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The Pyrenees display numerous paleomagnetic studies acquired during the past six decades after the pioneer works carried out by the University of Utrecht in the early sixties (Van der Voo, 1969 and references therein). Currently, the Pyrenean Paleomagnetic Database (of IGME) includes nearly 40,000 individual vectors (demagnetizations) from more than 3000 sampling sites and more than 170 magnetostratigraphic profiles (comprising more than 35 kilometres of sections) that are harmonized and synthesized. This implies a significant increase (ca. 20%) with respect to previous versions introduced in the Iberian paleomagnetic meeting in 2017. This outstanding amount of data (considering the rather small size of the Pyrenees) is due to: 1) excellent outcrop conditions of stratigraphic sequences and biostratigraphic calibrations with global interest; 2) the availability of synorogenic materials, allowing for an accurate dating of deformation processes; and 3) the occurrence of well-exposed areas affected by lateral transference of deformation (oblique structures) that have motivated abundant paleomagnetic studies focused on characterizing vertical-axis rotations.In this work we present the state of the art of the Pyrenean Paleomagnetic Database. About 75% of the compiled paleomagnetic data display fisherian means with alfa95 below 15° (84% below 20°) that are in agreement to standard reliability criteria of paleomagnetic data in tectonic studies. Most sites and localities are drilled in Cenozoic (Miocene to Paleocene) and Upper Cretaceous rocks, thus, coeval or younger than the Pyrenean convergence time. Sites in Lower Cretaceous and Jurassic rocks represent pre-orogenic stages and are coeval or older than the rotation of Iberia (Biscay Bay opening). Less than 15% of the paleomagnetic sites come from Triassic and Permian red-beds and display an uneven distribution along the mountain chain. A similar uneven distribution of sites is observed in Paleozoic rocks. Several studies have determined remagnetization processes in the Pyrenees from the Western Basque Palaeozoic massifs to other Palaeozoic rocks of the Axial Zone mostly in relation to burial processes. This is the case of Lower Cretaceous, highly subsiding basins, like Organyá, Mauléon, Cotiella or the Chaînons Béarnais, as well as other Ceno-Mesozoic sequences in the Internal Sierras and related units; Larra-Monte Perdido, Nogueras, Boixols, Cadí, etc. In most cases, the remagnetization ages are Cenozoic when maximum temperatures were acquired at the base of the sequences during the convergence period or, in any case, younger than the rotation of Iberia and the opening of the Biscay Bay. Van der Voo, R. (1969). Paleomagnetic evidence for the rotation of the Iberian Peninsula. Tectonophysics, 7(1), 5-56.

Upon shortening, salt distribution determines the formation of salients and reentrants in fold-and-thrust belts. Such distribution is controlled by the original sedimentary architecture of the salt basin and subsequent post-sedimentary salt tectonics. In the Southern Pyrenees, the South Pyrenean Central Salient detaches on Triassic evaporites (the regional décollement of the Pyrenees) and stands as a prominent feature bounded, to the north and to the south, by diapiric provinces. Despite its subsurface geometry has been characterized by 2D reflection seismic profiles and exploration wells, an accurate image of the distribution at depth of the Triassic evaporites remains unsolved. In this work, we present an updated observed residual gravity anomaly map of the South Pyrenean Central Salient together with three gravity-validated cross-sections that give structural meaning to gravity anomalies and therefore yields a further interpretation of them helping to interpret those areas lacking seismic images. Middle-Upper Triassic salt accumulations dominate in the western half of the South Pyrenean Central Salient. To the northwest, a prominent accumulation of Triassic evaporites is likely associated with an inherited accumulation predating the Pyrenean orogeny and associated with extensional to gravity-driven salt tectonics during the rift and post-rift stages. To the South, Triassic rocks core salt-detached anticlines. Along the southernmost (and youngest) thrust sheet of the salient, diapirs and evaporite accumulations are associated to an inflated area resulting from the north-coming migration of evaporites during the middle to late stages of the Pyrenean orogeny.

One of the main challenges facing geological storage is to identify cost-effective methodological workflows for characterizing and monitoring geological storage sites. In the framework of the ALGECO2 project, led by the IGME (Geological and Mining Institute, Spain), a preliminary study of the Lopín site in the NE of Spain indicated conditions were promising for geological storage of CO 2 . However, the poor quality of the legacy seismic reflection data precluded thorough characterization. Within the H2020 PilotSTRATEGY project, one of the possible selected target reservoirs was the Lopín structure. In order to characterize its geometry and physical properties as required to properly evaluate its storage potential, IGME applied a new emerging methodology that integrates reinterpreted reflection seismic data with newly acquired and interpreted gravity, passive seismic and petrophysical data. This methodology was successfully applied along one seismic profile. In this paper, we present the results of this integration as the first step towards characterizing the site and evaluating its suitability for storage.

Context. Wavefront sensing and control (WFSC) will play a key role in improving the stability of future large segmented space telescopes while relaxing the thermo-mechanical constraints on the observatory structure. Coupled with a coronagraph to reject the light of an observed bright star, WFSC enables the generation and stabilisation of a dark hole (DH) in the star image to perform planet observations. Aims. While WFSC traditionally relies on a single wavefront sensor (WFS) input to measure wavefront errors, the next generation of instruments will require several WFSs to address aberrations with different sets of spatial and temporal frequency contents. The multiple measurements produced in such a way will then have to be combined and converted to commands for deformable mirrors to modify the wavefront subsequently. Methods. We asynchronously operate a loop controlling the high-order modes digging a DH and a control loop that uses the rejected light by a Lyot coronagraph with a Zernike wavefront sensor to stabilize the low-order aberrations. Using the HiCAT testbed with a segmented telescope aperture, we implement concurrent operations and quantify the expected cross-talk between the two controllers. We then present experiments that alternate high-order and low-order control loops to identify and estimate their respective contributions. Results. We show an efficient combination of the high-order and low-order control loops, keeping a DH contrast better than 5 × 10−8 over a 30 min experiment and stability improvement by a factor of 1.5. In particular, we show a contrast gain of 1.5 at separations close to the DH inner working angle, thanks to the low-order controller contribution. Conclusions. Concurrently digging a DH and using the light rejected by a Lyot coronagraph to stabilize the wavefront is a promising path towards exoplanet imaging and spectroscopy with future large space observatories.

