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Abstract

During the Late Jurassic and Early Cretaceous, Iberia experienced extensional and transtensional stresses leading to a complex rifting time interval. Africa–America–Europe relative motions determined the definition of the Iberian plate boundaries and the generation of rifted sedimentary basins and sub-basins along its continental margins and in the plate interior. Complex extensional and salt tectonics controlled the geometry and subsidence of those basins, filled mainly by clastic sediments derived from emerged Variscan massifs and by marine carbonates. The chapter considers the North Iberian Continental Margin, including the Basque-Cantabrian and the Pyrenean basin, the South Iberian Continental Margin, and the Iberian Basin Rift System, including South-Iberian, Central-Iberian, Cameros, Maestrazgo/Maestrat, and Garraf Basins.

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... In contrast to other peri-Tethyan domains, the stratigraphy of the northern (Europe) and southern (Iberia) margins in the Pyrenees indicate a lack of Early-Middle Jurassic tectonic subsidence (Curnelle, 1983;Brunet, 1986Brunet, , 1994Martín-Chivelet et al., 2019). Rifting indeed occurred from Late Jurassic to Early Cretaceous and reached a climax in the Aptian-Albian along E-W-directed rift basins, from the Parentis and the Aquitaine basins in the West (Brunet, 1986(Brunet, , 1994Bois and Ecors Scientific Party, 1990;Jammes et al., 2009;Angrand et al., 2018) to Organyà in the south (Berástegui et al., 1990;Mencos et al., 2015), including evidence for ubiquitous hyper-extension with sub-continental exhumation in the North Pyrenean basins Clerc et al., 2015;Corre et al., 2016;Teixell et al., 2016;Espurt et al., 2019a;Angrand et al., 2021). ...
... Following the collapse of the Variscan orogen and Permian Ca-K magmatism, post-orogenic extensional basins formed during the late Permian-Triassic (López- . Subsidence resumed during the Late Jurassic (Tithonian)-Early Cretaceous after a period of tectonic quiescence associated with deposition of Hettangian-Kimmeridgian (200-160 Ma) marine carbonate platforms (Cámara, 2017;Pedrera et al., 2017;Martín-Chivelet et al., 2019), followed by deposition of Tithonian-Barremian (140-125 Ma) shallow marine sediments. By the late Aptian-early Albian, synrift subsidence increased as revealed by the deposition of 3 km deep-marine sediments. ...
... Whether this is related to the onset of oceanic spreading or to hyper-extended margin magmatism (Durand-Delga et al., 2000) remains unclear. A second phase of rifting is recorded from Late Jurassic (Bathonian, ∼ 170 Ma) to Early Cretaceous (Albian, 100 Ma) (Hanne et al., 2003;Martín-Chivelet et al., 2019). ...
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The West European collisional Alpine belts are the result of the inversion, initiated in the middle Cretaceous, of the complex western Neotethys and the Atlantic continental rift domains and closure of remnants of Tethys between North Africa and European cratons. While the kinematics of Africa relative to Europe is well understood, the kinematics of microplates such as Iberia and Adria, within the diffuse collisional plate boundary, are still a matter of debate. We review geological and stratigraphic constraints in the peri-Iberia fold-thrust belts and basins to define the deformation history and crustal segmentation of the West European realm. These data are then implemented with other constraints from recently published kinematic and paleogeographic reconstructions to propose a new regional tectonic and kinematic model of the Western Europe from the late Permian to recent times. Our model shows that the pre-collisional extension between Europe and Africa plates was distributed and oblique, hence building discontinuous rift segments between the southern Alpine Tethys and the Central Atlantic. They were characterised by variably extended crust and narrow oceanic domains segmented across transfer structures and micro-continental blocks. The main tectonic structures that are inherited from the late Variscan orogeny localized both rifting and orogenic belts. We show that several continental blocks, including the Ebro-Sardinia-Corsica block, have been key in accommodating strike-slip, extension, and contraction in both Iberia and Adria. Its existence further allows refining the tectonic relationship between Iberia, Europe and Adria in the Alps. By the Paleogene, the convergence of Africa closed the spatially distributed oceanic domains, except for the Ionian basin. From this time onwards, collision spread over the different continental blocks, allowing an efficient transfer of the deformation from Africa to Europe. The area was eventually affected by the West European Rift, in the late Eocene, which may have influenced the opening of the West Mediterranean. The low convergence associated with collisional evolution of Western Europe permits to resolve the control of the inherited crustal architecture on the distribution of strain in collision zone, that is otherwise lost in more mature collision domain such as the Himalaya.
... The Maestrat Basin is located in the eastern Iberian Chain (Fig. 1A). During the Late Jurassic and Early Cretaceous, basin evolution was mainly controlled by a rifting process, which recorded three discrete rift/post-rift stages (Salas et al. in Martín-Chivelet et al. 2019). These are (1) Kimmeridgian-Berriasian tectonic rifting, mainly related to the opening of the North Atlantic sea floor, (2) late Berriasian−late Hauterivian post-rift, in which the creation of depositional space was mainly controlled by thermal subsidence, and (3) Barremian-early Albian rifting, which was mainly associated with the opening of the Bay of Biscay (Tugend et al. 2015). ...
... These are (1) Kimmeridgian-Berriasian tectonic rifting, mainly related to the opening of the North Atlantic sea floor, (2) late Berriasian−late Hauterivian post-rift, in which the creation of depositional space was mainly controlled by thermal subsidence, and (3) Barremian-early Albian rifting, which was mainly associated with the opening of the Bay of Biscay (Tugend et al. 2015). Listric faults and local uplift shoulders produced a clear division of the Maestrat Basin into several smaller subbasins (Fig. 1B;Salas and Guimerà 1996;Salas et al. 2001;Salas et al. in Martín-Chivelet et al. 2019). The present-day structure and topographic relief are the result of tectonic inversion of the Mesozoic structures, which occurred during the Alpine Orogeny, lasting from the late Eocene to the early Miocene (e.g., Guimerà 2018;Nebot and Guimerà 2018). ...
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A combined micropalaeontological, taphonomical and sedimentological study was carried out in the non-marine Barremian of the Maestrat Basin (E Iberian Chain) to elucidate the palaeoecology of Barremian charophytes. Understanding the palaeoecology of fossil charophytes is of prime importance for the accurate application of charophyte biozonations, since most species used as biostratigraphic markers and/or biozone index species are restricted to facies formed in a particular environment. Five charophyte biocoenoses were distinguished. (1) Charophyte association from freshwater alkaline lakes receiving low clastic input, mainly composed of Atopochara trivolvis var. triquetra , Clavator harrisii , Ascidiella stellata , and A. triquetra . The thalli known as Munieria grambastii , corresponding to Clavator utricles, were extremely abundant in the shallowest facies of the lake margins, and Hemiclavator -rich populations were also locally dominant. (2) An association characteristic of freshwater alkaline lakes with high clastic input was mainly composed of Echinochara lazarii , Globator maillardii var. trochiliscoides , A. trivolvis var. triquetra , C. harrisii , Hemiclavator neimongolensis var. neimongolensis , and locally also Clavator calcitrapus . (3) Monospecific populations of Porochara maestratica thrived in brackish settings with little clastic influence, whereas (4) monospecific E. lazarii populations thrived in clastic-influenced brackish settings. (5) A charophyte association grew in lakes that developed in mudflat to floodplain environments and was mainly constituted by E. lazarii , A. trivolvis var. triquetra , and C. harrisii var. harrisii and var. reyi . Accordingly, the palaeoenvironmental conditions inferred indicate that most of the charophyte species were controlled by (i) bathymetry, (ii) clastic content in the sedimentary environment and (iii) salinity. The stratigraphic succession studied shows an upwards increase in clastic content from the base to the top, which is associated with the more humid period recorded along the margins of the Tethys and the Boreal realm during the early Barremian–early late Barremian. In consequence, those species restricted to clastic-poor settings are constrained to the lower part of the section, whereas those taxa that were able to thrive in clastic-rich settings persisted throughout the entire section. This observation establishes a link between the changes observed in the charophyte floras recognized and the environmental changes that occurred during the Barremian in western Europe.
... The Jurassic was a typical period of greenhouse climate (Berner, 1994(Berner, , 2003Bruce and Paul, 2008), with high sea levels and increased humidity in the atmosphere (Wierzbowski and Joachimski, 2007;Chivelet et al., 2019). Many lacustrine basins (e.g. ...
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Continental organic-rich shales are well developed in the Dameigou Formation within the Yuka Depression of the Qaidam Basin. Here, the Rock-Eval pyrolysis, biomarkers, organic petrology, and stable carbon isotope have been carried out on the Middle Jurassic Dameigou Formation source rocks from the northwest part of Yuka Depression, Qaidam Basin in order to study their thermal maturity, source of organic matter (OM), and palaeoenvironment changes. The Rock-Eval pyrolysis data (e.g. Tmax), vitrinite reflectance, and biomarker-derived thermal maturity parameters (e.g. carbon preference index, Ts/(Ts+Tm), C29 Ts/(C29Ts+C29 αβ hopane), C30 αβ/(αβ+βα) hopanes, C29 ααα 20S/(20S+20R) steranes, and C29 αββ/ (αββ+ααα) steranes) suggest all studied samples stay between immature and low mature stage. The maceral compositions, stable carbon isotope compositions, n-alkane distributions, and biomarker-derived source parameters (e.g. C27/C29 ααα 20R sterane, ternary diagram of C27-C28-C29 steranes, C24 tetracyclic terpane) indicate both aquatic organisms and higher plants are the source of OM in the shales, but land plants are dominant. Generally low gammacerane concentration and environment-related parameters (e.g. cross-plots of C27/C29 ααα 20R sterane versus Pr/Ph) indicate these source rocks may be derived from lacustrine and fluvial-deltaic environments with fresh water, which is also supported by the variations of stable carbon isotopes from OM in the source rocks. However, the stable carbon isotope compositions of OM in the source rocks were influenced by multiple factors (e.g. source types and depositional environment) in the Yuka Depression. Slightly brackish condition is recorded in the upper part of the ZK6-1 well favor the formation of lacustrine algae, as confirmed by high contents of C27 steranes and short-chain n-alkanes. The variation of reducing to oxidizing condition of study area is possibly associated with the periodical flooded river-influenced aquatic condition during the deposition of the Middle Jurassic Dameigou Formation.
