Betic Cordillera Research Articles

Middle Eocene carbonate platforms of the westernmost Tethys

A study of the paleoenvironmental evolution of the middle Eocene platforms recognized in the westernmost Tethys has been carried out in the well-exposed middle Eocene succession from Sierra Espuña-Mula basin (Betic Cordillera, S Spain). Eight microfacies (Mf1 to Mf8) have been recognized, based mainly on fossil assemblages (principally larger benthic foraminifera), and rock texture and fabric. The fossiliferous assemblage can be assigned to the ‘subtropical’ heterozoan association or to the low-latitude ‘foralgal facies’, which are dominated by non-framework building, light-dependent biota such as perforate larger benthic foraminifera, coralline algae, and sometimes green algae and solitary corals. Larger benthic foraminifer assemblages, corresponding from euphotic to oligophotic conditions and the large surface showed, suggest a progressive marine ramp under essentially oligotrophic conditions. Eventually, supply of detrital sediments from the continent and/or upwelling currents increases the nutrients of marine waters. Comparison with other Tethyan sectors allows stating that coral-reef buildups (z-corals) were widespread on shallow platforms of the central and eastern Tethys Ocean, but these were neither of great dimensions nor dominant because of the much more dominant presence of larger benthic foraminifera. Moreover, these coral constructions were completely absents in the westernmost Tethys. The dominance of larger benthic foraminifera and the absence of z-corals in the westernmost Tethys are explained by particular paleogeographic features due to the occurrence of a narrow and deep oceanic branch (i.e., the Maghrebian Flysch Basin) connecting the Tethys with the Atlantic Ocean. The various issues regarding the morphological characters and evolution of larger benthic foraminifera in the study area, such as sizes of tests, specific diversity and/or intraspecific variability, number of appearances and last occurrences during the middle Eocene are analyzed and compared with those appearing in other Tethyan sectors. In addition, the early to late Bartonian boundary is recognized in the study area as critical for the biological change as in other shallow-marine environments along the Tethys margins.

Palaeogeographical homogeneity of trace-fossil assemblages in Lower Jurassic spotted marls and limestones: comparison of the Western Carpathians and the Betic Cordillera

Abstract Micritic sediments containing dark, discrete, organic-rich burrows, situated in a light grey background carbonate mud, were deposited over a broad geographical area in deep-shelf, bathyal and basinal environments in the western margin of the Tethys Ocean during the Early and Middle Jurassic. These hemipelagic deposits represent a distinct depositional regime marked by low-energy, soft-bottom and only locally dysoxic environments. Still, it is unclear whether the trace-fossil assemblages occurring in these deposits pertain to a network of several community types – the ichnotaxa differing from basin to basin – or to a single community of environmentally broad-ranging, burrow-producing species. Lower Jurassic trace-fossil assemblages are found in the Western Carpathians and in the Subbetic, Betic Cordillera: that is, in basins separated by more than 2000 km in their original palaeogeographical areas. The stereotypical Chondrites and Zoophycos trace-fossil assemblages that occur in the analysed deposits share two ichnogenera of distinctive morphology ( Lamellaeichnus and Teichichnus ). Agglutinated foraminifera Bathysiphon occurs together with the described trace-fossil assemblage and determines the epibenthic palaeoenvironmental conditions. In the Western Carpathians, a Lamellaeichnus -dominated assemblage alternates with a Zoophycos -dominated assemblage in small, metre-scale cycles in the upper Pliensbachian, and the proportion of the Zoophycos assemblage increases stratigraphically upwards, probably owing to reduced basin ventilation during the early Toarcian. Within the southern Iberian palaeomargin, represented by the Betic Cordillera, Zoophycos is scarce in the facies.

