South Iberian Research Articles

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.

The Lithospheric Structure of the Gibraltar Arc System From Wide‐Angle Seismic Data

AbstractIn continental settings, seismic failure is generally restricted to crustal depth. Crustal structure is therefore an important proxy to evaluate seismic hazard of continental fault systems. Here we present a seismic velocity model across the Gibraltar Arc System, from the Eurasian Betics Range (South Iberian margin), across offshore East Alboran and Pytheas (African margin) basins, and ending onshore in North Morocco. Our results reveal the nature and configuration of the crust supporting the coexistence of three different crustal domains: the continental crust of the Betics, the continental crust of the Pytheas Basin (south Alboran Basin) and onshore Morocco, and a distinct domain formed of magmatic arc crust under the East Alboran Basin. The magmatic arc under the East Alboran Basin is characterized by a velocity structure containing a relatively high‐velocity lower crust (~7 km/s) bounded at the top and base by reflections. The lateral extension of this crust is mapped integrating a second perpendicular wide‐angle seismic profile along the Eastern Alboran basin, together with basement samples, multibeam bathymetry, and a grid of deep‐penetrating multichannel seismic profiles. The transition between crustal domains is currently unrelated to extensional and magmatic processes that formed the basin. The abrupt transition zones between the different crustal domains support that they are bounded by crustal‐scale active fault systems that reactivate inherited structures. Seismicity in the area is constrained to upper‐middle crust depths, and most earthquakes nucleate outside of the magmatic arc domain.

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.

Effects of habitat fragmentation on frugivorous birds and on seed removal from Pistacia lentiscus in two contrasting fruiting seasons

Successful animal seed dispersal is the result of the interaction between frugivore behavior and the distribution of food resources, which can vary over space and time. We evaluated the interaction between avian frugivores and the masting shrub Pistacia lentiscus in both connected and isolated forest fragments along the Guadalquivir valley (south Iberian Peninsula) in two contrasting fruiting seasons (mast and non-mast). We compared the abundance and composition of avian dispersers and seed predators, recorded fruit removal rates by dispersers and predators, and investigated potential changes in the arrival of seeds to forest fragments. Our results showed that there was a greater abundance of dispersers in connected than in isolated fragments in the mast season (i.e. high fruit availability) but the opposite pattern in the non-mast season (i.e. low fruit availability). The effects of habitat fragmentation were more noticeable on medium-sized than small bird dispersers. Medium-sized birds were more abundant in isolated forest fragments but their abundance was highly dependent on the season, while small bird dispersers were apparently unaffected by fragmentation. Seed removal rates were higher in isolated than in connected fragments in the mast season but not in the non-mast season; predation rates were negligible in both seasons. Seed arrival was consistent between seasons and microhabitat where the dispersed seeds were deposited, most seeds being dispersed under the canopy of female Pistacia plants. We highlight the influence of the interplay between seasonality and landscape configuration on patterns of frugivore-mediated seed dispersal. Thus, despite its direct link to plant–frugivore interaction, the effects of habitat fragmentation on frugivores and plants were decoupled in our study system. These decoupled responses seemed to be chiefly due to the high feeding dependence of dispersers on P. lentiscus fruits.

Atmospheric mercury pollution deciphered through archaeological bones

Mercury is a major environmental pollutant extensively used by humans, whose pollution dates back at least to c. 3250 BCE (South Iberian Peninsula). As it happens today, past populations were mostly affected by low dose chronic mercury exposure, with levels that varied with the intensity of some anthropogenic activities (mining and metallurgy in particular). Despite its toxic nature, mercury impact in humans themselves has been hardly addressed by Archaeology. The aim of this research is to increase our knowledge on mercury levels in past populations by 1) analysing human (cortical) bone from skeletons recovered in a necropolis from NW Iberia covering contrasting periods of atmospheric pollution: Roman, AD 1st to 4th centuries, and post-Roman, AD 5th to 7th centuries; 2) considering bone type variability; 3) contextualizing our findings with previous works. Samples from 3 types of bone (n = 143) as well as soils/sediments associated to the burials (n = 34) were analysed. Mercury concentrations in soil were below 5 ng g−1, while the average in bone was 36 ± 52 ng g−1, making post-depositional incorporation unlikely. We found significant differences between the two periods (Romans: 54 ± 60 ng g−1, post-Romans: 21 ± 23 ng g−1), but no effect of type of bone, sex, age, social status or diet of the individuals. Our results agree with the chronology of mercury pollution reconstructed from a local peatland, which suggests a predominant atmospheric source. This fact contrasts with previous research in which high mercury concentrations were mainly related to post-mortem burial customs and pre-mortem medical treatment and poisoning. Thus, mercury distribution in past communities was possibly more complex than previously thought, with different pre- and post-mortem sources interacting. Furthermore, our research also supports the use of archaeological bone as environmental archive of metal pollution, when metal cultural exposure is low.

