geologia de la Plana del Baix Empordà

The geological features of the Baix Empordà Plain are mainly related to the sedimentary processes that took place during the Holocen, when a stable sea level was reached at the end of the Versilian transgression. In this paper, all the sedimentary environments which have given rise to the present morphology are described: alluvial, coastal and palustrine environments as well as colluvial and aeolian deposits. We conclude with a scheme in which the geological evolution of the Plain is shown

Geologia del massís de les Gavarres

In the present paper, the diverse morphological aspects of the Les Gavarres Massif (Catalonian Coastal Ranges) are described. Also, the different outcrop rocks are shaped in a schematic geological chart

Sediments antics del litoral del Baix Empodà entre es Forn (Begur) i Vall-presona (Santa Cristina d'Aro)

A la Costa Brava hi ha, en comparació amb altres àrees mediterrànies, pocs testimonis de sediments litorals antics. El domini manifest dels processosd'erosió n'és la causa principal. Tanmateix, hi ha alguns dipòsits litorals fòssils, que se situen uns decimetres per sobre i per sota del nivell del mar actual. L'estudi detallat dels diferents nivells localitzats fins ara ha permès caracteritzar-los des d'un punt de vista estratigràfic. Així, s'ha pogut constatar que es tracta d'acumulacions de blocs aplegats al peu de penya-segats, de platges emergides sense cimentar, i de platges submergides que han patit un procés de cimentació. La seva edat és molt recent, en termes geològics, i es remunta a començaments de l'era cristiana

Restauración del Patrimonio Natural: una visión des de la geología

Descripció de diferents actuacions de restauració del patrimoni natural geològic de Catalunya

Depósitos litorales y variaciones del nivel del mar durante el Holoceno en la Costa Brava (NE de Catalunya)

Se describe un conjunto de depósitos litorales localizados en la Costa Brava, que aparecen unos pocos metros por encima y por debajo del nivel del mar actual. En base a su génesis se han agrupado en niveles de conglomerados de pie de acantilado, playas levantabas sincementar y playas sumergidas cementadas (beachrock). Su edad se ha establecido apartir de los fragmentos de cerámica que contienen y de dataciones absolutas de 14C. Estos depósitos permiten detectaroscilaciones recientes del nivel del mar que se enmarcan en los últimos estadios de la transgresión Flandriense

Mid Holocene in Sant Julià de Boada (Baix Empordà, Girona): Stratigraphical sequence and paleoenvironmental records of the paludal deposits

Descripció de la seqüència estratigràfica i dels registres paleoambientals dels sediments holocens de Sant Julià de Boada

Principales características geoambientales en la región del alto Fluvià (Gerona)

This study is about the main characteristics of a large area in the province of Girona, the utilization of which has been historically poor, basically due to gecsnorphological causes. The analysis has been made considering the possibilities -both positive and negative - that the geological medium offers by appropiate use of the area, bearing in mind the possible impacts that these uses could have on the medium. The conclusions drawn from this study are shown in a series of maps

Variables geoambientales en el Plan General de Ordenación Urbana de Cassá de la Selva

Se presentan de forma resumida los resultados geoambientales obtenidos en el estudio de un término municipal motivado más por sistemática de planteamiento por parte del responsable del Plan General, que por cuestión concreta planteada sobre este ámbito en aquel término municipal. Así y todo, la información obtenida influye sobre el Plan y pone de manifiesto circunstancias qenerales que sin ser aqudas son persistentes en el tiempo, por razones obvias del ámbito terrestre, al que pertenecen

Aportaciones al conocimiento del Mesozoico de la provincia de Girona: Jurásico

The general features of the mesozoic sediments of Girona province and also the detailed jurassic section are studied. In this section are identified paleontologically the Carixian, the Lower Domerian and the Midle Toarcian age

Caraterización de las inestabilidades gravitatorias en el área de Banyoles (Girona)

El entorno de la Depresión donde se ubica el lago de Banyoles presenta unas especiales características litológicas, morfológicas e hidrogeológicas que se traducen en unos claros ejemplos de inestabilidad gravitatoria. Esta ocasiona, en general, rápidas modificaciones de la superficie topográfica, que delimitan el uso territorial de la zona. Son relativamente frecuentes los fenómenos de inestabilidad de laderas, siempre coincidentes con episodiospluviométricos de carácter extraordinario, así como manifestaciones gravitatorias de hundimiento por colapso, ligadas a la carstificación del material yesífero infrayacente