Pacing of late Pliensbachian and early Toarcian carbon cycle perturbations and environmental change in the westernmost Tethys (La Cerradura Section, Subbetic zone of the Betic Cordillera, Spain)

Abstract Detailed assessment of high-resolution elemental and isotopic geochemical datasets collected from the marl–limestone alternations cropping out at La Cerradura (Subbetic domain of the Betic Cordillera, Spain) and chrono- and chemostratigraphic correlation with the reference Mochras borehole (Cardigan Bay Basin, UK) unveiled valuable new insights into understanding of late Pliensbachian–early Toarcian palaeoenvironmental dynamics in a key geographical area between the northern European seaway and the Tethys Ocean. This study shows that deposition in the study area took place under dominantly oxic water column conditions, indicated, for example, by the generalized lack of enrichment in organic matter and redox metals typically associated with anoxia and euxinia. Carbon isotope stratigraphy (δ 13 C TOC ) allowed recognition of the spinatum (= emaciatum in the Submediterranean Province), Pliensbachian–Toarcian, and early Toarcian Oceanic Anoxic Event negative carbon isotopic excursions and the late Pliensbachian positive carbon isotopic excursion. It is here suggested that the observed periodic changes in lithology and sedimentary geochemistry occur at orbital frequencies (i.e. long and short eccentricity and, tentatively, precession), hinting at an astronomical control of the local–regional climate and environment during the Pliensbachian and Toarcian in the mid- to low-latitude South Iberian palaeomargin area.

Morphological transition during prograde olivine growth formed by high-pressure dehydration of antigorite-serpentinite to chlorite-harzburgite in a subduction setting

Crystal morphologies are essential for deciphering the reaction history of igneous and metamorphic rocks because they often record the interplay between nucleation and growth rates controlled by the departure from equilibrium. Here, we report an exceptional record of the morphological transition of olivine formed during subduction metamorphism and high-pressure dehydration of antigorite-serpentinite to prograde chlorite-harzburgite in the Almirez ultramafic massif (Nevado–Filábride Complex, Betic Cordillera, SE Spain). In this massif, rare varied-textured chlorite-harzburgite (olivine+enstantite+chlorite+oxides) —formed after high–P dehydration of antigorite-serpentinite— exhibits large olivine porphyroblasts made up of rounded cores mantled by coronas of tabular olivine grains, similar to single tabular olivines occurring in the matrix. The correlative X-ray μ-CT and EBSD study of two varied-textured chlorite-harzburgite samples show that tabular olivine in coronas is tabular on (100)Ol with c > b >> a, and grew in nearly the same crystallographic orientation as the rounded olivine cores of the porphyroblast.Quantitative textural analysis and mass balance indicate that varied-textured chlorite-harzburgite is the result of a two-stage nucleation and growth of olivine during the progress of the high–P dehydration of antigorite-serpentinite to chlorite-harzburgite reaction. The first stage occurred under a low affinity (ΔGr) and affinity rate (ΔGr/dt) of the antigorite dehydration reaction that resulted in a low time-integrated nucleation rate and isotropic growth of olivine, forming rounded olivine porphyroblasts. With further progress of the dehydration reaction, a second stage of relatively higher affinity and affinity rate resulted in a higher time-integrated nucleation rate of olivine coeval with a shift from isotropic to anisotropic olivine growth, leading to tabular olivines. The two-stage evolution resulted in olivine porphyroblasts made up of rounded cores mantled by coronas of tabular olivine grains characteristic of varied-texture chlorite-harzburgite.Although a switch to anisotropic tabular olivine in the second stage is consistent with the relative increase in the affinity and affinity rate, these changes cannot solely account for the growth of Almirez olivine tabular on (100). Tabular olivines in komatiites and other igneous rocks are tabular on (010)Ol with either a > c >> b, or a ≈ c > > b, in agreement with experimentally determined growth rates of olivine phenocrysts under moderate to high undercooling and cooling rates. On the other hand, olivine tabular on (100) is expected in the presence of highly polymerized fluids where inhibited growth of the olivine (100) and (010) interfaces occurs, respectively, due to dissociative and molecular adsorption of water monolayers. Rounded and tabular olivines in Almirez varied-textured chlorite-harzburgite show differing trace element compositions that we interpret as due to the infiltration of external fluids during antigorite dehydration. Isothermal infiltration of highly polymerized fluids would explain the shift in the affinity and affinity rate of the antigorite dehydration reaction, as well as the olivine morphology tabular on (100) due to the inhibited growth on the (100) and, to a lesser extent, (010). Our study shows that surface-active molecules may play an essential role in shaping the morphology of growing crystals during fluid-present metamorphic crystallization.