... The opposite direction of slab retreat in the adjacent segments proposed by scenario 3 (Figure 1b and Vergés & Fernàndez, 2012) implies opposite symmetry in the crust and upper mantle structure as observed in our models (Figure 8). Scenario 3 is based on the pre-convergence geometry of the Iberia-Africa Ligurian-Tethys, characterized by markedly segmented margin configuration Frizon de Lamotte et al., 2011;Martín-Chivelet et al., 2019;Pedrera et al., 2020;Ramos et al., 2020;Schettino & Turco, 2011;Vergés & Fernàndez, 2012). The margin segmentation exerted a strong control on the further evolution of the Ligurian-Tethys realm allowing for opposed subduction polarities in adjacent segments. ...
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The geodynamic evolution of the Western Mediterranean for the past 35My is a matter of debate. Present-day structure and composition of the lithosphere and sublithospheric mantle may help in constraining the geodynamic evolution of the region. We use an integrated geophysical-petrological modeling to derive and compare the present-day thermal, density and compositional structure of the lithosphere and sublithospheric mantle along two NNW-SSE oriented transects crossing the back-arc Alboran and Algerian basins, from onshore Iberia to the northern Africa margin. The crust is constrained using available seismic data and geological cross-sections, whereas seismic tomography and mantle xenoliths constrain the upper mantle structure and composition. Results show a thick crust (37km and 30km) and a relative deep LAB (130km and150km) underneath the HP/LT metamorphic units of the Internal Betics and Greater Kabylies, respectively, which contrast with the 16km thick magmatic crust of the Alboran Basin and the 10km thick oceanic crust of the Algerian Basin. The sharp change in lithosphere thickness, from the orogenic wedge to the back-arc basins, contrasts with the gentler lithosphere thickening towards the respective opposed margins. Our results confirm the presence of detached slabs ∼400oC colder than upper mantle and a fertile composition than the continental lithospheric mantle beneath the External Betics and Saharan Atlas. Presence of detached quasi-vertical sublithospheric slabs dipping towards the SSE in the Betics and towards the NNW in the Kabylies and the opposed symmetric lithospheric structure support an opposite dipping subduction and retreat of two adjacent segments of the Jurassic Ligurian-Tethys realm.
... The Maestrat Basin is one of the Iberian intraplate rift basins that developed as a result of the spreading of the Atlantic Ocean and the opening of the Bay of Biscay throughout late Oxfordian to early late Albian times. Later, during the Paleogene, the Alpine orogeny caused the inversion of the Iberian Mesozoic rifts and gave rise to the Iberian Chain in the northeastern Iberian Peninsula (Salas and Casas, 1993;Salas et al., 2001;Salas et al. in Martín-Chivelet et al., 2019). The platform margin reconstructed here is of late early Aptian age, it has an extension of 1.2 km 2 and is situated in the central Galve sub-basin, which conforms the western marginal part of the Maestrat Basin (E Iberian Chain) (Fig. 2). ...
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The facies distribution in time and space of sedimentary successions is controlled by a complex interplay between physical, chemical and biological processes, which are nowadays difficult to construe from the geological record. Numerical models constitute a valuable tool to identify and quantify such controlling factors permitting a reliable 3D extrapolation and prediction of stratigraphic and facies architectures beyond outcropping rock strata. This study assesses the roles of three controlling parameters being carbonate production rate, relative sea-level changes and terrigenous clastic sediment supply, on the evolution of an Aptian carbonate system. The SIMSAFADIM-CLASTIC, a 3D process-based sedimentary-stratigraphic forward model, was used for this evaluation. The carbonate succession modelled crops out in the western Maestrat Basin (E Iberia), and corresponded to a platform-to-basin transition comprising three depositional environment-related facies assemblages: platform top, slope and basin. Testing of geological parameters in forward modelling results in a wide range of possible 3D geological scenarios. The documented distribution of facies and sequence-stratigraphic framework combined with a virtual outcrop model were used as a reference to perform geometric (quantitative) and architectural and stacking pattern (qualitative) research by model-data comparison. The time interval modelled spans 1450 ky. The best-fit simulation run characterizes and quantifies (1) relative sea-level fluctuations recording five different genetic types of deposit (systems tracts) belonging to two depositional sequences as expected from field-data analysis, (2) a rate of terrigenous clastic sediment input ranging between 0.5 and 2.5 gr/s, and (3) a mean autochthonous carbonate production maximum rate of 0.08 m/ky. Furthermore, the quantitative and qualitative sensitivity tests carried out highlight that the fluctuation of relative sea level exerted the main control on the resulting stratigraphic and facies architectures, whereas the effect of inflowing terrigenous clastic sediment is less pronounced. Facies assemblages show different sensitivities to each parameter, being the slope carbonates more sensitive than the platform top facies to inflowing fine terrigenous sediments. On slope depositional settings, siliciclastic input also controls stratal stacking patterns and the dimensions of the carbonate bodies formed. The final 3D model allows to spot architectural features such as stacking patterns that can be misinterpreted by looking at the resulting record in the outcrop or by using other 2D approaches, and facilitates the comprehension of reservoir connectivity highlighting the occurrence of initial disconnected regressive platforms, which were later connected during a transgressive stage.
... The cross-sections integrate the few available dip data, as well as stratigraphic thicknesses documented by Martín-Chivelet et al. (2019), after García-Senz (2002) and Lopez-Mir (2013). To interpret the structure at the subsurface, the top of the Anserola Formation was constructed using the Campo unconformity as reference horizon (Fig. 10). ...
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The Llert syncline is located in the South-central Pyrenees, between the eastern termination of the E-W trending Cotiella Basin and the north-western limb of the N-S trending Turbón-Serrado fold system. The Cotiella Basin is an inverted upper Coniacian-lower Santonian salt-floored post-rift extensional basin developed along the northern Iberian rift system. The Turbón-Serrado fold system consists of upper Santonian–Maastrichtian contractional saltcored anticlines developed above an inverted transfer zone of the Pyrenean rift system. Based on field observations, we have conducted a 3D reconstruction of the Llert syncline in order to further constrain the transition between these oblique salt-related structures. Our results suggest that the evolution of the Llert syncline was mainly controlled by tectonic shortening related to the positive inversion of the Cotiella Basin, synchronously to the growth of the Turbón-Serrado detachment anticline. This structure was also conditioned by the pre-compressional structural framework of the Pyrenean rift system. Our contribution provides new insight into the geometric and kinematic relationships of structures developed during the inversion of passive margins involving salt.
... Currently, following the NW-SE trend of the major Ventaniella Fault towards the south-east, it is possible to identify (Fig. 12): the Cabuérniga Basin and the Polientes Basin within the Basque-Cantabrian Zone; the Cameros Basin, the Central and South Iberian Basins and the Maestrazgo Basin as part of the Iberian Rift System, located at present within the Iberian Chain; the Columbrets Basin offshore, at the Eastern Iberian margin. Strong controversies about the structure and kinematic evolution of these basins prevail (e.g., Espina, 1997;Salas et al., 2001;Vergés and García-Senz, 2001;Tavani et al., 2018;Aurell et al., 2019;Martín-Chivelet et al., 2019). They might be developed within a diffuse and segmented transtensional corridor accommodating sinistral movements of Iberia relative to Europe, which led to the formation of lozenge shaped pull-apart basins. ...
Article
Current rift models propose polyphase rift evolutions that develop with the same kinematic framework and accommodate continuous and sequential extension, through the stacking of deformation modes. Several rifted margins show, however, evidence for multiple and out of sequence rift events, which developed within different kinematic frameworks, with a complex spatial and temporal evolution. In this work, we address the problem of multi-stage rift systems based on the study of the central North Iberian margin, located at the southern Bay of Biscay triangular oceanic domain. This magma-poor rifted margin recorded three major Mesozoic rift events and a subsequent Alpine compressional reactivation, representing a unique setting to study the architecture of a multi-stage rift system and the exerted control on subsequent reactivation. Relying on a dense set of 2D seismic reflection profiles, boreholes, and published velocity models, we map and describe structural domains and major extensional and compressional structures, and we construct depth and thickness maps of syn-rift units. These new maps display the geometry and spatial distribution of major rift basins and bounding structures. Distinctive scenarios resulting from this tectono-stratigraphic approach led us to define three rift systems. A first, diffuse and widespread Triassic system, with classical fault-bounded half-graben basins; a second, narrow, deep and localised Late Jurassic to Barremian transtensional system, including laterally confined pull-apart basins; and a third, widely distributed Aptian to Cenomanian hyperextended system. Our results show that each rift system controlled the successive extensional and compressional events, resulting in a complex 3D template. Deciphering the tectono-stratigraphic architecture of such, multi-stage systems provide key insights on the spatial, temporal, and thermal evolution of divergent plate boundaries. It is likewise indispensable to propose and test kinematic plate deformable models on conjugate rifted margins and to comprehend the implications for their reactivation.
