http://hdl.handle.net/10366/138651 2026-04-29T02:22:44Z http://hdl.handle.net/10366/169933 [EN]We present a new magnetobiostratigraphic study of the Izaga composite section (South Pyrenean foreland basin), performed to investigate the possibility of defining the Bartonian GSSP and to assess the yet unexplored sedimentary expression of the Middle Eocene Climate Optimum (MECO) in the deep palaeoenvironments of the basin. Our results indicate that the section spans from the uppermost part of Chron C19r to the uppermost part of C18n.2n, comprising calcareous nannofossil biozones CNE14 and CNE15. As found in most prospective sections studied previously, the occurrence of delayed magnetizations has prevented precise delineation of the marker of the Bartonian GSSP, the short lived Chron C19n, which reinforces the idea that an alternative biostratigraphic event might need to be chosen as the primary marker of the GSSP. In this regard, we propose the highest occurrence of Sphenolithus furcatolithoides B, whose persistent location close to the top of C19n has been corroborated at the Izaga composite section. If this datum accepted, the Izaga composite section can be regarded as one of the best prospective successions to host the Bartonian GSSP due to its expanded nature and superb outcrop conditions. Our results also reveal an increase in the input of reworked calcareous nannofossils and organic matter of continental origin concurring with a negative shift in the carbonate carbon and oxygen stable isotope record around the C19r/C18n.2n boundary, and hence demonstrate that the enhanced hydrological cycle induced by the MECO is manifested along a complete continental to deep marine transect along the South Pyrenean basin. 2025-01-01T00:00:00Z http://hdl.handle.net/10366/169931 [EN]Underground hydrogen storage (UHS) is emerging as a promising tool for managing surplus energy derived from renewable energy sources. Rock salt (halite) formations, particularly solution-mined salt caverns, offer a secure and efficient storage medium due to their low permeability, self-healing properties, and chemical stability. Laboratory experiments simulating reservoir-like conditions are essential for reducing uncertainties surrounding hydrogen–rock interactions prior to large-scale deployment. This study investigates the response of rock salt to hydrogen exposure under controlled conditions (10 MPa, 60 °C, 30 d) in an autoclave. Two samples from the Eocene Barbastro Formation (Southern Pyrenees), recovered from a deep borehole within a potential salt cavern-type storage site, were tested. The halite samples included impurities such as anhydrite, quartz, feldspars, dolomite, calcite, and phyllosilicates, allowing assessment of non-halite phase reactivity also. Results indicate no significant mineralogical changes after hydrogen exposure. Observed alterations were minor and limited to localised halite recrystallization, slight particle detachment, and occasional chloride precipitation. These findings suggest an overall mineralogical stability of the salt matrix and impurities under the tested conditions and scales. By improving our understanding of hydrogen–rock interactions in evaporitic settings, this study contributes to ongoing efforts to develop safe, science-based solutions for underground hydrogen storage in salt caverns. 2025-01-01T00:00:00Z http://hdl.handle.net/10366/169929 [EN]This special volume of Journal of Iberian Geology brings together a set of articles selected from the presentations given at the XIII MAGIBER congress, a meeting held at the Faculty of Sciences of the University of Porto from the 25th to the 28th of July 2023. The organization of the meeting was led by colleagues of this university and of the neighbouring Institute of Earth Sciences in close collaboration with the Paleomagnetic Commission of the Geological Society of Spain, and was dedicated to the general theme of “Magnetism in Iberia: Results and New Frontiers”. The meeting brought together more than 50 researchers and students from Portugal and Spain, allowing everyone who works in the field of paleo- and geomagnetism to share their results and research activities (Fig. 1). The laid-back atmosphere of the meeting favoured the strengthening of existing collaborations and the development of new partnerships between scientists of the two countries, reaffirming that Geosciences have no borders. The topics addressed during the meeting included the anisotropy of magnetic susceptibility, geomagnetism, rock and environmental magnetism, archaeomagnetism, paleomagnetism, magnetostratigraphy and magnetotectonics, in what is a clear presentation of the multidisciplinary character of the discipline and of the scientific community involved in the meeting. The congress included two days of oral and poster presentations, a hands-on workshop on the applications and limitations of remanent magnetization curves unmixing led by recognized experts R. Egli and E. Font, and a field trip to the Praia de Lavadores in Porto (see https://magiber2023.wixsite.com/xiii-magiber). The full book of abstracts (Sant´Ovaia et al., 2023) can be downloaded from the website of the Paleomagnetic Commission of the Geological Society of Spain (https://sociedadgeologica.org/magiber-xiii/). 