Diachronous folding and cleavage in an intraplate setting (Central High Atlas, Morocco) determined through the study of remagnetizations

Remagnetizations are common in intraplate basins. When remagnetizations occur at an intermediate stage between different tectonic processes, they can be used for paleo-geometrical reconstructions and relative dating of different structures. This has a particular interest in geological frameworks where other geological time markers are absent. In order to apply this methodology, it is necessary to calculate the regional remagnetization direction and subsequently to use this reference direction to restore the attitude of the beds at the moment of remagnetization acquisition. In this work, we use this methodology for dating a pervasive cleavage (whose time of formation is controversial) and the associated structures in the Central High Atlas (Morocco). Paleomagnetic directions from 64 sites were used to calculate the remagnetization direction (D = 330.9°, I = 35.1°, A/n = 6.107) which is coincident with the Albian-Cenomanian (ca. 100 M.a.) expected direction for NW Africa. This direction was used to restore the Mesozoic paleo-geometry of beds allowing us to analyze bedding orientation, cleavage and folding relationships between the present day and the Cretaceous geometry. After restoration we conclude that the development of cleavage post-dates remagnetization, being in relation with Cenozoic basin inversion. However, the paleo-geometry shows incipient folds at Cretaceous times, which can be related to an intra-Mesozoic compressional event

Unraveling Multiple Thermotectonic Events Accommodated by Crustal\u2010Scale Faults in Northern Iberia, Spain: Insights From K-Ar Dating of Clay Gouges

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 northern Iberia, the Río Grío and Vallès-Penedès Faults, were investigated by X-ray diffraction and K-Ar isotopic analysis. Illite polytype determinations of 44 subfractions (from <0.1 to 10 Œºm) allowed us to discriminate between authigenic/synkinematic illite crystals formed during faulting and detrital illite crystals inherited from the host rock. K-Ar dating provided a detailed set of ages corresponding to key stages of the thermotectonic evolution of the Iberian Plate: (a) the Permian to Late Triassic extensional/transtensional activity associated to the emplacement of Late Variscan magmatic bodies and hydrothermal mineralizations, (b) the opening of the Central Atlantic Rift during Late Triassic-Early Jurassic times, (c) the Late Jurassic-Early Cretaceous rifting that led to the development of Mesozoic extensional/transtensional basins in northern Iberia, (d) the final stage of the anticlockwise rotation of the Iberian Plate with respect to Eurasia and the accommodation of the first Pyrenean compressional pulses in Campanian time, and (e) the positive inversion of Mesozoic extensional basins due to far-field stresses associated with the Alpine orogeny during the Paleogene. The results highlight that thermotectonic conditions characterized by high-geothermal gradients strongly favor fault movement and neoformation of clay minerals in fault gouges, regardless of the prevailing tectonic regime

El embalse de Mularroya (Zaragoza): problemas geológicos de una obra en avanzado estado de construcción.

El embalse de Mularroya (más de 100 hm3 de capacidad), situado sobre el cauce del río Grío, uno de los afluentes del Jalón (afluente a su vez del Ebro por su margen derecha) es una obra en avanzado estado de construcción. Desde la fase de estudios previos (mediados de los años 90) hasta la actualidad, se han constatado problemas geológicos que ponen en entredicho la oportunidad de la realización de esta obra píblica. En este trabajo se revisan y se aportan nuevos datos sobre los problemas más significativos: (i) más de 1/5 de la superficie del vaso del embalse se asienta sobre unidades carbonatadas permeables del acuífero regional de las unidades del tránsito Triásico-Jurásico (formaciones Imón, Cortes de Tajuña y Cuevas Labradas), que forman una estructura sinclinal con inmersión NNO; (ii) su situación sobre un cauce cuya aportación anual es 20% la capacidad del embalse, lo que requiere el trasvase de agua desde el río Jalón por un tínel de desviación que atraviese estructuras complejas del macizo paleozoico que constituye la Rama Aragonesa de la Cordillera Ibérica; y (iii) los riesgos geológicos que conlleva, fundamentalmente por su localización sobre el sistema de fallas de río Grío, que incluye varios segmentos activos durante el Cuaternario capaces de generar sismos de magnitud entre 6,2 y 6,8. De acuerdo con la simulación realizada mediante el programa IBER, el riesgo de inundación asociado a un posible fallo geotécnico de la presa afectaría significativamente a poblaciones importantes, como Ricla o Calatorao, situadas aguas abajo de la presa. In this work we analyze the geological hazard associated with the Mularroya reservoir (whose total volume is more than 100 hm(3)), located on the Grio river, a tributary of the Jalon river, one of the right-bank main tributaries of the Ebro river. Its construction, about to be finished, is problematic because of (i) the particular geological setting of the reservoir, located on the permeable carbonate units belonging to the Triassic-Jurassic transition (Imon, Cortes de Tajuna and Cuevas Labradas formations), defining a NNW-plunging syncline; (ii) its location on a river whose streamflow per year is 20% of the total reservoir volume, thus needing a gravity fed tunnel from the Jalon river cutting accross complex structures of the Paleozoic massifs of the Aragonian Branch of the Iberian Chain; and (iii) geological risks associated with its particular location, close to the rio Grio fault system, that includes faults that were active during the Quaternary, and are able to generate earthquakes with magnitudes 6.2-6.8. According to our simulations by means of IBER program, flooding risk associated with a possible geotechnical fault of the Mularroya dam would cause severe damage in villages located downstream (Ricla and Calatorao)