SUMMARYAs 3-D geological models become more numerous and widely available, the opportunity arises to combine them into large regional compilations. One of the biggest challenges facing these compilations is the connection and alignment of individual models, especially in less explored areas or across political borders. In this regard, gravity modelling is suitable for revealing additional subsurface information that can support a harmonization of structural models. Here, we present an integrated geological and gravity modelling approach to support the harmonization process of two geological 3-D models of the North German Basin in the cross-border region between the federal states of Saxony-Anhalt and Brandenburg. Gravity gradient calculation, filtering and Euler deconvolution are utilized to reveal new insights into the local fault system and gravity anomaly sources. The independent models are merged and harmonized during 3-D forward and inverse gravity modelling. Herein, density gradients for individual layers are incorporated in the framework of model parametrization. The resulting geological 3-D model consists of harmonized interfaces and is consistent with the observed gravity field. To demonstrate the plausibility of the derived model, we discuss the new geophysical findings on the sedimentary and crustal structures of the cross-border region in the context of the regional geological setting. The cross-border region is dominated by an NW–SE oriented fault system that coincides with the Elbe Fault System. We interpret a low-density zone within the basement of the Mid-German Crystalline Rise as a northward continuation of the Pretzsch–Prettin Crystalline Complex into the basement of the North German Basin. Additionally, we observe two types of anticlines within the basin, which we link to provinces of contrasting basement rigidity. Our gravity modelling implies that the Zechstein salt has mostly migrated into the deeper parts of the basin west of the Seyda Fault. Finally, we identify a pronounced syncline that accommodates a narrow and up to 800 m deep Cenozoic basin.

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).

Context.The combination of large segmented space telescopes, coronagraphy, and wavefront control methods is a promising solution for producing a dark hole (DH) region in the coronagraphic image of an observed star in order to study planetary companions. The thermal and mechanical evolution of such a high-contrast instrumental setup leads to wavefront drifts that degrade the DH contrast during the observing time, thus limiting the ability to retrieve planetary signals.Aims.Lyot-style coronagraphs are starlight-suppression systems that remove the central part of the image for an unresolved observed star, that is, the point spread function, with an opaque focal plane mask (FPM). When implemented with a flat mirror containing an etched pinhole, the mask rejects part of the starlight through the pinhole which can be used to retrieve information about low-order aberrations.Methods.We propose an active control scheme using a Zernike wavefront sensor (ZWFS) to analyze the light rejected by the FPM, control low-order aberrations, and stabilize the DH contrast. We first present the concept formalism and then describe how we characterized the sensor behavior in simulations and in the laboratory. We performed experimental tests to validate a wavefront control loop using a ZWFS on the HiCAT testbed.Results.By controlling the first 11 Zernike modes, we show a decrease in the standard deviation of the wavefront error by a factor of up to 9 between open- and closed-loop operations using the ZWFS. In the presence of wavefront perturbations, we show the ability of this control loop to stabilize a DH contrast around 7 × 10−8with a standard deviation of 7 × 10−9.Conclusions.Active control with a ZWFS proves to be a promising solution in Lyot coronagraphs with an FPM-filtered beam for controlling and stabilizing low-order wavefront aberrations and DH contrast for exoplanet imaging with future space missions.

This article is composed of three independent commentaries about the state of Integrated, Coordinated, Open, Networked (ICON) principles (Goldman et al., 2021, https://doi.org/10.1002/essoar.10508554.1) in the Geomagnetism, Paleomagnetism, and Electromagnetism (GPE) section and discussion on the opportunities and challenges of adopting them. Each commentary focuses on a different topic: Global collaboration, reproducibility, data sharing and infrastructure; Inclusive equitable, and accessible science: Involvement, challenges, and support of early career, BIPOC, women, LGBTQIA+, and/or disabled researchers; Community engagement, citizen science, education, and stakeholder involvement. Data sharing practices and open repository use still varies strongly between GPE communities. Some have a long tradition of data sharing; others are only starting it. Globally, GPE leadership is strongly dominated by white males and diversity may increase through the creation of Science Equality Commissions. Improved global stakeholder involvement can increase research impacts and help fight inequalities. In all investigated topics we see promising beginnings but also recognize obstacles that include a lack of funding, a lack of understanding of diversity, and prioritizing short-term gain over long-term benefit. Nonetheless, we are hopeful that our community will embrace ICON science

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. Once this is known, it is possible to determine the magnetization age as well as the degree of bed tilting at this moment. The SC tools are based on some assumptions, among which the coaxiality between the different deformation events is the one addressed in this work (i.e. absence of vertical axis rotations, VARs, or differential horizontal axis rotations, dHARs). This assumption is based on the necessity of knowing the rotation axis for folding after the acquisition of the remagnetization, and SC tools consider the bedding strike as this axis, something that is only accomplished under coaxial folding. In order to explore how non-coaxiality affects the solutions derived from the SC methods, we first (i) identify the variables that control these errors through simple models that only consider two theoretical palaeomagnetic sites, after that it is possible (ii) to derive the mathematical relationships between them. Finally, we (iii) simulate errors derived from the use of SC tools using a population of 30 palaeomagnetic sites recreating different possible scenarios with VARs and dHARs in nature., Research financed by the projects DR3AM- CGL2014-55118 and CGL2016-77560-C2 from the Spanish Ministry of Science (MINECO) and by the Applied Geology (GeoAP-E0117R) and Geotransfer groups of the Government of Aragon, as well as by the project BU235P18 (Junta de Castilla y Leon, Spain) and the European Regional Development Fund (ERD). It has also benefited from the MAGIBER-II network (CGL2017-90632-REDT) funded by the Ministry of Science, Innovation and Universities.

