Search Results (25)

The Onil and Ibi sections (Prebetic Zone, Betic Cordillera: Alicante, SE Spain) record a late Ypresian (Cuisian) to early Lutetian (~51 to ~43 Myr) carbonate platform succession, dated using larger benthic foraminifera (LBF) and planktonic foraminifera. Seven field lithofacies (L1 to L7) and five thin-section microfacies (Mf1–Mf5) were identified, indicating inner- to mid-ramp environments (from seagrass meadows to Maërl-LBF-dominated) in warm-water and low-latitude conditions. A distinctive feature of these platforms is their dominance by LBF in association with rhodophyceae, contrasting with typical coral reef factories. We propose a novel carbonate production model, “TC-factory”, to describe these warm-temperate systems. Integrated field logging, drone imagery, and microfacies data allowed us to define a sequence stratigraphic framework comprising five lower-frequency sequences (LFS: ~2 Myr average duration), each of them nesting various numbers of high-frequency sequences (HFS: ~0.25 to ~1 Myr). The LFSs belong to a higher-rank sequence bounded by regional unconformities. The five LFSs only broadly match the upper Ypresian and lower Lutetian cycles in global eustatic curves (~51 to ~43 Myr), indicating that other regional or local controls were important. The number of HFSs being fewer than expected also suggests additional controls, such as local tectonics, erosion during lowstands, or carbonate production feedback. Full article

In the Betic-Rif Cordilleras, recent works have evidenced the existence of well-developed Eocene (Ypresian-Bartonian) carbonate platforms rich in Larger Benthic Foraminifera (LBF). Contrarily to other sectors of the western Tethys, like the Pyrenean domain in the North Iberian Margin, where these platforms started in the early Ypresian (Ilerdian), in the Betic-Rif chains, the recorded Eocene platforms started in the late Ypresian (Cuisian) after a widespread gap of sedimentation including the Ilerdian time span. In this work, the Aspe-Terreros Prebetic section (External Betic Zone) is studied. An Eocene succession with gravity flow deposits consisting of terrigenous and bioclastic turbidites, as well as olistostromes with olistoliths, was detected. In one of these turbidites, we dated (with the inherent limitations when dating bioclasts contained by gravity flow deposits) the middle Ilerdian, on the basis of LBF, representing a vestige of a missing Illerdian carbonate platform. The microfacies of these turbidites and olistoliths rich in LBF have been described and documented in detail. The gap in the sedimentary record and absence of Ilerdian platforms in the Betic-Rif Cordillera have been related to the so-called Eo-Alpine tectonics (Cretaceous to Paleogene) and sea-level variations contemporarily with the establishment of shallow marine realms in the margins of the western Tethys. Full article

The Sierra Seca aquifer system is located in the northeast (NE) of the province of Granada, in the Prebetic Domain (Betic Cordillera). It is composed of different aquifer units hosted in the Lower Cretaceous and Upper Cretaceous limestones. The two aquifers are separated by a low permeability marl layer, which effectively acts as a barrier between them. To outline the behavior of the hydrogeological system, 407 samples of precipitation and 67 samples of groundwater were obtained from May 2020 to Oct. 2022 and isotopically (${\delta }^{18}O$ and ${\delta }^{2}H$) analyzed. For the estimation of the recharge elevation, a new methodology has been applied to estimate the isotopic content of recharge as a function of precipitation. This allowed the evaluation of the vertical gradient of both precipitation (${\nabla }_Z{\delta }^{18}{O}_P=-2.9‰/\mathrm{k}\mathrm{m}$) and aquifer recharge (${-4.4‰/\mathrm{k}\mathrm{m}\le \nabla }_Z{\delta }^{18}{O}_R\le -2.9‰/\mathrm{k}\mathrm{m}$). Therefore, estimating (1) the recharge zone elevation associated with the aquifer system, which is comprised between 1500 and 1700 m a.s.l., and (2) the transit time of recharge to reach the outflow point of the aquifer system, which varies between 4 and 5 months, is possible. Additionally, three tracer tests were conducted to outline the hydrologic connection between the recharge and discharge zones of the aquifer system. The results show that the Fuente Alta spring drains the limestones of the Lower Cretaceous, while La Natividad spring does the same with the limestones of the Upper Cretaceous. In the case of the Enmedio spring, groundwater discharge is related to infiltration through the streambed of the watercourse fed by the Fuente Alta spring. Full article