Interevaporitic deposits of Las Minas Gypsum Unit: A record of Late Tortonian marine incursions and dolomite precipitation in Las Minas Basin (eastern Betic Cordillera, SE Spain)

The Las Minas Gypsum Unit consists of more than 100 m of alternations of gypsum, carbonates and marls in Las Minas Basin (Betic Cordillera). Although this unit has been previously described as lacustrine, a marine influence in the basin has been suggested. This study provides new geochemical and paleontological data supporting the marine influence during the interevaporitic episodes, allowing to refine the palaeogeography of the eastern Betic Seaway during the Late Tortonian.87Sr/86Sr ratios in gypsum (0.70797 to 0.70825) suggest recycling of Triassic evaporites. The sulphate isotopic values in gypsum (11.5 < δ34SVCDT < 21.9‰; 16.6 < δ18OVSMOW < 28.1‰) are indicative of microbial sulfate-reduction activity. Carbonates are mainly composed of dolomite formed by subspherical crystal aggregates related to bio-mediated processes. The 87Sr/86Sr values in the interevaporitic carbonates (0.70823 to 0.70851) are higher than those expected for Triassic marine authigenic carbonates but lower than expected for the Late Miocene ones, suggesting a mixing of continental and marine water contributions. The ‘non-marine’ isotopic values in gypsum and carbonates contrast with an abundant content of marine siliceous fossils (radiolarians, diatoms, porifera, etc.) in the marls and carbonates that reveals marine incursions into the basin between periods of gypsum precipitation. A tephra layer identified in Las Minas and in the nearby El Cenajo Basin, located in a more inland position, allows a precise correlation between both basins, showing marine fossils in Las Minas and lacustrine in El Cenajo. In El Cenajo Basin, marine microfossils have been found but only in some levels, while others show lacustrine diatoms. A new palaeogeographic model of evaporitic lakes with temporal marine connections is proposed for the latest Tortonian in this region, when the uplift of the Betic Cordillera was very active accelerating the palaeogeographic evolution.

Uranium content and uranium isotopic disequilibria as a tool to identify hydrogeochemical processes

This paper studies the uranium content and uranium isotopic disequilibria as a tool to identify hydrogeochemical processes from 52 groundwater samples in the province of Granada (Betic Cordillera, southeastern Spain). According to the geological complexity of the zone, three groups of samples have been considered. In Group 1 (thermal waters; longest residence time), the average uranium content was 2.63 ± 0.16 μg/L, and 234U/238U activity ratios (AR) were the highest of all samples, averaging 1.92 ± 0.30. In Group 2 (mainly springs from carbonate aquifers; intermediate residence time), dissolved uranium presented an average value of 1.34 ± 0.13 μg/L, while AR average value was 1.38 ± 0.25. Group 3 comes from pumping wells in a highly anthropized alluvial aquifer. In this group, where the residence time of the groundwater is the shortest of the three, average uranium content was 5.28 ± 0.26 μg/L, and average AR is the lowest (1.17 ± 0.12). In addition, the high dissolved uranium value and the low AR brought to light the contribution of fertilizers (Group 3). In the three groups, 235U/238U activity ratios were similar to the natural value of 0.046. Therefore, 235U detected in the samples comes from natural sources. This study is completed with the determination of major ions and physicochemical parameters in the groundwater samples and the statistical analysis of the data by using the Principal Component Analysis. This calculation indicates the correlation between uranium isotopes and bicarbonate and nitrate anions.