... BasinVis Version 1.0 was particularly aimed at quantitative analyses and 2D and 3D visualization of the stratigraphic setting and subsidence of sedimentary basins based on well data and/or stratigraphic profiles. Functions of this program have been applied to various published research projects and case studies (e.g., Barber et al., 2018;Farahzadi et al., 2019;Kaya et al., 2019;Wagreich, 2016, 2017;Martín-Chivelet et al., 2019). Based on these application studies, feedbacks and communications with users, we have revised the user interfaces of BasinVis 1.0 and supplemented new analysis functions, to expand its applications to sedimentary basin analysis and modelling in academic and industry fields. ...
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BasinVis 1.0, a MATLAB-based modular open-source program released in 2016, has been used for multiple application studies of sedimentary basin analysis and modelling in both academic and industry fields. Based on these studies and user feedbacks, we have improved the workflow, revised user interfaces and developed novel techniques for the compaction trend estimation of infilling sediments and its applications (decompaction process) to sedimentary basin reconstruction and visualization. These improved functions are implemented in BasinVis, upgrading the software to Version 2.0. This study introduces BasinVis 2.0 and demonstrates its functions through extensive case studies comprising of well data from the Perth Basin (Australia) and the Vienna Basin (Austria). Compaction trend estimation and decompaction process are crucial for analyzing numerical basin evolution (e.g., subsidence) and evaluating hydrocarbon reservoirs and geological storages. The compaction trend is estimated with improved accuracy using linear and exponential trending equations. The quality is evaluated using porosity-depth data from IODP Site U1459 and the industry well Houtman-1 in the northern Perth Basin, offshore southwestern Australia. Data from 38 industry wells in the southern Vienna Basin, central Europe, are applied to demonstrate the redesigned interfaces and new functions using the decompaction technique in the stratigraphic visualization process for basin reconstruction. The results provide useful and more detailed information for the compaction trends and the sedimentation setting during basin formation as well as changes during burial.
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A lower and upper Barremian 690 metre-thick succession composed of freshwater and brackish limestones, marls and clays was measured and sampled in the Maestrat Basin, Eastern Iberian Chain (Castelló, Spain). Thirty-three taxa were identified from charophyte fructifications and thalli, belonging to the three families that coexisted during the Early Cretaceous, i.e. Porocharaceae, Characeae and Clavatoraceae. Up to 25 different Clavatoraceae utricles were identified. This high species richness of clavatoraceans has not been observed elsewhere and sheds light on the role of Iberia, and particularly the Maestrat Basin, as a diversity hotspot for this family during the Barremian. Several of them have been taxonomically revisited, as regards both utricles and thalli. The Echinochara lazarii utricle is reinterpreted as showing bilateral rather than triradial symmetry. Anagenetic evolution within Clavator calcitrapus has been documented and has enabled us to distinguish between two varieties linked by intermediate morphotypes of biostratigraphic and palaeobiogeographic interest. The taxon Clavator grovesii var. jiuquanensis is reported for the first time in the Iberian Chain and in Spain. The structure of Charaxis spicatus is revisited and a new type of cortication is defined, called the double triplostichous cortication, which is unknown in either fossil or extant charophytes. This thallus is found in anatomical connection with Echinochara lazarii utricles, enabling a whole-plant reconstruction of the Echinochara plant. Lastly, new characters were found in Munieria grambastii thalli that confirm the membership of genus Munieria to the clavatoracean charophytes, particularly the calcification pattern of the internodal cell, which recalls that of clavatoroid utricles.
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Peritidal carbonate-evaporite successions, since they are developed in the transition between continental and marine realms, provide essential keys for palaeobathymetric and palaeoclimatic interpretations. As a result, several facies models have been proposed to assist on the interpretation of ancient tidal flat deposits, and peritidal successions have been extensively used for cyclicity analyses. In this study, well-exposed, Lower Cretaceous peritidal deposits (Oncala Group, Cameros Basin, N Spain) are analysed and compared with the most commonly-used present-day analogues (from Shark Bay, the Arabian Gulf and the Bahamas) and with ancient peritidal successions, providing their palaeoenvironmental and palaeoclimatic interpretation, assessing the usefulness and limitations of the facies models, and evaluating the suitability of these deposits for analysis of decimetre to metre-scale cycles. The studied peritidal deposits consist of thinly-bedded to laminated dolostones, dolomitic stromatolites, stromatolite breccias, flat-pebble and edgewise breccias, and calcite and quartz pseudomorphs after anhydrite nodules. Abundant resemblances of the peritidal deposits of the Oncala Group with those of Shark Bay, including that they are largely composed of microbialites and intraclasts, makes the peritidal deposits of the Oncala Group one of the best fossil analogues of this present-day setting. However, the presence of anhydrite nodules indicates pervasive evaporite precipitation in the supratidal zone, which is a feature that does not occur in supratidal flats of Shark Bay, but is characteristic of arid sabkhas of the Arabian Gulf. Nevertheless, the fact that carbonate-evaporite tidal flats of the Oncala Group were laterally related with siliciclastic tidal flats with large freshwater input and broadly inhabited by dinosaurs, suggests that anhydrites precipitated under less arid climates than those of the Arabian Gulf nowadays, pointing to semiarid climatic conditions during deposition. Moreover, the fact that peritidal deposits with anhydrite nodules were exclusively formed in a low-subsidence area of the Cameros Basin suggests that the rate of accommodation space creation also played an important role in their development. Regarding the comparison with other fossil peritidal sediments, the studied deposits show more abundant similarities with Proterozoic and Cambrian successions, composed mainly of stromatolites, microbial laminites, and intraclasts, than with other Mesozoic peritidal deposits, in which bioclasts and burrowing are usually more abundant. This highlights the difficulties for assigning specific features to certain geological ages. Finally, peritidal facies of the Oncala Group may change laterally and vertically to any other facies, showing a patchy lateral distribution of facies and an unsystematic vertical stacking pattern. The sedimentary features of the stromatolite, breccia and thinly-bedded to laminated carbonate facies do not allow their assignment to a unique tidal zone. Moreover, sedimentary features indicative of subaerial exposure, such as anhydrite nodules formed in the capillary zone, occur within any of the carbonate facies and show limited lateral extent. This results in a succession that cannot be clearly subdivided into subsequent shallowing-upward cycles not even by using erosive surfaces or the anhydrite nodule layers as marker horizons of the upper part of the cycles, because their limited lateral extent prevents reliable correlations. Similar composite lateral and vertical facies relationships have been documented both in the present-day analogues and in ancient successions, which suggests that this kind of facies relationships may be common in peritidal successions and highlights the caution that must be taken when trying to perform cyclicity analysis on them.
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The fossil record of spinosaurid theropods from the Lower Cretaceous of the Iberian Peninsula is relatively abundant, but not very informative. This record, as generally occurs in other geographic areas, is mainly represented by isolated teeth, probably due to the distinctive features of the dentition of these theropods. However, cranial and postcranial elements attributed to spinosaurids have been described and reported from different Iberian fossil sites. The currently known record of these theropods spans from the upper Hauterivian to the lower Aptian of the Cameros and Maestrazgo basins in Eastern Spain whereas it is early Barremian in age in the Lusitanian Basin of Western Portugal. Spinosaurid remains from the Iberian fossil record were traditionally attributed to Baryonyx, firstly described in the upper Barremian–lower Aptian of United Kingdom. However, the recent description of a specimen collected in the locality of Santa Águeda (Vallibona, Castellón), from sediments of the Morella Formation, implies the presence of a new taxon with a combination of derived features more closely related with some Gondwanan spinosaurines than with Baryonyx. Therefore, the currently known Iberian spinosaurid record would be made up of at least three taxa: Baryonyx (or a closely related baryonychine), the spinosaurine Vallibonavenatrix cani, and possibly Camarillasaurus cirugedae, which was recently re-interpreted as belonging to a megalosauroid tentatively related with spinosaurids. This faunal diversity is also compatible with the assortment of spinosaurid tooth morphotypes (distinguished mostly by the presence or absence of serrated mesial carina) that has been described in the Lower Cretaceous of the Iberian Peninsula.
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The Lower Cretaceous Leza Formation is an essentially carbonate unit deposited at the northernmost active margin of the Cameros Basin (N Spain) under an extensional tectonic regime. This unit is composed of freshwater, marine-influenced, marginal-marine and hypersaline marine carbonate facies, interbedded with variable amounts of alluvial deposits, mainly derived from the erosion of the Jurassic substrate. 87Sr/86Sr, δ18O and δ13C analyses were obtained from carbonate facies of the Eastern and Western sectors of the basin. δ18O values follow the expected trend in both sectors: they are more negative (down to − 7.9‰) in freshwater carbonates and more positive (up to + 2.8‰) in marginal-marine to hypersaline facies. However, independently of the seawater or freshwater influence, in the Western Sector the 87Sr/86Sr values (0.707373–0.707801) are significantly lower and closer to the published Lower Cretaceous seawater 87Sr/86Sr ratios, than those of the Eastern Sector (0.707988–0.709033), where the overall marine influence was relatively high and the alluvial input low. These data strongly suggest that 87Sr/86Sr ratios were mainly controlled by those of the riverine freshwater arriving to the coastal and marine areas after the weathering and erosion of the Jurassic carbonates or siliciclastic rocks, in the Western and Eastern sectors, respectively. Thus, data indicate that, in coastal and shallow marine carbonates, the influence of the riverine water on the 87Sr/86Sr ratios should be systematically evaluated. This is particularly necessary in active tectonic settings, where the uplifted areas are significantly prone to weathering and erosion and where alluvial fan systems commonly developed, eventually discharging into coastal and shallow marine areas.
