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Geologica Acta, vol. 23, no. 27, 21 p. Bover-Arnal T., Pascual-Cebrian E., Moreno-Bedmar J.A. & Salas R. (2025).- Strontium-isotope stratigraphy of the Aptian–Albian transition in the western Maestrat Basin (E Iberia)- The Aptian–Albian transition in the Maestrat Basin (E Iberian Chain) encompasses two lithostratigraphic units: the Benassal and Escucha formations. In some sectors of the basin, such as the western Galve and Las Parras sub-basins, this stratigraphic interval recorded a progressive shift from widespread carbonate platform settings to coastal siliciclastic-influenced and coal-bearing environments. Due to the transitional nature of this interval, establishing a clear stratigraphic boundary between the upper part of the Benassal Formation and the lower part of the Escucha Formation is challenging. Additionally, there is no unanimous agreement on the age range of these formations. To shed light on the stratigraphic location of the boundary between the Aptian and the Albian, strontium-isotope analyses were carried out on thirteen low-Mg calcite oyster shells to derive numerical ages. In the Las Parras Sub-basin, the 87Sr/86Sr values obtained from the siliciclastic-influenced transitional deposits between the Benassal and Escucha formations, as well as from the lowermost part of the Escucha Formation, range from 0.707282±0.000002 to 0.707410±0.000002. These Sr-isotope ratios translate into numerical ages that constrain this stratigraphic interval to the early Albian. The oyster shells collected in the Galve Sub-basin exhibit a higher degree of diagenetic alteration. Nevertheless, the least altered specimens analysed from the lower part of the transitional facies between the Benassal and Escucha formations in this latter sub-basin yielded Sr-isotope ratios between 0.707197±0.000003 and 0.707256±0.000002. These values correspond to ages spanning from the latest Aptian to the earliest Albian. Accordingly, in most sectors of the western Maestrat Basin, the Aptian–Albian boundary is likely to be stratigraphically located at the lowermost part of the transitional facies between the Benassal and Escucha formations. Geologica Acta, vol. 23, no. 28, 18 p. Calugaru M.E., Munteanu M., Wäll M. & Isac A. (2025).- Trace element contents in bornite, chalcopyrite and pyrite (LA-ICP-MS) from Miocene porphyry copper-gold deposits from Metaliferi Mountains, Romania- In porphyry systems, valuable elements such as Au, Ag, Te, Se and Bi are found in trace contents associated with Cu and Fe sulfides. The relations between sulfide and the trace element contents, as well as the role of physicochemical factors in the uptake of different trace elements are still being assessed. This study focused on understanding how these elements are concentrated in selected sulfides (pyrite, chalcopyrite and bornite) and on the relation between the measured trace element composition of these sulfides and the hydrothermal alteration types in six porphyry deposits from Romania: Roșia Poieni, Bucium-Tarnița, Colnic, Rovina, Valea Morii and Bolcana. Based on LA-ICP-MS micro-analytical data, bornite is revealed as the main host for Bi (1077ppm), Se (810ppm), Ag (312ppm) and Te (43.73ppm). Chalcopyrite is also relatively rich in Se (199-403ppm), Ag (1.88-49.97ppm) and Te (1.95-36.06ppm). Pyrite is enriched in Co (98.81-704ppm), Ni (3.81-20.68ppm), As (2.13-166ppm), Se (24.65-729ppm) and Te (0.99-11.75ppm). These elements occur in the host sulfides as solid solution and as mineral microinclusions. Gold content is <0.2ppm in both Cu-Fe sulfides and pyrite. There is no significant variation in trace element ratio in chalcopyrite (Se/In) and in pyrite (Co/Ni, Co/Cu, Ag/Co) when comparing results from potassic-altered with chloritic-sericitic altered samples. Based on trace element results and micro-textural features of studied minerals, we suggest that these elements were initially incorporated in the crystal lattice during the potassic alteration and the overprinting of chloritic-sericitic alteration caused the exsolution and redistribution of trace elements within their host minerals. Geologica Acta, vol. 23, no. 29, 21 p. Travé A., Nadal J., Playà E., Salas R., Cantarero I., Baqués V., Cruset D., Gomez-Rivas E. & Martín-Martín J.D. (2025).