Antonio Casas | University of Zaragoza (original) (raw)
Papers by Antonio Casas
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.
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Geologica Acta, 2014
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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.
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Journal of Geophysical Research, 1992
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Computers & Geosciences, 2014
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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...
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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.
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Geologica Acta, 2014
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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.
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Journal of Geophysical Research, 1992
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Computers & Geosciences, 2014
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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...
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