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Integration of extensive fieldwork, remote sensing mapping and 3D models from high quality drone photographs relates tectonics and sedimentation to define the Jurassic–early Albian diapiric evolution of the N‐S Miravete anticline, the NW‐SE Castel de Cabra anticline and the NW‐SE Cañada Vellida ridge in the Maestrat basin (Iberian Ranges, Spain). The pre‐shortening diapiric structures are defined by well‐exposed and unambiguous halokinetic geometries such as hooks and flaps, salt walls and collapse normal faults. These were developed on Triassic salt‐bearing deposits, previously misinterpreted because they were hidden and overprinted by the Alpine shortening. The Miravete anticline grew during the Jurassic and Early Cretaceous and were rejuvenated during Cenozoic shortening. Its evolution is separated into 4 halokinetic stages, including the latest Alpine compression. Regionally, the well‐exposed Castel de Cabra salt anticline and Cañada Vellida salt wall confirm the widespread Jurassic and Early Cretaceous diapiric evolution of the Maestrat basin. The NE flank of the Cañada Vellida salt wall is characterized by hook patterns and by a 500‐m long thin Upper Jurassic carbonates defining an upturned flap, inferred as the roof of the salt wall before NE‐directed salt extrusion. A regional E‐W cross‐section through the Ababuj, Miravete and Cañada‐Benatanduz anticlines shows typical geometries of salt‐related rift basins, partly decoupled from basement faults. These structures could form a broader diapiric region still to be investigated. In this section, the Camarillas and Fortanete minibasins displayed well‐developed bowl geometries at the onset of shortening. The most active period of diapiric growth in the Maestrat basin occurred during the Early Cretaceous, which is also recorded in the Eastern Betics, Asturias and Basque‐Cantabrian basins. This period coincides with the peak of eastward drift of the Iberian microplate, with speeds of 20 mm/yr. The transtensional regime is interpreted to have played a role in diapiric development.
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Las Hoyas, a locality of the La Huérguina Formation in the southwestern Iberia Basin (Cuenca province, Spain), is a well-known late Barremian Konservat-Lagerstätte highly rich in coprolites that have a wide variety of morphologies. Thin sections of twenty specimens were prepared from seven coprolite morphotypes. All of the examined coprolites exhibit a microcrystalline calcium phosphate groundmass lacking recrystallization and containing fine inclusions. Three different coprofabrics have been characterized and reflect the diet and digestive processes of the animal producers. The fish scale coprofabric is formed by ganoine scales likely attributed to Semionotiformes; the decapod cuticle coprofabric includes exoskeletal fragments which might be assigned to Atydae shrimps and Astacidae crayfish prey. A combination of decapod cuticles and fish scales can occasionally occur in the same coprolite. The third coprofabric contains few or no inclusions, and likely denotes the presence of coprolite producers with very efficient digestive systems. The exceptional preservation of the Las Hoyas coprolites reveals the trophic importance of small crustaceans with thin and delicate exoskeletons, a food resource that is not usually evident in coprolites. The number of coprofabrics relative to the number of possible fecal producers is low, and may reflect taphonomic biases. Nevertheless, the coprofabric contents demonstrate that decapods and fishes were important food resources in this Barremian ecosystem.
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The northern margin of the Organyà basin (Southern Pyrenees) has a complex structure in which syn-rift Lower Cretaceous carbonates flank a wide Keuper evaporite province, featuring the leading edges of the basement-involved thrust sheets of the Pyrenean antiformal stack. Recent observations show that Keuper diapirs and salt walls grew during the Cretaceous extensional episode, conditioning the development of differentiated depocenters and minibasins. The role of salt tectonics during the Pyrenean orogeny has not been addressed in previous structural studies, but present-day cross-sections indicate a Keuper evaporite-bearing vertical thickness of up to 3000 m in the Senterada-Gerri de la Sal area. We infer that salt migration was a determinant mechanism in triggering a gentle northward tilting of the Organyà basin during the Eocene-Oligocene, recorded in the La Pobla de Segur and Gurp syn-tectonic conglomerates in a basin-wide progressive unconformity and a large north-directed onlap, opposite to the main sedimentary influx direction. Contemporaneously, salt migration, promoted by conglomerate differential loading, enabled the sinking and rotation of the unrooted Nogueres thrust units (têtes plongeantes). We use new and published structural data for the Lower Cretaceous margin of the Organyà basin, combined with structural and clast provenance data from the Cenozoic alluvial fan conglomerates of La Pobla and Gurp, to understand the Lutetian to late Oligocene evolution of the northern margin of the Central South-Pyrenean Unit. The tectono-sedimentary evolution of this area and the salt evacuation patterns are closely related to the exhumation history of the stacked Paleozoic thrust sheets of the Pyrenean hinterland to the north. In this study we correlate the movements over a mobile substratum and the paleogeographic changes of conglomeratic basins at the toe of an exhuming orogenic interior.
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We review geological data all over W Europe to study the geodynamic and kinematic evolution of the W Tethys-W Mediterranean region since the late Paleozoic. We propose a new kinematic model that shows the influence of pre-collisional extension between Europe and Africa plates on the subsequent Cenozoic evolution.
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Intraplate ranges are topographic features that can occur far from plate boundaries, the expected position of orogens as described in the plate tectonics theory. To understand the lithospheric structure of intraplate ranges, we focused on the Spanish‐Portuguese Central System (SPCS), the most outstanding topographic feature in the central Iberian Peninsula. The SPCS is an Alpine range that exhumes Precambrian‐Paleozoic rocks and is located at >200 km from the northern border of the Iberian microplate. Here, we provide a P‐wave velocity model based on wide‐angle seismic reflection/refraction data of the central SPCS (Gredos sector). Our results show: (a) a layered lithosphere characterized by three major interfaces: Conrad, Mohorovicic, and Hales discontinuities, (b) an asymmetry of the crust‐mantle boundary under the SPCS, (c) the extent of the Variscan batholith forming the main outcrops of Gredos, and (d) the thinning of the lower crust toward the south. This model suggests that the exhumation of the SPCS basement was driven by a south‐vergent thick‐skinned thrust system, developed in the southern part of the SPCS and that promoted crustal imbrication and a Mohorovicic discontinuity's offset under the SPCS. Thus, the deformation mechanisms of the crust seem to be controlled by the presence of the late‐ to post‐Variscan granitoids that assimilated the Variscan mid‐crustal detachment creating a new rheological boundary. This tectonic structure allowed the formation of Alpine crustal‐scale thrust systems that eased coupled deformation of the upper and lower crust, leading to limited underthrusting of both crustal layers.
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Palaeonitella trifurcata n. sp. is a minute ecorticate thallus of a charophyte from a non-marine upper Barremian–Lower Aptian section of the Garraf Massif, near Barcelona (Catalonia, Spain). Whorls of trifurcated branchlets built glomerules about 1 mm across. Small radial branchlets were trifurcated once in three terminal acuminate dactyls. Longer and more robust branches, two per whorl emerge from a basal trifurcation, bore opposite secondary branchlets and ended in three terminal branchlets bearing one oospore. The whole set of characters suggests affinity with Nitella, making of this fossil one of the oldest and unique possible records of thalli of this extant genus. The thallus of P. trifurcata n. sp. was encrusted by a thin micrite film, and additionally, the whorls were coated by a thicker crust while the plant was still alive. It is suggested that this crust was formed upon the periphyton which grew perhaps upon a mucilage covering the whorls and apical heads, as it happens in extant Nitella. After encrustation, a small (ca. 5 mm across) constructive micrite envelope, called a cortoid, was formed attached to the plant, preserving in the inside the thallus articulated and slightly encrusted. Once the plant died, such cortoids accumulated on the lake bottom and were buried and lithified, forming a “cortolite.” This is the first report of constructive micrite envelopes protecting delicate and poorly calcified charophyte thalli from being destroyed.
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The Aptian to lower Cenomanian succession from the Serranía de Cuenca region (Eastern Iberia, Spain) comprises a time-span largely understudied regarding palynology and biostratigraphy. This research studies the deposits of three stratigraphic units that crop out in this region (the Contreras Formation, the El Burgal Member and the Utrillas Group), allowing identification, study and sampling of the palynofloras from the Aptian–?early Cenomanian time-interval. The studied sections are grouped into three sectors based on the palynostratigraphic ages obtained: the MPB, TU, and CT sectors, respectively. The palynoflora is dominated by gymnosperm pollen grains and diversified spores of ferns and allies. The palynofloral evidence and regional geology indicate that the sampled levels in the MPB sector are Aptian in age, whereas those levels sampled at the TU and CT sectors are dated as middle Albian–?early Cenomanian. The Aptian palynofloras of this sector differ from other contemporaneous sites of Europe and North America in the possible occurrence of tricolpate angiosperm pollen. In general, angiosperm pollen does not present high percentages; however, it becomes more diversified from the middle Albian in the TU and CT sectors, where more than 20 taxa were recorded on average. The studied pollen assemblages conform with the characteristics of the early Cenophytic palynofloras. Likewise, an increase in dinocysts towards the upper levels of the sedimentary succession in the TU and CT sectors is consistent with the transgressive nature of the deposits, documenting the progressive landward expansion of Western Tethys in Iberia during Albian to ?early Cenomanian times.
