Antonio Casas - Profile on Academia.edu (original) (raw)

Papers by Antonio Casas

Research paper thumbnail of Estructura y cinemátIca de los pliegues y cabalgamientos de Belchite-Sierra de Arcos (Cordillera Ibérica)

Journal of iberian geology: an international publication of earth sciences, 1999

El borde norte de la Cordillera Iberica en la region de Belchite-Sierra de Arcos presenta un conj... more El borde norte de la Cordillera Iberica en la region de Belchite-Sierra de Arcos presenta un conjunto de pliegues y cabalgamientos de direccion E-O y NO-SE originados por un acortamiento regional N-S a NNE-SSO durante el Terciario. Las estructuras de la cobertera estan controladas por la orientacion de pliegues y fallas en el zocalo hercinico y por la existencia de niveles de despegue de caracter regional. El anticlinal de Belchite se situa sobre un anticlinal del zocalo que limita por el NE la cubeta terciaria de Azuara, la cual constituye un amplio sinclinal (o sinclinorio) de origen compresivo. Los pliegues y cabalgamientos que aparecen entre el anticlinal paleozoico de Montalban y la Sierra de Arcos son el resultado de la inversion positiva durante el Terciario de fallas extensionales mesozoicas, que actuaron al menos durante el Cretacico Inferior, o corresponden a cabalgamientos nucleados en escalones de zocalo creados por algunas de estas fallas.

Research paper thumbnail of Reverse magnetic anomaly controlled by Permian igneous rocks in the NE Iberian Chain (N Spain)

Geologica Acta, 2014

Two important reverse dipolar magnetic anomalies in the Iberian Chain (Spain) are located over Pe... more Two important reverse dipolar magnetic anomalies in the Iberian Chain (Spain) are located over Permian igneous rocks. A detailed study of one of them, the Loscos magnetic anomaly, where the geological structure is well constrained, reveals that the source of the anomaly must be a reverse remanent magnetisation carried by igneous rocks, acquired during the period of the Kiaman reverse magnetic superchron. Magnetic and gravimetric detailed survey (with 50 new gravimetric measurements and 8 main magnetic profiles-six of them N-S and the rest E-Wwith a total length of 40km), together with a study of the petrophysical characteristics of igneous materials, data processing and interpretation (upward continuation, 2.5D modelling, etc.) allowed to characterize qualitatively the anomaly and its source. Two overlapping anomalies with different wavelength were identified, indicating the presence of a shallower strongly altered igneous body with heterogeneous magnetic properties, and a deeper, large igneous body, responsible for the main, long-wavelength anomaly.

Research paper thumbnail of yRdiagram User'sGuide

Research paper thumbnail of El Pirineo, territorio afectado por el Plan Hidrológico Nacional

El Pirineo, territorio afectado por el Plan Hidrológico Nacional

Research paper thumbnail of Estructura y cinemática del sector occidental de las Sierras Marginales (Unidad Surpirenaica Central)

In this work we address the study of the geological structure of the area located at the western ... more In this work we address the study of the geological structure of the area located at the western end of the Sierras Marginales thrust sheet (South Pyrenean Central Unit, South Pyrenean Zone). A structural contour map, based on detailed geological mapping and seriated, balanced cross sections has been built. Two main domains (northern and southern), with different vergence of structures (North and South, respectively) can be recognized. Locally, diapiric structures pierce the Mesozoic-Tertiary cover. The relation between syntectonic Oligocene-Miocene deposits and the rest of the sedimentary cover allow establishing a relative timing of the emplacement of structures, which include thrusts, backthrusts, out-of-sequence thrusts, strikeslip faults and diapirs.