The geological storage of CO2 requires the search and characterization of a suitable porous formation and caprock to ensure a favorable and safe trap. One of the first steps of this search consists of performing a detailed definition of its geometry at depth. The structure of Lopín (southern Ebro basin, Spain) was identified as a potential structure valid for CO2 storage in the frame of the ALGECO2 project (Selection and characterization plan of favorable areas and structures for Geological CO2 Storage in Spain, 2009-2014) led by IGME. A preliminary characterization carried out during these years showed positive conditions for the storage of this gas. However, the poor quality of the available reflection seismic data precluded accurate enough conclusions to select this location as geological storage site. The biggest uncertainty was the closure of the structure in its SE margin and further exploration was ruled out at that time. Within the PilotStrategy project (2021-2026), funded by UE on the frame of the H2020, the structure of Lopin is proposed for further studies and a gravimetric and passive seismic surveys have been carried out for in order to resolve this question. The Lopín structure constitutes an antiform affecting Paleozoic and Mesozoic sequences overlain by subhorizontal Neogene deposits located in the southern Ebro basin. It is defined by NW-SE and NNW-SSE oriented faults several tenths of kilometres long which are subparallel to the orientation of the dominant structures of the Iberian Chain, located to the South of the study area. At the Lopín structure, the target reservoir and seal formations consist of the Lower and Upper Triassic rocks, respectively. The aim of the new geophysical surveys is to improve the geometric characterization at depth of the Lopín structure. The gravimetric surveys have coverage of two stations for km2 in the structure area. In addition, 7 profiles have been built up in the uncertainty area with a coverage of a station every 250 m. The models have been constrained by the newly acquired passive seismic data and the reinterpretation of some of the vintage seismic reflection profiles. The preliminary results of the joint modelling improve the geometrical characterization of the Lopín structure at depth in order to define its suitability as geological CO2 reservoir site.

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 evolution and (ii) provide new insights on the deposition of volcanic materials in this tectonically controlled sedimentary basin. To establish a comparison with the petrofabric of rocks, AMS was complemented with observations and orientation analyses at the outcrop scale, in oriented polished blocks and in thin sections under the microscope. High resolution sampling (620 specimens from 56 sites located in five transects along a sequence 150 m thick) allowed to characterize the volcaniclastic and lava flow series. The AMS results show a fairly constant average magnetic lineation oriented WNW-ESE (in situ and tilt-corrected) and two secondary maxima (N-S to NE-SW in some areas). The magnetic mineralogy analyses indicate the contribution of paramagnetic and ferromagnetic (magnetite, Tc 580 °C) phases to susceptibility. The magnetic fabric has a close relationship with the spatial distribution and orientation of the mineral and grain components of the studied rocks, mainly controlled by depositional processes, with a negligible contribution of the tectonic imprint. Therefore, the magnetic lineation (i.e. K1 axes) can be reliably used as a paleoflow indicator. Nevertheless, it was not possible to establish a clear correspondence between lithological and magnetic fabric types. The results obtained indicate that the AMS approach represents a powerful tool to infer the paleoflow pattern in ancient volcanic and volcaniclastic rocks, even under a priori unfavourable conditions., This work was supported by projects grants CGL2017-84901-C2-2-P, PID2020-114273GB-C22, PID2019-108753GB-C22 and FPU19/02353 funded by MCIN/AEI/10.13039/501100011033, “ERDF A way of making Europe” and “ESF Investing in your future”.

This work presents preliminary paleomagnetic results from the Cadí basin, one of the Pyrenean Late-Carboniferous-Permian basins.These basins are the consequence of a complex tectonic evolution. At the outset, they were controlled by an extensional or transtensional regime during the progressive dismantling of the Variscan chain that gradually changed to a strike-slip fault regime. Afterwards, during Pyrenean compression (Late Cretaceous to Cenozoic) most of these basins were inverted and transported southwards as a part of the basement units. All of them are characterized by a similar subsidence pattern interpreted as graben or half-graben continental troughs. In a close relationship with its genesis, during Late-Carboniferous-Permian times, several magmatic events took place. Because of that, fluvio-lacustrine sediments present lateral changes to volcanic and volcanoclastic deposits and materials are sometimes cut by intrusions.The studied zone, the Cadí basin, is located at the eastern Pyrenees, south of the Axial Zone, and shows a high variability of Late-Carboniferous-Permian volcanic products in E-W continuous outcrops that reach several hundred meters of thickness with a good preservation and exposition. The Late Carboniferous-Permian evolution of the Cadí basin was strongly controlled by tectonics and volcanism. In order to characterize this stage and its volcanic rocks, we applied in a previous work the anisotropy of magnetic susceptibility (AMS) technique to determine the primary magnetic fabric of lava flows and volcanoclastic materials. A dominant WNW-ESE direction of the magnetic lineation was recognized related to the paleoflow direction. Paramagnetic minerals and magnetite were recognized as the main carriers of the AMS.In this work we present the paleomagnetic results from 15 sites (about 150 specimens) in volcanic, volcanoclastic and intrusive materials sampled along four N-S cross sections. The obtained results indicate that the carrier of the magnetization are both magnetite and haematite. The thermal demagnetization of samples shows a paleomagnetic component with unblocking temperatures from 480ºC with reversed polarity and very low inclination after bedding correction. In some sites a normal polarity component is also recognized. These results seem to be coherent with a magnetization coetaneous with the emission and deposition of these materials during Permian times. In cases where the samples record a normal component is important to take into account the complex structural situation of these outcrops.

El suroeste de los Pirineos muestra algunas de las características geométricas clave de la cordillera: 1) la terminación hacia el oeste del afloramiento principal de la Zona Axial, la columna vertebral de la cadena donde emergen las rocas del basamento 2) el afloramiento de unidades de basamento aisladas más al oeste (los llamados Macizos Vascos) y 3) la variación lateral de las geometrías de la corteza, caracterizada por la subestimación de la corteza ibérica inferior por debajo de la europea, con la corteza superior formando una cuña orogénica. El número, la secuencia, la cronología y las relaciones laterales de los empujes del sótano que forman esta cuña de la corteza superior son complejos y el foco del debate científico.En este, mostramos el primer modelo 3D basado en la interpretación de 142 secciones de reflexión sísmica de tiempo disponible en la región (campañas PP, DP, JAT, JA, JAW, PJ & DP, que comprenden en total más de 1600 km de imágenes del subsuelo que cubren más de 9.000 km 2). Para realizar la conversión de tiempo a profundidad, se considera un modelo de velocidad sísmica basado en registros sónicos de varios pozos (ecuación tiempo-profundidad promedio obtenida de los pozos Roncal-1, Sangüesa-1, Aoiz-1 y Pamplona sur). Los resultados preliminares de los datos sísmicos, superficiales y de pozos evidencian que la estructura del área de estudio consiste en un sistema de empuje imbricado en el sótano que está dirigido al sur y se conecta al sistema de cubierta de pliegue y empuje que forma las Sierras Externas. El sistema de empuje del sótano está separado dentro del Paleozoico (con un nivel de desprendimiento identificado a una profundidad de ~ 4 km por debajo de la parte superior del sótano) y avanzando hacia las evaporitas del Triásico Superior hacia el sur. El sistema de empuje del sótano involucra dos empujes principales que en parte resultan de la reactivación de fallas extensionales heredadas del Pérmico-Triásico durante la convergencia cenozoica. Producen con todo diferencias de altura del nivel estratigráfico de referencia (Cretácico Superior) de más de 8000 m. Unidades de sótano en el muro colgante del empuje norte (empuje de Gavarnie) progresivamente poco profundas hacia el este mientras que las unidades de sótano en la hoja de empuje sur (empuje de Guarga) poco profundas hacia el oeste. Las geometrías de los muros colgantes consiste en grandes paneles planos escalonados que también pueden complicarse con empujes de menor escala oblicuos a la principal tendencia pirenaica.