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Some of the major Carbon cycle perturbations of the Phanerozoic occurred during the Aptian, in relation to magmatism. The highest temperatures reconstructed for the Cretaceous Period correspond to the Oceanic Anoxic Event of the early Aptian (OAE 1a), an episode of accelerated global change. Here we present a chemostratigraphic study based on osmium isotopes integrated with high-resolution Carbon-Oxygen stable isotope data from the Cau Core (Western Tethys, SE Spain), including a 6.4 Ma record from the early to the late Aptian. This high-resolution study of the continuous and expanded Cau section permits a thorough understanding of the duration of the Aptian events, as well as an evaluation of the mechanisms triggering the abrupt changes of the global carbon and osmium cycles and their interdependence. Here we show that the large Igneous Province (LIP) Aptian magmatism initiated 550–750 kyr prior to the OAE 1a, and persisted for 1.4 Myr after the event, influencing the composition of seawater for 2.8 Myr. We show a continuous Os isotope record encompassing the OAE 1a and the late Aptian for the first time, and demonstrate that the recovery from the exceptionally unradiogenic composition of seawater Os produced by the dominance of the Ontong Java Plateau volcanism, was slow. Our results demonstrate the different time duration of some events, and the asynchronous relationship between the carbon and osmium cycles
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In the northern Iberian Peninsula, the Pyrenean-Cantabrian orogenic belt extends E-W for ca. 1000 km between the Atlantic Ocean and Mediterranean Sea. This orogen developed from the collision between Iberia and Eurasia, mainly in Cenozoic times. Lower-middle Permian sediments crop out in small, elongated basins traditionally considered independent from each other due to misinterpretations on incomplete lithostratigraphic data and scarce radiometric ages. Here, we integrate detailed stratigraphic, sedimentary, tectonic, paleosol and magmatic data from well-dated lithostratigraphic units. Our data reveal a similar geodynamic evolution across the Pyrenean-Cantabrian Ranges at the end of the Variscan cycle. Lower-middle Permian basins started their development under an extensional regime related to the end of the Variscan Belt collapse, which starts in late Carboniferous times in the Variscan hinterland. This orogenic collapse transitioned to Pangea breakup at the middle Permian times in the study region. Sedimentation occurred as three main tectono-sedimentary extensional phases. A first phase (Asselian-Sakmarian), which may have even started at the end of the Carboniferous (Gzhelian) in some sections, is mainly represented by alluvial sedimentation associated with calc-alkaline magmatism. A second stage (late Artinskian–early Kungurian), represented by alluvial, lacustrine and palustrine sediments with intercalations of calc-alkaline volcanic beds, shows a clear upward aridification trend probably related to the late Paleozoic icehouse-greenhouse transition. The third and final stage (Wordian-Capitanian) comprised of alluvial deposits with intercalations of alkaline and mafic beds, rarely deposited in the Cantabrian Mountains, and underwent significant pre- and Early Mesozoic erosion in some segments of the Pyrenees. This third stage can be related to a transition towards the Pangea Supercontinent breakup, not generalized until the Early/Middle Triassic at this latitude because the extensional process stopped about 10 Myr (Pyrenees) to 30 Myr (Cantabrian Mountains). When compared to other well-dated basins near the paleoequator, the tectono-sedimentary and climate evolution of lower-middle Permian basins in Western and Central Europe shows common features. Specifically, we identify coeval periods with magmatic activity, extensional tectonics, high subsidence rates and thick sedimentary record, as well as prolonged periods without sedimentation. This comparison also identifies some evolutionary differences between Permian basins that could be related to distinct locations in the hinterland or foreland of the Variscan orogen. Our data provide a better understanding of the major crustal re-equilibration and reorganization that took place near the equator in Western-Central Europe during the post-Variscan period.
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We study the structure of the Llevant ranges in Mallorca with special emphasis on the Cenozoic extensional evolution of the island, which we integrate in a new geodynamic model for the Westernmost Mediterranean. Mallorca underwent two Cenozoic rifting phases in the Oligocene and Serravallian, before and after the development of its Foreland Thrust Belt (FTB). The first extensional event produced Oligocene semigrabens (≈29–23 Ma) that were inverted during the Early‐Middle Miocene (19–14 Ma) WNW‐directed FTB development. The second rifting event produced the extensional collapse of the Mallorca FTB during the Serravallian (≈14–11 Ma). This later rifting was polyphasic, with two orthogonal extensional systems, producing first NE‐SW, and then NW‐SE extension. The Oligocene extension affected a major part of the Western Mediterranean, opening the Liguro‐Provençal and other basins after the collapse of the Palaeogene AlKaPeCa orogen, and Mallorca, its former hinterland. Continued plate convergence nucleated a new subduction system in the Early Miocene that initiated along the Ibiza transform, producing the Mallorca WNW‐directed FTB and subduction of the South‐East Iberian passive margin. This process individualized the Betic‐Rif slab and initiated its westward retreat. Serravallian extension occurred at the northern edge of the subduction system coeval to the Algero‐Balearic basin opening. Extension initiated toward the SW direction of slab tearing and later rotated to a NW‐SE direction, probably in response to flexural and isostatic rebound. Through these processes the Alboran domain archipelago was driven toward the southwest until the Late Miocene, contributing to the present isolation of Mallorca from its Betic hinterland.
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Deciphering the palaeoenvironmental and palaeoclimatic setting of ancient successions that include deposits typical of different climates can be challenging. This is the case in the Late Jurassic succession cropping out in eastern Spain (South-Iberian and western Maestrazgo basins), where deposits characteristic of both arid to semiarid and humid to subhumid settings have been identified through a detailed analysis of eight stratigraphic sections. These sections comprise shallow marine carbonates changing upward and laterally to a predominantly siliciclastic coastal and alluvial succession, including abundant dinosaur remains. Deposition of coastal and alluvial sediments occurred in flood plains, ephemeral and perennial fluvial channels, aeolian dunes, deltas, distributary mouth-bars and associated distributary channels, and shallow water bodies influenced by both fresh and marine waters. Some of these deposits, notably those of aeolian and ephemeral fluvial origin, are characteristic of arid to semiarid climates. However, there are also abundant deposits that can be demonstrably shown to have a coeval origin, which are indicative of permanent water courses: (i) sediments of seasonal discharge fluvial channels with perennial to semi-perennial flow, displaying subcritical and supercritical flow sedimentary structures; (ii) deltaic sediments deposited in permanent freshwater bodies; and (iii) abundant plant and dinosaur remains, especially of herbivorous dinosaurs, which required the presence of permanent water sources and abundant vegetation. These apparently contrasting sedimentary features indicate that deposition occurred under a seasonal climate controlled by monsoonal-type precipitation. These deposits are analogous to those observed nowadays in the Lençóis Maranhenses National Park (north-east Brazil), where a subhumid tropical climate with a seasonal precipitation pattern prevails. Thus, this study shows that only through careful facies analysis and interpretation of depositional processes that can be shown to be occurring concurrently in neighbouring and related depositional systems can the detailed palaeoenvironmental and palaeoclimatic setting of complex coastal sedimentary successions be confidently reconstructed in detail.
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Coelacanths are very rare in the upper Barremian fossil site of Las Hoyas (Cuenca, Spain). However, being one of the few predatory ichthyophagous fishes preserved at the locality, understanding their ecology is fundamental to continue advancing in our comprehension of the dynamics of this palaeowetland. A previous study based on the size distribution of the coelacanth specimens suggests that a natural population of this species did not inhabit the excavated area of Las Hoyas, perhaps due to them practicing habitat partitioning. Here we analyze the sedimentological characteristics of the laminae where these fossils were preserved. In the light of the extensive previous knowledge on the stratigraphy, depositional environments and evolution of Las Hoyas, we conclude that coelacanth fossils are preserved in wet facies associations, indicating that they were not present in this part of the wetland permanently, but during periods of overall flooding of the system and high connectivity among the different environments composing the regionalscale wetland.
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Underground gas storage is one of the solutions required for reducing CO2 emissions and ensure the transition to a renewable power supply. The Hontomín pilot-plant in N-Spain is a well-studied CO2 facility located in the Burgalesa Platform, a fold belt in the Southern Basque-Cantabrian Basin. Previous works agree that crustal extension and evaporite migration controlled the subsidence in the area. The discrepancies lie in the salt expulsion models proposed during syn-rift and post-rift stages and the basin deformation during Cenozoic contraction. The models range from thin-skinned tectonics, basement-involved thrusting, strike-slip faulting, and interference between thick- and thin-skinned thrusting with lateral extrusion. There is multiple working hypothesis often with contradictory predictions of the underground structure. Understanding these structural styles is critical for identify the main salt structures suitable for gas storage in the Burgalesa Platform. We integrate multidisciplinary data from 2D seismic to wellbore, gravity and field data, allowing us to construct three restored cross-sections that illustrate the process of progradational loading and salt expulsion towards the SW during the Early Cretaceous, which led to the development of the Hontomín and other trap structures within the salt overburden. Differential loading occurred diachronously along strike during the Cenozoic, younging to the SE by evacuation of the remaining salt, which caused diapirism and salt welding. We found that most of the structures in the cover were formed by salt migration, whereas Cenozoic shortening caused the rejuvenation of salt-structures and local diapir squeezing. Shortening in the basement is consumed in the frontal thrust that overrides the Duero foreland and in the partial reactivation of the former Mesozoic transfer faults as transpressional faults. The results of this work have implications for a further understanding of the tectonic evolution of the external area of rift structures, and as tectonic analogues in other salt-bearing basins.
