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

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

Frequency-Domain Electromagnetic Mapping of an Abandoned Waste Disposal Site: A Case in Sardinia (Italy)

For decades, bad practices inmunicipal and industrial wastemanagement have had negative environmental impacts, generating high health risks for people and the environment. The use of badly designed, not engineered, and not well-operated landfills has, around the world, produced a large number of potentially contaminated sites, for which there are urgent needs to assess the actual risk and to proceed, in case, with reclamation activities. One of these sites, an abandoned waste disposal site located near a Site of Community Importance on the central-eastern coast of Sardinia (Italy), is the subject of the case history described in this work. As a part of a multi-method geophysical characterisation, a frequency-domain electromagnetic (FDEM) mapping survey was carried out with the specific aim of detecting the presence of buried materials (waste) and of delineating the lateral extent of the landfill by identifying the electrical conductivity anomalies produced, for the most part, by the conductive waste fill. Using an EM31 device in the vertical-dipole configuration, at a height of 0.9 m above the ground, both quadrature and in-phase electromagnetic responses were collected over a 7-hectare area with elevation varying between 6 m and 2.8 m above sea level. After removing the measurements identified as data coming from any recognisable surface man-made features within the survey area or near its perimeter, the filtered quadrature response (expressed as apparent conductivity) ranged from 5.5 mS/m to about 188.6 mS/m. All values are beyond the low induction number (LIN) condition and valid for the classical EM31 mapping, thus requiring advanced data processing. To obtain undistorted, meaningful, and interpretable high-resolution maps, measured data have been processed to correct the bias, introduced by the nonlinearity of the device, as a function of height above ground and the topography. The comparative analysis of the apparent conductivity map, obtained by the properly processed EM31 data and some aerial photos that clearly documented the site history, has allowed unequivocal delineation of the landfill extent, in good agreement with the results obtained with other geophysical methods (not described in this paper) and with the ground truthing data provided by three boreholes, which were core-drilled at the end of the study at three locations selected on the basis of the apparent conductivity map

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

Rainfall distribution and trends of the daily precipitation concentration index in northern Morocco: a need for an adaptive environmental policy

A national priority at the Moroccan level is to understand the spatiotemporal rainfall irregularity to anticipate suitable strategies for water and agriculture management. The most northern mountainous region shows intense sensitivity to extreme hydroclimatic hazards which may compromise the future of socioeconomic acceleration and further weaken environmental balances. However, planning and decision making require accurate data, on a detailed scale and with good spatial distribution which is not the case in several south-Mediterranean countries where rainfall data and/or well- established hydro-meteorological network is lacking. In this paper, abundant rain gauge measurements combined with time-series open data (1958-2015) were used to study the rainfall variability. Results show an annual rainfall increase trend since 1996 with frequent, intense and abundant rains causing violent torrents and floods. This humid trend alter- nates with short but severe dry periods. Spatial distribution shows a rainfall increase from eastern to western area and from the coastal plains to high mountains. Based on a continuous daily rainfall dataset (from 1988 to 2012) from six scat- tered stations, it appears that the pattern of heavy and extreme wet days takes the form of an irregular interannual cycle. Trends of the annual precipitation daily concentration indicate a significant positive trend in the center than in the East of the study area. Considering these observations, a review of water needs/obligations priorities seems crucial so that a new conscious and adaptative environmental policy would approve new procedures for a sustainable management