Antonio M. Casas-Sainz

University of Zaragoza | UNIZAR · Department of Earth Sciences

From a 3-D reconstruction based on serial cross-sections, structural observations, and potential field geophysical data we characterize the major structural frame of the Moroccan Central High Atlas. Its overall structure shows two fold-and-thrust systems (each one showing particular features) at the northern and southern borders of the chain, resul...

Many works in the last decades underline the role of evaporites, not just as a conditioning factor but as the engine for subsidence and eventually basin inversion. The western Mediterranean alpine ranges are being investigated in this regard because of the presence of discontinuous units of Permian to Triassic evaporites, deposited in the western T...

A magnetic fabric study was carried out in Permo-Triassic continental sedimentary red beds from the Cadí Basin (Eastern Pyrenees). These rocks were deposited on the top of a volcanic sequence when the regional tectonic regime changed from transtension to extension. Standard paleomagnetic cores (cylinders), cubes and irregular fragments were obtaine...

Resumen El "túmulo" de La Llana de Hereña es una estructura de 90 metros de diámetro y 9,2 metros de altura que ocupa una superficie de unos 6.000 m 2. Se sitúa entre las pedanías de Caicedo Sopeña y Hereña (Ribera Alta, Álava). Tiene una forma circular con un pasillo perimetral que lo hace resaltar en el terreno de un modo singular como correspond...

La secuencia de desarrollo de estructuras en el sinclinal de Las Cuevas de Cañart (CC) (Zona de Enlace de la cordillera Ibérica), ofrece una oportunidad singular, para entender la distribución de mecanismos de deformación en cabalgamientos formados en niveles estructurales superficiales. La cuenca de CC contiene familias de estructuras con tres dir...

La zona de estudio, en las inmediaciones de La Seu d’Urgell (Zona Axial pirenaica), está constituida por una serie estratigráfica de rocas Cambro-Ordovícicas, en su mayoría detríticas, donde la discordancia Sarda se identifica claramente entre la Serie de Jujols y la Fm. Conglomerados de la Rabassa. Las principales estructuras son pliegues N-S de p...

We present a new cross-section across the Jaca basin in the southern Pyrenees, aiming to analyze the temporal and spatial distribution of deformation in a fold-and-thrust belt. In this study, we have integrated all available subsurface data, including seismic sections and well data, with surface data to construct a balanced cross-section and partia...

In this work, we present results of the application of paleomagnetism and the analysis of synsedimentary structures in order to clarify the age and origin of transversal anticlinal ridges in the northern border of the Central High Atlas (CHA). The results are interpreted in terms of paleogeometry of the main structures. The High Atlas fold-and-thru...

The purpose of this work is to use paleomagnetic data to determine the tectonic evolution of the inverted High Atlas basin in the area of the Taguelft syncline. This syncline shows two well defined rock types of Jurassic age: marly limestones and red beds, and therefore provides the opportunity of comparing paleomagnetic results from rocks with dif...

La Sierra de Cantabria y los Montes Obarenes suponen el límite meridional de la Cuenca Vasco-Cantábrica, cuya inversión tectónica se produjo como consecuencia de la Orogenia Alpina. En este estudio se presenta un análisis estructural de las principales estructuras de un sector de los Montes Obarenes, poniendo especial énfasis en la geometría y evol...

In this work we present three magnetic surveys in an intensively exploited agricultural area from Tuscania (Lazio region, Italy) whose soils are derived from volcanic rocks with different degrees of reworking, from weathering of the in situ rocks to sedimentary transport forming extensive piedmont deposits. Magnetic surveys were done with a GSM Ove...

During the Jurassic, Iberia and western North Africa underwent extensional tectonics conditioned by their position with respect to the African, Eurasian and North American plates and related to the Central and North Atlantic opening and westward expansion of the Tethys. In Iberia, the Jurassic is characterized by the presence of wide shallow marine...

The Devonian is a period of climatic and biodiversity changes and known "black shales" events that are linked with hypoxia/anoxia, eustatic fluctuations, faunal variations and geochemical anomalies. Magnetic susceptibility measurements are used as a complementary tool for correlation and more recently, as a tool for paleogeographic reconstructions...

In this work we present three magnetic surveys in an intensively exploited agricultural area from Tuscania (Lazio region, Italy) whose soils are derived from volcanic rocks with different degrees of reworking, from weathering of the in situ rocks to sedimentary transport forming extensive piedmont deposits. Magnetic surveys were done with a GSM Ove...

In this introductory chapter we summarize the geological evolution of the atlasic domain, making reference to many (not all) of the significant previous works carried out in the area. The geological setting of the Moroccan Central High Atlas is characterized by a complex Mesozoic-Cenozoic evolution that included (i) an extensional to transtensional...