- Fracture-related dolostones replacing Upper Jurassic–lowermost Cretaceous syn-rift deposits in the eastern Iberian Chain (eastern Spain)- Upper Jurassic and Lower Cretaceous limestones and dolostones serve as hydrocarbon reservoirs in the offshore area of NE Spain. Since similar dolomitized rocks crop out in the adjacent onshore Maestrat Basin in the SE Iberian Range, understanding the dolomitization and other diagenetic processes is key to assessing reservoir properties. The Maestrat Basin dolostones crop out as elongated, asymmetric bodies, ranging from tens of centimetres to kilometres in length and up to 150m thick, with a wedge-shaped geometry closely associated with fractures. These dolostones are calcium-rich with low concentrations of Mn, Sr, and Na, but variable Fe, indicating that the replacement of the host limestone was followed by dolomite cement precipitation. Fluid inclusion data suggest that dolomitization took place at temperatures ranging between 70 and 120ºC. Such temperatures, together with the high 87Sr/86Sr ratio and fluid salinity (16 to 23% wt. NaCl equivalent), reveal that the dolomitization process took place in burial conditions, from fluids that were infiltrated and likely interacted with Triassic, Liassic, and basement rocks. Although the exact age of dolomitization is not fully constrained, it is thought to coincide with fault-related dolomitization events of the same type previously described in the Maestrat Basin, likely during the latest Early Cretaceous and/or during the Late Cretaceous, in relation to the post-rift basin stage. Geochemical differences between the depocenters and structural highs may reflect the controls of the Maestrat Basin basin architecture on the composition and distribution of fluids. Geologica Acta, vol. 23, no. 30, 17 p. Gòmez-Ortiz, D., Martín-VelÁzquez, S., Martín-Crespo, T., Rodríguez-Santalla, I., de Ignacio-San José, C., Martínez-PagÁn, P., Martínez-Segura, M. (2025).- Electrical resistivity imaging to monitor water infiltration and contamination risk assessment in tailings ponds- This study investigates the internal structure and water content variations of the abandoned tailings ponds in the Hiendelaencina Ag-mining district, Spain, using Electrical Resistivity Imaging (ERI). The objectives were to delineate the geometry of the tailings deposits and to assess the spatial and temporal changes in water content within the ponds and the underlying geological units. The pollution risk assessment was evaluated as well. Six resistivity profiles were obtained during two separate field campaigns in September 2020 and May 2021, allowing for a comparison of resistivity data under different moisture conditions.The results revealed three distinct resistivity zones corresponding to the tailings, Cenozoic sedimentary deposits, and the underlying metamorphic basement, respectively. Temporal variations in resistivity indicates significant changes in water content between the two field campaigns, with increased water infiltration following spring rainfall. While no direct soil moisture measurements were available for calibration, the ERI results provide robust qualitative insights into relative water content changes and infiltration pathways.Notably, the fractured metamorphic basement showed higher water saturation, indicating vertical and lateral water flow from the tailings. These findings suggest that the tailings ponds are not impermeable, with water infiltrating into deeper layers, potentially transferring pollutants into the groundwater system. The study highlights the effectiveness of ERI as a non-invasive tool for investigating mining sites and provides important insights into the hydrological behavior of mine tailings, which is critical for environmental monitoring and risk assessment. Geologica Acta, vol. 24, no. 1, 25 p. Hernaiz-Huerta P.P., Ramos A. & Ardévol L. (2026).- The Muschelkalk (Middle Triassic) in the SE sector of Sierra del EspadÁn (Iberian Range, Spain)- Detailed mapping of the southeastern sector of the Sierra del EspadÁn (Eastern Iberian Range) shows that the Muschelkalk M2 intermediate unit is extensively distributed across the region, including its coastal areas. The M2 unit forms a thin (up to 25–30m), incompetent horizon predominantly composed of marly-dolomitic facies. Local stratigraphic omissions of this unit, resulting from facies changes or lateral wedging, occasionally led to continuous dolomitic successions corresponding to the Muschelkalk M1 plus the lower M3 (M3i) units. The M1 unit has been consistently mapped throughout the area, maintaining stratigraphic continuity with the underlying Röt facies, which cap the Buntsandstein B2 succession. Similar stratigraphic patterns have been observed in the adjacent Sierra Calderona to the South. These features collectively support the interpretation that both mountain ranges belong to the Mediterranean Triassic Domain, rather than to the Levantine-Balearic Domain. The Muschelkalk is transitionally overlain by a previously undescribed thick marly-clayey succession, which includes thin, well-bedded dolostones, resembling