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Theropod behaviour and biodynamics are intriguing questions that paleontology has been trying to resolve for a long time. The lack of extant groups with similar bipedalism has made it hard to answer some of the questions on the matter, yet theoretical biomechanical models have shed some light on the question of how fast theropods could run and what kind of movement they showed. The study of dinosaur tracks can help answer some of these questions due to the very nature of tracks as a product of the interaction of these animals with the environment. Two trackways belonging to fast-running theropods from the Lower Cretaceous Enciso Group of Igea (La Rioja) are presented here and compared with other fast-running theropod trackways published to date. The Lower Cretaceous Iberian fossil record and some features present in these footprints and trackways suggest a basal tetanuran, probably a carcharodontosaurid or spinosaurid, as a plausible trackmaker. Speed analysis shows that these trackways, with speed ranges of 6.5–10.3 and 8.8–12.4 ms−1, testify to some of the top speeds ever calculated for theropod tracks, shedding light on the question of dinosaur biodynamics and how these animals moved.
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The mid-Albian to lower Cenomanian Utrillas Group is interpreted as an arid braidplain system in the Serranía de Cuenca region (Iberian Basin, Spain). In its proximal locations, it consists of an interaction of alluvial facies and subordinate aeolian deposits, with the occurrence of tidally-influenced deposits that reflect a general transgressive trend to the top of the succession. However, the distal areas of this braidplain system, where there was a more intense interaction with the Tethys Ocean, have remained understudied to date. We present a sedimentological study of two outcrops (Pajaroncillo and Reíllo) located at the distal sector of the braidplain system and 12 km apart, defining an along-strike relative position. Both outcrops differ notably regarding the arrangement and distribution of the facies associations identified despite their relative closeness. Based on the sedimentological analysis, the main transgressive and regressive trends of the succession have been identified, along with several correlatable stratigraphic surfaces. This has permitted us to distinguish 5 stages (T1-T5), which reflect the overall transgressive evolution of the succession: a continental aggradational stage (T1), dominated by alluvial deposition; an initial transgression stage (T2) dominated by an open coast setting in Reíllo and a restricted mudflat system in Pajaroncillo; a regressive stage (T3), during which continental alluvial to supratidal environments deposited; a resumption in transgression (T4), characterised by an array of inter- to subtidal environments; a deepening stage (T5), when the transgression advanced landward, giving rise to the most distal deposits of the studied succession. The studied outcrops, located at the basin edge, have been integrated within the regional sequence stratigraphy framework, which was originally devised for more central areas of the Iberian Basin (Valencia Domain) and the Prebetic. This regional approach has allowed interpreting the studied deposits as third-order depositional sequences. Besides, the supra-regional implications of this research are discussed within the broader context of Iberia and the subtleties of its tectono-sedimentary evolution during the Albian to Cenomanian times.
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During the Aptian-Albian transition, an extensional phase of the Central Atlantic which affected the Prebetic carbonate platform (South Iberian Continental Margin, northwestern margin of the Tethys) occurred. A graben morphology was developed in the platform coeval to a relative sea level fall. As a consequence, palustrine facies characterized by rhizoliths and some pond deposits of black lutites were established. Over these palustrine sediments, a second shallow carbonate platform was built during the early Albian. However, this process was not abrupt, as several levels with orbitolines and rudists were deposited intercalated between the continental facies, recording the transition to a new shallow marine carbonate platform developped during the Early Albian. The presence of these continental palustrine sediments between two episodes of shallow carbonate platform is described for the first time in the Prebetic. The demise of an upper Aptian isolated shallow carbonate platform drove to the deposition of these palustrine sediments in an extensional tectonic regime.
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A detailed study of calcareous nannofossil assemblages from twelve uppermost lower Barremian–lower Aptian sections in the Subbetic domain of the Betic Cordillera was performed. Seven new nannofossil species (Crucibiscutum bastetanum, Crucibiscutum gracile, Chiastozygus lamprostauros, Cyclagelosphaera platyaspis, Lithraphidites aichmoides, Lithraphidites pugio, and Rhagodiscus sicutclipeus) are described, one species is emended (Lithraphidites magnus) and the taxonomic concept of the marker species Hayesites irregularis is discussed and clarified. The detailed stratigraphic ranges of the new species, together with those of other relevant taxa, are determined and correlated to standard ammonite biostratigraphy. Age estimates of biostratigraphically relevant calcareous nannofossil biohorizons are calculated using astrochronologically tuned cyclostratigraphic data. Five new calcareous nannofossil subzones are proposed which enhance upper Barremian biostratigraphic resolution at a regional scale and are directly correlated with respect to the standard Tethyan ammonite zonation. Two of the new species described here are used as biostratigraphic markers for the newly proposed subzones. The duration of each subzone is provided through astrochronological calibration. This study allows the refinement of the calcareous nannofossil zonation for the Mediterranean–Atlantic province of the Tethyan domain. The implications of these new results are discussed regarding the extant definition and use of the Barremian/Aptian boundary. The morpho-evolutionary trends of selected nannofossil groups are reviewed in relation to the latest Barremian–Aptian paleogeographic changes, showing these were a prominent factor controlling calcareous nannoplankton evolution and biogeographical distribution in the west European-Atlantic region.
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We describe a trackway (LH-Mg-10-16) occurring in laminated carbonated limestones of the Las Hoyas locality, Serranía de Cuenca, Spain. It is unmistakably a large theropod dinosaur trackway encompassing two unusual aspects, namely, wide-steps, and a set of equally deformed left footprints (with a dislocated digit). The layer also preserves other vertebrate trails (fish Undichna ) and different impressions in the sediment. To address these complex settings, we devised a multidisciplinary approach, including the ichnological and taphonomical descriptions, characterisation of the rock lithofacies using thin-sections, 3D structured-light digitalisation with a high precision of 200–400 μm, and a geometric morphometric comparison with a large sample of bipedal dinosaur trackways. Sedimentary analyses showed that the trackway was produced in a humid, benthonic microbial mat, the consistency and plasticity of which enabled the preservation of the details of the movement of the animal. The results of the geometric analysis indicate that the “wide-steps” of the trackway is not unusual compared to other trackways, providing evidence that it was made by a single individual with an estimated hip height approximately 2 m. Analogous pathologies in extant archosaurs that yield the combination of wide steps and deformed digits in the same trackway were considered. All results mutually support the hypothesis that a large theropod dinosaur, with a pathological foot, generated the trackway as it crossed an area of shallow water while slowly walking towards the main water source, thus stepping steadily over the benthonic mat over which multiple fish were swimming.
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Plate kinematic reconstructions available for the Late Jurassic-Early Cretaceous eastward drift and counterclockwise rotation of the Iberian plate imply a major left-lateral motion of Iberia with respect to Eurasia. According to most authors, this displacement has been accommodated along the transform North Pyrenean Zone. However, no relevant field evidence exists for the proposed >400 km of horizontal displacement along the North Pyrenean Fault. Several Permian-Mesozoic basins are distributed around the Iberia/Eurasia plate boundary and have been more or less inverted during the Cenozoic Pyrenean Orogeny (i.e. Iberian Chain basins, North and South Pyrenean basins, Basque-Cantabrian Basin, Parentis Basin, Bay of Biscay/Asturian margins). All of these basins experienced a complex kinematic history and shared the same tectono-stratigraphic evolution, with two successive rifting stages: (i) Permian-Triassic rifting following the dismantling of the Variscan belt and recording the early breakup of Pangea and (ii) Late Jurassic-Early Cretaceous rifting developing after a Jurassic post-rift thermal cooling stage. Depending on the different techniques of investigation and on the interpretation of controversial datasets, authors proposed either opening by orthogonal rifting or by transtensional/pull-apart tectonics for these basins. In this work, we propose a reappraisal of the processes responsible for the Mesozoic Iberia/Eurasia plate boundary compartmentalization by reviewing the tectono-sedimentary history and the kinematic evolution of the sedimentary basins involved in this domain. We shed light on the fact that the Cretaceous left-lateral movement within the plate boundary was not accommodated by localized deformation along the single North Pyrenean Fault wrench structure, but rather by a distributed zone of deformation in which the transtensional regime was recorded by the sedimentary basins therein. We also suggest that other Permian-Mesozoic depocenters located below the Cenozoic foreland basins of the Pyrenean belt (i.e. the Ebro and Aquitaine basins) may have been active segments of this rift system. We then propose that the real extent of the Mesozoic plate boundary is roughly defined by two NW-SE trending lineaments corresponding to the southwestern margin of the Iberian Chain, on the Iberian side, and to the southern Armorican margin and the southwestern border of the French Central Massif, on the Eurasian side. The complex pre-Cretaceous tectono-sedimentary history of this region determined its peculiar pre-rift structure. Such structural inheritance may have favored a distributed rather than a localized mode of deformation at the Iberia/Eurasia diffuse plate boundary during the Late Jurassic-Early Cretaceous, whilst mechanisms related to the eastward propagation of the Bay of Biscay system might have been responsible for the final localization of the plate boundary along the Basque-Cantabrian/North Pyrenean corridor.