Sedimentary history and palaeogeography of the Cenozoic clastic wedges of the Malaguide Complex, Internal Betic Cordillera, southern Spain

The Cenozoic sedimentary cover of the Malaguide Complex (Internal Betic Cordillera, Spain), in the Almería and Málaga areas, consists of a suite of sedimentary successions from continental and shallow-marine to deep-marine environments. Structural and stratigraphic relations, and petrological and geochemical signatures reveal the sedimentary evolution of the Cenozoic Malaguide Complex (CMC) from pre-orogenic (Palocene-Eocene) to syn-orogenic (Oligocene-Early Miocene) stages. Sandstones detrital modes of the overall succession are heterogeneous testifying to a multi-source area, marked by exhumation of the Malaguide basement terranes and of the Internal Betic Zone (Alpujárride Complex) in lower position. Pre-orogenic and syn-orogenic strata consist of four main depositional sequences: the Mula Group (Paleocene), the Xiquena Group (Eocene) for the preorogenic successions; and Ciudad Granada Group (Oligocene-Aquitanian) and Viñuela Group (Burdigalian) for the synorogenic successions. Pre-orogenic strata evolve from intra-arenite to hybrid arenites to progressive increase of sandstones in abundance of detrital supply from sedimentary cover of the internal Betic units. The unroofing history of the internal Betic Units, predominantly in the Malaguide Complex, is clearly testified in strata of the synorogenic clastic units, where detrital supply is coming from the Malaguide Complex. Sedimentary lithic fragments were derived from the Mesozoic strata of the Malaguide Complex while metamorphic detritus is related to the Internal Betic Zone basement that was exhumed starting from the Oligocene. Pre-orogenic mudrocks mainly show abundance of calcite and dolomite over quartz and phyllosilicates. Syn-orogenic mudrocks, record an abrupt decrease in calcite and dolomite and an increase of phyllosilicate, quartz and feldspars mainly in the Malaga section. The geochemical signatures attest to a compositional variation of the samples from pre-to-synorogenic successions, with palaeoweathering indices showing moderate values and a weak up-section decrease. The Cenozoic Malaguide Complex played a key role in the geodynamic evolution of the Betic Cordillera, representing the key tectonic element of the western Mesomediterranean domains.

Quantification of Erosion and Uplift in a Rising Orogen—A Large-Scale Perspective (Late Tortonian to Present): The Case of the Gibraltar Arc, Betic Cordillera, Southern Spain

The present study deals with the morphometric quantification of erosion and illustrates the uplift component triggered by denudation (isostasy) in the growth and evolution of a rising orogeny by the application of Airy isostasy concepts. The Gibraltar Arc, located in the Western–Central sector of the Betic Cordillera, developed an exceptional geological scenario during the Messinian Salinity Crisis since the thin emerged fringe of the uprising Cordillera disconnected the Atlantic and Mediterranean basins, generating a relevant misbalance and asymmetry in the fluvial erosion between the two slopes of the emergent orogeny. Our analysis was applied to 50 individual drainage basins (spatial isostatic units) in the Western–Central Betic Cordillera, allowing us to obtain individual and bulk estimates for these isostatic parameters. GIS-based numerical estimations were obtained using LiDAR Digital Elevation Models (DEMs) provided by the Spanish Geographical Institute and reconstructed pre-incision surface models obtained from proxy paleo-elevation data, estimated from stratigraphic and geomorphological littoral to shallow marine markers. The obtained values for geophysical relief, denudation plates, erosion/uplift rates and computed accumulated uplift (245–407 ±20 m) are higher for the ancient Mediterranean slope of the orogen. On the contrary, the Atlantic slope presents an accumulated uplift of only 138–236 ±20 m, indicating the strong control of the ancient Messinian Atlantic–Mediterranean water divide. The temporal study of erosion indicates that most of the difference in uplift in the Mediterranean slope was achieved during or soon after the Messinian Salinity Crisis, resulting in mean uplift rates of 0.21 mm/y, but practically null (0.01 mm/y) for the Atlantic slope. The comparison of the geophysical relief models with proxy paleo-elevation data allowed us to assess the current state of the denudation process in the range. The results indicate that, towards the west of the range denudation compensated elevation, and is actively back-feeding isostatic rebound. Therefore, the contribution of external processes to mountain range elevation through isostasy is quantitatively estimated using elevation data. In this case, a relevant part of the surface uplift (50-55%) is undertaken by the orogen. Ultimately, the Messinian Salinity Crisis-related isostatic response to differential denudation may be behind the quaternary westward tilting of Iberia, causing more than 70% of the Peninsula to drain towards the Atlantic.

