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

Prospección gravimétrica en el sistema transversal catalán

En el presente trabajo se plantea la elaboración e interpretación del mapa de anomalías de Bouguer del Sistema Transversal Catalán. La característica más destacada del mapa es el marcado dominio de la tendencia regional, producida por el aumento de grosor de la corteza terrestre hacia el NW. La sustracción de este efecto regional se ha realizado utilizando el método de ajuste a superficies polinómicas por mínimos cuadrados. La interpretación cuantitativa del mapa de anomalías residuales obtenido refleja la estructura en bloques del basamento.A Bouguer gravity anomaly may of the Transversal Subpirinean System is presented and interpreted. The most prominent feanire of the map is the strong regional effect produced by the Earth's crust thickening. The polinomial surface fit technique is used to substract this regional trend. The qualitative interpretation o£ the residual anomaly map obtained reflects a structure with block faulted basement

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.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

Quantification and Identification of Road Organic Matter in an Absorbing Storm Basin, RN 20 Olivet-Orléans, France.

The deterioration of the quality of superficial and subsurface waters by motorway organic pollution is a problem of great concern nowadays. The absorption of road runoff waters through sinkhole clay filled in a karstic area has been proposed as a way to the attenuation pollution. The groundwaters near of surface are very vulnerable at this pollution. The study of the storm basin of Belle-Croix (RN 20 Loiret) indicates a diminution of DOC levels through the first meter of infiltration in sinkhole, and then little change occurs down 5 meters. However only the > 10 KD (10 nm) organic fraction is retained. This fraction is weakly fluorescent and should correspond to black carbon (BC) matter associated to clays as it is suggested by Electron Microscopy in Transmission EMT observation. The < 10 KD fraction which are the more fluorescent account for up to 80 % of total DOC at 5 meter depth, at the contact with the limestone

Estructura y relleno sedimentario de la semifosa neógena de Vilanova (Garraf, Barcelona)

A joint study involving geological mapping, well subsurface data and gravity modelling has been carried out in the Vilanova half graben in order to define the substralum structure and the character of the sedimentary in fill.The half graben is oriented following a regional ENE-WSW fault direction. Its structure is controlled by normal faults along the NW boundary and by an unconformity in the SE basin boundary. A perpendicular to the main direction fault system, configurate a block shaped hasement. From the residual gravity map a 3D density model, constrained with the depths infered kom bore oles, has been obtained. The sedimentary infill has been divided in four litostratigraphic units. One of them constitutes a marginal complex associated and genetically related with the main faults that bound the basin. The otber three units show a vertical evolution from continental alluvial environrnent at the bottom to marine (littoral and restricted shelf-bay) at tbe top.The paleomastological data allow ps to attribute to the autcropping sedimentary infill a Serravallian age. Nevertheless, an Aquitanian-Early Burdigalian age to the basal conglomeratic unit can't be definitively rejected

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

Messinian salinity crisis impact on the groundwater quality in Kert aquifer NE Morocco: Hydrochemical and statistical approaches.

Groundwater's studies at middle Kert aquifer in northeast of Morocco are very important due to the semi-arid character and its geological history. The region is recognized by messinian salinity crisis already 5.6 Ma. Water chemistry is mainly dominated by dissolution of evaporate rocks (Halite and Gypsum) related to outcropping and basement limits developed in Messinian age. Freshwater with total dissolved solids 740 mg/l (average value) in Tafersite district is chemically distinct from saline water with total dissolved solids of 9803 mg/l in the south zone. In wadis, water is S04-Cl-Ca type; they are influenced by the surrounding highlands located at the south of the plain. The investigation reveals that weathering of evaporated rocks is the processes responsible for high Na+, Ca2+, Mg2+, Cl andSO42- concentrations. Also, hydro chemical data displays that freshwater observed in the northwest part reflect the influence of freshwaters coming from metamorphic massive of Temsamane. The factorial analysis reveal three sources of salinization, the principal one is described above, whilst the dissolution of carbonates and human influence represented by NO3- played only a secondary role

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

Geochemical exploration in the Montseny Mountains (NE Spain)

A five year program of systematic multi-element geochemical exploration of the Catalonian Coastal Ranges has been initiated by the Geological Survey of Autonomic Government of Catalonia (Generalitat de Catalunya) and the Department of Geological and Geophysical Exploration (University of Barcelona). This paper reports the first stage results of this regional survey, covering an area of 530 km2 in the Montseny Mountains, NE of Barcelona (Spain). Stream sediments for metals and stream waters for fluoride were chosen because of the regional characteristics. Four target areas for future tactic survey were recognized after the prospect. The most important is a 40 km* zone in the Canoves-Vilamajor area, with high base metal values accompanied by Cd, Ni, Co, As and Sb anomalie