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 granitic complexes, La Maladeta and Andorra-Mont Louis granites, to infer the geometry at depth of the basement host rocks. This cross section is ca. 65 km long and extends from the Mesozoic Bóixols basin in the South to the Late Variscan Bassiès granite to the North, close to the northern end of the Axial Zone. It is based on available geological maps, previous published works and new geological field data; together with newly acquired gravimetric stations (1141), to improve the existent spatial resolution of the gravity data from the databases of the Spanish and Catalan Geological Surveys, and density values from 65 rock samples covering all different lithologies in the cross section. Thus, its geometry at depth is constrained by means of an integrated 2.5D gravity/structural/petrophysical modelling.The La Maladeta and Andorra-Mont Louis granites appear aligned in a WNW-ESE direction and both lie within the same Alpine basement unit, the Orri thrust sheet. They are separated about 40 km by the WNW-ESE-oriented Llavorsí syncline, formed by Devonian and Silurian rocks and limited to the north and south by south vergent thrusts. This syncline is located between two large Cambro-Ordovician anticlinorium structures, the La Pallaresa and Orri massifs to the north and south respectively, formed by a monotonous alternation of shales and sandstones with some intercalations of limestones and conglomerates affected by very low to medium grade of metamorphism. Most structures show southern vergence along the cross section, and its southern part is characterized by the occurrence of Triassic evaporites, a significant detachment level decoupling deformation between the Paleozoic basement and the Mesozoic-Cenozoic cover rocks.The observed residual anomaly along the cross section shows a relative maximum, coinciding with the southern edge of the Axial Zone (Nogueras Zone) and southern half of the Orri massif, followed to the north by a relative large minimum. This gravity minimum in the core of the Axial Zone coincides with the northern half of the Orri massif, the Llavorsí syncline and southern half of the La Pallaresa massif and must be related at depth with rocks of lower density with respect to rocks located to the North and South. Two possible solutions have been postulated to explain the presence of lower density rocks: (i) the presence of Triassic evaporites at depth as a continuation to the North of the Triassic evaporites outcropping in the Rialp window located to the South and/or (ii) the presence of buried granitic bodies equivalent to the adjacent La Maladeta and Andorra-Mont Louis granites.

The presence of multiple evaporite levels strongly influence the structural style and kinematics of fold-and-thrust belts. Particularly (but not exclusively) in their fronts, it is common for these décollements to favor the formation of triangle zones. In the central portion of the Pyrenees, the South Pyrenean Triangle Zone represents the frontal part of this chain, that involves the Oligocene-Miocene Ebro Basin foreland deposits. We have focused on its western termination, characterized by a salt-cored anticline that laterally passes to a backthrust which dies out to the west. These structures are detached on the Upper Eocene-Lower Oligocene syntectonic evaporite Barbastro Formation (and lateral equivalents) that acted as a multidetachment unit. To the north, the south-directed Pyrenean thrust unit detached on Middle-Upper Triassic evaporites to finally glide along the Upper Eocene-Lower Oligocene décollement horizons.In this contribution, we present a detailed structural and stratigraphic model of this triangle zone termination, constructed accordingly to two major approaches (1) constraining the geometry and structural architecture based on surface geology, interpretation of seismic lines (>900 km) and wells and, (2) obtaining the 3D density distribution of the detachment level (Barbastro Fm. and lateral equivalents as well as deeper, Triassic evaporites) using gravity stochastic inversion by means of more than 7000 gravity stations and 1500 actual density data from surface rocks. All in all, this multidisciplinary approach allows us to characterize the western termination of the South Pyrenean Triangle zone as the transition from a ramp-dominated and multiple triangle zone to a detachment-dominated one whose geometry, kinematics, and location were controlled by the distribution and heterogeneity of the Upper Eocene-Lower Oligocene syntectonic décollements and the southern pinch-out of the basal detachment of this unit.

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 southern flank, fully records its folding kinematics and witnesses for two distinct deformation periods in relation to the basement activity (Gavarnie gentle folding and Guarga paroxism) (stop #1). (B) The remarkable conical geometry of the fold termination (San Marzal area) that is completely documented by structural and palaeomagnetic analyses (stop #2). (C) The rotational kinematics of this structure recorded in its northern flank. Both the folding and the rotational kinematics can be wholly time-bracketed by means of seven long magnetostratigraphic sections and numerous additional palaeomagnetic sites within the syn-tectonic (syn-rotational) sequence (stop #3). We also describe the overall structure of the Western Pyrenees from a panoramic view from the summit of the anticline (1520 m). All these stops are accessible by car (dirt roads). Finally, an additional field stop (#4) is devoted to the sedimentology of the Lutetian-Bartonian carbonates following a hiking path (3 km) from stop #3.