PALAEOENVIRONMENTAL CONTEXTS FOR MICROBIAL COMMUNITIES FROM Fe-Mn CRUSTS OF MIDDLE-UPPER JURASSIC HARDGROUNDS (BETIC-RIFIAN CORDILLERA)

The Middle-Upper Jurassic transition within the External Subbetic (Betic Cordillera) and the Jbel Moussa Group (Rifian Calcareous Chain) is characterised by numerous stratigraphic breaks recorded as palaeoreliefs, omission surfaces and hardgrounds. One common characteristic is the presence of microbial Fe-Mn crusts and Mn crusts. Three different contexts of microbially mediated Fe-Mn crusts can be distinguished: a) hydrogenetic surficial Fe-Mn crusts and macro-oncoids, b) hydrogenetic cryptic Fe-Mn crusts, and c) hydrothermal surficial Mn crusts. Encrusting foraminifera (Thurammina, Placopsilina, Tolypammina and nubeculariids) and fungi fed on bacteria, while the bacteria and fungi took advantage of the nutrient-rich foraminiferal excretions. The cryptic Fe-Mn crusts are also hydrogenetic crusts developed in the walls of submarine cavities and fractures in the External Subbetic at the time of the hardground development. They are endostromatolites consisting almost exclusively of Frutexites in the case of thin neptunian dykes, or serpulid-Frutexites assemblages in a large neptunian sill. This assemblage reflects the colonization of unfavourable environment (aphotic with low oxygenation) as a response to the photophobic behaviour of chemosynthetic and cryptobiontic microorganisms. Finally, the hydrothermal Mn crusts registered in the Rif are characterised by the record of bacillus-shaped bacteria and different type of filaments. The precipitation of manganese minerals is interpreted as induced by the chemo-organotrophic behaviour of benthic microbial communities, since manganese oxides may form as a result of the direct metabolic activity of bacteria in hydrothermal environments. Very well-preserved fungal hyphae evidence the presence of fungi that probably fed on bacterial communities and their by-products

Integration of gamma ray spectrometry, magnetic susceptibility and calcareous nannofossils for interpreting environmental perturbations: An example from the Jenkyns Event (lower Toarcian) from South Iberian Palaeomargin (Median Subbetic, SE Spain)

The Pliensbachian-Toarcian sedimentary rocks of the Median Subbetic (Betic Cordillera, SE Spain) were deposited in the South Iberian Palaeomargin under hemipelagic conditions. In the Arroyo Mingarrón section (SE Spain) these deposits are composed by a marl and marl and limestone alternation with abundant radiolarians. The application of magnetic susceptibility and gamma ray spectrometry to these deposits allows to interpret environmental changes related to the fluctuations in the continental influx of terrigenous and phytodetritus to a hemipelagic setting in the South Iberian Palaeomargin. The increase of terrigenous input was coincident with the negative carbon isotopic excursion (CIE) at the base of the NJT6 nannofossil Zone that correlates with the Jenkyns Event. The increase of Th and K content is related to enhanced detrital input, especially oxides and silicates, including clay minerals. The gamma ray signal derived from U is comparatively low with respect to K and Th. Nevertheless, the U content shows an increase in the base of NJT6 nannofossil Zone that indicates a relative increase of organic matter content coincident with the Jenkyns Event. Changes in the calcareous nannofossil assemblages at the beginning of the NJT6a nannofossil Subzone and, in particular, the sharp decrease in abundance of the species Mitrolitus jansae during the negative CIE of the Jenkyns Event are interpreted as related to sea-water stratification and a probable poor oxygenation making inhospitable the deep photic zone during this event.