Research paper thumbnail of La Geología es noticia_A 50 años de la catástrofe de Vajont: Riesgos de deslizamiento en el embalse de Yesa

La Geología es noticia_A 50 años de la catástrofe de Vajont: Riesgos de deslizamiento en el embalse de Yesa

Research paper thumbnail of Folded Variscan duplex in the Herrera Unit of the Iberian Range

Folded Variscan duplex in the Herrera Unit of the Iberian Range

ABSTRACT The Herrera Unit is located in the central sector of the Aragonese Branch of the Iberian... more ABSTRACT The Herrera Unit is located in the central sector of the Aragonese Branch of the Iberian Range (Zaragoza-Teruel). This unit constitutes the NE limb of a kilometric scale Variscan major anticline, with a predominant NW-SE to NNW-SSE trend and NE vergence. In its SW limb the Badules Unit crops out. The Datos thrust, a first order structure, superimposes the Badules unit onto the Herrera unit. Cambrian to Ordovician materials compose its hanging-wall, whereas Upper Cambrian to Devonian materials appear in its foot-wall. In this footwall a 4000 m thick series, essentially detrital, with Silurian and Devonian carbonate levels can be seen. South of the studied zone, the Lower Cambrian (Badules Unit) thrust over the Devonian (Herrera Unit). The Herrera Unit is characterized by thin-skinned tectonics involving two detachment levels: the lower one is constituted by Precambrian shales, and the upper one by Upper Silurian shales. The Silurian level, more than 1000 m thick, separates two structural levels with different deformation styles. In the Cambrian to Silurian materials that form the lowermost structural level, a duplex system characterizes the general structure, related to both detachment levels, with intermediate minor detachments. The East dipping thrusts could probably be the result of folded and tilted thrusts with eastward vergence, according to the general Variscan trend. This folding could be associated either with the late stages of the Datos thrust or represent the front of an antiformal stack. This structural configuration could also be explained by a backthrust system. A well developed cleavage (S1) affects the whole Cambrian to Silurian series and a second cleavage (S2) locally appears. The main system is an axial plane cleavage related to NNW-SSE folds, with a dominant East vergence and SSE plunge. Slaty cleavage appears in pelitic levels and fracture cleavage in sandstones. Depending on the spatial relation with the thrust, the upper detachment level shows different deformation styles attending to cleavage type and fold geometry. In general, NNW-SSE crenulation cleavage appears due to a previous sedimentary planar anisotropy. The Devonian, upper structural level is characterized by E.verging, NNW-SSE thrust and fault-related folds with axial plane cleavage.

Research paper thumbnail of Stress deflection in a tectonic compressional field: A model for the northwestern Iberian Chain, Spain

Journal of Geophysical Research, 1992

By means of fault population analysis (using the right dihedra, y-R diagram and Etchecopar's meth... more By means of fault population analysis (using the right dihedra, y-R diagram and Etchecopar's methods), the states of stress in a number of sites of the Cameros Massff (Northwestern Iberian Chain, Spain) and nearby areas of the Ebro Basin have been determined. These states of stress have been used as a framework in order to infer a model of the actual stress field in that area during the main stage of the Alpine compression (Oligocene-lower Miocene). The three main compression directions obtained (NW-SE, NNE, NE-SW)can be explained by a single compression field with horizontal o, trending NNE and vertical 02, whose primary trajectories are deflected due to (1) largescale strike-slip faults or lateral ramps of thrusts or (2) frontal ramps of thrusts oblique to the main compressire axis. The reliability of this scheme has been checked by means of a two-dimensional mathematical model based upon the finite element method and applied on a sheet whose theological properties are similar to those of a standard limestone. This model simulates the main features of the regional stress field, and it was constructed after determining the average parameters of the possible external or "primary" field and simulating the major faults that could deflect the stress trajectories. INTRODUCTION Palaeostresses can be determined by means of analysis of fault populations on an outcrop scale. Several methods for this kind of analysis have been performed in the last l0 years [

Research paper thumbnail of y-gRaph: An OpenOffice application to reconstruct paleostress fields from striated faults

Computers & Geosciences, 2014

y-gRaph, a user-friendly spreadsheet for reconstructing paleostress fields by means of the y-R di... more y-gRaph, a user-friendly spreadsheet for reconstructing paleostress fields by means of the y-R diagram is presented. The y-R diagram is based on Bott's equation and translates the parameters of the stress ellipsoid to a XY plot representing the maximum horizontal stress orientation (s y) and the stress ratio (R), compatible with a given set of striated faults. In cases where several stress tensors fit the dataset, y-R diagram aids in visualizing unrealistic solutions or changes in the stress field with time. Furthermore, the spreadsheet allows to rotate planes and lines, thus simplifying the work with tilted fault populations. Histograms and rose diagrams showing the strike of faults and the trend of striae complement the y-gRaph main output. The application was built using Apache OpenOffice software and supports a variety of input data formats: (i) strike, dip and dip direction (SDD), (ii) azimuth and dip (AD) according to the "Right-hand rule", and (iii) dip and dip direction (DD).