From the application of the magnetic techniques (Anisotropy of Magnetic Susceptibility and paleomagnetism) it can be seen that to determine the age (and origin) of structures in the Moroccan Central High Atlas is not straightforward from geometrical features only and that similar structures can have different origins, or that the two limbs of a par...

The anisotropy of magnetic susceptibility provides valuable information on the imprint of the different tectonic processes occurred in the Central High Atlas (CHA), complementing the structural analysis and paleomagnetic information. Different types of magnetic ellipsoids, related with extensional, diapiric or intrusive processes occurred during th...

The so-called Henkel's plot (1976) allows relating density and magnetic susceptibility of rocks. In this work we focused on three paramagnetic Pyrenean granites from the Mont Louis-Andorra, Maladeta and Marimanha granitic plutons. In total, 128 sites with 310 density measurements and > 2600 susceptibility readings cover the main range of variabilit...

The Pyrenees constitutes an exceptional example of an Alpine orogenic belt characterized by basement thrust sheets involving Paleozoic rocks and Mesozoic and Cenozoic cover units detached on the Triassic evaporites, the main décollement level. This work is located in the Central Pyrenees, where gravity data help to better constrain the internal arc...

Centrifuge analog modeling incorporating thickness variations of décollement and overlying sedimentary cover is used to study thrust-wedge evolution on salt-detached contractional systems involving tapered sedimentary cover. From simpler, layer-cake to 3D tapered décollement-cover sequences, our models constrain wedge evolution: a more advanced fro...

The analysis of the Anisotropy of Magnetic Susceptibility (AMS) constitutes a fast and non-destructive technique that has gained the acceptance of structural geologists because it provides valuable information related to the orientation and intensity of the strain ellipsoid of deformed rocks. Part of its strength results from the possibility of (i)...

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...

A new gravity survey (1164 gravity stations and 180 samples for density analysis) combined with two new geological cross sections has been carried out in a sector of the Central Pyrenees in order to improve the characterization of basement and cover architecture. From North to South, the study area comprises the southern half of the Axial Zone and...

The aim of this work is the application of the anisotropy of magnetic susceptibility (AMS) to the study of volcanic materials from the Late Carboniferous-Permian Cadí basin (southern Pyrenees) in order to (i) explore the limits of this technique in ancient volcanic materials that have undergone strong chemical alteration and a complex tectonic evol...

In this work, we present new Bouguer and residual Bouguer anomaly maps of the Central Pyrenees calculated from 3590 stations, of which 1141 are new observations acquired from surveys performed between 2018 and 2019. The most prominent feature of the Bouguer anomaly is the long wavelength elongated minimum in its central part that continues to the W...

This paper presents a new approach based on Anisotropy of Magnetic Susceptibility, that aims to define the spatial evolution of deformation in shales through the analysis of non-oriented fragments. This technique facilitates and speeds up sampling and measurements, and consequently, hundreds of samples can be analyzed in a few weeks of work. The pr...

La modelización analógica de estructuras tectónicas ha permitido avanzar en el conocimiento de la cinemática de los sistemas de pliegues y cabalgamientos desarrollados en contextos compresivos, de los sistemas de fallas normales conjugadas y lístricas desarrolladas en contextos extensionales, así como de las estructuras asociadas a grandes fallas d...

Las relaciones geométricas y cinemáticas entre las unidades de basamento de los Pirineos Suroccidentales, específicamente entre la terminación de la Zona Axial y el afloramiento de los Macizos Vascos, son desconocidas y potencialmente muy complejas (Oliva-Urcia, 2018). La gravimetría se ha aplicado con éxito en otras regiones pirenaicas para resolv...

A short video (8 min) allows, on the one hand, to spread information and on the other hand to determine its educational purpose of the Pyrenean geology. The script is based on a dialogue between the Posets Mountain and a geologist who is sampling for studying its deformation. Concepts about geological time and paleogeographic reconstructions (Scote...

Magnetic fabric analyses are a fast and non-destructive method used to determine the fabric in rocks, since the first studies of magnetic fabric, a parallelism between the magnetic fabric and the rock fabric was observed. The mineral distribution in rocks is modified by stress. Magnetic fabric analyses in relation with deformation in folded rocks c...

The interfolding remagnetizations are those acquired between two deformational stages, and they are common in inverted sedimentary basins. They can be used as a tool to restore the structure at the remagnetization time (Villalaín et al., 2016). This technique is used in the Central High Atlas (Morocco) in the frame of the CGL2016-77560-C2-P researc...

To deal with magnetic modelling, remanent magnetization as well as susceptibility of the rocks that generate an induced magnetic field by the interaction with the Earth Magnetic field has to be addressed. In presence of primary and/or secondary fields, it is essential to consider the total magnetization as the sum of induced and remanent components...