Main faults of the Betic Cordillera

In the Betic Cordillera the faults correspond to thrusts forming tectonic units and to three important sets of vertical or quasi-vertical faults. In the Internal Zone the thrusts formed mainly during the Oligocene, under an approximately N-S compression. Later, in the Burdigalian, the Internal Zone collided with the External Zone, which underwent major deformations. Then N60ºE-S60ºW to E-W dextral strike-slip faults formed. These faults formed under nearly E-W compression. From the end of the middle Miocene, the near N-S compression was reestablished and then formed two conjugated sets of faults whose directions are: NNE-SSW (with sinistral character) and NNW-SSE to NW-SE (with dextral character). Not only are the aforementioned major faults, but the rocks also have many other small faults and joints that formed under the same stresses.

Geometry and kinematics of the Baza Fault (central Betic Cordillera, South Spain): insights into its seismic potential

The geometry and kinematics of active faults have a significant impact on their seismic potential. In this work, a structural characterization of the active Baza Fault (central Betic Cordillera, southern Spain) combining surface and subsurface data is presented. Two sectors are defined based on their surface geometry: a northern sector striking N–S to NNW–SSE with a narrow damage zone and a southern sector striking NW–SE with a wide damage zone. A kinematic analysis shows pure normal fault kinematics along most of the fault. Geometric differences between the northern and southern sectors are caused by i) a heterogeneous basement controlling the fault geometry at depth and in the cover; ii) different orientations of the Baza Fault in the basement with respect to the regional extension direction and iii) interaction with other active faults. We use this structural characterization to analyse the segmentation of the Baza Fault. According to segmentation criteria, the entire Baza Fault should be considered a single fault seismogenic segment. Consequently, the seismic potential of the fault is defined for a complete rupture. Magnitude for the Mmax event is calculated using several scale relationships, obtaining values ranging between Mw 6.6 and Mw 7.1. Recurrence times range between approximately 2,000 and 2,200 years for Mmax events and between 5,300 and 5,400 years for palaeo-events. A geodetic scenario modelled for an Mmax event of Mw 6.7 shows permanent vertical displacements of more than 0.40m and an overall WSW–ENE extension during entire ruptures of the Baza Fault.

Geology and evolution of the Cortes de Pallás diapir (Eastern Iberia)

ABSTRACT This paper presents an 1:20,000 geological map and cross-sections of the Cortes de Pallás diapir (eastern Iberia). This structure is located at the junction of the Iberian Chain and the Betic Cordillera, in the northernmost part of the eastern Prebetic Zone. The diapir is an ENE to NE oriented saltwall, parallel to the regional structural trend of the Betic Cordillera. Our results support the hypothesis of a polyphase tectonic evolution from Oligocene to Pliocene times: (a) An extensional phase, Oligocene–Early Miocene in age, in which the graben system formed and the diapir rose. (b) A Middle Miocene compressive phase characterized by at least the partial closure of the diapir and thrusting of its old southern margin over the previous half-graben infill. (c) Finally, a Late Miocene–Pliocene extensional phase in which, synchronous to the normal faulting in the graben system, the diapir was reactivated and cut the previous structures.

Volcanic rocks in Lower Jurassic marine carbonate successions in the southeastern Iberian Range (Spain): biochronostratigraphic dating

The Ligurian Tethys began to open in a roughly NE–SW direction in Pliensbachian times. West of the Ligurian oceanic crust, a carbonate-platform system constituted the eastern Iberian paleomargin. Lower and Middle Jurassic marine sediments deposited in these shallow platforms are well exposed today in the southeastern Iberian Range and host multiple volcanogenic deposits, mainly volcaniclastic in nature. Regional mapping reveals that volcanic outcrops show NW and NE (or NNE) oriented lineaments following tracks of cortical weakness. Volcanic ages were estimated by using biochronostratigraphic methods and sequence-stratigraphic correlations. As a result, ten Lower Jurassic volcanic episodes have been identified. The chronostratigraphic positions of the volcanic deposits span from the early Pliensbachian (Jamesoni Zone or later) to the late Toarcian (Thouarsense Zone). The extension-dominated regime of the eastern Iberian paleomargin also affected the southern Iberian paleomargin (Betic Cordillera) as a result of the eastward prolongation of the central Pangea fragmentation. The break-up of wide platforms and the first volcanic emissions seem to be roughly coeval in the Betic and Iberian domains and synchronous with the onset of rifting and spreading events of the Ligurian Tethys Ocean.