This study uses heavy detrital minerals to determine actualistic fluvial and beach sand provenance across the Betic Cordillera (Spain), along the coast from Almeria to Marbella. The Betic Cordillera, primarily composed of metamorphic rocks to the east, supply an assemblage dominated by almandine and graphite, with a longshore dispersal from Almeria to Malaga. Buergerite and hypersthene indicate the provenance of calcalkaline lavas east of Cabo de Gata. The western part of the Betic Cordillera, which comprises the Ronda Peridotite Complex, supplies a chromite and diopside assemblage, with a dispersal from Marbella to Algeciras. Considering these mineralogical suites, the effects of source rock compositions and weathering are evaluated. The heavy mineral species mirror the mineralogy of the source rocks of local outcrops and wider source terranes. The fluvial heavy mineral suites do not differ significantly from those in the beaches except for some unstable species. Unstable species such as olivine, pyroxene, and amphibole do not show evidence of loss because of elevated topography and semiarid climate, which do not affect heavy minerals. This contribution also evaluates the potential of some heavy detrital species as ideal pathfinders in searching for diamonds. Full article

A hydrochemical and mineral study of groundwaters and damaged rocks from the Tíscar and Larva fault zones (Betic Cordillera, Iberian Peninsula) was carried out in order to (a) describe the physical and chemical properties of the groundwaters; (b) recognize significant locations with deep-origin fluids related to active tectonics; (c) and to describe the water–rock interaction and the neoformation of clay mineral processes and their importance in the seismicity of the faults. A sampling campaign was completed between November 2012 and November 2013, during which data were obtained from 23 different groundwater sites in the fault areas. Two main groups of waters were distinguished: (a) Ca²⁺-Mg²⁺-HCO₃⁻ facies characterized by poor conductivity and salinity; and (b) saline waters (up to 30 meq/L) rich in Ca²⁺-Mg²⁺-SO₄-Cl⁻ and with an elevated conductivity (frequently > 1000 μS/cm). In addition, a minor group of saline and warm waters (T > 16.5 °C) was found to be Na⁺-rich and show moderately high B values (>0.33 ppm), and which mig ht be hosted in aquifers deeper than the two main groups. This group of deep-origin waters is oversaturated in clay minerals and is in equilibrium for Ca-Mg carbonate minerals. X-ray diffraction and scanning and transmission electron microscopy data corroborate the crystallization forecast of authigenic smectite, which appears as thin films coating carbonate fragments. The origin of smectite is related to the fragile strain and thermal–fluid–mineral interactions in fault rocks. Smectite could lubricate carbonate rocks, which favor creep deformation versus seismic slip. This work provides locations where groundwater physico-chemical properties and composition suggest tectonic fault activity. Full article

The Betic Cordillera was formed by the collision between the Alboran Domain and the South Iberian paleomargin in the frame of the NW–SE convergent Eurasia–Nubia plate boundary. The central region is undergoing a heterogeneous extension that has not been adequately analysed. This comprehensive study addressed it by collecting structural geologic, seismologic, and geodetic data. The region west of the Sierra Nevada is deformed by the extensional system of the Granada Basin, which facilitates E–W to NE–SW extension. Moreover, the southern boundary of Sierra Nevada is affected by a remarkable N–S extension related to E–W normal to normal–dextral faults affecting the shallow crust. However, geologic and geodetic data suggest that the western and southwestern Granada Basin boundary constitutes a compressional front. These data lead to the proposal of an active extensional collapse from the uplifted Sierra Nevada region to the W–SW–S, over an extensional detachment. The collapse is determined by the uplift of the central Betics and the subsidence in the Alboran Basin due to an active subduction with rollback. Our results indicate that the central Betic Cordillera is a good example of ongoing extensional collapse in the general context of plate convergence, where crustal thickening and thinning simultaneously occur. Full article