3D Imaging of southernmost Triassic archosaur footprints from Europe (Southern Spain)

The application of 3D photogrammetric models to the analysis of rauisuchian archosaur footprints of the Middle-Upper Triassic of the south Iberian palaeomargin improves the knowledge and interpretation of the behaviour of rauisuchian archosaurs that inhabited this area. Two outcrops rich in footprints were scanned at Santisteban del Puerto and Cambil in Jaen (SE Spain). The footprints of Santisteban del Puerto consist of three subparallel concave impressions including two long lateral traces, and a shorter medial one. The footprints of Cambil are preserved as convex hyporeliefs, counter-moulds, at the bottom of inverted strata and record manus and pes impressions. The 3D photogrammetric models provide new data sets such as depth distribution maps, contour line maps, and topographic profiles of the footprints that implement the interpretation obtained during fieldwork. These are useful tools for the study, preservation, and dissemination of such outcrops. Digitally generated depth distribution maps display darker (blue) colours for the most depressed areas of the traces. The contour line maps and digital elevation models of the footprints improve the understanding of the locomotion of the tracemaker. The footprints of Cambil and Santisteban del Puerto represent the only ichnological record of Triassic terrestrial vertebrates in the southern Iberian Peninsula, and the southernmost record of trace fossils of the Triassic in Europe. These outcrops also provide information about different locomotion styles of Triassic archosauromorphs including swimming/floating of bipeds (Santisteban del Puerto) and walking of quadrupeds (Cambil).

Injuries, healing and management of common dolphins (Delphinus delphis) in human-impacted waters in the south Iberian Peninsula

AbstractThis study focuses on the dolphins populating the water between Gibraltar and Algeciras in the south Iberian Peninsula, an area subjected to pressure due to high human activity. The area is considered an important feeding and breeding ground for common dolphins (Delphinus delphis). Due to the degree of residence of some specimens, and the large gap in knowledge about the evolution of wounds inD. delphisspecimens with lacerations, this work sought to perform the following analyses: identify lacerated individuals; characterize sequences of ‘before – during – after’ with respect to the occurrence of lacerations; and associate the type of injury with its severity. This work will inform future studies by expanding a database on injured individuals and contribute to periodical monitoring of specimens that frequent these geographic areas. Between 2013 and 2017, we were able to track the healing process of five injured individuals of common dolphins from a whale-watching platform thanks to photo identification. The animals exhibited fresh external wounds from different sources. In the majority of individuals, the wound-healing processes lasted 3–21 weeks. The frequency with which sightings are made and knowledge about the local population will help track injured animals, follow their wound evolution, and document their survival rates. The documented injuries inflicted by human interactions described in this paper may include fishing interactions and propeller strikes, probably as a consequence of the high intensity of recreational fishing and whale-watching activities in the area.

Geochemical compositional mapping of Lower Jurassic trace fossils: Palaeoenvironmental significance and methodological implications

Analyses of X-ray microfluorescence (XRF) elemental maps of the ichnofossil assemblages from the upper Pliensbachian-lower Toarcian marl-limestone rhythmite of the South Iberian Palaeomargin (Betic Cordillera, SE Spain) show that the compositions of burrow infills are geochemically and mineralogically different with respect to the surrounding sediment. XRF elemental maps and back-scattered electron images show pyrite framboids within the burrows and enrichment in Fe and S relative to the host sediment. This is congruent with the position of burrows beneath the redox boundary at the time of their active or passive sedimentary infilling. Organic matter that accumulated at the seafloor was not preserved due to oxidation and consumption by benthic organisms. However, burrows located beneath the redox boundary served as traps for organic matter preservation. The composition of burrow fills reflects the original signal of the redox conditions of pore-waters below the sediment-water interface, which was not preserved in the surrounding sediment. The XRF elemental maps also show that some trace fossils from limestone and marly-limestone intervals contain high concentrations of Si, Al, K, Zn, Cr, and Ti with respect to the surrounding sediment. This may reflect enrichment of clay minerals in the burrow fills derived from overlying marly layers. This work proposes the use of elemental imaging of trace fossils prior bulk-rock geochemical analyses in order to evaluate the potential for biogenic heterogeneity and elemental partitioning before sampling. Geochemical analysis of trace fossils represents an additional tool that may be of use in hydrocarbon exploration.