Context. The nearby and young β Pictoris system hosts a well resolved disk, a directly imaged massive giant planet orbiting at ≃9 au, as well as an inner planet orbiting at ≃2.7 au, which was recently detected through radial velocity (RV). As such, it offers several unique opportunities for detailed studies of planetary system formation and early evolution. Aims. We aim to further constrain the orbital and physical properties of β Pictoris b and c using a combination of high contrast imaging, long base-line interferometry, and RV data. We also predict the closest approaches or the transit times of both planets, and we constrain the presence of additional planets in the system. Methods. We obtained six additional epochs of SPHERE data, six additional epochs of GRAVITY data, and five additional epochs of RV data. We combined these various types of data in a single Markov-chain Monte Carlo analysis to constrain the orbital parameters and masses of the two planets simultaneously. The analysis takes into account the gravitational influence of both planets on the star and hence their relative astrometry. Secondly, we used the RV and high contrast imaging data to derive the probabilities of presence of additional planets throughout the disk, and we tested the impact of absolute astrometry. Results. The orbital properties of both planets are constrained with a semi-major axis of 9.8 ± 0.4 au and 2.7 ± 0.02 au for b and c, respectively, and eccentricities of 0.09 ± 0.1 and 0.27 ± 0.07, assuming the HIPPARCOS distance. We note that despite these low fitting error bars, the eccentricity of β Pictoris c might still be over-estimated. If no prior is provided on the mass of β Pictoris b, we obtain a very low value that is inconsistent with what is derived from brightness-mass models. When we set an evolutionary model motivated prior to the mass of β Pictoris b, we find a solution in the 10–11 MJup range. Conversely, β Pictoris c’s mass is well constrained, at 7.8 ± 0.4 MJup, assuming both planets are on coplanar orbits. These values depend on the assumptions on the distance of the β Pictoris system. The absolute astrometry HIPPARCOS-Gaia data are consistent with the solutions presented here at the 2σ level, but these solutions are fully driven by the relative astrometry plus RV data. Finally, we derive unprecedented limits on the presence of additional planets in the disk. We can now exclude the presence of planets that are more massive than about 2.5 MJup closer than 3 au, and more massive than 3.5 MJup between 3 and 7.5 au. Beyond 7.5 au, we exclude the presence of planets that are more massive than 1–2 MJup. Conclusions. Combining relative astrometry and RVs allows one to precisely constrain the orbital parameters of both planets and to give lower limits to potential additional planets throughout the disk. The mass of β Pictoris c is also well constrained, while additional RV data with appropriate observing strategies are required to properly constrain the mass of β Pictoris b.

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 Upper Eocene‐Lower Oligocene syntectonic evaporite‐rich formation that acted as a multidetachment unit. Northward, the south directed Pyrenean thrust unit (i.e., Gavarnie‐Sierras thrust sheet) detached along the Middle‐Upper Triassic evaporitic rocks to finally ramp up and glide along the same Upper Eocene‐Lower Oligocene multidetachment unit. A multidisciplinary approach allowed constructing a detailed structural and stratigraphic model of the study area. The workflow consisted of (1) constraining the geometry and structural architecture based on surface geology, interpretation of seismic lines (>900 km), and wells and (2) obtaining the 3‐D density distribution of the multidetachment unit using gravity stochastic inversion (more than 7,000 gravity stations and 1,500 density data). The geometry of the sole thrust of the Gavarnie‐Sierras thrust sheet was controlled by the distribution of the evaporite‐rich units of the Barbastro Fm. Weak detachments promoted thrust salient formation and thrust flat geometries. The western termination of the South Pyrenean triangle zone is defined as a westward transition from a ramp‐dominated and multiple triangle zone to a detachment‐dominated one. Its geometry, kinematics, and location were controlled by the heterogeneous lithology of the Barbastro Fm. and its basal, halite‐based detachment southern pinch‐out., This work was financed by the DR3AM (CGL2014‐54118‐C2‐2‐R) and E‐28(GeoApp Research Group) projects by the Spanish Ministry of Science and the Aragón Government, respectively. This work has received support from and it also aligns with methodological goals of the GeoERA project 3DGeoEU (ERANET Cofund action 731166 [H2020], Project code GeoE.171.005) and GeoPiri3D project (from the Spanish Ministry of Education and Universities, project code CGL2017‐84901‐C2‐2‐P). We acknowledge the TopoIberia project for providing the gravity data from SITOPO databases.The Academic agreement with MVE is also acknowledged. The IHS is also acknowledged for providing the Kingdom Suite software. José María Llorente and Agustín Gonzalez are here acknowledged for gravity data acquisition and processing. We also want to thank reviewers Christoph v. Hagke and Jonas Kley and Editor Laurent Jovilet for their productive suggestions and comments that helped to enrich our work and improve the manuscript.

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 demonstrated that ∂18O or [SiO2] display a negative correlation to density and to magnetic susceptibility. These relationships are particularly stable (and linear) in the so-called “non-magnetic” granites (susceptibilities falling within the paramagnetic range; between 0 and 500 10-6 S.I.) and usually coincident with calc-alcaline (CA) compositions (very common in Variscan domains). In this work we establish robust correlations between density and magnetic susceptibility at different scales in CA granites from the Pyrenees. Other plutons from Iberia were also considered (Veiga, Monesterio). The main goal is to use the available and densely sampled nets of anisotropy of magnetic susceptibility (AMS) data, performed during the 90’s and early 2000’s, together with new data acquired in the last few years, as an indirect measurement of density in order to carry out the 3D modelling of the gravimetric signal. We sampled some sections covering the main range of variability of magnetic susceptibility in the Mont Louis-Andorra, Maladeta and Marimanha granite bodies (Pyrenees), all three characterized by even and dense nets of AMS sites (more than 550 sites and 2500 AMS measurements). We performed new density and susceptibility measurements along two main cross-sections (Maladeta and Mont Louis-Andorra). In these outcrops, numerous measurements (usually more than 50) were taken in the field with portable susceptometers (SM20 and KT20 devices). Density data were derived from the Arquimedes principle applied on large hand samples cut in regular cubes weighting between 0.3 and 0.6 kg (whenever possible). These samples were subsampled and measured later on with a KLY-3 susceptibility bridge in the laboratory. Additionally, some density data were derived from the geometry and weighting of AMS samples. After the calibration of portable and laboratory susceptometers, density and magnetic susceptibility were plotted together. Regressions were derived for every granite body and they usually followed a linear function similar to: r = 2600 kg/m3 + (0.5 * k [10-6 S.I.]). As previously stated, this relationship is only valid in CA and paramagnetic granites, 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). These relationships allow transforming magnetic susceptibility data into density data helping in the 3D modelling of the gravimetric signal when density data from rock samples are scarce. Given the large amount of AMS studies worldwide, together with the quickness and cost-effectiveness of susceptibility measurements with portable devices, this methodology allows densifying and homogenizing the petrophysical data when modelling granite rock volumes based on both magnetic and gravimetric signal.