Research paper thumbnail of Evolución tectónica de un sector del borde N de la Cadena Ibérica (provincia de Teruel)

Evolución tectónica de un sector del borde N de la Cadena Ibérica (provincia de Teruel)

Research paper thumbnail of El deslizamiento rotacional de 1970 en Tudela (Navarra): análisis geométrico y de estabilidad

El deslizamiento rotacional de 1970 en Tudela (Navarra): análisis geométrico y de estabilidad

Research paper thumbnail of El valle del Yaracuy (límite S de la placa Caribe, Venezuela): ejemplo de cuenca cuaternaria asociada a una curvatura de falla

El valle del Yaracuy (límite S de la placa Caribe, Venezuela): ejemplo de cuenca cuaternaria asociada a una curvatura de falla

Research paper thumbnail of La fracturación distensiva cuaternaria en el sector occidental de la Cuenca del Ebro

La fracturación distensiva cuaternaria en el sector occidental de la Cuenca del Ebro

Research paper thumbnail of The Role of Backstop Thickness Lateral Variations on the Tectonic Architecture of Orogens: An Experimental Approach and Comparison with the Pyrenees

The Role of Backstop Thickness Lateral Variations on the Tectonic Architecture of Orogens: An Experimental Approach and Comparison with the Pyrenees

Research paper thumbnail of Modelling the geometry of inverted basins by means of paleomagnetic studies. Examples from the Iberian Ranges and Basque-Cantabrian basin (Northern Spain)

Modelling the geometry of inverted basins by means of paleomagnetic studies. Examples from the Iberian Ranges and Basque-Cantabrian basin (Northern Spain)

Research paper thumbnail of Comparison between extensional AMS ellipsoids and brittle mesostructures in the Basque-Cantabrian basin (N Spain)

Comparison between extensional AMS ellipsoids and brittle mesostructures in the Basque-Cantabrian basin (N Spain)

Research paper thumbnail of Geometry of the Naval diapir (western end of the Sierras Marginales, Southern Pyrenees), based on gravimetric, surface and seismic data

Geometry of the Naval diapir (western end of the Sierras Marginales, Southern Pyrenees), based on gravimetric, surface and seismic data

Research paper thumbnail of Reactivación alpina de pliegues y fallas del zócalo hercínico de la Cordillera Ibérica: ejemplos de la Sierra de la Demanda y la Serranía de Cuenca

Reactivación alpina de pliegues y fallas del zócalo hercínico de la Cordillera Ibérica: ejemplos de la Sierra de la Demanda y la Serranía de Cuenca

Research paper thumbnail of Petrophysical Characterization of Non-Magnetic Granites; Density and Magnetic Susceptibility Relationships

Geosciences

In this work we establish reliable correlations between density and magnetic susceptibility in th... more In this work we establish reliable correlations between density and magnetic susceptibility in three paramagnetic granites from the Pyrenees. In total, 128 sites (310 density measurements and >2600 susceptibility ones) were studied in the Mont Louis-Andorra, Maladeta and Marimanha granitic plutons covering the main range of variability of magnetic susceptibility. Regressions were calculated for every granitic body and an integrated linear function was obtained for the entire dataset: ρ (kg/m3) = 2566 (kg/m3) + 0.541κ (10−6 S.I.) (R:0.97). This relationship is only valid in the paramagnetic domain, where iron is mostly fractioned in iron-bearing phyllosilicates and the occurrence of magnetite is negligible (or at least its contribution to the bulk susceptibility). This relationship, likely different in other bodies, allows for transforming magnetic susceptibility data into density data, helping to constrain gravity modelling when density data from rock samples are scarce. Given th...