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Spinosaurid dinosaurs show a wide geographical and temporal distribution, being present in Gondwanan and Laurasian landmasses, at least, during the Lower Cretaceous and the Cenomanian. European spinosaurids are more diverse than previously thought with five, and probably six, currently recognised genera. The revision of CPI 477, a fragment of a left maxilla from the Lower Cretaceous of La Rioja (Spain) previously assigned to Baryonyx, demonstrates that this specimen cannot be referred to this genus and likely belongs to an indeterminate baryonychine closer to Baryonyx than to Suchomimus. CPI 477 exhibits a tooth replacement process comparable to that of other theropods and, besides, similar to other large theropods, two replacement teeth could simultaneously be developed in the same alveolus, partly explaining high replacement ratios and the overabundance of spinosaurid teeth in some fossil sites. Furthermore, the Oxalaia maxilla shares the anteriorly located external naris with Irritator and baryonychine spinosaurids, which differ from the more retracted ones in African spinosaurines. Finally, in addition to the previously noticed differences between Baryonychinae and Spinosaurinae, the paradental groove of African spinosaurines and Oxalaia differs from that of baryonychines in being sinusoidal instead of straight.
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Eustatic controls on Early Cretaceous (Aptian) sedimentation in the western Tethys are discerned in outcrops of carbonate platforms that developed in the Maestrat rift basin located at the eastern margin of the Iberian Plate. The relative sea-level fluctuations with a dominant eustatic contribution investigated had estimated magnitudes of between 50 and 60 m in <0.9 My and ≥ 115 m in <3 My, and occurred respectively during the late early and early late Aptian. The major relative sea-level falls of mainly eustatic nature were recorded as forced regressive sedimentary wedges or as incised valleys carved into highstand carbonate platforms, whereas the subsequent sea-level rises back-filled the incised topographic lows created, or favoured the development of lowstand platforms. The finding of 50–115 m amplitude fluctuations of Aptian age is of relevance in that show magnitudes of relative sea-level fall in the order of that recorded during the last glacial maximum in the late Pleistocene (c. 120 m). The current knowledge on Cretaceous climate history shows an Earth with non-uniform greenhouse conditions. However, geological evidence of temporary icehouse states with ice-cap magnitudes close to late Pleistocene scales during the Aptian is absent, or at least has not been reported so far. Thus, although falling within the glacio-eustatic domain, the driving processes of these widespread drops and subsequent rises in relative sea level remain a mystery. Finally, this paper is an example of how sequence stratigraphy can be applied to carbonate successions, and of how this methodology indeed permits to unravel ancient relative sea-level fluctuations which controlled carbonate production and accumulation.
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Fine-peloidal- to coarse oolitic-bioclastic grainstones with hummocky cross stratification (HCS) occur interbedded in Jurassic pelagic lime-mudstone successions (Subbetic, Betic ranges, Southern Spain). These strata were deposited in pelagic troughs and swells, away from continental areas, in the Southern Iberian Paleomargin of the Western Tethys. Selected examples presented in this study include: a) coarse oolitic grainstones, encased in pelagic marls, holding characteristics similar to the ridge-berm-swash zone of modern beaches; b) peloid grainstones with HCS interbedded with radiolarite marls deposited on the flanks of volcanic guyots. The interbedded lime muds and marls contain “filaments”, sponge spicules and radiolarians; c) peloid-bioclastic (radiolarians, “filaments”, etc.) grainstone beds with HCS, interbedded with pelagic lime muds; d) crossbedded peloidal-skeletal (Saccocoma) grainstones with HCS and wave ripples on top, interbedded with pelagic mudstones and wackestones with abundant bioturbation and ammonites (Ammonitico Rosso facies). All the examples here presented share: 1) grainstone beds are interbedded with pelagic mudstones and marls; 2) grainstone components were reworked by oscillatory flows superimposed to unidirectional tractive flows (unidirectional ripple lamination and HCS); 3) components, either derived from shallow-water environments (e.g., ooids) or produced in pelagic conditions (e.g., radiolarians, Saccocoma, “filaments”, peloids, etc) were reworked by high-energy processes unrelated to surface storm waves; 4) Internal waves (IWs) propagating along a pycnocline and breaking against a sloping surface are the best candidates to induce the sedimentary structures and sediment organization that characterize these grainstone beds. Coarser sediments “trapped” at the breaker zone form sediment accumulations similar to the sediments caught by the “littoral fence” in the surface beach. This scenario evidences the HCS not to be necessarily linked to the surface storms but to the pycnocline bathymetry, solving the problem of having HCS in pelagic zones where the storm and hurricanes wave action can be considered “out-of-context”.
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A review of the onset of the synrift sedimentation and synsedimentary extensional tectonics of the Oliete sub-basin (north- western Maestrazgo basin, East Spain) is presented here based on new data acquired after extensive sedimentological, struc- tural and palaeontological analysis of the Barremian Blesa Fm. The lower boundary of the Blesa Fm is a prominent basal synrift unconformity overlying Jurassic units. This formation has been divided into three genetic stratigraphic sequences bounded by sub-basin-wide unconformities. The lower Blesa sequence (LBS) is characterized by distal alluvial to palustrine marls/clays grading upward to palustrine–lacustrine limestones. The LBS is bounded on top by a planar to irregular trans- gressive, hardened ferruginous surface, locally encrusted by oysters. Above this discontinuity, the middle Blesa sequence consists of oyster-rich limestones and marls deposited in a shallow restricted bay, which grade to distal alluvial and palus- trine–lacustrine marls/clays and limestones towards the marginal areas of the basin. The boundary between the middle and upper Blesa sequence (UBS) is a regressive surface outlined by the local presence of an erosive conglomeratic bed. The UBS generally starts with red clays deposited in distal alluvial fan environments, which grade upwards to palustrine and lacustrine carbonates and marls/clays. The local presence of heterolithic alternations of clay with ne-to-medium sandstone and of cross-bedded sandstones indicates the local occurrence of siliciclastic coastal environments in the UBS. The upper bound- ary of the Blesa Fm is marked by widespread transgression, giving rise to the bioclastic limestones of the Alacón Fm. In the present paper, the stratigraphic position and palaeoenvironmental context of the abundant vertebrate remains found across the de ned sequences within the Blesa Formation is reviewed. The results obtained are relevant for a further understanding of the tectosedimentary evolution of the studied basin. Successive stages of evolution are distinguished, including the initial uplift, breakup and erosion of the earlier Jurassic carbonate platform that took place during the Tithonian–Hauterivian; the onset of synrift sedimentation during the early Barremian, which was highly controlled by extensional faulting and di eren- tial block subsidence; the homogenization of the basin subsidence accompanied by the incursion of marine waters (sourced from southeastern areas) during the middle part of the Barremian; and the signi cant fall in base level, of possible climatic origin and also involving signi cant siliciclastic input in the northern areas of the Oliete sub-basin around the middle part of the late Barremian.
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Geophysical Research Abstracts Vol. 20, EGU2018-PREVIEW, 2018 EGU General Assembly 2018 © Author(s) 2018. CC Attribution 4.0 license. High-resolution C and O stable-isotope geochemistry and correlation of three lower Aptian sediment cores (D1, D3 and D4) at Cau (Prebetic Zone, Spain): Preliminary results Pedro Alejandro Ruiz-Ortiz (1), Roque Aguado (1), José Manuel Castro (1), Ginés Alfonso de Gea (1), Ian Jarvis (2), Carmina López Rodríguez (1), José Miguel Molina (1), Luis Miguel Nieto (1), Richard David Pancost (3), María Luisa Quijano (1), Matías Reolid (1), Rafael Martínez-Rodríguez (1), Peter William Skelton (4), and Helmut Jürg Weissert (5) (1) Centre for Advanced Studies in Earth Sciences, Universidad de Jaén, Spain (paruiz@ujaen.es), (2) Department of Geography and Geology, Kingston University, UK, (3) School of Chemistry and Cabot Institute, University of Bristol, UK, (4) The Open University, Milton Keyes, UK, (5) Department of Earth Sciences, ETH Zürich, Switzerland The Aptian Oceanic Anoxic Event 1a (OAE1a, 120 Ma) is associated to massive burial of organic matter in marine sediments and is recorded in all major ocean basins. It represents an excellent example of an OAE, and is believed to reflect a major perturbation in climatic and oceanic environmental conditions that caused abrupt changes in the global carbon cycle. Several previous studies have documented the stable C-isotope stratigraphy of OAE1a through different sections worldwide. Nevertheless, detailed high-resolution studies across the entire event are still required to accurately determine the precise timing and rates of the different environmental and biotic changes that occurred. The Cau section is located in the easternmost part of the Prebetic Zone (Betic Cordillera), which represents the platform deposits of the Southern Iberian palaeomargin. The Lower Aptian of the Cau section consists of a hemipelagic unit (Almadich Formation, ca. 200 m thick), deposited in a highly subsiding sector of a tilted block, located in the distal parts of the Prebetic Platform. Previous work on the exposed Lower Aptian succession at Cau has focused on the stratigraphy, bioevents, C-isotope stratigraphy, and organic and elemental geochemistry, and on reconstructing pCO2 from organic geochemistry proxies. These studies reveal that the Cau section represents an excellent site to investigate OAE1a, based on its unusually high thickness and stratigraphic continuity, and the quality and preservation of fossils and the geochemical signatures. Here we present results of three high-resolution C-isotope profiles based on the analysis of samples from the three Cau sediment cores, which were drilled in autumn 2015. The three drills were separated by about 193 m, with D1 being about 20 m topographically higher than D3, and D3 15 m higher than D4. Cores D3 and D4 show an overlap of about 18 m, which corresponds to the lowest part of D3 and the highest part of the D4 core. The shape of the �13C profiles in the overlapping portions of these two cores is essentially identical, allowing for the lower resolution of the basal D3 profile, for which a smaller number of samples were analyzed. The overlap between the D1 and D3 remains unclear, which necessitated the drilling of an intervening site (D2) in November 2017. The data from the previous cores extend the C-isotope record of the Cau core into the upper part of OAE1a and represent a more continuous record at much higher resolution than published outcrop studies. This leads to the refining of the correlation with previously defined C-isotope segments of Menegatti et al. (1998), recognised worldwide. Along with the C-isotope stratigraphy, correlated with biostratigraphic and geochemical data from outcrop studies, profiles of magnetic susceptibility (measured from core in the laboratory) and geophysical log profiles measured down-hole are presented. A preliminary sedimentological study of the facies types in the cores provides information on the environmental and diagenetic changes accompanying OAE1a on the Prebetic Platform. Acknowledgements: This work is a contribution of research project CGL2014-55274-P (Government of Spain) and Research Group RNM-200 (PAIDI).