Multidisciplinary approach to constrain kinematics of fault zones at shallow depths: a case study from the Cameros–Demanda thrust (North Spain)

Determining transport direction in thrusts is one of the main issues to study deformation and to achieve reliable balanced cross-sections reconstruction of inverted basins and thrust systems. Anisotropy of Magnetic Susceptibility provides a tool to study deformation in fault rocks through the relationships between the magnetic susceptibility ellipsoid and deformational structures. The Cameros-Demanda Thrust (N Spain) shows a relatively simple history, with an average N-directed movement during the Cenozoic, and provides the possibility of determining the relationships between magnetic fabrics and transport directions in thrusts. The outcropping rocks are Mesozoic limestones in the hangingwall of the main thrust and Cenozoic conglomerates and Albian sandstones and coal in its footwall. Illite crystallinity and organic matter maturity indicate P-T conditions on the order of....The study of AMS in fault rocks (more than 400 samples distributed in 25 sites with fault gouge, breccia and microbreccia) in the Cameros thrust and its comparison with kinematic indicators (foliation, S/C structures and slickenside striations) indicates, in spite of the a priori simple relationships inferred from thrust geometry, a complex history of movements, changing from top-to-the-NW to top-to-the-NE along the history of Cenozoic thrusting. The transport direction is either oblique to the magnetic lineation and perpendicular to the strike of magnetic foliation, and can be checked with shear structures observed in thin sections and other kinematic indicators. The results obtained indicate that AMS can give clues about the transport direction in thrusts depending on the particular structures developed in each studied area

Assessing the internal uppermost crustal structure of the central pyrenees by gravity-constrained cross sections

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 architecture of the upper crust of the southern half of the Axial Zone and the northern part of the South Pyrenean Zone, a key area to understand the orogenic evolution of the chain. Previous and new gravity, petrophysical and geological data have been used to obtain the Bouguer and residual anomaly maps of the study area and six serial gravity-constrained cross sections perpendicular to the main structural trend. The residual anomaly map shows a good correlation between basement units involved in thrust sheets of the study area and gravity highs whereas negative anomalies are interpreted to correspond with Mesozoic/Cenozoic basins, Triassic evaporites, Late Variscan igneous bodies, and Ordovician gneisses. The six gravity-constrained cross sections highlight strong along-strike variations on the gravity signal due to lateral differences of the superficial and subsurface occurrence of Triassic evaporites, different geometry at depth of the Late Variscan igneous bodies outcropping in the study area, and geometric lateral variations of the basement thrust sheets and their relationship with the Mesozoic-Cenozoic units.This work was funded by projects CGL2017-84901-C2-2-P funded by MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe”, PID2020-114273GB-C22 funded by MCIN/AEI/10.13039/501100011033 from the Spanish Ministry of Science and Innovation, and "Severo Ochoa” extraordinary grants for excellence IGME-CSIC (AECEX2021).Peer reviewe

Costs and benefits of automation for astronomical facilities

The Observatorio Astrof\'isico de Javalambre (OAJ{\dag}1) in Spain is a young astronomical facility, conceived and developed from the beginning as a fully automated observatory with the main goal of optimizing the processes in the scientific and general operation of the Observatory. The OAJ has been particularly conceived for carrying out large sky surveys with two unprecedented telescopes of unusually large fields of view (FoV): the JST/T250, a 2.55m telescope of 3deg field of view, and the JAST/T80, an 83cm telescope of 2deg field of view. The most immediate objective of the two telescopes for the next years is carrying out two unique photometric surveys of several thousands square degrees, J-PAS{\dag}2 and J-PLUS{\dag}3, each of them with a wide range of scientific applications, like e.g. large structure cosmology and Dark Energy, galaxy evolution, supernovae, Milky Way structure, exoplanets, among many others. To do that, JST and JAST are equipped with panoramic cameras under development within the J-PAS collaboration, JPCam and T80Cam respectively, which make use of large format (~ 10k x 10k) CCDs covering the entire focal plane. This paper describes in detail, from operations point of view, a comparison between the detailed cost of the global automation of the Observatory and the standard automation cost for astronomical facilities, in reference to the total investment and highlighting all benefits obtained from this approach and difficulties encountered. The paper also describes the engineering development of the overall facilities and infrastructures for the fully automated observatory and a global overview of current status, pinpointing lessons learned in order to boost observatory operations performance, achieving scientific targets, maintaining quality requirements, but also minimizing operation cost and human resources.Comment: Global Observatory Control System GOC

Hidratos de gas marinos: ¿un recurso futuro de gas natural para Europa? M.