Research paper thumbnail of De la gran urbe a la modesta villa: aplicación de la prospección magnética a la arqueología romana

Research paper thumbnail of Estructura y cinemátIca de los pliegues y cabalgamientos de Belchite-Sierra de Arcos (Cordillera Ibérica)

Journal of iberian geology: an international publication of earth sciences, 1999

El borde norte de la Cordillera Iberica en la region de Belchite-Sierra de Arcos presenta un conj... more El borde norte de la Cordillera Iberica en la region de Belchite-Sierra de Arcos presenta un conjunto de pliegues y cabalgamientos de direccion E-O y NO-SE originados por un acortamiento regional N-S a NNE-SSO durante el Terciario. Las estructuras de la cobertera estan controladas por la orientacion de pliegues y fallas en el zocalo hercinico y por la existencia de niveles de despegue de caracter regional. El anticlinal de Belchite se situa sobre un anticlinal del zocalo que limita por el NE la cubeta terciaria de Azuara, la cual constituye un amplio sinclinal (o sinclinorio) de origen compresivo. Los pliegues y cabalgamientos que aparecen entre el anticlinal paleozoico de Montalban y la Sierra de Arcos son el resultado de la inversion positiva durante el Terciario de fallas extensionales mesozoicas, que actuaron al menos durante el Cretacico Inferior, o corresponden a cabalgamientos nucleados en escalones de zocalo creados por algunas de estas fallas.

Research paper thumbnail of Reverse magnetic anomaly controlled by Permian igneous rocks in the NE Iberian Chain (N Spain)

Geologica Acta, 2014

Two important reverse dipolar magnetic anomalies in the Iberian Chain (Spain) are located over Pe... more Two important reverse dipolar magnetic anomalies in the Iberian Chain (Spain) are located over Permian igneous rocks. A detailed study of one of them, the Loscos magnetic anomaly, where the geological structure is well constrained, reveals that the source of the anomaly must be a reverse remanent magnetisation carried by igneous rocks, acquired during the period of the Kiaman reverse magnetic superchron. Magnetic and gravimetric detailed survey (with 50 new gravimetric measurements and 8 main magnetic profiles-six of them N-S and the rest E-Wwith a total length of 40km), together with a study of the petrophysical characteristics of igneous materials, data processing and interpretation (upward continuation, 2.5D modelling, etc.) allowed to characterize qualitatively the anomaly and its source. Two overlapping anomalies with different wavelength were identified, indicating the presence of a shallower strongly altered igneous body with heterogeneous magnetic properties, and a deeper, large igneous body, responsible for the main, long-wavelength anomaly.

Research paper thumbnail of yRdiagram User'sGuide

Research paper thumbnail of El Pirineo, territorio afectado por el Plan Hidrológico Nacional

El Pirineo, territorio afectado por el Plan Hidrológico Nacional

Research paper thumbnail of Estructura y cinemática del sector occidental de las Sierras Marginales (Unidad Surpirenaica Central)

In this work we address the study of the geological structure of the area located at the western ... more In this work we address the study of the geological structure of the area located at the western end of the Sierras Marginales thrust sheet (South Pyrenean Central Unit, South Pyrenean Zone). A structural contour map, based on detailed geological mapping and seriated, balanced cross sections has been built. Two main domains (northern and southern), with different vergence of structures (North and South, respectively) can be recognized. Locally, diapiric structures pierce the Mesozoic-Tertiary cover. The relation between syntectonic Oligocene-Miocene deposits and the rest of the sedimentary cover allow establishing a relative timing of the emplacement of structures, which include thrusts, backthrusts, out-of-sequence thrusts, strikeslip faults and diapirs.

