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.
The Garraf Mountain Range (GMR), located in Catalonia, NE Spain, is a calcareous karstic region subjected to intense anthropogenic influence, primarily due to the presence of numerous urban areas and extractive activities. Utilizing a new 2x2 m LIDAR-derived Digital Elevation Model (DEM), we updated the doline inventory, increasing the count from 710 collapse dolines to 968. The main objective of this study was to provide a preliminary characterization of the spatial distribution of the updated doline dataset across the entire GMR relative to hydrological issues and geological hazards. Factors that influence karst development like lithology, regional lineaments, and drainage network, along with slope, and altimetry were reviewed. Altogether, these aspects facilitated the delimitation of four distinct geomorphological blocks for GMR: Calafell, Ordal-Vilanova i la Geltru, Central, and Pallej & agrave;-Gava. No direct proximity relationship with structural lineaments traces was observed over doline occurrence. Dolines were more frequently associated with proximity to river streams and areas of high drainage density which do show structural control in their trend. These two facts aid in the definition of preferential directional paths for water running/infiltration that are important for quantifications of karst capture in water balance evaluations for GMR watersheds. Also, high concentrations of dolines near urban zones, landfills, and quarries were observed in the northeastern and southeastern sectors of the GMR, particularly in the municipalities of Vallirana and eastern Sitges, respectively. The updated inventory can be used in improving accuracy in water balance and karst hazard evaluations.
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 & Aacute;guila 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 & Aacute;guila Fault from the Interministerial Flight, all with a spatial resolution of 2 & times; 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.
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).
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.
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.
Detailed mapping of the southeastern sector of the Sierra del Espad & aacute;n (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 R & ouml;t 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.
Based on field data collected in the northern and southern Falcón Basin (Venezuela), this paper presents a comprehensive monograph that reports on the age and sedimentary evolution of the San Luis and Churuguara formations. It integrates platform-to-basin depositional models through facies distribution and stratal architecture, a palaeogeographic reconstruction, larger foraminifera biostratigraphy, sequence stratigraphy, and the evaluation of the accommodation history. An additional aim is to compare these onshore mixed carbonate-siliciclastic systems with the Oligo-Miocene subsurface carbonate reservoir of Perla in offshore Gulf of Venezuela, considered the largest gas discovery ever in Latin America. The carbonate platforms studied formed as a result of a secondorder transgressive event, and corresponded to distally steepened or undifferentiated ramps dominated by coralline algae and larger foraminifera. The presence of Miosorites americanus and Annulosorites spiralis dates the San Luis and Churuguara formations to the Early Miocene. The miogypsinid associations identified further distinguish between the Aquitanian and Burdigalian stages. The San Luis and Churuguara platforms exhibit a general aggradational trend, while the Perla carbonates have been interpreted as a retrogradational unit. Thirdorder T-R sequences interpreted from these successions were mainly influenced by differential tectonic subsidence. Additionally, major regional regressive events in the Falcón Basin and Perla Field coincide with global glaciations, highlighting the influence of eustatic changes. However, the Perla reservoir exhibits significant differences in thickness, spatial extent and sedimentary architecture compared to the onshore equivalents. The differences arise from variations in tectonic and palaeotopographic settings, accommodation and sedimentation rates and influence of adjacent siliciclastic systems. As a result, predicting the sedimentary architecture of carbonate reservoirs in this region using a generalized depositional model has proven to be challenging.
The Tampico-Misantla basin is a mature oil rich province in northeastern Mexico with large unconventional oil plays currently being explored. Results of a 3-D seismic reflection study of the basement and Jurassic sequences are used to analyze the basement influence on the sedimentary sequence and basin structure, by mapping the seismostratigraphic horizons for the (Tithonian) Pimienta, (Kimmeridigian) Taman/San Andrés, (Oxfordian) Santiago, (Callovian) Tepexic/Huehuetepec and (Bathonian) Cahuasas formations. The basement is characterized by stepped NW-SE tilted blocks of horst and grabens. The horst sections to the northeast are found at depths of 3,200m and get deeper up to 6,500m to the southwest. Blocks bounded by planar curved high angle normal faults with NW-SE and NE-SW orientation form a Triassic-Jurassic system, with two major pulses during the Bajocian and Oxfordian. Vertical slips of main faults are variable and may reach 2,000m. Basement blocks play major roles in defining the depositional processes, with thickness and distribution of overlying sedimentary units. Based on our analysis the Middle Jurassic Cahuasas Formation units were deposited predominantly in continental environments and exhibit large thickness variations. The Callovian Tepexic and Huehuetepec formations were deposited in transitional and shallow marine environments, with relatively uniform thickness and distribution. The Oxfordian to Tithonian Santiago, Taman/San Andres and Pimienta formations were deposited in marine environments, showing multiple fault deformation with tendency of progressively pinching out against the topographic highs. The thickness variation in the Santiago Formation suggests episodes of increasing subsidence and fault reactivation. The seismic volume models constraint the basement structures and Jurassic sequence stratigraphy in the Tampico-Misantla basin.