Reappraisal of the 1863 Huércal-Overa Earthquake (Betic Cordillera, SE Spain) by the Analysis of ESI-07 Environmental Effects and Building Oriented Damage

This work reviews the 1863 Huércal-Overa earthquake (VI-VII EMS) based on the environmental seismic intensity scale (ESI-07) and oriented archaeoseismological building damage. The performed analysis identifies 23 environmental effects (EEEs) and 11 archaeoseismological effects (EAEs), completing a total of 34 intensity data-points within the intensity zone ≥ VI EMS. The new ESI intensity data quintuplicate the previous intensity data-points ≥ VI EMS (five localities) for this event. Sixteen of the identified EEEs indicate the occurrence of intensity VII-VIII within the Almanzora valley, south of Huércal-Overa, over an area of ca. 12–15 km2. Anomalies in water bodies, slope movements, hydrogeological anomalies, ground cracking, and other effects (gas emissions, tree shaking) are the more diagnostic EEEs—with one of them indicating a local maximum intensity of VIII-IX ESI-07 (Alboraija lake). Environmental earthquake damage of intensity ≥ VI covers an area of c. 100 km2, compatible with a VIII ESI intensity event. The spatial distribution of EEEs and EAEs indicates that the zone of Almanzora River Gorge, which was depopulated during the earthquake epoch, was the epicentral area, and compatible with seismotectonic data from active shallow blind thrusting beneath the Almagro Range. The use of ESI data in nearly unpopulated areas help to fill gaps between damaged localities (EMS data) multiplying intensity data-points, providing a better definition of the intensity zones and offering a geological basis to look for suspect seismic sources.

Newmark displacement data for low to moderate magnitude events in the Betic Cordillera.

Land-use decisions in relation to seismic-induced landslide hazard are usually made through the preparation of hazard maps. The rigid-block method is probably the most used for this purpose. Under this method, Newmark displacement is computed for each slope unit and this displacement is used as a guide for establishing categories of hazard. At present, most relations used for computing Newmark displacement are established from moderate-to-high magnitude earthquakes (Mw ≥ 6.5). This data article provides Newmark displacements computed from accelerograms recorded in the Betic Cordillera for low-to-moderate magnitude earthquakes (Mw = 3.5–6.3). Records come from the Spanish Strong Ground Motion database (Instituto Geográfico Nacional). Newmark displacements were computed focusing on yield accelerations frequently recorded in such scenarios (0.02, 0.03, 0.04, 0.05, 0.06, 0.08 and 0.10), although higher accelerations were also considered (0.125, 0.15, 0.20, 0.25 and 0.30 g's). These data are useful for the study of the hazard in seismic scenarios of low-to-moderate magnitude, very frequent in practice. These data have been used in the study by Delgado et al. [1].

Quaternary tectonic and climate changes at the origin of travertine and calcrete in the eastern Betics (Almería region, SE Spain)

Continental carbonate bodies are widespread in the Tabernas basin, eastern Betic Cordillera. Their relationships with the topographic evolution, climate changes and extensional regional tectonic processes recognized in the region are, however, still unclear. Travertine deposits exhibit facies of cascade and pool environments often reported as related to water–air surface processes. Calcretes show a large panel of facies, indicating control by groundwater and pedogenic processes. New U/Th dates on both travertine and calcrete reveal that they precipitated from 354 ka ± 76 to 8 ka ± 0.2. The U/Th dates obtained on calcretes are in good agreement with global climate changes and support that precipitation of recent CaCO 3 is episodic and occurs mainly during warm and wet conditions. C and O stable isotope geochemistry reveals travertines are thermogenic and characterized by hydrothermal fluids enriched in CO 2 that interacted with aquifers. This thermogenic origin suggests a deep source of CO 2 (higher positive δ 13 C values) likely triggered by the presence of an anomalously hot mantle that reflects thinning of the regional lithosphere and volcanism. Further analyses of the distribution of calcrete show they are carbonate-rich fluvial terraces, whose formation is controlled by the response of the river network to regional uplift and climate. Supplementary Materials : reproducibility for δ 13 C and δ 18 O of the NSB-18 internal standard available in Supplementary Table 1 (SP1) and reproducibility for U and Th of the HU-1 standard available in Supplementary Table 2 (SP2) at https://doi.org/10.6084/m9.figshare.c.4996514