This paper introduces a Python application for visualizing an imbricate thrust system. The application uses the traditional geologic information to create an HTML geological map with real topography and a set of geological cross-sections with the essential structural and stratigraphic elements. On the basis of the high geological knowledge gained during the last three decades, the Palomeque sheets affecting the Cenozoic Malaguide succession in the Internal Betic Zone (SE Spain) were selected to show the application. In this area, a Malaguide Cretaceous to Lower Miocene succession is deformed as an imbricate thrust system, with two thrusts forming a duplex, affected later by a set of faults with a main strike-slip kinematic. The modeled elements match well with the design of the stratigraphic intervals and the structures reported in recent scientific publications. This proves the good performance of this Python application for visualizing the structural and stratigraphic architecture. This kind of application could be a crucial stage for future groundwater, mining, and civil engineering management. Full article

The Ojén nappe, an allochthonous unit that underlies the Ronda peridotites (Betic Cordilleras), is composed of Triassic marbles overlying a metapelitic sequence. In order to carry out an LA-ICP-MS U-Pb age determination and provenance analysis, detrital zircon grains from two quartzites interlayered within marbles and metapelites were extracted. The obtained results yield the youngest zircon population of 254 ± 3 Ma (Late Permian) with a mean Th/U ratio of 0.34 that supports both the Permian–Triassic age of the marble member and the felsic magma nature for zircon-bearing protoliths. The Permian zircons exhibit tight age peaks in three main populations of 292 ± 2 Ma, 278 ± 3 Ma, and 254 ± 3 Ma, in agreement with the main age populations reported from rhyolites and shallow crustal basaltic–andesite subalkaline rocks emplaced in transtensional Permian basins of the Variscan Orogen during the break-up of Pangea. Moreover, the analyzed detrital zircon grains yield age distributions with clear Tonian–Stenian (ca. 950–975 Ma), Ediacaran–Cryogenian (ca. 560–615 Ma), Ordovician (ca. 460–465 Ma), and Cisuralian peaks (ca. 280–290 Ma) and smoothed Mesoproterozoic peaks that point to a weak and residual Cadomian peri-Gondwanan terrane inheritance. The identified Middle Ordovician detrital zircon populations (460–465 Ma) strengthen the hypothesis that the Alborán domain would be located along the southern passive margin of the European Hunic superterrane. Full article

The El Robledal deposit is a Mg-Fe-B skarn hosted in a dismembered block from the footwall contact of the Ronda orogenic peridotites in the westernmost part of the Betic Cordillera. The skarn is subdivided into two different zones according to the dominant ore mineral assemblage: (1) the ludwigite–magnetite zone, hosted in a completely mineralized body along with metasomatic forsterite, and (2) the magnetite–szaibelyite zone hosted in dolomitic marbles. In the ludwigite–magnetite zone, the massive mineralization comprises ludwigite (Mg₂Fe³⁺(BO₃)O₂), Mg-rich magnetite, and magnetite, with minor amounts of kotoite (Mg₃(BO₃)₂), szaibelyite (MgBO₂(OH)), accessory schoenfliesite (MgSn⁴⁺(OH)₆), and pentlandite. The ratio of ludwigite–magnetite decreases downwards in the stratigraphy of this zone. In contrast, the mineralization in the magnetite–szaibelyite zone is mainly composed of irregular and folded magnetite pods and bands with pull-apart fractures, locally associated with a brucite-, szaibelyite-, and serpentine-rich groundmass. The set of inclusions identified within these ore minerals, using a combination of a focused ion beam (FIB) and high-resolution transmission electron microscope (HRTEM), supports the proposed evolution of the system and reactions of the mineral formation of the skarn. The analysis of the microstructures of the ores by means of electron backscatter diffraction (EBSD) allowed for the determination that the ores experienced ductile deformation followed by variable degrees of recrystallization and annealing. We propose a new classification of the deposit as well as a plausible genetic model in a deposit where the heat source and the ore-fluid source are decoupled. Full article