The study explores the Precambrian tectonic evolution and the growth of continental crust in the southern region of the North Odisha Singhbhum Craton (NOSC), delving into the potential petrogenetic processes and source characteristics. The Tikiba Granitic Complex (TGC) is in the contact area of the Eastern Ghat Mobile Belt (EGMB) and the NOSC. The present study involves the geochemical characteristics of TGC granitoids and their geochemical variations. Petrographically, the TGC is comprised of alkali feldspar granite, monzogranite to granodiorite. The major element geochemistry reveals calc-alkalic, ferroan to magnesian affinities, and a metaluminous, peraluminous and peralkaline character. It is enriched in LILE and HFSE like Yb, Sm, Zr and Y. The (La/Yb)(N) values range from 4.0-26.1 and exhibit distinct negative Eu anomalies (Eu/Eu*) (0.4-0.6). This granitic complex shows high Sigma REE contents of 176-860ppm with variable enrichment in LREE. Both REE and other incompatible element compositions define an A-type affinity. Based on geochemical data, we conclude that these granitoids have probably derived from a predominant crustal source with variable mantle characteristics in a post-orogenic setting.
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 120 degrees C. Such temperatures, together with the high( 87)Sr/Sr-86 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.
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.
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: Rosia Poieni, Bucium-Tarnita, 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.
The collision between the Arabian and Eurasian plates resulted in the uplift of The East Anatolian Province of Shortening (EAPS). Within the EAPS, the faulting mechanism is characterized by right- and left-lateral strike-slip faults, thrust faults, and a relatively limited occurrence of normal faults. When examined on a regional tectonic scale, about 70% of the deformation of the EAPS is controlled by strike-slip faults. However, the proportion of right- and left-lateral strike-slip faults contributing to this deformation remains unknown and is poorly understood. Two adjacent fault zones located at the southeastern margin of EAPS were selected to investigate the deformation associated with right- and left-lateral strike-slip mechanisms using morphometric analysis along with field observations. These fault zones are the & Scedil;emdinli Yuksekova Fault Zone (& Scedil;YFZ), which exhibits right lateral deformation and is defined as a seismic gap, and the Ba & scedil;kale Fault Zone (BFZ), which has a left lateral deformation and that caused a destructive earthquake in (23/02/2020 ,Mw:5.9). To elucidate the relative degree of active tectonics of both fault zones, morphometric analysis were applied alongside field surveys. An adaptation of the Relative active tectonic index (Iat) was computed for Ba & scedil;kale and Yuksekova-& Scedil;emdinli sub-basins in the region. The results supported by field observations indicate that the drainage basins are largely controlled by fault activity and exhibit a youthful topographic character. Moreover, quantitative data derived from the Index of Active Tectonics (IAT) reveal that the & Scedil;emdinli-Yuksekova Fault Zone (SYFZ) demonstrates very high tectonic activity, while the Ba & scedil;kale Fault Zone (BFZ) displays moderate levels of active tectonic deformation. These numerical findings, which indicate ongoing deformation, are further corroborated by field observations that clearly reflect the surface expressions of tectonic activity.
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 Sr-87/Sr-86 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.
Active plate tectonics require weak boundaries that accommodate large strain over long time periods. Many studies argue that shear heating converted from dissipated mechanical energy may be responsible for the necessary weakening in the mantle lithosphere to initiate and sustain weak plate boundaries. Here, I present simple numerical simulations of pure olivine systems with a composite diffusion-dislocation creep rheology coupled to a self-consistent grain-size evolution model to investigate the effect of grain-size reduction on shear heating. Results demonstrate that the weakening related to grain-size reduction and the activation of grain-size-sensitive diffusion creep undermines the importance of shear heating in mantle shear zones. Depending on shear zone width, shear velocity and apparent stresses, estimations on ideal shear zone widths and viscosities are presented.