An Early Aptian coral fauna from the Prebetic (southern Spain)

From the Lower Aptian of the Betic Cordillera a small hermatypic coral fauna is reported. The sampled outcrop is located in the Sierra de la Muela (Prebetic, South Spain). The studied corals come from a carbonate platform megasequence, deposited in the Southern Iberian Palaeomargin during the Early-Late Aptian transition. The coral fauna consists of 19 species in 13 genera belonging to the suborders Archeocaeniina, Faviina, Fungiina, Meandrinina, Microsolenina, and Stylinina. The coral fauna consists of typical and common species. It shows relationship of mainly Barremian to Early Albian faunas from the Western Tethys

Seismicity in Strike‐Slip Foreland Faults (Central Betic Cordillera Front): Evidence of Indentation Tectonics

AbstractUnexpected seismicity has been detected in the past few years along the northern Guadiana Menor River (Guadalquivir foreland basin) at the northern boundary of the Betic Cordillera. Earthquake focal mechanisms evidence the activity of N‐S to NNE‐SSW sinistral faults in the basement. Yet continuous GPS (CGPS) data show a westward movement in both the Prebetic Arc and the eastern Guadalquivir basin infill, which disagrees with the strike‐slip faults. To more precisely describe the structure and evolution of the area, new Bouguer anomaly data from the southeastern basin combined with seismicity data, electric resistivity tomography profiles (ERT), and surface studies are provided. Given the soft consistency of the sedimentary infill in the area, surface evidence of faulting is scarce, limited to elongated channel and minor vertical faults affecting Quaternary sediments, where ERT profiles suggested the presence of faults. These results suggest that the Guadalquivir basin infill, the Prebetic Arc and the central Betic Cordillera move towards the west, independent from the Iberian crust, but indicating to some extent an upward propagation of the basement deformation. However, the basement is coupled with the Alboran Domain and undergoes NNW‐SSE Eurasia‐Nubia convergence and orthogonal extension. This scenario is suggestive of the initial stages of indentation tectonics, better developed in the eastern Betic Cordillera and the central Alboran Sea.

Tectono‐Stratigraphic and Thermal Evolution of the Western Betic Flysch: Implications for the Geodynamics of South Iberian Margin and Alboran Domain

AbstractThe Betic‐Rif orogen is a key region to understand the evolution of the plate boundary between Africa and Iberia/Europe. This study focuses on the Flysch Complex, which is considered the sedimentary cover of a domain originally positioned between the Iberian and Alboran margins. Based on stratigraphic and depositional evolution constraints, evidence for salt tectonics, combined with new apatite fission‐tracks (AFT) and (U‐Th‐Sm)/He ages from the Flysch Complex and the Subbetic Zone, we propose a geodynamic interpretation for the formation of the Betic Cordillera, accounting for moderate N‐directed transport of the Flysch Complex and synchronous exhumation between External and Internal Zones of the Betic. Early contraction between Africa and Iberia/Europe is reflected in the Cretaceous Flysch basin by a prolonged period of residence in the partial annealing zone for AFT and onset of foreland subsidence at 50 Ma. This stage lasted until the Early to Middle Miocene (20–15 Ma), marked by the rapid succession, in less than 5 Ma, of the deposition of Cenozoic flysch and their rapid exhumation. This event is interpreted to reflect the W‐directed retreating mantle delamination between Africa and Iberia margins at the origin of the collapse of the proto‐Betic orogenic domain and formation of the Alboran domain.