those of the lower M3 (M3i) unit, and abundant packages of dolomitic breccias. This newly identified interval is herein provisionally interpreted as a possible stratigraphic unit, the “supra-Pina de Montalgrao” facies referring to its position overlying the uppermost Muschelkalk M3 (M3s) Pina de Montalgrao Formation, pending paleontological evidence to confirm its age. The dolomitic breccias are interpreted as the result of fragmentation of thin, well-bedded dolostones, possibly triggered by gravitational instabilities associated with late-stage reactivation of Permian-Triassic rifting. Nonetheless, a dissolution process involving stratigraphically related evaporitic deposits remains a plausible alternative origin for some of these breccias. Geologica Acta, vol. 24, no. 2, 7 p. Corchete V. (2026).- Electrical conductivity inside Mars calculated beneath the InSight landing site- In a pioneer study, the electrical conductivity structure is determined beneath a fixed location on the Martian surface: the InSight landing site. The dataset used to attain this goal is the magnetic data recorded by InSight, from which are calculated the magnetic field variations in both high and low frequency, by spectral analysis. These variations are used to determine the surface ratios of vertical to horizontal magnetic field components, which are considered as the observed data that must be described/satisfied by some electrical conductivity models proposed. These models are the expression of the electrical conductivity structure of Mars, beneath the InSight landing site, and they should be recalculated when the data provided by future missions will be available (e.g. the Exobiology on Mars (ExoMars) Mission). Geologica Acta, vol. 24, no. 3, 19 p. Carlorosi J., TonarovÁ P., Gutiérrez-Marco J.C. & Hints O. (2026).- Discovery of Ordovician scolecodonts from Peru, with a review of Palaeozoic jawed polychaete records from South America- The fossil record of jaw-bearing polychaetes from South America is scarce, and only a few occurrences of Ordovician scolecodonts have been reported so far. Here, we document a monospecific jawed polychaete assemblage from the Darriwilian Lenodus crassus conodont zone of the San José Formation in the eastern Cordillera of Peru. The single species, Protarabellites luztejadae sp. nov., represents the oldest record of the family Ramphoprionidae worldwide and may point to the biogeographic origin of this group in Gondwana. The reconstructed jaw apparatus of P. luztejadae bears primitive characters such as the slightly enclosed myocoele, distinguishing it from the younger members of the family and providing insights into the evolutionary relationships with other labidognath families. The described assemblage is the first record of Ordovician scolecodonts from Peru, as well as from the northern part of the Central Andean Basin, and one of very few cases from where apparatus-based classification has been applied. However, the Palaeozoic scolecodonts in South America appear to be more common than generally thought. A review of poorly known regional literature shows that scolecodonts have been mentioned in various sites from Ordovician, Silurian, Devonian,and Carboniferous–Permian strata of Argentina, Bolivia, Brazil, Colombia, Peru, and Uruguay. This highlights the potential for future scolecodont studies in South America.. Geologica Acta, vol. 24, no. 4, 24 p. Santamaría-Pérez E., Medina-Cascales I., Martin-Rojas I. & Alfaro P. (2026).- Active faulting in the Betic External Zones (SE, Spain): The Alcoy Fault Zone- Evidence of active faulting is presented from a fault in the eastern Betic External Zones (SE Spain). New fault data are provided for the Alcoy Fault Zone, a structure whose Quaternary activity is currently under debate. This study includes a detailed structural and geomorphic characterization, along with a preliminary palaeoseismological analysis. This fault is ca. 13 km long, and two main sectors are defined based on its surface geometry: a SW sector striking N060E formed by a border fault strand, and a NE sector striking N040E to N065E, formed by a border and an intrabasinal fault strands. The Alcoy Fault Zone displays oblique kinematics, with a predominant left-lateral and a subordinate dip-slip component. Quaternary fault activity is evidenced by a qualitative and quantitative geomorphic analysis, where three geomorphic indices were applied (Smf, Vf and Bs). The fault presents a marked mountain front with low sinuosity. Cross-fault streams, which are deflected in a left-lateral sense, exhibit knickpoints that coincide with the fault traces and display highly incised valleys. Moreover, the morphology of their watersheds is consistent