Tesis doctoral: Estudio Gravimétrico del Pirineo Oriental

This dissertation is primarily a gravimetric study of Eastern Pyrenees based on gravity prospecting techniques combined with seismic reflection profiles, magnetic survey, and the existing bore-holes. The two main objectives of the study are interpret the gravity anomalies produced by superficial bodies and the anomalies produced by deep bodies in the area lying between the Segre River to the West, the Mediterranean Sea to the East, the city of Manresa to the South, and the city of Perpinyi to the North. The general disposition of these anomalies is composed of negative values in NW part of the studied zone and positive values along the coastline. This disposition is due to the enlarged upper crust under Pyrenean Axial Zone as a result of Iberian and European plates collision, and the thinning crust near the Coast To verify the existence of sorne of the anomalies, several macroscale maps of residual gravity anomalies of the area were compiled. The regional gravity component is assimilated to a second and third degree by polynomical surfaces. A residual isostatic map was also realised. Other smaller-scale maps were drawn up later because the use of lower-degree polynomes it is possible to obtain a more acceptable adjustment of regional-residual separation. After calculating gravity models in several zones, it was concluded that negative gravity anomalies are produced by Neogene materials landing in the Empordh and Cerdanya grabens, detritic Eocene materials in the Rocacorba area, and marls accumulation resulting from duplex structures and halite diapires. Positive gravity anomalies are caused by Carnbro-Ordovician materials, anhydrites, and basic volcanic rocks

Tesis doctoral: Estudio Gravimétrico del Pirineo Oriental

This dissertation is primarily a gravimetric study of Eastern Pyrenees based on gravity prospecting techniques combined with seismic reflection profiles, magnetic survey, and the existing bore-holes. The two main objectives of the study are interpret the gravity anomalies produced by superficial bodies and the anomalies produced by deep bodies in the area lying between the Segre River to the West, the Mediterranean Sea to the East, the city of Manresa to the South, and the city of Perpinyi to the North. The general disposition of these anomalies is composed of negative values in NW part of the studied zone and positive values along the coastline. This disposition is due to the enlarged upper crust under Pyrenean Axial Zone as a result of Iberian and European plates collision, and the thinning crust near the Coast To verify the existence of sorne of the anomalies, several macroscale maps of residual gravity anomalies of the area were compiled. The regional gravity component is assimilated to a second and third degree by polynomical surfaces. A residual isostatic map was also realised. Other smaller-scale maps were drawn up later because the use of lower-degree polynomes it is possible to obtain a more acceptable adjustment of regional-residual separation. After calculating gravity models in several zones, it was concluded that negative gravity anomalies are produced by Neogene materials landing in the Empordh and Cerdanya grabens, detritic Eocene materials in the Rocacorba area, and marls accumulation resulting from duplex structures and halite diapires. Positive gravity anomalies are caused by Carnbro-Ordovician materials, anhydrites, and basic volcanic rocks

Aportaciones de la prospección geofísica al estudio del subsuelo del Berguedà y Solsonés. (pre-Pirineo Catalán, N.E. de la Península Ibérica)

A combined gravity and seismic study of a sector located in the limit of the Pre-Pyrenees and Catalonian Central Depresión structural units is presented. Two sets of geophysical data are used: gravity and seismic reflection, which are complementary since one detects subhorizontal limits while the other serves to locate heterogeneous density masses. To emphasize the local gravity anomalies, a residual map was obtained by removing the regional field, which is best represented by a second order trend surface. The most prominent features of this map are the gravity lows aligned over anticline structures. Gravity modelling constrained by seismic reflexion data reveals the existence of a low density plastic marls tectonically acumulated on the nucleus of the anticlines

Aportaciones de la prospección geofísica al estudio del subsuelo del Berguedà y Solsonés. (pre-Pirineo Catalán, N.E. de la Península Ibérica)

A combined gravity and seismic study of a sector located in the limit of the Pre-Pyrenees and Catalonian Central Depresión structural units is presented. Two sets of geophysical data are used: gravity and seismic reflection, which are complementary since one detects subhorizontal limits while the other serves to locate heterogeneous density masses. To emphasize the local gravity anomalies, a residual map was obtained by removing the regional field, which is best represented by a second order trend surface. The most prominent features of this map are the gravity lows aligned over anticline structures. Gravity modelling constrained by seismic reflexion data reveals the existence of a low density plastic marls tectonically acumulated on the nucleus of the anticlines

Modelización gravimétrica 2D de la fosa de l'Empordà (NE de la Península Ibérica)