Research paper thumbnail of La Geología es noticia_A 50 años de la catástrofe de Vajont: Riesgos de deslizamiento en el embalse de Yesa

La Geología es noticia_A 50 años de la catástrofe de Vajont: Riesgos de deslizamiento en el embalse de Yesa

Research paper thumbnail of Folded Variscan duplex in the Herrera Unit of the Iberian Range

Folded Variscan duplex in the Herrera Unit of the Iberian Range

ABSTRACT The Herrera Unit is located in the central sector of the Aragonese Branch of the Iberian... more ABSTRACT The Herrera Unit is located in the central sector of the Aragonese Branch of the Iberian Range (Zaragoza-Teruel). This unit constitutes the NE limb of a kilometric scale Variscan major anticline, with a predominant NW-SE to NNW-SSE trend and NE vergence. In its SW limb the Badules Unit crops out. The Datos thrust, a first order structure, superimposes the Badules unit onto the Herrera unit. Cambrian to Ordovician materials compose its hanging-wall, whereas Upper Cambrian to Devonian materials appear in its foot-wall. In this footwall a 4000 m thick series, essentially detrital, with Silurian and Devonian carbonate levels can be seen. South of the studied zone, the Lower Cambrian (Badules Unit) thrust over the Devonian (Herrera Unit). The Herrera Unit is characterized by thin-skinned tectonics involving two detachment levels: the lower one is constituted by Precambrian shales, and the upper one by Upper Silurian shales. The Silurian level, more than 1000 m thick, separates two structural levels with different deformation styles. In the Cambrian to Silurian materials that form the lowermost structural level, a duplex system characterizes the general structure, related to both detachment levels, with intermediate minor detachments. The East dipping thrusts could probably be the result of folded and tilted thrusts with eastward vergence, according to the general Variscan trend. This folding could be associated either with the late stages of the Datos thrust or represent the front of an antiformal stack. This structural configuration could also be explained by a backthrust system. A well developed cleavage (S1) affects the whole Cambrian to Silurian series and a second cleavage (S2) locally appears. The main system is an axial plane cleavage related to NNW-SSE folds, with a dominant East vergence and SSE plunge. Slaty cleavage appears in pelitic levels and fracture cleavage in sandstones. Depending on the spatial relation with the thrust, the upper detachment level shows different deformation styles attending to cleavage type and fold geometry. In general, NNW-SSE crenulation cleavage appears due to a previous sedimentary planar anisotropy. The Devonian, upper structural level is characterized by E.verging, NNW-SSE thrust and fault-related folds with axial plane cleavage.

Research paper thumbnail of Stress deflection in a tectonic compressional field: A model for the northwestern Iberian Chain, Spain

Journal of Geophysical Research, 1992

By means of fault population analysis (using the right dihedra, y-R diagram and Etchecopar's meth... more By means of fault population analysis (using the right dihedra, y-R diagram and Etchecopar's methods), the states of stress in a number of sites of the Cameros Massff (Northwestern Iberian Chain, Spain) and nearby areas of the Ebro Basin have been determined. These states of stress have been used as a framework in order to infer a model of the actual stress field in that area during the main stage of the Alpine compression (Oligocene-lower Miocene). The three main compression directions obtained (NW-SE, NNE, NE-SW)can be explained by a single compression field with horizontal o, trending NNE and vertical 02, whose primary trajectories are deflected due to (1) largescale strike-slip faults or lateral ramps of thrusts or (2) frontal ramps of thrusts oblique to the main compressire axis. The reliability of this scheme has been checked by means of a two-dimensional mathematical model based upon the finite element method and applied on a sheet whose theological properties are similar to those of a standard limestone. This model simulates the main features of the regional stress field, and it was constructed after determining the average parameters of the possible external or "primary" field and simulating the major faults that could deflect the stress trajectories. INTRODUCTION Palaeostresses can be determined by means of analysis of fault populations on an outcrop scale. Several methods for this kind of analysis have been performed in the last l0 years [

Research paper thumbnail of y-gRaph: An OpenOffice application to reconstruct paleostress fields from striated faults

Computers & Geosciences, 2014

y-gRaph, a user-friendly spreadsheet for reconstructing paleostress fields by means of the y-R di... more y-gRaph, a user-friendly spreadsheet for reconstructing paleostress fields by means of the y-R diagram is presented. The y-R diagram is based on Bott's equation and translates the parameters of the stress ellipsoid to a XY plot representing the maximum horizontal stress orientation (s y) and the stress ratio (R), compatible with a given set of striated faults. In cases where several stress tensors fit the dataset, y-R diagram aids in visualizing unrealistic solutions or changes in the stress field with time. Furthermore, the spreadsheet allows to rotate planes and lines, thus simplifying the work with tilted fault populations. Histograms and rose diagrams showing the strike of faults and the trend of striae complement the y-gRaph main output. The application was built using Apache OpenOffice software and supports a variety of input data formats: (i) strike, dip and dip direction (SDD), (ii) azimuth and dip (AD) according to the "Right-hand rule", and (iii) dip and dip direction (DD).