with an ongoing tectonic uplift in the area. Additionally, the palaeoseismological analysis performed in deformed colluvial deposits suggests a Holocene surface rupture history involving two events during the last ca. 1160 years. The results of this work represent the first step for the seismogenic characterization of the Alcoy Fault Zone and the base for further seismic hazard assessment studies in the External Zones of the eastern Betic Cordillera. However, additional seismicity studies will be required to determine whether the fault is basement-involved or represents a decoupled structure controlled by the Triassic evaporitic layer between the Variscan basement and the pre-Neogene Betic rocks. Geologica Acta, vol. 24, no. 5, 22 p. Molins-Vigatà J., Blanch X., Martín-Banda R., García-Sellés D., Gòmez-Novell O., García-Mayordomo J., Insua-Arévalo J.M. & Ortuño M. (2026).- Digital surface models derived from historical aerial imagery in highly anthropized areas applied to active fault studies (eastern Betics, Spain)- Landform recognition and surface analysis are critical in geomorphological and morphotectonic studies. In particular, the detailed study of the surface expression of active faults is essential for their characterization as seismic sources in fault-based seismic hazard models. However, increasing anthropogenic action has profoundly altered the natural landscape, degrading or erasing tectonic landforms, and limiting the accurate characterization of active faults in many regions worldwide. A paradigmatic example is the southeastern Iberian Peninsula, where extensive agricultural development over last decades has completely transformed the natural landscape. To address this limitation, we produced three historical Digital Surface Models (DSMs) using historical aerial imagery across two active faults in the Betic Cordillera: the Palomares and Llano del Águila faults. Two DSMs were generated for the Palomares Fault (one from the American B-series Flight, 1956–1957, and one from the Interministerial Flight, 1973–1986), and one DSM was generated for the Llano del Águila Fault from the Interministerial Flight, all with a spatial resolution of 2 × 2 m. We introduce Surface Roughness as a new diagnostic metric to assess quality and to identify model artifacts, while DEM of Difference analyses were used to quantify elevation changes and assess the consistency of the reconstructed surfaces. Rather than focusing solely on absolute geolocation accuracy, our approach emphasizes evaluating the reliability of the historical surface reconstruction. This methodology highlights the potential of historical aerial imagery to enhance active fault characterization and near-fault morphotectonic analyses in landscapes heavily modified by anthropogenic activity. Geologica Acta, vol. 24, no. 6, 17 p. Mercedes-Martín R. & Walaszczyk I. (2026).- Inoceramid constraints on the timing of Sant Corneli anticline uplift (Tremp Basin, South-Central Pyrenees, NE Spain)- The Sant Corneli Anticline is an asymmetric, westward-plunging structure at the termination of the Boixols Thrust (Tremp Basin, Spanish Pyrenees), which was emplaced in the Late Cretaceous and generated an elongated, westward-deepening foredeep basin. A stratigraphic and paleontological study of inoceramid bivalves in the southern flank of the Sant Corneli Anticline has provided refined constraints on the timing and lateral distribution of the synorogenic carbonate-marly units (growth strata) predating the emplacement of the mixed depositional systems during anticline uplift.Two stratigraphic units were identified and dated via inoceramid biostratigraphy: the upper Podega Member (marly limestone with slumps), and the Montesquiu Member (limestone alternating with marls). The upper Podega Member unit can be traced laterally southwest of the Sant Corneli Anticline, decreasing in thickness from 230 m in the west to 170 m in the east. Meter- to decemeter-scale soft-sediment deformation structures and syn-sedimentary faults attest to the occurrence of gravitational collapses. This unit spans the upper Santonian through the basal upper Campanian (in the European bipartite stage subdivision). In turn, the Montesquiu Member laterally decreases in thickness from 226 m in the west to 150 m in the east, and exhibits frequent intraformational unconformities and meter- to decemeter-scale soft-sediment deformation, indicative of active tectonism. This unit, placed in the middle- upper Campanian based on inoceramid biostratigraphy, precedes the sedimentation of shallower mixed depositional environments which are marginally affected by soft-sediment deformation features. | |
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