A gravimetric study of the Empordà Basin has been developed in this paper. Seismic reflection profiles and boreholes have furnished valuable data in order to build gravity models. The aim of this paper is the 2D modelling of the Empordà basin, and the calculation of neogene sediment thickness. 2D gravity profiles have been calculated parallel to the principal seismic lines

Estudio de viabilidad de canteras de yeso mediante tomografía eléctrica

La producción de yeso en España ha ido disminuyendo durante los últimos años; sin embargo, España sigue teniendo una posición destacada como productor mundial de yeso. Además, nuestro país se mantiene líder en Europa tanto a nivel de producción como de exportación de yeso (Marchan et al., 2010). Un factor importante a tener en cuenta durante la explotación de una cantera de yeso es la pureza y continuidad de los niveles estratigráficos que se explotan. En las campañas de prospección (previa o durante la explotación) es habitual el uso de sondeos (helicoidales o de testimonio continuo) para la valoración de los recursos. Esta técnica, sin embargo, es muy cara y aporta sólo información puntual

Modelización Gravimétrica 3D del diapiro de Cardona, Cuenca del Ebro (NE de España)

En este trabajo se presentan los resultados derivados de la interpretación de 320 estaciones gravimétricas realizadas sobre el diapiro de Cardona con el objetivo de obtener información sobre su geometría tridimensional. Para obtener una distribución tridimensional de la masa salina que explique las anomalías observadas se ha aplicado un método iterativo de ajustes sucesivos basado en un algoritmo de inversión automática. Esta metodología ha mostrado ser muy rápida, fácil de usar y con suficiente poder de resolución para perfilar no sólo la geometría del cuerpo salino, sino también la de estructuras similares. El diapiro salino de Cardona presenta un mínimo gravimétrico relacionado con el anticlinal de Pinòs-Cardona que se prolonga hacia el SW. El análisis cualitativo de la anomalía residual permite apreciar que el diapiro muestra una cierta vergencia hacia sur con un flanco sureste subvertical y un flanco noroeste con pendientes más suaves.The interpretation of more than 300 gravity stations over the Cardona salt diapir is presented. The aim of this study was to precise its 3D geometry. The Cardona salt diapir shows a gravity low related to the Pinòs-Cardona anticline that extends to the SW. A qualitative analysis of the anomaly pattern permits to recognise that the diapir displays a vergence to the south with gently dips to the north-west and a subvertical limb to the south-east. An iterative method was applied to get a 3D density distribution that explains the observed anomalies. This very fast and easy to use methodology has proved to have enough resolution for interpreting the external 3D geometry of the diapir, and will be useful to study similar structures

Geofísica ambiental: técnicas no destructivas para el reconocimiento de zonas contaminadas por vertidos

Industrial countries face the consequences of decades of inappropiate handling of hazardous waste. The dumping of al1 types of hazardous materials has been ongoing in most industrialised countries for hundreds of years. Large quantities of industrial and other waste material have been buried in landfill sites. A relatively large number of these lack reliable man-made or natural geological barriers and toxic fluids are scaping and polluting the groundwater. The problem is greatly aggravated when a soil covenng is placed over the waste and there is no information about the dumping practices used in the past. One of the first tasks in any remedial action is to delineate the physical extent of the sites and its encroachment into the surrounding area. Test borings and limited excavations are very valuable but the information obtained is not continuous and dheir destructive nature makes it possible that waste could inadvertently be released during the probing phase. In this regard, both borehole drilling and excavation are very dangerous to workers and the environment and expensive and tedious to conduct.Many of these problems may be alleviated by using a geophysical assisted system approach to determine where the pollutants will go in the subsurface, gain more complete understanding of site conditions and asses the optimal placement of exploration drills and monitonng wells. At hazardous waste sites, the main objectives must commonly include:- Determine the presence, location, distribution, depth and composition of possible buried wastes.- Determine the presence and extent of contaminant and leachate plumes within the unsaturated and saturated zones.- Characterise and asses the local (and regional) geohydrologic regime for groundwater flow paterns, recharge areas and localised permeable pathways

Modelización gravimétrica 2D de la fosa de l'Empordà (NE de la Península Ibérica)

El presente trabajo contiene un estudio gr avimétrico de la Depresión del Empordà, complementado con datos de sísmica de reflexión y sondeos. El objetivo es modelizar esta fosa utilizando las anomalías de la gravedad, para poder deducir la estructura neógena y la potencia de los materiales que la rellenan. Se han realizado modelos gr avimétricos 2D paralelos a los principales perfiles sísmicos existentes en la zona