2025-01-01T00:00:00Z http://hdl.handle.net/10366/169928 [EN]The detailed analysis of the fracture geometry in the Panticosa granitoid (Axial Zone, Pyrenees) highlights the key role of structural analysis studies in characterizing water flow within fractured aquifers. Several fracture sets (striking ENE–WSW, NW–SE and north–south) were identified through photogrammetry (with nearly 30 000 mapped fractures) and fieldwork. A hierarchical classification of the fracture systems was established based on their continuity along-strike. The most prominent set, comprising individual faults that extend over several kilometres and exhibiting normal displacements of 10–50 m, also coincides with the dominant ENE–WSW orientation observed across multiple scales. These large, continuous structures probably result from recent tectonic activity or gravitational collapse. A second-order system includes NE–SW and NW–SE fractures ranging from metres to hundreds of metres in length. The distribution of the third-order set is more scattered and links longer fractures. Additionally, a set of dykes (mostly west–east striking) displays discontinuity contacts with the granite. We interpret that the studied fault sets are responsible for the upflow of thermal water (c. 45°C at the sources) of the deep aquifer from depths of 2 km. The higher continuity and transmissivity of the recent ENE–WSW fault system (showing thicker fault zones) made them more relevant for conditioning water flow. 2026-01-01T00:00:00Z http://hdl.handle.net/10366/169916 [EN]The North Pyrenean Zone results from the Late Cretaceous‐Cenozoic inversion of the Mesozoic rift system extending along the Iberia‐Europe plate boundary. The western part of this inverted rift (from the Tardets‐Mauléon basin in the West to the Bigorre basin in the East) is strongly decoupled from the basement along Upper Triassic evaporites and slightly, internally overprinted by orogenic processes. These conditions make the area an ideal candidate for the study of rift‐related structures and mineral fabrics registering the kinematics of the rifting process. This work focuses on the study of meso and micro‐scale rift inheritance through a combination of structural analysis, anisotropy of magnetic susceptibility (AMS) and mineral shape fabrics extracted from X‐Ray microtomography analysis. Previous AMS results (Mauléon basin) are integrated with data from 64 new AMS sites, acquired across both the Mesozoic, syn‐rift cover and the Paleozoic basement. In syn‐rift units, magnetic and mineral fabrics are in agreement and at a great extent inherited from syn‐ and post‐rift stages. The compressional overprint of the Late‐Cretaceous‐Cenozoic inversion is limited and localizes along the south‐western margin of the inverted basin. In the Paleozoic, a partial overprint of Mesozoic extension on AMS occurs in areas where rift‐related peak temperatures exceeded ∼350°C. Rift‐related mineral and magnetic lineations reveal a regional and constant through time NNW‐SSE to NE‐SW extension that attests this ample domain of the Pyrenean rift opened under a roughly orthogonal or slightly oblique rifting. Its easternmost part registered a partitioning between N‐S and NW‐SE extension directions, likely controlled by pre‐rift faulting. 2025-05-29T00:00:00Z http://hdl.handle.net/10366/169537 [EN]The oxidation of pyrite involves a series of chemical reactions that, depending on climatic conditions, can give rise to different mineral phases and morphologies. When oxidation takes place in semi-arid climate, the development of efflorescent salts on the surface of mine tailings is characteristic. These salts are mainly composed of Fe, Al and Mg sulfates and may accumulate valuable metals liberated through the dissolution of tailing minerals. This research aims to describe the evolution of salt precipitation from the economic and environmental perspective. For this purpose, we sampled efflorescent salts formed during the summer season on the surface of a tailing impoundment located in the north of Chile. The materials underwent comprehensive characterization utilizing X-ray techniques and scanning electron microscopy. The findings reveal a fractional precipitation in the crystallized salts. In an advanced oxidation system, characterized by multiple seasons of crystallization, dissolution and oxidation, the dry season begins with the precipitation of sulfates from a highly acidic solution dominated by Fe3+. This solution results from the dissolution and oxidation of the previous season sulfates. This initial stage is characterized by the presence of jarosite and gypsum, which are subsequently replaced by ferricopiapite. Towards the progress of the dry season, copiapite becomes more magnesian and precipitates alongside coquimbite and alunogen. Finally, halotrichite and pickeringite begin to crystallize. Base metal cations such as Co, Cu, Mn, Ni and Zn are preferentially incorporated into halotrichite-pickeringite sulfates during the most advanced evaporation phase. 