Research paper thumbnail of Evolución tectónica de un sector del borde N de la Cadena Ibérica (provincia de Teruel)

Evolución tectónica de un sector del borde N de la Cadena Ibérica (provincia de Teruel)

Research paper thumbnail of El deslizamiento rotacional de 1970 en Tudela (Navarra): análisis geométrico y de estabilidad

El deslizamiento rotacional de 1970 en Tudela (Navarra): análisis geométrico y de estabilidad

Research paper thumbnail of El valle del Yaracuy (límite S de la placa Caribe, Venezuela): ejemplo de cuenca cuaternaria asociada a una curvatura de falla

El valle del Yaracuy (límite S de la placa Caribe, Venezuela): ejemplo de cuenca cuaternaria asociada a una curvatura de falla

Research paper thumbnail of La fracturación distensiva cuaternaria en el sector occidental de la Cuenca del Ebro

La fracturación distensiva cuaternaria en el sector occidental de la Cuenca del Ebro

Research paper thumbnail of The Role of Backstop Thickness Lateral Variations on the Tectonic Architecture of Orogens: An Experimental Approach and Comparison with the Pyrenees

The Role of Backstop Thickness Lateral Variations on the Tectonic Architecture of Orogens: An Experimental Approach and Comparison with the Pyrenees

Research paper thumbnail of Modelling the geometry of inverted basins by means of paleomagnetic studies. Examples from the Iberian Ranges and Basque-Cantabrian basin (Northern Spain)

Modelling the geometry of inverted basins by means of paleomagnetic studies. Examples from the Iberian Ranges and Basque-Cantabrian basin (Northern Spain)

Research paper thumbnail of Comparison between extensional AMS ellipsoids and brittle mesostructures in the Basque-Cantabrian basin (N Spain)

Comparison between extensional AMS ellipsoids and brittle mesostructures in the Basque-Cantabrian basin (N Spain)

Research paper thumbnail of Geometry of the Naval diapir (western end of the Sierras Marginales, Southern Pyrenees), based on gravimetric, surface and seismic data

Geometry of the Naval diapir (western end of the Sierras Marginales, Southern Pyrenees), based on gravimetric, surface and seismic data

Research paper thumbnail of Reactivación alpina de pliegues y fallas del zócalo hercínico de la Cordillera Ibérica: ejemplos de la Sierra de la Demanda y la Serranía de Cuenca

Reactivación alpina de pliegues y fallas del zócalo hercínico de la Cordillera Ibérica: ejemplos de la Sierra de la Demanda y la Serranía de Cuenca

Research paper thumbnail of Petrophysical Characterization of Non-Magnetic Granites; Density and Magnetic Susceptibility Relationships

Geosciences

In this work we establish reliable correlations between density and magnetic susceptibility in th... more In this work we establish reliable correlations between density and magnetic susceptibility in three paramagnetic granites from the Pyrenees. In total, 128 sites (310 density measurements and >2600 susceptibility ones) were studied in the Mont Louis-Andorra, Maladeta and Marimanha granitic plutons covering the main range of variability of magnetic susceptibility. Regressions were calculated for every granitic body and an integrated linear function was obtained for the entire dataset: ρ (kg/m3) = 2566 (kg/m3) + 0.541κ (10−6 S.I.) (R:0.97). This relationship is only valid in the paramagnetic domain, where iron is mostly fractioned in iron-bearing phyllosilicates and the occurrence of magnetite is negligible (or at least its contribution to the bulk susceptibility). This relationship, likely different in other bodies, allows for transforming magnetic susceptibility data into density data, helping to constrain gravity modelling when density data from rock samples are scarce. Given th...

Research paper thumbnail of De la gran urbe a la modesta villa: aplicación de la prospección magnética a la arqueología romana