In the western part of the Sierra de los Filabres area, there are fine-grained metamorphic rock bands, showing a field aspect simitar to slates, as previously described in the geological literature of the studied region. They are variable in thickness, from millimeters to tens of meters and appear intercalated in the schist succession. The geochemical resemblance between both types of rocks (major, minor and trace elements), determined by a statistical approach and the comparison of depositional condition indices, points to a similar sedimentary origin of the protolith but different clay content. Mineral facies and illite “crystallinity” indices in the so-called slates indicate that they followed the same metamorphic path and reached the same metamorphic grade than schists. According to compositional zoning detected in micas and garnets present in both lithologies and the P-T conditions deduced from garnets, the mineral nucleation and growth episode of the main mineral paragenesis in these fine-grained schists was more remarkable during the high-pressure event, with a no significant effect of the latter low-pressure–high-temperature episode. In contrast, the coarse-grained schists developed higher size minerals during the low-pressure–high-temperature episode. A differential mylonitization process during the metamorphism is proposed to justify the discrepant field appearance and the contrasting response of both types of metapelitic rocks to the latter metamorphic event. Full article

This work presents the chronology of the Holocene filling of the Guadalentín Tectonic Depression (Murcia, SE Spain) combining ¹⁴C and OSL age data. This work studies the sediments and paleosols interbedded in the sedimentary sequence between Totana and Librilla, using as reference the Espuña Karting section (Alhama de Murcia), which has been fully sampled for its geochronological analysis. The entire dated sequences record the last c. 20–19 ka BP, although local basal travertine beds extend back to the Late Pleistocene (30–33 ka). Soil morphology and properties from dated paleosols record different environmental crises in SE Spain, but also a progressive aridification throughout the Holocene. The Chalcolithic Paleosol develops soon after c. 4.6–4.0 BP, nearly coinciding with the start of the Meghalayan stage, evidencing a drastic change from relatively humid to arid conditions, coincident with the crisis of the Copper Age civilizations in Spain. The Bronze Age paleosol also developed under arid but relatively more humid conditions, indicating a more important and longer gap in the sedimentary sequence soon after c. 2.5–2.7 ka BP. This stop in the sedimentation are correlative to the first stages of fluvial incision at basin center locations and the desiccation and fragmentation of the ancient wetlands coinciding with the collapse of the Bronze Age civilizations in SE Spain (Argaric Culture). During the Ibero-Roman Humid Period (IRHP), c. 2.6–1.6 ka BP, the last pedogenic cycle occurred under relatively humid conditions. This preluded the progressive establishment of exorheic fluvial environments as well as a period of paleoseismic activity in the area around 2.0–1.8 ka BP. Full article

This study reveals mineral and deformation processes associated with faulting of lacustrine unconsolidated sediments in the Guadix-Baza Basin (Betic Cordillera, S Spain) affected by the Baza Fault. Brittle carbonate and silt sediments develop deformation bands frequently sealed by dolomite crystallization, whereas ductile clay-rich sediments form clay smearing bands where late crystallization of gypsum can be observed. Granular flow and local cataclasis were the main deformation mechanisms in the brittle deformation bands. Flow alignment, grain-boundary sliding, and extrusion were predominant in the clay smearing bands. These water and clay-rich bands reduced shear strength of the faulting process due to their lubricating effect. Beidellitic smectite defines shear foliation of the smeared bands, but Mg-Fe, a K-rich smectite (Fe + Mg > 1 and K content up to 0.8 a.p.f.u), crystallizes in the micropores surrounding brittle clasts produced by deformation pressure shadows. These data suggest that the interaction of micromechanical events, which increased sediment porosity by the generation of pressure shadows, and the flow and concentration of saline fluids in these pores promoted structural diagenesis processes that favoured the beginning of local illitization. Full article