2024-06-20T00:00:00Z http://hdl.handle.net/10366/168666 [EN]Calcium carbonate (CaCO3) polymorphs are some of the most abundant minerals in natural environments on Earth’s surface. They are normally linked to fields including biomineralization, global CO2 exchange or pollutants remediation due to the strong surface interaction with heavy metals in the environment. The aim of this work is to study the crystallization of CaCO3 through precipitation experiments from aqueous solutions in the presence of different amounts of As(V), thus evaluating the capacity of the precipitating phases to remove As from solutions. Surprisingly, the results confirmed that the uptake mechanism operates relatively well, decreasing the initial concentration of arsenic in all the experiments conducted. On the other hand, the presence of this element controls the crystallization of calcite by inhibiting it, and stabilizing the less stable phase, vaterite, which under As-free conditions acts as a transient intermediate phase during the crystallisation process of amorphous calcium carbonate to the most stable polymorph, calcite. Different characterization techniques, including X-ray diffraction and ICP spectroscopy, were used to corroborate that the formation and stabilization of vaterite is linked to the presence of that pollutant. This phenomenon should be taken into account since natural CO2 sink, in the form of carbonate rocks, must be affected by the presence of this element, even at low concentrations, thus being the arsenic element even more poisoning than we thought until now. 2025-12-24T00:00:00Z http://hdl.handle.net/10366/168480 [EN] We present a new structural study of a D2–M2 tectono-thermal structure in SW Iberia (Ponte de Sor–Seda gneiss dome) characterized by a spatial distribution of telescoping isograds providing a record of Buchan-type metamorphic conditions. The gneiss dome comprises an infrastructure made up of a lower gneiss unit (LGU) and an intermediate schist unit (ISU), separated by early D2 ductile extensional shear zones. The LGU and the ISU are composed of Ediacaran–Cambrian rocks that experienced the highest-grade M2 metamorphic conditions (amphibolite facies). Late Ediacaran–Early Terreneuvian and Late Miaolingian–Early Furongian protolith ages for LGU (496 ± 3 Ma) and ISU (539 ± 2 Ma) orthogneisses are reported. A superstructure made of Cambrian–Devonian rocks (Upper Slate Unit, USU) deformed under M2 greenschist facies conditions, tectonically overlies the ISU across a D2 extensional shear zone. Kinematic criteria associated with D2–M2 fabrics indicate top-to-ESE–SE sense of shear. A late-D2 brittle-ductile high-angle extensional shear zone (Seda shear zone) crosscuts the gneiss dome. D3 upright folds, thrusts and transpressive shear zones caused the steepening of D2 structures and the local crenulation of S2 foliation. The Mississippian D2–M2 event recorded in the Ossa–Morena Zone may be regarded as a regional-scale phenomenon that markedly influenced the crustal architecture of North Gondwana during the assembly of Pangaea. 2023-01-01T00:00:00Z http://hdl.handle.net/10366/166875 [EN]Below the central nave of the Gothic Cathedral of Palencia (14th to 16th centuries) lies the Crypt of San Antolín, which represents the remains of a Visigothic building from the mid-7th century. The crypt itself has suffered recurrent episodes of flooding over the centuries. However, the latest flooding, which began in mid-2021 and ended in mid-2023, is one of the most long-lasting episodes on the historical record. To establish the origin of these flooding episodes, the geological and hydrological properties of the subsoil have been determined by direct prospecting techniques (drilling) and indirect geophysical techniques (Electrical Resistivity Tomography). The prospecting has determined that the aquifer in the area has a basin-like geometry, which favors the accumulation of water below the crypt. This work has shown that the recurrent floods suffered by the crypt prior to 2021 are related to episodes of intense rainfall. However, after 2021, there is a direct relationship between the persistent flooding and the onset of landscaping at the Plaza de San Antolín, one of the squares near the cathedral. In addition, previous archaeological excavations carried out in 1965 in that same square had disrupted the stratigraphic column, easing the percolation of water. We conclude that the increase in landscaped areas in archaeological environments may modify the hydrogeological dynamics of the subsoil and affect the surrounding buildings. 2025-01-01T00:00:00Z http://hdl.handle.net/10366/166873 [EN]Slates are common metasedimentary rocks in the Iberian Peninsula, ranging in deposition age from Proterozoic to Ordovician. Spain is currently the primary producer of high-quality slate products. The excellent cleavage is related to microstructures with very strong preferred orientation of white mica and chlorite. In this study we explore preferred orientation of eleven slates and one phyllite of different composition and metamorphic grade from Northern Spain with high energy synchrotron X-ray diffraction and study microstructures with scanning electron microscopy. While phyllosilicates display high crystallographic and shape preferred orientation, quartz, with also highly flattened grains, has in most samples a random crystallographic orientation. The microstructural and texture data are used to model anisotropic seismic properties with a self-consistent method and to explore the influence of crystal shapes on elastic anisotropy. Anisotropy for these slates is very high compared with gneiss and shale and, due to its prevalence, slate anisotropy contributes significantly to seismic anisotropy in the upper crust. 