Upper Pliensbachian-Lower Toarcian methane cold seeps interpreted from geochemical and mineralogical characteristics of celestine concretions (South Iberian palaeo-margin)

Abundant sulfate mineralizations are recorded in the Upper Pliensbachian-Lower Toarcian marly-limestones and marls of La Cerradura section (Betic Cordillera, South Spain). These mineralizations are celestine concretions (6–41 cm in diameter), sulfated wood coal remains and yellow-powder patches composed mainly of natrojarosite, native sulfur and gypsum. These deposits are mostly recorded in the base of Serpentinum Zone (Lower Toarcian) in the interval with the highest TOC values (0.4 wt%) and a negative carbon isotopic excursion, correlative with the Toarcian Oceanic Anoxic Event. The 87Sr/86Sr and δ18O values of celestine are within the values of the Early Toarcian seawater but δ34S values are anomalously high. The isotopic composition of these sulfates is congruent with their precipitation from fluids that have been submitted to variable degrees of microbial sulfate-reduction combined with anaerobic oxidation of methane, as reported from recent examples. The record of thin laminated crusts composed of celestine with calcite as the nucleus of concretions containing fossil filaments (observed under scanning electron microscopy) is compatible with the activity of sulfate-reducing bacteria. Therefore, celestine concretions have been related to methane cold seeps or high methane concentrations in the sediment. The source of the methane, which moved within the pore-space of marine sediment via diffusion or as bubbles, was the microbial methanogenesis of the organic-rich marls. The very high δ34S values indicate that celestine crystals formed in a semi-closed system below the sediment-water interface, which favored the efficient microbial sulfate-reduction that preferentially removed the light 32S isotope from pore-water. The celestine crystals grew from mixing of this 34S-enriched sulfate pool with reducing and Sr-rich seep fluids advecting with the methane hydrates. The precipitation of celestine in the dark marls of the Serpentinum Zone occurred in some cases over wood coal remains. Fossil chimneys related to the cold seeps have not been recorded in the studied outcrop indicating that the amount of methane hydrates reaching the sea-bottom was not enough for building this kind of structures. The growth of each celestine concretions ended when the source of methane, the organic matter, was spent and the activity of methanogenic microbes and sulfate-reducing bacteria decreased. New celestine concretions developed when new methane bubbles were channeled upwards in different layers.

Phenological patterns in Mediterranean south Iberian serpentine flora

Phenological phases have been studied in Mediterranean serpentine shrubland vegetation in the south of the Iberian Peninsula to obtain a phenological characterization of the serpentine flora and to make a comparison between endemic serpentine and non‐serpentine plants in different years and altitudes. For this purpose, data were taken in the serpentine ecosystem of Sierra Bermeja (Andalusia, Spain) establishing two plots on two altitudinal bioclimatic belts and during two different years. A total of 28 persistent taxa were studied, including both serpentinophytes, their magnesicolous allies and non‐serpentinophytes, to detect possible differences between serpentine and non‐endemic taxa. Phenological calendars and phenological patterns (phenophasic indexes) were obtained. The species showed phenophasic patterns similar to those of other studied Mediterranean flora: a phenological pause coinciding with summer and most species behaving as summer semi‐deciduous with seasonal dimorphism. There were no statistically significant differences in phenology and in phenological indexes due to altitude or serpentine affinity. The best represented active phenophasic period of the species was 9–11 months of activity although showing the summer phenological pause. Species with low index of reproductive/vegetative activity of the species predominated, employing more time/resources for vegetative functions, and with synchronous phenophases, where flowering and growth coincide. The phenophasic period of serpentinophytes and magnesicolous taxa pointed to a certain delay in the period of flowering with respect to the group of non‐serpentinophytes, a result which could have important implications for reproduction.

