Detection of underground cavities by combining gravity,magnetic and ground penetrating radar surveys: a case study from the Zaragoza area,NE Spain

A geophysical survey routine is proposed to detect underground cavities and dolines; it is based on the sequential application of magnetic, low-frequency ground penetrating radar (GPR) and microgravity techniques. A case study near Zaragoza (Ebro valley, Spain) demonstrates the applicability of these methods. The strong contrast of magnetic and electromagnetic properties (and to a lesser scale, of density) between the doline filling and the surrounding stratified Tertiary and Quaternary rocks allows the shape of filled cavities to be clearly outlined by these methods.     

Measurement of the relative composition of the Cosmic-ray iron group with Lexan polycarbonate

Relative abundances for the VH group of Cosmic Radiation (20≤Z≤28) at energiesE≤600 MeV nucl^?1 have been measured by means of plastic detector LEXAN. The stack was exposed to cosmic rays during a 82 hr balloon flight at Sioux Falls (South Dakota) at an average altitude equivalent to 4 g cm^?2 of residual atmosphere. A total number of 1058 events have been analyzed, out of which 675 have been unambiguously identified. Two different discrimination methods have been applied in order to test their influence on final spectra. Extrapolation to the top of the atmosphere has been achieved in the frame of the regular model including an energy loss term that has led to corrections of the order of 60% in the extrapolated abundances. The relative abundances so obtained are in reasonable agreement with those reported by other authors using electronic detectors. Abnormal high abundances of manganese and cobalt can be attributed to wide temperature variations during the registration interval. In spite of the poor mass resolution, a high abundance of⁵⁴Fe has been evidenced, indicating a non-stellar origin for cosmic iron.     

Strata-bound As-Au mineralization in pre-Caradocian rocks from the Vall de Ribes,Eastern Pyrenees,Spain

In the lower part of a pre-Caradocian series associated with volcanics there are disseminations and lenses of arsenopyrite and pyrite with gold and Bi-Ag-Cu-Pb-Zn-W minerals. These ores are accompanied by veins and epigenetic masses of the same mineralogical composition. The disseminations are found in psammopelitic rhythmites and dolomites which also contain cmthick lenses. The epigenetic bodies, also enclosed in the rhythmites and dolomites, are interpreted as reconcentrations of preexisting disseminations and lenses caused by subsequent phases of deformation.     

Deep structure of the Betic Cordillera derived from the interpretation of a complete Bouguer anomaly map

A complete Bouguer-anomaly map of the Betic Cordillera and surrounding areas has been compiled from 2995 land-gravity observations. The measurements used to construct the map come from previous surveys as well as from a survey carried out specially for this project.A large negative anomaly reaching −145 mGal is centered on the intra-mountain basins of Loja-Granada and Baza-Guadix, and systematically displaced from the region of greatest topographic relief. This gravity low is interpreted as produced by the thickeming of the earth's crust at a principal contact between two domains of continental crust having different origins and geological evolution.Three gravity profiles selected to investigate the deep structure of the crust in the Betic Cordillera are presented and discussed.     

Non-invasive Geophysical Surveys in Search of the Roman Temple of Augustus Under the Cathedral of Tarragona (Catalonia,Spain): A Case Study

An integrated geophysical survey has been conducted at the Tarragona’s Cathedral (Catalonia, NE Spain) with the aim to confirm the potential occurrence of archaeological remains of the Roman Temple dedicated to the Emperor Augustus. Many hypotheses have been proposed about its possible location, the last ones regarding the inner part of the Cathedral, which is one of the most renowned temples of Spain (twelfth century) evolving from Romanesque to Gothic styles. A geophysical project including electrical resistivity tomography (ERT) and ground probing radar (GPR) was planned over 1 year considering the administrative and logistic difficulties of such a project inside a cathedral of religious veneration. Finally, both ERT and GPR have been conducted during a week of intensive overnight surveys that provided detailed information on subsurface existing structures. The ERT method has been applied using different techniques and arrays, ranging from standard Wenner–Schlumberger 2D sections to full 3D electrical imaging with the advanced Maximum Yield Grid array. Electrical resistivity data were recorded extensively, making available many thousands of apparent resistivity data to obtain a complete 3D image after a full inversion. In conclusion, some significant buried structures have been revealed providing conclusive information for archaeologists. GPR results provided additional information about shallowest structures. The geophysical results were clear enough to persuade religious authorities and archaeologists to conduct selected excavations in the most promising areas that confirmed the interpretation of geophysical data. In conclusion, the significant buried structures revealed by geophysical methods under the cathedral were confirmed by archaeological digging as the basement of the impressive Roman Temple that headed the Provincial Forum of Tarraco, seat of the Concilium of Hispania Citerior Province.     