2022-01-01T00:00:00Z http://hdl.handle.net/10366/166860 [EN]At least two sub-Moho reflectors have been identified in different seismic refraction and wide-angle reflection experiments conducted in western Iberia since the early 1990s. The wavelet kinematics and characteristics of the shallowest event are probably produced by an increase in P-wave velocity that forward modeling places at ∼70–75 km depth beneath the Ossa-Morena Zone (OMZ) shallowing up to 50–60 km beneath the Central Iberian Zone (CIZ). Synthetic modeling suggests that the coda and amplitude of this arrival may correspond to a ∼10-km-thick heterogeneous layer. We used a two-dimensional second-order finite-difference acoustic full wavefield modeling scheme with an input model which includes a layer of randomly distributed bodies thinner than one-fourth of the wavelength of the source waves and ΔVp = ±0.1 km/s at the considered depth range. The resulting synthetic data reproduce well the observed amplitudes and codas because of the constructive interferences caused by this heterogeneous zone. The origin of this layer also discussed here in detail, is very likely related to the phase transition from spinel to garnet lherzolite, the so-called Hales discontinuity. A second reflection also observed in some of the experiments suggests the presence of a velocity inversion at greater depths. Forward modeling places this discontinuity at around 90 km depth beneath the OMZ, deepening to 105–110 km depth beneath the southeast CIZ and shallowing up to 80 km depth in the northeast CIZ. The observed characteristics of this event are consistent with those of the lithosphere-asthenosphere boundary. 2021-01-01T00:00:00Z http://hdl.handle.net/10366/166859 [EN]The renaissance botanical garden of ‘El Bosque’ in Béjar (Salamanca, Spain) presents a pond bounded by a dam in its western part. The latter is formed by two masonry walls interconnected by buttresses. Cubic spaces in between are filled with a variable grain-size material (silty sand) that allows limited water flow. In recent years, the southern part of the dam has experienced localized and random subsidence that jeopardizes the entrance to part of the garden. To regain access, a proper and reliable diagnosis of the origin, magnitude and relevance of the subsidence must be made. In this regard, we have undertaken a microgravity survey in the dam area to identify places with an anomalous distribution of the filling material in order to foresee further sinking or potential collapsing areas. The precise positioning (2 mm resolution) and accurate terrain correction needed in this kind of high-resolution gravity surveys (points every 1.5 m) were achieved by creating a detailed digital terrain model (cm resolution) with a remotely piloted aircraft. In addition, we performed three electric resistivity tomography (ERT) profiles at different levels of the garden: (i) on the dam itself; (ii) right on the foot of the dam and parallel to it (5 m below and ∼17 m to the W); and (iii) a bit farther, but also parallel to the dam (8 m below and ∼27 m to the W). The ERT profiles identified high conductivity in water-saturated areas and determined the paths that rainfall and pond’s seepage water follow in the dam and its underground, formed by granites. The geophysical studies were paired with geotechnical analyses of the sunk materials. The study concluded that the thinnest fraction of the dam’s filling material (i.e., silts) is being washed away, leaving behind sand with less density and stability, susceptible to collapse. Thus, the observed sinking is related to soil piping, that is to soil internal erosion and compaction issues that force the soil material to re-adjust geometrically and volumetrically 2023-01-01T00:00:00Z http://hdl.handle.net/10366/166858 [EN]Interference between orogenic systems and deformation phases within them may lead to reworking and reactivation of previous structures. The eastern sector of the Spanish-Portuguese Central System holds evidence of two orogenic systems, Variscan and Alpine, plus a stage of Permian extension. We perform an integrated structural analysis to identify reworking and reactivation processes throughout the geological record. The Variscan record starts with crustal thickening (D1; E-verging overturned folds). A second phase features the intraorogenic collapse of an overthickened crust (D2; top-to-the-SE ductile extensional shear zone), which produced intense structural reworking at the core of the shear zone and moderate reworking at its hanging wall. During subsequent strike-slip tectonics, crustal thickening parted transpressional deformation into a dextral shear zone and upright folds (D3). Variscan deformation did not reactivate previous structures, but exploited a weak rheological boundary defined by contrasted lithologies (sedimentary versus igneous rocks) to accommodate D2 shearing. Reactivation played a role afterwards: Variscan strike-slip shear zone acted as a transfer fault to accommodate Permian extension (post-orogenic collapse), and then Alpine contraction. The Permian extension record is blurred by Alpine inversion, although the trend of Alpine structures in Central Iberia, and the Spanish- Portuguese Central System, may result from Permian structural inheritance. 