Rare earth elements in mud volcano sediments from the Gulf of Cadiz, South Iberian Peninsula

Eight gravity cores (GC) were retrieved from the deep mud volcanoes Sagres, Bonjardim, Soloviev and Porto in the Gulf of Cadiz. Cores with 137 to 317 cm long were sliced in intervals of 15 to 20 cm thickness, and 46 samples were analyzed for grain size distribution, loss on ignition, Al, Fe, Ca, Mg, Mn, Sr, Ba and the rare earth elements (REE) La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu. REE profile normalized to Post-Archean Australian Average Shale (PAAS) was dominated by a mid-REE bulge with a pronounced Eu enhancement. Sediment reducing conditions resulting from the anaerobic oxidation of methane probably contributed to the positive-Eu anomaly (1.18–2.19, PAAS normalization). Most likely, reactions near the sulfate-methane transition zone such as the precipitation of barium sulfate found at layers around 50-cm depth explain the enhancement of Eu/Eu* ratios. The Ce anomalies (0.93–1.09) were almost absent.

The Middle-Upper Jurassic unconformity in the South Iberian Palaeomargin (Western Tethys): a history of carbonate platform fragmentation, emersion and subsequent drowning

A wide diversity of processes occurred during the fragmentation of the shallow carbonate platform of the Middle Jurassic in the South Iberian Palaeomargin. A detailed study of the Middle-Upper Jurassic discontinuity from the Prebetic (Betic Cordillera) has allowed identifying the formation of hardgrounds and the emersion, erosion and formation of hydromorphic soils. The contact between oolithic and oncolithic limestones of the Middle Jurassic and the spongiolithic limestones of the Middle and Upper Oxfordian is represented by a palaeorelief that suggests the emersion and erosion of the carbonate platform. Locally, erosive palaeorelief is not developed and a hardground characterized by an iron crusts and abundant borings is preserved on the top of the Middle Jurassic oolithic and oncolithic limestones. In other localities, iron crusts were recorded on the top of the Middle Jurassic limestones, which include iron ooids and pisoids and shows an Al-substitution in goethites of 10%. This is an indicator of hydromorphic soils (plinthite) as well as of the presence of kaolinite. This kind of soils developed in coastal plains under tropical climate. The subsequent drowning of the platform in the Middle Oxfordian is recorded by a bed of ferruginous oolithic limestone with abundant planktic foraminifera and ammonites, also bearing iron ooids and pisoids reworked from eroded palaeosoils. Following drowning, sponge meadows proliferated resulting in spongiolithic limestones in the Middle-Upper Oxfordian. This was a mid-shelf environment with hemipelagic influence as evidenced by the occurrence of siliceous sponges (hexactinellids), planktic foraminifera and ammonites. The comparison of the Prebetic sections studied in this work with other records of the Western Tethys during the same interval highlights the wide variability of features related to this discontinuity in the South Iberian Palaeomargin.

Trace metal characterization and fluxes from the Guadiana, Tinto-Odiel and Guadalquivir estuaries to the Gulf of Cadiz

Metals transported into the coastal zone by the South Iberian rivers are key to understand the biogeochemical cycles and distribution of trace elements in the Gulf of Cadiz (GoC hereinafter) and the exchange with the Mediterranean Sea. Previous studies carried out in the 80s have suggested that metal enrichment in the Alboran Sea (Western Mediterranean) is related with fluvial inputs from acid mine drainage from the Tinto and Odiel rivers. The present study evaluates the contribution of dissolved trace metal concentrations (i.e. Cd, Co, Cu, Fe, Mo, Ni, Pb, V, Zn) from the three main rivers discharging into the GoC (i.e. Guadiana, Tinto-Odiel and Guadalquivir rivers). Our results show that the metal composition of water discharged from each river is impacted by the activities developed in the course of the rivers, which clearly influence the GoC coastal surface waters composition. Metal fluxes from the Guadalquivir river are quantitatively higher than those from the Tinto-Odiel (e.g. up to 73% and 19% higher for Ni and Cu, respectively). Although the metal concentrations spatial distributions in the GoC are dominated by the circulation pattern between the Atlantic and the Mediterranean Sea, the concentrations within the GoC continental shelf could be explained by a greater contribution from the Guadalquivir estuary (e.g. 80.5%, 54.6%, 56.5% and 56.6% for Ni, Cu, Mo, and V respectively).