Los hidratos de gas son compuestos cristalinos donde una molécula de gas, principalmente metano, queda atrapada en una red de moléculas de agua en forma de hielo. La importancia de los hidratos de gas en la naturaleza es muy alta ya que constituye una fuente alternativa de energía y a su vez juegan un papel importante en el delicado equilibrio del clima a nivel global y en los riesgos geológicos en el ámbito marino. La acción COST MIGRATE está diseñada con el fin de integrar la experiencia de un gran número de grupos de investigación europeos y agentes del sector para promover el desarrollo de conocimientos multidisciplinarios sobre el potencial de los hidratos de gas como fuente de energía en Europa. Dos de los objetivos de esta acción son realizar un inventario europeo de hidratos de gas explotables y evaluar los riesgos ambientales. En este trabajo se muestran los principales indicios de hidratos de gas en los márgenes europeos incluida la Península Ibérica, con una primera aproximación sobre el espesor y situación de la zona de estabilidad de hidratos de gas en el margen Ibérico.Gas hydrates are crystalline compounds where a molecule of gas, mainly methane, is trapped in a cage of icewater molecules. The importance of gas hydrates in nature is very high because it is an alternative source of energy and play a major role in the delicate balance of the global climate and in the marine geological risks. MIGRATE COST action is designed to integrate the experience of a large number of European research groups and industrial players to promote the development of multidisciplinary knowledge on the potential of gas hydrates as energy resource in Europe. Two of the objectives of the action aim to estimate the European inventory of exploitable gas hydrates and to assess environmental risks. In this work we show the occurrences of gas hydrates described in European margins including the Iberian Peninsula, with a first approximation on the thickness and location of the area of stability of gas hydrates in the Iberian margin.COST Action ES1405 (MIGRATE)Versión del edito

Estudio de las rocas paleozoicas y los macizos graníticos que afloran en el Parc Natural de l'Alt Pirineu y zonas colindantes mediante datos geológicos, geofísicos y petrofísicos

The Parc Natural de l’Alt Pirineu is located between the La Maladeta and Andorra- Mount Louis granites. The characterization of the Parc’s geology at depth can help to know the emplacement mechanism of these granites, their relationships with the plutonic and volcanic rocks outcropping to the North and South of the Parc, respectively, and if all these rocks belong to the same magmatic system. To achieve these objectives, in the frame of the present research project, we have compiled and homogenezed previous gravimetric and magnetic data, and acquired new geophysical data, in particular, gravity data. We have also constructed new geological cross-sections oriented NE-SW from previous and new acquired geological data and characterized the petrophysical properties of the geological units in order to obtain the density and magnetic susceptibility of all different rocks outcropping in the study area. The geological cross-sections together with the petrophysical data will be used in the 2,5 and 3D gravimetric modelling to improve our understanding of the subsurface geology of this part of the Central Pyrenees and of the Parc Natural de l’Alt Pirineu.El Parc Natural de l’Alt Pirineu se encuentra en la zona situada entre el granito de La Maladeta y el granito de Andorra-Mount Louis. Conocer y entender la geología del subsuelo del Parc nos ayudará a saber cómo se produjo el emplazamiento de ambos macizos graníticos, su relación con las rocas plutónicas y volcánicas que afloran en la parte norte y sur del Parc, respectivamente, y si forman parte de un mismo sistema magmático. Para alcanzar estos objetivos, se está realizando una recopilación y homogeneización de datos gravimétricos y magnéticos ya existentes, así como la adquisición de nuevos datos geofísicos, en particular de gravimetría. Además, partiendo de estudios geológicos previos y datos propios, se está llevando a cabo la realización de cortes geológicos de dirección NE-SO y el estudio petrofísico de las unidades geológicas para obtener los valores de densidad y susceptibilidad magnética de todos los tipos de rocas que afloran en el área de estudio. Los cortes geológicos junto con los datos de petrofísica se utilizarán en la modelización gravimétrica 2,5D y 3D para mejorar la interpretación de la geología del subsuelo en este sector de II Jornades de Recerca del Parc Natural de l‘Alt Pirineu 87 los Pirineos Centrales y del Parc Natural de l’Alt Pirineu.Este trabajo se está llevando a cabo en el marco de los subproyectos CGL2017-84901-C2-1 y CGL2017-84901-C2-2-P del Ministerio de Ciencia, Innovación y Universidades. Los desarrollos metodológicos en exploración con técnicas geofísicas se encuentran alineados con el proyecto europeo 3DGeoEU- GeoERA (ERANET Cofund action 731166 [H2020], Project code GeoE.171.005). Los autores agradecen al Parc Natural de l’Alt Pirineu las facilidades prestadas y la organización de las jornadas de investigación para mostrar los trabajos realizados