2022-01-01T00:00:00Z http://hdl.handle.net/10366/166857 [EN]Many di erent processes for manufacturing of magnetic particles are present in scientific literature. However, the large majority are not able to be applied to large-scale real operations. In this study, we present an experiment undertaken to determine advisable values and options for the main variables and factors for the application of the reverse co-precipitation method to produce magnetic particles for real environmental applications. In such, we have tried a conjugation of values/factors that has led to 12 main experiments and production of 12 di erent particles. After an initial study concerning their main characteristics, these 12 di erent particles were applied for the sorption removal of COD from real wastewater samples (e ciencies between 70% and 81%) and degradation of Methylene blue by Fenton reaction (degradation e ciencies up to 100%). The main conclusion from this work is that the best set of values depends on the target environmental application, and this set of values were determined for the two applications studied. 2020-01-01T00:00:00Z http://hdl.handle.net/10366/166856 [EN]The Middle Allochthon of the Galicia-Trás-os-Montes Zone (GTMZ) in NW Iberia is an assemblage of oceanic units representing the Variscan suture of one or more peri-Gondwanan oceans. This contribution brings new geochronological and geochemical data from the Middle Allochthon of the Morais Complex, in northern Portugal. There, the oceanic ensemble consists of a stack of five tectonic units which from bottom to top are the Junqueira, Pombais and Izeda oceanic supracrustals and the Remondes and Morais-Talhinhas ophiolitic units. The Junqueira and Pombais units consist of greenschists and metapelites. No age data are available for these two units, but a correlation is established with a Cambro-Ordovician unit in the Órdenes Complex of Galicia (NW Spain) dated at 500 Ma. The Izeda Unit consists of fine-grained, low-grade amphibolites transitional to epidote-amphibolites and greenschists, for which an age of 484 ± 3 Ma has been obtained for a metabasic tuff. In the ophiolitic ensemble, the Remondes and Morais-Talhinhas units consist of fine-grained amphibolites associated with deformed metagabbros, mafic cumulates and serpentinized ultramafics. In this study, two plagiogranite samples from the Remondes Unit yielded a complex spread of age data with Silurian ages representing the dominant population. This suggests that the newly defined Remondes Unit is younger than the Izeda Unit but older than the previously published age for these rocks, which are considered part of the overlying Morais- Talhinhas Unit, dated as Devonian (406–395 Ma) in a previous study. The geochemistry of the basic rocks in the five units is that of NMORB with a subduction-derived component that varies from weak to null. The ages, together with new and previously published whole rock geochemical data obtained from basic igneous samples, are interpreted to date and reflect the formation of igneous protoliths in oceanic ridge settings associated with the Mid-Variscan Ocean, a part of the Rheic oceanic realm that registered magmatic activity between the late Cambrian and the Lower Devonian. 2024-01-01T00:00:00Z http://hdl.handle.net/10366/166851 [EN]The allochthonous complexes of Galicia–Trás-os- Montes Zone (NW Iberia) are part of a rootless tectonic stack which preserves part of a Variscan accretionary prism. They are formed by individual tectonic slices marked by specific tectonometamorphic evolutions, which were piled up in a piggy-back mode onto its relative autochthon, the Central Iberian Zone (CIZ). Allochthony decreases from the structurally upper thrust sheets towards the lower ones. The lowermost unit of the stack is known as the Parautochthon or Schistose Domain. It is characterized by a low metamorphic grade in contrast with higher temperatures and/or pressures estimated for the overlying allochthonous units and shares the stratigraphic sequence with the underlying autochthon. The Parautochthon is divided in two structural and stratigraphic sub-units: (i) the Lower Parautochthon (LPa) is made of synorogenic flysch-type sediments with varied turbiditic units and olistostrome bodies, showing Upper Devonian– lower Carboniferous age according to the youngest zircon populations and fossiliferous content; (ii) the Upper Parautochthon (UPa) is composed of highly deformed preorogenic upper Cambrian–Silurian volcano-sedimentary sequence comparable with the nearby autochthon and to some extent, also with the high-P and low-T Lower Allochthon laying structurally above. The UPa was emplaced onto the LPa along the Main-Trás-os-Montes Thrust, and the LPa became detached from the CIZ relative autochthon by a regional-scale structure, the Basal Lower Parautochthon Detachment, which follows a weak horizon of Silurian carbonaceous slates. 2021-01-01T00:00:00Z