U-Pb ages of detrital zircons from the Internal Betics: A key to deciphering paleogeographic provenance and tectono-stratigraphic evolution

Zircons from the Nevado-Filábride Complex metamorphic rocks yielded 891 concordant inherited detrital ages. The 342 concordant ages from the Aulago Fm indicate a Pennsylvanian maximum depositional age, while the age density distribution indicates that this formation is closely related to the Cantabrian Zone (north of the Iberian Massif). The dominant Ediacaran and Cryogenian populations, at ca. 596 and 788 Ma respectively, relate the Nevado-Filábride Complex to northern Gondwana terranes. A discrete Mesoproterozoic zircon population at ca. 1031 Ma (Tonian-Late Estenian population) suggests that the basement of the Nevado-Filábride Complex could have been located near of the Saharan Metacraton and west of the East African Orogen at the beginning of the Paleozoic. The 549 concordant ages from the Tahal Fm yield an Early Permian age for the protoliths. The age density distribution pattern records erosion of rocks from the Variscan belt, including Late-Variscan magmatic rocks. Zircon spectra differ from those of the Alborán Domain, supporting the hypothesis that the Nevado-Filábride Complex is part of the South Iberian Domain. Furthermore, data from the Tahal Fm are similar to those of Permo-Triassic rocks from the Iberian Ranges.

Carbon-isotope stratigraphy and pelagic biofacies of the Middle–Upper Jurassic transition in the Tethys–Central Atlantic connection

A bulk carbon-isotope stratigraphy, based on high-resolution sampling of five stratigraphic ammonite-dated sections from pelagic swells of the Subbetic basin (External Zones of the Betic Cordillera, southern Spain) is presented. The studied sections are characterized by Callovian–Oxfordian stratigraphic successions located in the South Iberian palaeomargin, a key area connecting the Central Atlantic to the Tethys oceans. The rocks are mainly nodular limestones with common extreme condensation (rosso ammonitico facies). Discontinuities with hiatuses of variable duration, submarine “hardgrounds”, Fe-Mn ooids, limonite crusts, and neptunian dykes are observed around the Callovian/Oxfordian boundary. The stratigraphic record, although very time-averaged, allows for a consistent and accurate ammonite chronostratigraphy. The carbon isotopes of marine carbonates show a marked trend towards high δ13C values from Lower Oxfordian to the Middle Oxfordian (~4.3‰, near the Plicatilis/Transversarium boundary). The isotopic values stand between 2.7 and 3.0‰ at the Upper Oxfordian (Bifurcatus and Hypselum Zones) and lowermost Kimmeridgian (Bimammatum Zone); afterward δ13C values decrease and reach a relative minimum (~2.3–2.5‰) in the Lower Kimmeridgian (Bimammatum/Planula boundary). Finally, isotopic values increase again (~2.6–2.7‰) in the lower Kimmeridgian (mid part of the Planula Zone). Comparison of carbon-isotope stratigraphy between Subbetic and other Tethyan areas shows similar trends. The replacement of thin-shelled bivalves by planktonic foraminifers and radiolarians that took place in the Callovian/Oxfordian boundary can be associated to the widening of the trans-Pangaean seaway. This, in turn, triggered the global warming which increased nutrients concentration in upper water column due to intensified nutrient input by river plumes. These phenomena are concomitant with the major Oxfordian δ13C positive excursion and with a transgressive cycle.

Testing thin-skinned inversion of a prerift salt-bearing passive margin (Eastern Prebetic Zone, SE Iberia)

Detailed geologic mapping combined with well and seismic data from the Eastern Prebetic Zone (SE Iberia) reveal extensional and contractional structures that permit characterization of passive margin development and its incorporation into a thin-skinned fold-and-thrust belt. The study area is represented by NW-directed, ENE-trending folds and thrusts faults locally disrupted by the NW-trending Matamoros Basin and the active Jumilla and La Rosa diapirs. These structures resulted from the thin-skinned inversion of the proximal part of the Eastern South Iberian passive margin containing prerift salt. Here, Upper Jurassic to Santonian thick-skinned extension controlled the accumulation of sediment over mobile prerift salt. This in turn defined the style of salt tectonics characterized by monoclinal drape folds, suprasalt extensional faults and diapirs. The structural and sedimentological analysis suggests that during extension, salt localizes strain thus decoupling sub- and suprasalt deformation. Thick-skinned extension controls suprasalt deformation as well as its location and distribution which changes over time. Salt also localizes strain during inversion. The preexisting salt structures, weaker than adjacent areas, preferentially absorb the contractional deformation. In addition, the stepped subsalt geometry that results from thick-skinned extension also controls the shortening propagation. Therefore, the degree of strain localization depends on the thickness of the suprasalt cover and on the dip of subsalt faults relative to the thin-skinned transport direction.