Cenozoic contractional deformation in the Central Pyrenees generated several basement thrust sheets involving Paleozoic rocks and decoupled Mesozoic and Cenozoic cover units detached on the main décollement level, the Triassic evaporites. The overall geometry and structural architecture of the chain have already been established based on numerous geological and geophysical data obtained during several decades. This work aims to validate the overall accepted geometry of the Central part of the chain by the construction of six serial cross-sections constrained by gravity data and 2.5D gravity modelling. The study area comprises the southern half of the Axial Zone between La Maladeta and Andorra-Mont Louis granites and its southern leading edge as well as the northernmost part of the South-Pyrenean Zone.New gravity data were acquired and combined with previous existing databases to obtain Bouguer anomaly and residual anomaly maps of the study area. Six serial gravity-constrained cross sections have been built using available geological maps, previous published works, new geological and gravity data and 2.5D gravity modelling. Density values for gravity modelling were derived from 231 laboratory measurements of rock samples collected in the field from non-weathered outcrops that include all rock types outcropping in the study area. The residual anomaly map shows a good correlation between basement thrust sheets and gravity highs whereas negative anomalies seem to correspond to (1) Mesozoic basins, (2) Triassic evaporites and (3) Late Variscan igneous bodies. The 2.5D gravity modelling along the six cross sections highlights: (i) strong along-strike variations on the gravity signal due to lateral differences of the surficial and subsurface occurrence of Triassic evaporites, (ii) different geometry at depth of the Late Variscan igneous bodies outcropping in the study area and (iii) geometric lateral variations of the basement thrust sheets and their relationship with the Mesozoic-Cenozoic units.

EGU2020: Sharing Geoscience Online, 4-8 May 2020, 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 Permian times the extensional or transtensional regime dominant during the progressive dismantling of the Variscan belt resulted in the development of E-W elongated intra-mountainous basins. This process was coeval with an exceptional episode of magmatic activity, both intrusive and extrusive. The Cadí basin represents a good example of these structures were Stephano-Permian rocks are aligned along an E-W continuous outcrop and reach thickness of several hundreds of meters. The stratigraphy of the study area is characterized by fluviolacustrine sediments changing laterally to volcanoclastic and pyroclastic rocks with interbedded andesitic lava flows. A total of 75 sites (733 standard specimens) were studied and analysed throughout the volcanoclastic, volcanic and intrusive materials of the Stephano-Permian outcrops in the Cadí basin. Samples were drilled in the field along 5 sections with N-S or NW-SE direction in the Grey and Transition Unit. Afterwards, standard specimens were measured in a Kappabridge KLY-3 (AGICO) at the Zaragoza University to characterise the magnetic fabric. The susceptibility bridge combined with a CS-3 furnace (AGICO) was used for the temperature-dependent magnetic susceptibility curves (from 20 to 700 °C) to recognize the magnetic mineralogy. In addition, textural and mineralogical recognition in thin-sections of the samples was carried out in order to recognize the relationship between magnetic and petrographic fabrics. The results shows that the bulk magnetic susceptibility of the specimens ranges between 118 and 9060·10-6 SI but most of the values are bracketed between 160 to 450·10-6 SI. Taking into account magnetic parameters (Km, Pj and T) there is no correlation between magnetic fabrics and magnetic mineralogy and there is a dominance of triaxial and prolate ellipsoids. Thermomagnetic curves indicate the dominance of paramagnetic behaviour in all the samples and except in one case there is a ferromagnetic contribution due to the generalised presence of magnetite. Magnetic ellipsoids can be divided into four main types depending on the orientation of the main axes and associated with the lithologic types: 1) Kmax vertical and Kint and Kmin horizontal for small intrusive bodies (no restoring); 2) Kmax horizontal or subhorizontal and Kint and Kmin included in a subvertical plane (before and after restitution) for volcanic breccias; 3) Kmin vertical (after restoring) and three directional maxima for lava flows and 4) non-defined fabric for the explosive materials (probably due to their complex depositional mechanisms). In general, a dominant E-W magnetic lineation is observed in many sites, resulting either from dominant flow direction, or to secondary processes. This is the case for some of the magnetic ellipsoids, that seems to be affected by deformation, Kmin is not normal to bedding and therefore, they do not become vertical after bedding restitution.

An extense systematic description of the Eocene larger foraminiferal faunas recorded in the South Pyrenean Basin (Sierras Exteriores) is presented herein. The large dataset provided in this work includes both Nummulites and Alveolina species, along with a variety of other porcellaneous and hyaline taxa with lesser biostratigraphic relevance, are represented. The larger foraminifera described in this work correspond mainly to the Lutetian (SBZ13 to SBZ16 biozones) interval, but late Ypresian (SBZ11, Cuisian) and Bartonian (SBZ17) shallow benthic zones have also been identified.As one of the most relevant results of this systematic analysis, a new species, Idalina osquetaensis, is described. The systematic revision of middle to late Lutetian alveolines led to a reassessment of A. fusiformis and the finding of two new precursor forms, described as affinis of their corresponding species, A. aff. fragilis and A. aff. elongata. The new forms A. aff. elongata and A. aff. fragilis fill the gap in the middle to late Lutetian alveolinid biostratigraphy. Despite not being exclusive to SBZ16, these new forms provide realiable biostratigraphic information where Nummulites are not present. This realibility lies on the correlation of Nummulites and Alveolina biomarkers in the same sections and their calibration to the global time scale through magnetostratigraphy. In fact, magnetostratigraphic calibration of all described taxa is also provided, along with an update of the SBZ calibration to the current Geologic Time Scale (Gradstein et al., 2012).