La zonación estructural del hercínico del Pirineo Central en el anticlinorio de la Pallaresa

The Pyrenees are an alpine chain with hercynian basement rocks that outcrop in a large area called the Axial Zone. These rocks have been involved in the alpine deformation events although their main structural features resulted from the Hercynian orogeny. A relevant characteristic of the Hercynian basement is a change in structural style in depth which has been commonly studied and interpreted in the Pallaresa Anticlinorium, in the Central Pyrenees. This anticlinorium is a complex hercynian structural unit whose southern part belongs to the suprastructure whereas the northern part corresponds mostly to a transition zone between the infrastructure and the suprastructure. Rocks of the suprastructure show a steeply dipping slaty cleavage as the dominant structure, which is overprinting folds and thrusts rarely going with pervasive deformation. The transition zone results from a slaty cleavage, very often close to the bedding, overprinted by one or two steep crenulation cleavages. A gradual boundary exists between both structural levels and it can be observed that the deformation developing slaty cleavage in the suprastructure grades to a crenulation foliation in the transition zone. The gradual character of that boundary, as seen in the northern end of the transition zone, suggests that the southern sharp boundary is not original. That boundary is interpreted as a northward dipping inverse fault, possibly with Alpine age. That fault causes a relative uplift of the rocks of the transition zone and gives this sharp boundary with the suprastructural levels. It provokes the asymmetry in the Pallaresa anticlinorium

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

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 characteristicsand 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

Reflexiones sobre el diseño por competencias en el trabajo de campo en Geología

Learning activities outside the classroom in Earth Sciences are considered fundamental to achieve an adequate level of knowledge. New pedagogical perspectives, structured in competency-based activities, provide a useful tool to improve the effectiveness of field geology classes. In this paper, we point out some general educational aspects, and we propose a curriculum design focused on accomplishing the competencies that go with fieldtrips in Geology courses

Globally aligned photomosaic of the Lucky Strike hydrothermal vent field (Mid-Atlantic Ridge, 37°18.5’N): Release of georeferenced data, mosaic construction, and viewing software

We present a georeferenced photomosaic of the Lucky Strike hydrothermal vent field (Mid-Atlantic Ridge, 37°18’N). The photomosaic was generated from digital photographs acquired using the ARGO II seafloor imaging system during the 1996 LUSTRE cruise, which surveyed a ~1 km2 zone and provided a coverage of ~20% of the seafloor. The photomosaic has a pixel resolution of 15 mm and encloses the areas with known active hydrothermal venting. The final mosaic is generated after an optimization that includes the automatic detection of the same benthic features across different images (feature-matching), followed by a global alignment of images based on the vehicle navigation. We also provide software to construct mosaics from large sets of images for which georeferencing information exists (location, attitude, and altitude per image), to visualize them, and to extract data. Georeferencing information can be provided by the raw navigation data (collected during the survey) or result from the optimization obtained from imatge matching. Mosaics based solely on navigation can be readily generated by any user but the optimization and global alignment of the mosaic requires a case-by-case approach for which no universally software is available. The Lucky Strike photomosaics (optimized and navigated-only) are publicly available through the Marine Geoscience Data System (MGDS, http://www.marine-geo.org). The mosaic-generating and viewing software is available through the Computer Vision and Robotics Group Web page at the University of Girona (http://eia.udg.es/_rafa/mosaicviewer.html)

Determinación de la longitud de la falla y velocidad de ruptura para terremotos de magnitud media

En el proceso de inversión de la función de directividad para la obtención de la longitud de falla y velocidad de mptura, en el caso de terremotos de magnitud media, es muy dificil obtener ambos parámetros independientemente y deben hacerse hipótesis sobre uno de los dos parámetros. Proponemos una solución a este problema mediante un proceso iterativo, que iniciamos con un valor hipotético de la velocidad de ruptura. El resultado final resulta ser independiente del valor de partida. Mediante este proceso hemos obtenido la longitud de falla y velocidad de ruptura de dos terremotos, el del 18-nov-1970, ocurrido en la Dorsal Oriental del Pacifico, y el del 4-jul-1966, ocurrido en la Dorsal Centro-Atlántica. Para el sismo del 18-nov-1970 los valores obtenidos en la b = (18 4- 1) km v = (2.3 f 0.1) kmls y para el sismo del 4-jul-1966 b = (19 f 2) km, v = (2.1 i 0.1) kmls. Las desviaciones tipicas de estos parámetros, del orden del 5-10 %, son inferiores a las obtenidas en trabajos previos.