Miocene tectono-sedimentary evolution of the eastern external Betic Cordillera (Spain)

ABSTRACTAn interdisciplinary study of Miocene successions in the eastern External Betic Zone (South Iberian Margin) was carried out. Evidences of syn-sedimentary tectonic activity were recognized. The results enabled a better reconstruction of the stratigraphic architecture (with an improved chronostratigraphic resolution) in the framework of the Miocene foredeep evolution of the eastern EBZ. Two main depositional sequences were dated as uppermost Burdigalian-upper Serravallian p.p. and middle-upper Tortonian. p.p., respectively. The vertical and lateral diversification of lithofacies associations and thicknesses resulted from the syn-depositional tectonic complexity of the area. A great variety of sedimentary depositional realms is due to different subsidence rates, and the growing of anticlines and synclines during the Langhian p.p.-Serravallian. After a regression with an early Tortonian erosional gap, platform to hemipelagic realms developed during the middle Tortonian. The end of the sedimentation coincided with the emplacement of an important olisthostrome-like mass consisting of Triassic material related to either the development of thrust systems or diapirs emerged in the middle-late Tortonian, during the nappe emplacement. Correlations with other external sectors of the Betic Chain, and the external domains of the Rif, Tell, and northern Apennine Chains highlighted a similar Miocene foredeep evolution during the building of these orogens.

Uppermost Pliensbachian-Lowermost Toarcian ostracod assemblages from the Western Tethys: Comparison between Traras Mountains (Algeria), Subbetic (Spain), and Algarve (Portugal)

Major changes in ostracod assemblages have been recorded in the Lower Jurassic of Western Tethys related to biotic crises of the Pliensbachian-Toarcian boundary and the Polymorphum-Levisoni boundary (Toarcian Oceanic Anoxic Event). The study is focused on the ostracods assemblages from Benzerka section (Traras Mountains, Algeria) and their comparison with sections from External Subbetic and Algarve Basin (South Iberian Palaeomargin). Three stratigraphic intervals coincident with the ammonite zones have been differentiated with important fluctuations in the composition of ostracod assemblages. In the ostracod assemblages from the Traras Mountains the turnover related to this benthic biotic crisis is shown by assemblages previous to the biotic crisis (uppermost Pliensbachian) mainly composed by families Healdiidae and Cytherellidae to assemblages just after the T-OAE (upper part of the Levisoni Zone) with assemblages dominated by families Protocytheridae and Polycopidae and the extinction of family Healdiidae (suborder Metacopina). The Toarcian Oceanic Anoxic Event (T-OAE) probably resulted in restricted conditions but a barren interval due to oxygen-depleted conditions in this setting is not recorded. In this context, the change of components of ostracod assemblages looks gradual. In the Southiberian Palaeomargin, represented by the External Subbetic the turnover of ostracods assemblages is also recorded but the families involved are different than in Traras Mountains. Therefore, different phases have been differentiated in the ostracod turnover occurring from Upper Pliensbachian (assemblages dominated by families Pontocyprididae, Healdiidae and Bairdiidae) to end of Lower Toarcian (assemblages dominated by family Cytherellidae and the extinction of family Healdiidae). In the Algarve Basin the families Healdiidae and Bairdiidae were dominant previously to the Toarcian Oceanic Anoxic Event. Differences in the composition of ostracod assemblages between Traras Mountains and External Subbetic may be related to the fragmentation of these palaeomargins related to early stages of rifting in the Western Tethys. Moreover, the incidence of oxygen-depleted conditions was higher in External Subbetic than in Traras Mountains where some ostracod genera survive during the biotic crisis.