EGU General Assembly 2020, Online, 4-8 may 2020, In the Central Pyrenees, where density contrast between the Paleozoic rocks and the intruded granitic bodies is measurable, geological cross-sections constrained with gravity data help to unravel the subsurface geometry of the granites. With this goal in mind, during 2018 and 2019 several gravimetric surveys were carried out in the Central Pyrenees to improve the existent spatial resolution of the gravity data from the databases of the Spanish and Catalan Geological Surveys, especially in La Maladeta and Andorra Mont-Louis granites¿ area. After the gravity reductions, we obtained the Bouguer gravity anomaly from which we calculated the residual gravity anomaly by subtracting a third degree polynomial which represents the regional anomaly in agreement with the geometry of the crust in this region. The gravimetric response over La Maladeta and Andorra Mont-Louis granites is markedly dissimilar pointing out differences in the composition and geometry at depth of the two granites. La Maladeta granite shows a gravimetric zonation with small variations in its amplitude from one zone to the next, consistent with small lateral changes in its composition, predominantly granodioritic. By contrast, the Andorra Mont-Louis pluton is characterized by a relative minimum suggesting a more granitic composition. With respect to the inferred geometry at depth, the results obtained from gravity modelling show that the La Maladeta granite displays a laccolithic shape with its basal contact deeping to the North whereas the Andorra Mont-Louis granite has a more batholitic shape. Although the emplacement age of both granites is similar (Late Carboniferous ¿ Early Permian), their different geometry at depth suggests that either (1) their emplacement mechanisms were different or (2) the subsequent Alpine orogeny affected both granites in different ways better preserving the original geometry of the Andorra Mont-Louis granite.

The Santo Domingo Anticline (External Sierras, Southern Pyrenees), which separates the Jaca piggyback basin from the Ebro foreland basin, is a key structure of the Pyrenees. Its geometry has been interpreted both as a detachment fold and as a hangingwall anticline associated with an underlying thrust. In this paper, we present the results from a gravity survey and 2.5D gravity modelling carried out around the Santo Domingo Anticline. Density measurements indicate a sharp density contrast between the Triassic evaporites-mudstones in the core of the anticline and the sedimentary sequence (limestones and sandstones) at its limbs. Gravity anomalies together with 2.5D gravity models allow to discern the along-strike structural changes. From east to west, we document a change from the ramp-associated fold to the detachment anticline. The capabilities and limitations of the gravimetric method for the determination of fold geometry are also discussed. Copyright © 2017 John Wiley & Sons, Ltd.

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 and gravimetry. New gravity data (938 stations) and density determinations (827 samples) were acquired and combined with previous existing databases to obtain Bouguer anomaly and residual Bouguer anomaly maps of the study area. Seven serial and balanced cross sections were built, their depth geometries being constrained through the 2.5-D gravity modeling and the 3-D gravity inversion that we accomplished. The residual Bouguer anomaly map shows a good correlation between basement antiforms and gravity highs whereas negative anomalies mostly correspond to (i) Meso-Cenozoic synclines and (ii) Neogene-Quaternary basins. Cross sections depict a southern, thick-skinned domain where extensional, basement faults inherited from Late Jurassic-Early Cretaceous times were inverted during the Cenozoic. To the north, we interpret the existence of both Triassic-detached and basement-involved deformation domains. The two deformation styles are vertically overlapped in the southernmost part of the Catalan Coastal Ranges but relay both across and along strike in the Eastern Iberian Range. These basement and cover relationships and their along-strike variations are analyzed in terms of the interplay between structural inheritance, its obliquity to the shortening direction, and the continuity and effectiveness of Triassic décollements in the study area., This study has been supported by the Instituto para la Reestructuracion de la Mineria del Carbon y el Desarrollo Alternativo de las Comarcas Mineras Ministry of Energy and Industry, Spain. Additional support has also come from the DR3AM and SALTCRES Projects (CGL2014-54118) from the Science National Plan of Spain (MINECO). The authors also acknowledge Midland Valley Exploration for providing Move software academic licenses. The contribution of Jose Maria Llorente, Agustin Gonzalez, and Israel Perez was essential for the acquisition of the geophysical data and the density measurements. The financial support of the Aragonian Goberment is also acknowledged (Applied Geology Group-GeoAp, E01_17R). The data used in this work can be found in the manuscript itself or in previous works listed in the references. Elevation reference data from the Instituto Geografico Nacional (http://www.ign.es/ign/main/index.do) were used in the gravity processing as well as digital terrain models from the Spanish Army Geographical Survey (http://www.ejercito.mde.es/unidades/Madrid/ceget/).Geological maps are available at the IGME website (http://info.igme.es/cartografiadigital/), whereas well data from the Water Authority (CHE) are accessible at the IBER website (http://iber.chebro.es/sitebro/sitebro.aspx?hydrogeoebro).

Dating the sedimentary infill of the northern margin of the Ebro foreland basin informs about the orogen-basin evolution. A magnetostratigraphic section of ~5 km-thick combines new magnetostratigraphic results from the syntectonic alluvial Uncastillo Fm (Upper Oligocene-Lower Miocene, 1 km-thick, the Fuencalderas section) with previous (3.3 km-thick) and new (0.7 km-thick) magnetostratigraphic data from the underlying fluvial Campodarbe Fm (Luesia and San Marzal sections, Eocene-Oligocene). This composite section allows dating the entire basin infill in this sector, therefore bracketing the timing of the deformation in the southern margin of the Pyrenees after considering previous kinematic studies. Deformation recorded by the continental deposits spans from syn-Gavarnie nappe activity (Broto and Fiscal basement thrust sheets) from 31.3 to 24.55 Ma, Rupelian-Chattian (Oligocene) to the syn-Guarga thrust activity, from 24.55 to 21.2 Ma Chattian-Aquitanian (Oligocene-Miocene). The Accumulation rates vary from ca. 22 to ca. 39 cm/kyr between the genetic stratigraphic units in the Uncastillo Fm through the section. These rates are close to those of the underlying deposits of the Campodarbe Fm (average of ca. 36 cm/kyr). Deformation for the latest Pyrenean front (syn-Guarga thrust) is younger than previously assigned in ~5.4. ~1.5 and ~1.1 Myr of the beginning of the Punta Común thrust sheet (from 29.4 Ma to 24 Ma), Lower Riglos thrust sheet system (from 24 to 22.5 Ma) and the Upper Riglos thrust system (22.5 to 21.4 Ma) respectively. Other significant changes in accumulation rate and its derivative also indicate variations in the tectonic activity ca. 33 and 28 Ma. © 2019 Elsevier B.V., Financial support was provided by the Spanish Ministry with the SEROS project, reference: CGL2014-55900-P/BTE and the project DR3AM-CGL2014-54118-C2-2-R. Thanks to the Paleomagnetic Laboratory CCiTUB-ICTJA CSIC, the Geomodels Research Institute, the Grup de Geodinàmica i Anàlisi de Conques - 2017SGR00596 and Geotransfer Group at the University of Zaragoza.