The Gibraltar Arc includes the Betic and Rif Cordilleras surrounding the Alboran Sea; it is formed at the northwest–southeast Eurasia–Nubia convergent plate boundary in the westernmost Mediterranean. Since 2006, the Campo de Dalias GNSS network has monitored active tectonic deformation of the most seismically active area on the north coast of the Alboran Sea. Our results show that the residual deformation rates with respect to Eurasia range from 1.7 to 3.0 mm/year; roughly homogenous west-southwestward displacements of the northern sites occur, while the southern sites evidence irregular displacements towards the west and northwest. This deformation pattern supports simultaneous east-northeast–west-southwest extension, accommodated by normal and oblique faults, and north-northwest–south-southeast shortening that develops east-northeast–west-southwest folds. Moreover, the GNSS results point to dextral creep of the main northwest–southeast Balanegra Fault. These GNNS results thus reveal, for the first time, present-day interaction of the roll-back tectonics of the Rif–Gibraltar–Betic slab in the western part of the Gibraltar Arc with the indentation tectonics affecting the eastern and southern areas, providing new insights for improving tectonic models of arcuate orogens. Full article

Based on the LA-ICP-MS U-Pb zircon ages of four metamorphic samples, we discuss the geochronology and provenance of the Guadaiza nappe, an allochthonous unit that underlies the Ronda peridotites (Betic Cordilleras, Spain). The Guadaiza nappe is composed of Triassic marbles overlying a metapelitic sequence with schists and migmatites. Zircons from a quartzite interlayered with the marbles yield a maximum depositional age of ca. 289 Ma that supports the Triassic age. The idiomorphic morphology of these Paleozoic zircon crystals and the lack of late-Variscan metamorphism (ca. 300 Ma) supports a proximal source area, and suggests that the marbles were discordantly deposited over the metapelitic sequence, along the northern margin of the Alboran microplate. The zircon patterns from the metapelitic sequence mainly yield Paleoproterozoic (ca. 1.6–2.5 Ga), Tonian–Stenian (ca. 1000 Ma), Ediacaran–Cryogenian (ca. 600 Ma) and Paleozoic (ca. 500 Ma) age clusters. These results suggest provenance from areas within the triangle bound by the West African Craton, the Metasaharan Craton and the Hun Superterrane during the Paleotethys opening (Silurian–Devonian). A Silurian–Carboniferous deposition age for the schist protoliths is constrained by the youngest detrital zircon population (ca. 443 Ma) and the Variscan age of their migmatization by an additional peak of around 299 Ma in the migmatites. Full article

The use of drones in mining and geological exploration is under rapid development, especially in the field of magnetic field prospection. In part, this is related to the advantages presented for over ground surveys, allowing for high-density data acquisition with low loss of resolution, while being particularly useful in scenarios where vegetation, topography, and access are limiting factors. This work analyzes results of a drone magnetic survey acquired across the old mines of Don Jacobo, where Copper-Cobalt-Nickel stratabound mineralizations were exploited in the Estancias mountain range of the Betic Cordillera, Spain. The survey carried out used a vapor magnetometer installed on a Matrice 600 Pro Hexacopter. Twenty-four parallel survey lines were flown with a speed of 5 m/s, orthogonal to the regional strike of the geological structure, and mineralization with 50 m line separation and 20 m flight height over the ground was studied. The interpretation of the magnetic data allows us to reveal and model two high magnetic susceptibility bodies with residual magnetization, close to the old mines and surface mineral shows. These bodies could be related to potential unexploited mineralized areas whose formation may be related to a normal fault placed to the south of the survey area. Our geophysical survey provides essential data to improve the geological and mining potential of the area, allowing to design future research activities. Full article