Brachiopod faunal exchange through an epioceanic-epicontinental transitional area from the Early Jurassic South Iberian platform system

The La Mola region (eastern External Betic Zone) can be regarded as one of the easternmost complete Jurassic successions of the Betic Cordillera in the Iberian Peninsula, but the paleogeographical setting of their outcrops remains widely discussed. Analysis of brachiopod assemblages from the Lower Jurassic improves the accuracy of previous paleogeographical data, enabling identification of a mainly epioceanic transitional area in which influences of epicontinental habitats are also detected. Assemblage 1, mainly with a Mediterranean affinity but also sharing several constituents with the African and Northeastern Iberian basins, typifies the Sinemurian–Pliensbachian transition. Assemblage 2, as a whole, shows a transitional character between epioceanic and epicontinental habitats; it is subdivided into two successive and interrelated sub-assemblages: Ass. 2a (Demonense–Tenuicostatum Zones) reveals a free connection with the epioceanic Subbetic area, whereas Ass. 2b (Uppermost Pliensbachian–Lower Toarcian) shows a closer relationship with epicontinental environments. Assemblage 3 (Uppermost Spinatum–basal Serpentinum Zones) is commonly recorded in the peri-Iberian epicontinental platform system integrated within the NW-European bioprovince, but it can also be regarded as a marginal assemblage that is widespread in the westernmost Tethyan margin prior to the Early Toarcian extinction event. Assemblage 2 constitutes a suitable index for assessing the paleobiogeographical affinity of the La Mola region, as Ass. 2a is progressively replaced by Ass. 2b, thus triggering the arrival of epicontinental taxa to the more intra-epioceanic Subbetic environments, inferring a possible connection through the La Mola transitional slope. Consequently, this region enabled a faunal mixing and exchange between both environments, and La Mola likely remained as an area that would facilitate migration and an effective dispersal seaway or, at least, did not constitute an ecological filter-barrier for brachiopods. Biostratigraphical data from brachiopods and ammonites are correlated for the first time in La Mola, refining and calibrating biochronostratigraphical gaps in the pre-Domerian deposits where biochronological markers are usually scarce, and around the Pliensbachian–Toarcian boundary, a crucial timespan in which the Early Toarcian extinction event took place.

Revisiting the Late Jurassic-Early Cretaceous of the NW South Iberian Basin: new ages and sedimentary environments

The study of the Upper Jurassic-Lower Cretaceous deposits (Higueruelas, Villar del Arzobispo and Aldea de Cortes Formations) of the South Iberian Basin (NW Valencia, Spain) reveals new stratigraphic and sedimentological data, which have significant implications on the stratigraphic framework, depositional environments and age of these units. Moreover, these new data encourage revising the previously proposed stratigraphic correlations between the studied units and those deposited in adjacent areas of the Iberian Basin. The Higueruelas Fm was deposited in a mid-inner carbonate platform where oncolitic bars migrated by the action of storms and where oncoid production progressively decreased towards the uppermost part of the unit. The overlying Villar del Arzobispo Fm has been traditionally interpreted as an inner platform-lagoon evolving into a tidal-flat. Here it is interpreted as an inner-carbonate platform affected by storms, where oolitic shoals protected a lagoon, which had siliciclastic inputs from the continent. The Aldea de Cortes Fm has been previously interpreted as a lagoon surrounded by tidal-flats and fluvial-deltaic plains. Here it is reinterpreted as a coastal wetland where siliciclastic muddy deposits interacted with shallow fresh to marine water bodies, aeolian dunes and continental siliciclastic inputs. The contact between the Higueruelas and Villar del Arzobispo Fms, classically defined as gradual, is interpreted here as gradual and rapid, because the transition between both units comprises few meters. More importantly, the contact between the Villar del Arzobispo and Aldea de Cortes Fms, previously considered as unconformable, is here interpreted as gradual. The presence of Alveosepta in the Villar del Arzobispo Fm suggests that at least part of this unit is Kimmeridgian, unlike the previously assigned Late Tithonian-Middle Berriasian age. Consequently, the underlying Higueruelas Fm, previously considered Tithonian, should not be younger than Kimmeridgian. Accordingly, sedimentation of the Aldea de Cortes Fm, previously considered Valanginian-Hauterivian, probably started during the Tithonian and it may be considered part of the regressive trend of the Late Jurassic-Early Cretaceous cycle. This is consistent with the dinosaur faunas, typically Jurassic, described in the Villar del Arzobispo and Aldea de Cortes Fms.