The characterization of the basement architecture of the Pyrenean Axial Zone, backbone of the chain, is crucial to understand its geodynamic evolution and the interplay between tectonism and magmatism. In this work, a new gravity-constrained cross section was built along the Central Pyrenees, between two of the largest Pyrenean Late Variscan granit...

We introduce a field trip to the southwestern termination of the Pyrenean sole thrust: the Santo Domingo anticline. The field trip is articulated in three main stops with panoramic views. We pursue to emphasize some outstanding characteristics of this structure: (A) the large-scale progressive (laterally angular) unconformity that crops out in its...

Epiglyptic thrusts can be misinterpreted as paleolandslides since they underwent displacement on the Earth surface. The Daroca Thrust has been object of controversial interpretations owing to (i) the particular style of its frontal structure (a thin slab of Cambrian dolostones overthrusting syntectonic Miocene deposits), and (ii) its relatively you...

Resumen A pesar de sus modestas dimensiones y de su grado de deformación relativamente moderado, el Pirineo es una de las cordilleras más y mejor estudiadas del planeta. Por ello, la cadena constituye un ejemplo excelente para examinar la evolución de las teorías orogénicas en relación con la Tectónica de Placas. En este trabajo se exponen diferent...

The South Pyrenean triangle zone represents the southernmost front of the Pyrenees at its central portion deforming the Upper Eocene‐Miocene Ebro Basin deposits. Two main structures characterize its western termination, the Barbastro anticline and the San Román backthrust, which detached on the Barbastro Formation (and lateral equivalents), an Uppe...

The Small Circle (SC) tools analyse the stereographic tracks (small circles) followed by the palaeomagnetic vectors during folding processes. Working with interfolding and synfolding remagnetizations, the Small Circle Intersection (SCI) method allows finding the best solution of grouping that should correspond with the remagnetization direction. On...

The GeoPiri3D project aims to characterize the geometry and kinematics of the Permo-Carboniferous batholiths of the Central Pyrenees through a combination of potential fields and structural data. During 2018 we have acquired 824 new gravity stations and 186 rock samples. The gravity data were processed and integrated into the IGME database and a ne...

Geophysical surveying (both gravity and magnetic) is of great help in 3D modeling of granitic bodies at depth. As in any potential-field geophysics study, petrophysical data (density [r], magnetic susceptibility [k] and remanence) are of key importance to reduce the uncertainty during the modeling of rock volumes. Several works have already demonst...

Shear zones, or their counterparts in near-surface conditions, the brittle fault zones, constitute crustal-scale, narrow, planar domains where deformation is strongly localized. The variation with depth of deformation conditions (P-T), rheology and strain rates entails a wide range of fault rock types, characterized by different petrofabrics and cl...

The Jurassic carbonates of the Central High Atlas (CHA) are affected by a widespread and homogeneous chemical remagnetization. This is an interfolding remagnetization (dated in ca. 100 Ma by comparison with the GAPWP of the African plate) that separates two deformational events; the first one is related to the basinal period in the Atlas (Triassic...

The Atlas system, an ENE-WSW intracontinental chain in the NW of Africa, grew because of the inversion of Mesozoic extensional basins during the Cenozoic convergence between the African and European plates. The Central High Atlas (CHA) is located in the mid-western sector of the chain and is characterized by (i) the presence of an Upper Triassic dé...

New residual magnetic map is presented to help decipher the magnetic imprints in the Central High Atlas (CHA) fold-and-thrust belt. The total intensity map shows a main direction mimicking the N070 trend which features the Atlas range. Detailed structural and paleomagnetic studies performed in the selected area demonstrate that similar shortening f...

The aim of this work is to apply the anisotropy of magnetic susceptibility (AMS) to determine the primary and tectonic fabrics of lava flows and volcanoclastic materials in one of the Pyrenean Stephano-Permian basins. The Pyrenean Range is a double vergence orogen located at the northern end of the Iberian Peninsula. During Carboniferous-Early Perm...

Multiple constraints, including poorly known parameters, determine along-strike changes of frontal thrust structures in fold-and-thrust belts. Along the 400 km long, continuous Central Moroccan Atlas belt, structural style shows significant changes, preserving similar figures of shortening. This implies the absence of large-scale vertical-axes rota...

The Atlas system is an ENE-WSW intracontinental chain that extends from Morocco to Tunisia. It is the result of the Cenozoic inversion of a set of intraplate extensional basins that started its development during the Triassic and continued during the Jurassic. The Central High Atlas (CHA) is located at the Moroccan part of the Atlas System, charact...