This paper describes the Alto de las Picarazas site (Andilla-Chelva, Valencia) which is made up of a group of karst cavities that contains Lower and Middle Pleistocene deposits. In Cavity I, a wide Early Pleistocene sequence under a Middle Pleistocene deposit has been preserved. In Stratum IV, evidence of human presence, such as lithic industry and mammal bones with butchery marks, has been found. Remains of Allophaiomys ruffoi and Soergelia minor in this stratum give the site a Early Pleistocene chronology.

Lightning impacts on forests and trees are still understudied from a tree-ring perspective. Lighting causes direct and indirect damages on forests and trees. Trees struck by lightning can show a growth reduction and lightning storms also trigger wildfires in seasonally dry areas such as Mediterranean mountains. Here we combined dendroecological and magnetic analyses to reconstruct and assess the impact of lightning on radial growth and the magnetic properties of wood in Scots pine (Pinus sylvestris) and Black pine (Pinus nigra) in two sites with a high density of lightning impacts located in eastern Spain. We dated several lightning scars, particularly in Scots pine, formed during 1982, when a wildfire was initiated by lightning during a dry summer storm. Growth was reduced during the year when the scar was formed in both pine species, albeit this effect could be masked or amplified by other disturbances (drought, outbreaks). However, despite that short-term growth reduction scarred trees showed higher growth rates than non-scarred trees in the case of Scots pine. The intensity of magnetization did not significantly differ in wood produced before and after the lightning scar was formed. This could be due to multiple lightning hits in the same or nearby stands affecting the magnetization of wood. Wood magnetic properties should be further explored as proxies of lightning impacts in sites where scars are not formed and tree-ring information is limited such as tropical forests. Further cross-disciplinary research is required to assess the impacts of lightning on tree growth and magnetism.

Paleomagnetism is a technique very useful in structural geology providing that the rocks keep a stable record of the paleoearth magnetic field information. Paleomagnetism has been used in deciphering the evolution and geometry of orogens and extensional basins. The evolution of an orogen has many points of view, but the use of paleomagnetism allows (i) calculating vertical and/or horizontal rotations during basin and orogen evolution and hence providing actual data to calculate out-of-plane movements particularly important when constructing cross-sections to calculate shortening, (ii) dating syntectonic sediments at foreland basins, which in combination with exhumation rates, for example, allow for a complete reconstruction of the evolution of the orogen, and (iii) deducing chemical interactions when remagnetization occurs. At larger scale, paleomagnetism has been fundamental for paleogeographic reconstructions and evolution of tectonic plates.

"This is a post-peer-review, pre-copyedit version of an article published in Studia Geophysica et Geodaetica. The final authenticated version is available online at DOI: http://doi.org/10.1007/s11200-017-0143-6", Magnetic fabric allows to unravel the petrofabrics of sedimentary rocks and to assess their deformational history. The use of this technique, in addition to classical structural field observations in the limbs of seven asymmetric folds in the Pyrenees, helps to determine the differences of internal deformation as well as the folding kinematics. Three folds developed during the Variscan Orogeny in Ordovician and Devonian rocks, and four folds developed during the Pyrenean Orogeny in Eocene rocks, are studied. Folds show a variety of structural locations, in different thrust sheets of the Southern Central Pyrenees, different cleavage development, age, geometry and lithology. Sampling follows an equivalent lithological layer in the two limbs, except for one case, of the selected folds. Results show a modified tectonic magnetic fabric in most sites with the magnetic lineation on the tectonic foliation plane. A larger scattering of the magnetic lineation (maximum magnetic anisotropy axis) and a higher intensity of the preferred orientation of minerals (eccentricity of the anisotropy of magnetic susceptibility - AMS ellipsoid) is better observed in the overturned (short) limb of the asymmetric Variscan folds than in the normal (long) limb. On the other hand, the shape parameter in Alpine folds is generally larger in the overturned (short) limb then in the normal (long) one. A good clustering of the minimum magnetic anisotropy axes is observed in all limbs. The combination of the AMS data with the structural data helps to understand and better constrain the deformation degree in these asymmetric folds and to unravel the deformational history, Financial support came from the Spanish Ministry of Science and Innovation - FEDER Funds (MICINN) and from the National Parks Organism, Spain.

The structure of the Pyrenean Axial Zone laterally transitions from an imbricate thrust system to an antiformal stack displaying downward facing structures in its frontal part (the Nogueras zone). We carried out a paleomagnetic study through this structural transition to better constrain thrust kinematics and better define the factors controlling the occurrence of antiformal stacks. Triassic red beds unconformably overlying the Paleozoic basement were sampled across three main thrust sheets (the Nogueras zone, the Bielsa, and the Orri thrust sheets). From 31 new sites, two meaningful magnetizations were defined, both carried by hematite: (1) the primary magnetization, that unblocks at 660–685 °C and (2) an intermediate-temperature, syn-orogenic remagnetization. Paleomagnetic data indicate variable, clockwise vertical axis rotations, with mean, thrust-scale values that range from 0 to +38°. They increase both from the base to the top of the stacked units and from west to east and display a thrust-scale directional dispersion that is higher for the lower wavelength thrusts. Results evidence that increasing thrust displacements in the upper thrusts units are a key factor for the formation of antiformal stacks showing downward facing structures. Displacement gradients in the basement are transferred to cover units and can account for important rotations such as those registered by the Mesozoic-Cenozoic units to the south of the study area.

Restoration of geological structures helps understand and validate the reconstruction of subsurface structures. In many restoration algorithms, the surface is triangulated and then unfolded, starting from an undeformed location (pin-element). The aim of this paper is to assess the impact of the pin-element location and triangulation of the mesh (density and type) on restoration by best fitting of finite elements, with and without a rotation constraint. The deformation of complex structures is simulated at laboratory scale. First, a reference mesh is set on the undeformed models. Then, a deformation is applied to obtain the new mesh coordinates using photogrammetry. Finally, the mesh is restored and the deformation calculated on the restored model. Comparing the actual and computed deformation, it is found that dense meshes can help locate expected deformation areas, if a rotation constraint is used to reduce error propagation. Mesh type and density seem to play a secondary role in the final result for smooth surfaces, but become relevant for highly deformed surfaces. Pin-element location influences the restoration result, especially when no rotation constraint is considered. Overall, the results suggest that the accuracy and reliability of restoration methods based on triangular meshes can be significantly improved by using a rotation constraint.