The magnetic fabrics (or anisotropy of magnetic susceptibility) are used in this work to decipher thrust kinematics in the Cantabrian (western) Pyrenees. Most of the analyzed rocks (total of 51 sites) correspond to the Mesozoic rifting and post-rifting stages (Triassic, Jurassic and Cretaceous) rocks in the Asturian-Leonese region, whose alpine structure is controlled by south-verging, basement-involved thrusts. Paramagnetic minerals are scarce as shown by the thermomagnetic analyses, and maghemite/hematite predominates as carriers of the magnetic fabric. The rifting phase is recorded by a primary fabric that remained unaltered during the alpine contraction, whereas the magnetic fabric of the Albian and Upper Cretaceous rocks show a reorientation due to contraction, which is better recorded in the fine grained continental facies of the Utrillas Group than in the carbonatic rocks overlying them. In the contractional fabrics found, the magnetic lineation delineates the thrust front enhancing the changes of the local shortening direction along. This reinforces the hypothesis of a strong control of the thrust direction by inherited structures.
This research investigates microstructures and crystallographic preferred orientation in a high-temperature Variscan small-scale shear zone within marbles from the south-western Ossa-Morena Zone (Iberian Variscan Belt). Quantitative microstructural analysis, and crystallographic preferred orientation data obtained via neutron diffraction and electron backscatter diffraction mapping allowed to infer the deformation mechanisms and active slip systems. The primary S2 foliation, formed during the Variscan D2 deformation phase, is characterized by high-temperature grain boundary migration recrystallization mechanism, coupled with intracrystalline slip on the c(0001)<-12-10> system. Ductile shear zone development, marked by a coarse-grained microstructure with pronounced shape preferred orientation parallel to the shear plane, involved both high-temperature grain boundary migration recrystallization and intracrystalline dislocation creep, accommodated by f{-1012} <10-11> and r{10-14} <-2021> slip systems. These results indicate a high-temperature extensional origin for the S2 foliation and the shear zone formation during the D2 deformation event of the Ossa-Morena Zone, linked to thermal effects from the Beja Igneous Complex plutonism and regional partial melting driven by asthenosphere upwelling (similar to 353-335Ma).
Coralgal buildups from the mixed carbonate siliciclastic succession of the upper Eocene Sant Marti Xic Formation (Oris, Vic, SE Ebro Basin, Spain) were studied. During the upper Eocene, the sedimentation in the Oris area was strongly influenced by global and local factors associated with the evolution of the Ebro Basin. The stratigraphic series in Oris shows first a transgressive sedimentary sequence characterized by floatstone to rudstone limestone with Discocyclina and Nummulites, which developed in a deeper and oligophotic environment and in a general context of humid climate conditions. The second sequence is formed by progradational deltaic deposits rich in Nummulites and developed under more arid climate conditions. Coralgal buildups occur interdigitated with these deltaic deposits forming two different lens-shaped bioherms that resulted in a coalescentbuildup, with coral colonies sparse in a skeletal matrix of different grain-size. Corals grew in the mesophotic zone of the deltaic system affected by light fluctuations during periods of low siliciclastic input. The coralgal buildups of Sant Marti Xic Formation were thus influenced both by climatic changes and by the local detrital input from a deltaic system, associated with the uplift of the Catalan Coastal Range, highlighting the resilience of Eocene corals to environmental change.
The Aptian shallow-water carbonate platform of the Benassal Formation in eastern Spain (Maestrat Basin) contains facies dominated by scleractinian corals. Corals and coral reefs are widely used as environmental archives; however, the effects of their complex diagenetic evolution are a major factor impacting reliable reconstructions of the environments. This study addresses the environmental signatures (i.e. relative sea-level changes) and burial conditions that controlled the various diagenetic minerals present in the Aptian coral facies. A multiproxy approach including petrographic and geochemical evaluation reveals the diagenetic pathways, fluid compositions and timing accounting for the syn-to post-depositional history of this ancient coral facies. Cc1, which shows low Fe and Mn content and high Na content, precipitated within the primary porosity, alongside the replacement of coral skeletons, in a mixing zone dominated by marine waters. Cement Cc2, characterized by its higher Fe and Mn content and low Na values, precipitated in the mixing zone dominated by meteoric waters related to a relative sea-level drop. Cement Cc3, distinguished by low Fe and Mn content and high Na content, reflects a subsequent phase of increased marine influence, likely associated with a relative sea-level rise. Silica and isolated rhombohedral dolomite crystals formed concurrently in this mixing zone. During intermediate burial, saddle dolomite and cement Cc4 precipitated from high-temperature formation brines. Finally, during uplift, meteoric fluids caused the calcitization of previously formed dolomite rhombohedra.