A detailed magnetic survey combined with the study of magnetic properties and spectral analysis in the Tusculum archaeological site (Alban Hills, Italy) indicates the existence of magnetic anomalies (total field and gradient, showing amplitudes up to thousands of nT) resulting from combined geological and archaeological features. In this paper we p...

La caracterización de la fábrica constructiva de edificaciones previa a su restauración o evaluación de estabilidad requiere estudios históricos previos y análisis del estilo constructivo del momento de construcción. En ocasiones dicha información es limitada o requiere ser contrastada por métodos de caracterización directa. En este trabajo se abor...

Large‐scale faults in the continental crust are significant features that control the evolution of sedimentary basins and intraplate mountain chains. Deciphering their evolution is a significant task because faults slip and reactivate in a variety of geological settings. In this work, clay gouges of two major orogen‐scale, long‐lived faults in nort...

Resumen: En este trabajo se aplica el análisis de la anisotropía de la susceptibilidad magnética (ASM) con la finalidad de ayudar a descifrar la evolución mesozoica y cenozoica de un sector del Alto Atlas Central. El Atlas es la cadena intraplaca más importante del norte de África, resultado de una compleja evolución durante el Mesozoico y Cenozoic...

Resumen: El objetivo de este trabajo es identificar posibles correlaciones entre las propiedades petrofísicas del granito de Marimanha. Se han medido cuatro propiedades petrofísicas, densidad, velocidad sísmica, susceptibilidad magnética y resistividad. Estas propiedades son fundamentales en la prospección geofísica, y en la modelización de la estr...

Resumen: Las cuencas sedimentarias invertidas con un importante apilamiento de sedimentos presentan frecuentemente remagnetizaciones muy intensas y ubicuas que, en la mayoría de los casos, sustituyen la magnetización primaria en áreas muy extensas. El Atlas es una cadena intracontinental generada por la inversión de cuencas extensionales mesozoicas...

Resumen: La interacción de los fluidos con las rocas, tanto ígneas como metamórficas o sedimentarias, es responsable de numerosos procesos físico-químicos relacionados, por ejemplo, con transformaciones minerales, concentración de determinados elementos, remagnetizaciones, incrementos de temperatura y gradiente térmico, migración y maduración de hi...

Contractional deformation in the transition between the Iberian and Catalan Coastal Ranges (Linking Zone) generated both thin‐skinned structures detached in low‐strength Triassic units and basement‐involved structures. To evaluate their extent and relative contribution to the overall structure, we carried out a study combining structural geology an...

A global view of the Mesozoic-Cenozoic geodynamic evolution of the Iberian microplate is necessary to determine the role of inherited Variscan structures in the configuration of the Alpine Cycle. Furthermore, it is important to reconstruct the extensional Mesozoic geome

A global view of the Mesozoic-Cenozoic geodynamic evolution of the Iberian microplate is necessary to determine the role of inherited Variscan structures in the configuration of the Alpine Cycle. Furthermore, it is important to reconstruct the extensional Mesozoic geometries of the Iberian margins, presently inverted during the Cenozoic compression...

The interior of the Iberian Peninsula contains two types of Variscan crust: (i) unaffected or slightly affected by the Mesozoic extensional events related to the breakup of Pangea, and (ii) stretched during the Mesozoic and eventually thickened during the Alpine orogenesis. The Iberian Massif, the largest outcrop of the European Variscides, as well...

The Alpine orogeny is well recorded onshore and offshore by tectonic inversion of the Mesozoic rift basins. Large scale linear seamounts (more than 250 km long and with up to 5 km of uplift) involving oceanic and continental lithosphere were carried on top of thrusts, such as the Gorringe seamount and the Estremadura Spur in the SouthWest and West...

During the Late Jurassic and Early Cretaceous, Iberia experienced extensional and transtensional stresses leading to a complex rifting time interval. Africa–America–Europe relative motions determined the definition of the Iberian plate boundaries and the generation of rifted sedimentary basins and sub-basins along its continental margins and in the...

During the Triassic, Iberia and western North Africa displayed a unique situation in relation with the Central and North Atlantic opening and westward expansion of the Tethys. Unravelling the stretching direction in Triassic deposits of the studied area can help in our understanding of this scenario. The tectonic setting is characterized by localiz...

AMS and structural analysis are here applied to study the deformed zone associated with a large-scale, active normal fault in the central Betic Cordillera (Spain), namely the Baza fault system, to determine: i) the kinematics of structures and their relation with fault zone architecture and segmentation degree, ii) the correlation between deformati...

In the frame of the GEOPIRI3D Project (financed by the Spanish Ministry of Science, Innovation and University), two new gravity-constrained cross sections have been made. The goal of this study is to analyze the Axial Zone of the central part of the Pyrenees to better constrain the geometry of the basement host rocks and genesis of the Late Varisca...