New discoveries of mud volcanoes on the Moroccan Atlantic continental margin (Gulf of Cádiz): morpho-structural characterization

During the MVSEIS-08 cruise of 2008, ten new mud volcanoes (MVs) were discovered on the offshore Moroccan continental margin (Gulf of Cádiz) at water depths between 750 and 1,600?m, using multibeam bathymetry, backscatter imagery, high-resolution seismic and gravity core data. Mud breccias were recovered in all cases, attesting to the nature of extrusion of these cones. The mud volcanoes are located in two fields: the MVSEIS, Moundforce, Pixie, Las Negras, Madrid, Guadix, Almanzor and El Cid MVs in the western Moroccan field, where mud volcanoes have long been suspected but to date not identified, and the Boabdil and Al Gacel MVs in the middle Moroccan field. Three main morphologies were observed: asymmetric, sub-circular and flat-topped cone-shaped types, this being the first report of asymmetric morphologies in the Gulf of Cádiz. Based on morpho-structural analysis, the features are interpreted to result from (1) repeated constructive (expulsion of fluid mud mixtures) and destructive (gravity-induced collapse and submarine landsliding) episodes and (2) interaction with bottom currents.     

A comparison of sample handling and analytical methods for determination of acid volatile sulfides in sediment

Proper sample storage and analytical techniques are required when analyzing anoxic sediment for acid volatile sulfide (AVS), because a change in redox state may alter sediment parameters. The goal of this study was to determine the optimum sample handling, storage, and analytical techniques to adopt when determining AVS concentrations in sediment. To determine the correct handling and storage protocols for use with anoxic sediment, samples of three different AVS levels were manipulated under a combination of the following handling and storage plans: handled on benchtop or under nitrogen atmosphere; preserved with zinc acetate (ZnAc) or not preserved, and stored at 4 °C or frozen (< − 20 °C). The data indicate that sulfide levels are best maintained when samples are handled under a nitrogen atmosphere, stored at 4 °C or frozen, and analyzed within 2 weeks of collection. To determine the best analytical procedure for the determination of AVS in sediment, the following methods were compared: colorimetric, gravimetric, ion-selective electrode, and photoionization detection. The colorimetric method was preferred.     

Scientific management of Mediterranean coastal zone: a hybrid ocean forecasting system for oil spill and search and rescue operations

The oil spill from Prestige tanker showed the importance of scientifically based protocols to minimize the impacts on the environment. In this work, we describe a new forecasting system to predict oil spill trajectories and their potential impacts on the coastal zone. The system is formed of three main interconnected modules that address different capabilities: (1) an operational circulation sub-system that includes nested models at different scales, data collection with near-real time assimilation, new tools for initialization or assimilation based on genetic algorithms and feature-oriented strategic sampling; (2) an oil spill coastal sub-system that allows simulation of the trajectories and fate of spilled oil together with evaluation of coastal zone vulnerability using environmental sensitivity indexes; (3) a risk management sub-system for decision support based on GIS technology. The system is applied to the Mediterranean Sea where surface currents are highly variable in space and time, and interactions between local, sub-basin and basin scale increase the non-linear interactions effects which need to be adequately resolved at each one of the intervening scales. Besides the Mediterranean Sea is a complex reduced scale ocean representing a real scientific and technological challenge for operational oceanography and particularly for oil spill response and search and rescue operations.     

Rainfall spatial organization and areal reduction factors in the metropolitan area of Barcelona (Spain)

The rainfall spatial organization in the metropolitan area of Barcelona (Spain) has been studied from records of an urban rain gauge network in the period 1994–2009. Using statistical and regional analysis techniques, correlation between data recorded by the different rain gauges has been calculated, and the effective number of independent stations (n _eq) equivalent to the used network has been determined. It has been found out that for durations longer than 20 min, the areal rainfall return period observed for a storm registered by the network approximately decreases by a factor of 1/n _eq in relation to the current point rainfall intensity–duration–frequency relationships for the metropolitan area of Barcelona. Using objective analysis techniques, continuous precipitation fields have been generated on a regular grid with a spatial resolution of 300?×?300 m for the storms registered by the rain gauges from 1994 to 2009, for durations from 10 min to 24 h. The precipitation fields obtained have been useful to estimate the characteristic areal reduction factors in the metropolitan area of Barcelona. A direct relationship has been found between the areal reduction factor for all the area corresponding to the urban rainfall network of Barcelona and the effective number of n _eq for every duration considered.