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Recent models support the view that the Pyrenees were formed after the inversion of a previously highly extended continental crust which included exhumed upper mantle rocks. Mantle rocks remain near to the surface after compression and mountain building, covered by the latest Cretaceous to Paleogene sequences. 3D lithospheric-scale gravity inversion demands the presence of a high-density mantle body placed within the crust in order to justify the observed anomalies. Exhumed mantle, having ~50 kilometers of maximum width, continuously extends beneath the Basque-Cantabrian Basin and along the northern side of the Pyrenees. The association of this body with rift, post-rift and inversion structural geometries are tested in a balanced cross-section across the Basque-Cantabrian Basin that incorporates a major south-dipping ramp-flat-ramp extensional detachment active between Valanginian and early Cenomanian times. Results indicate that horizontal extension progressed circa 48 km at variable strain rates which increased from 1 to ~4 mm/yr in middle Albian times. Low-strength Triassic Keuper evaporites and mudstones above the basement favor the decoupling of the cover with formation of minibasins, expulsion roll-overs and diapirs. The inversion of the extensional system is accommodated by doubly-verging basement thrusts due to the reactivation of the former basin bounding faults in Eocene-Oligocene times. Total shortening is estimated in ~34 km and produced the partial subduction of the continental lithosphere beneath the two sides of the exhumed mantle. Obtained results help to pinpoint the original architecture of the North-Iberian Margin and the evolution of the hyperextended aborted intracontinental basins.
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The Maestrat basin was one of the most subsident basins of the Mesozoic Iberian Rift system, developed by a normal fault system which divided it into sub-basins. Its Cenozoic inversion generated the N-verging Portalrubio–Vandellòs fold-and-thrust belt in its northern margin, detached in the Triassic evaporites. In the hinterland, a 40 km wide uplifted area, in the N–S direction, developed, bounded to the N by the E–W-trending, N-verging Calders monocline. This monocline is interpreted as a fault-bend fold over the ramp to flat transition of the E–W-trending, N-verging Maestrat Basement Thrust, and also indicates the transition from a thickskinned (S) to a thinskinned (N) style of deformation. This paper presents a kinematic evolutionary model for the northern margin of the basin and a reconstruction of the Maestrat Basement Thrust geometry, generated by the inversion of the Mesozoic normal fault system. It contains a low-dip ramp (9°) extended southwards more than 40 km, attaining a depth of 7.5 km. As this thrust reached the Mesozoic cover to the foreland, it propagated across the Middle Muschelkalk evaporitic detachment, generating a nearly horizontal thrust which transported northwards the supra-salt cover, and the normal fault segments within it, for c. 11–13 km. The displacement of the basement in the hanging-wall of the low-dip basement ramp generated the 40 km wide uplifted area, while the superficial shortening was accumulated in the northern margin of the basin – which contains the thinnest Mesozoic cover – developing the Portalrubio–Vandellòs fold-and-thrust belt.
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The Cretaceous was punctuated by several episodes of accelerated global change, defined as Oceanic Anoxic Events (OAEs), that reflect abrupt changes in global carbon cycling. The Aptian Oceanic Anoxic Event (OAE1a; 120 Ma) represents an excellent example, recorded in all major ocean basins, and associated with massive burial of organic matter in marine sediments. The OAE1a is concomitant with the "nannoconid crisis", which is characterized by a major biotic turnover, and a widespread demise of carbonate platforms. Many studies have been published over the last decades on OAE1a's from different sections in the world, and provide a detailed C-isotope stratigraphy for the event. Nevertheless, new high-resolution studies across the event are essential to shed light on the precise timing and rates of the multiple environmental and biotic changes that occurred during this critical period of Earth history. Here we present a new drill core recovering an Aptian section spanning the OAE1a in southern Spain. The so-called Cau section was drilled in the last quarter of 2015. The Cau section is located in the easternmost part of the Prebetic Zone (Betic Cordillera), which represents platform deposits of the southern Iberian palaeomargin. The lower Aptian deposits of the Cau section belong to a hemipelagic unit (Almadich Formation), deposited in a highly subsident sector of the distal parts of the Prebetic Platform. Previous work on the early Aptian of the Cau succession has focused on stratigraphy, bioevents, C-isotope stratigraphy, and organic and elemental geochemistry. A more recent study based on biomarkers has presented a detailed record of the pCO2 evolution across the OAE1a (Naafs et al., 2016). All these studies reveal that the Cau section represents an excellent site to further investigate the OAE1a, based on its unusually high sedimentation rate and stratigraphic continuity, the quality and preservation of fossils, and the well-expressed geochemical signatures.
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The Maestrat Basin experienced two main rifting events: Late Permian-Late Triassic and Late Jurassic-Early Cretaceous, and was inverted during the Cenozoic Alpine orogeny. During the inversion, an E-W-trending, N-verging fold-and-thrust belt developed along its northern margin, detached in the Triassic evaporites, while southwards it also involved the Variscan basement. A structural study of the transition between these two areas is presented, using 2D seismic profiles, exploration wells and field data, to characterize its evolution during the Mesozoic extension and the Cenozoic contraction. The S-dipping Maestrat basement thrust traverses the Maestrat Basin from E to W; it is the result of the Cenozoicinversion of the lower segment–within the acoustic basement–of the Mesozoic extensional fault system thatgenerated the Salzedella sub-basin. The syn-rift Lower Cretaceous rocks filling the Salzedella sub-basin thicken progressively northwards, from 350m to 1100m. During the inversion, a wide uplifted area –40km wide in the N-S direction– developed in the hanging wall of the Maestrat basement thrust. This uplifted area is limited to the North by the E-W-trending Calders monocline, whose limb is about 13km wide in its central part, dips about 5ºN, and generates a vertical tectonic step of 800-1200m. We interpreted the Calders monocline as a fault-bend fold; therefore, a flat-ramp-flat geometry is assumed in depth for the Maestrat basement thrust. The northern synformal hinge of the Calders monocline coincides with the transition from thick-skinned to thin-skinned areas. The vast uplifted area and the low-dip of the monocline suggest a very low-dip for the basement ramp, rooted in the upper crust. The Calders monocline narrows and disappears laterally, in coincidence with the outcrop of the Maestrat basement thrust. The evaporitic Middle Muschelkalk detachment conditioned the structural style. Salt structures are also related to it; they developed during the Late Triassic extension, as deduced from the Keuper seismic reflectors that onlap the folded Upper Muschelkalk and form growth strata above some basement normal faults.
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The relatively well-studied Lusitanian Basin in coastal west-central Portugal can be used as an analogue for the less well-known Peniche Basin in the deep offshore. In this paper the Lusitanian Basin is reviewed in terms of stratigraphy, sedimentology, evolution and petroleum systems. Data comes from published papers and technical reports as well as original research and field observations. The integration and interpretation of these data is used to build up an updated petroleum systems analysis of the basin. Petroleum systems elements include Palaeozoic and Mesozoic source rocks, siliciclastic and carbonate reservoir rocks, and Mesozoic and Tertiary seals. Traps are in general controlled by diapiric movement of Hettangian clays and evaporites during the Late Jurassic, Late Cretaceous and Late Miocene. Organic matter maturation, mainly due to Late Jurassic rift-related subsidence and burial, is described together with hydrocarbon migration and trapping. Three main petroleum systems may be defined, sourced respectively by Palaeozoic shales, Early Jurassic marly shales and Late Jurassic marls. These elements and systems can tentatively be extrapolated offshore into the deep-water Peniche Basin, where no exploration wells have so far been drilled. There are both similarities and differences between the Lusitanian and Peniche Basins, the differences being mainly related to the more distal position of the Peniche Basin and the later onset of the main rift phase which was accompanied by Early Cretaceous subsidence and burial. The main exploration risks are related to overburden and maturation timing versus trap formation associated both with diapiric movement of Hettangian salt and Cenozoic inversion. ON-LINE FULL VERSION http://onlinelibrary.wiley.com/doi/10.1111/jpg.12648/epdf
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The study of the Upper Jurassic-Lower Cretaceous deposits (Higueruelas, Villar del Arzobispo and Aldea de Cortés 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 Cortés 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 Cortés 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 Cortés 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 Cortés Fms.
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The Pyrenees at the Iberia-Europe collision zone contain sediments showing Albian- Cenomanian high-temperature metamorphism, and coeval alkaline magmatic rocks. Stemming from different views on Jurassic-Cretaceous Iberian microplate kinematics, two schools of thought exist on the trigger of this thermal pulse: one invoking hyperextension of the Iberian and Eurasian margins, the other suggesting slab breakoff. Competing scenarios for Mesozoic Iberian motion compatible with Pyrenean geology, comprise (1) transtensional eastward motion of Iberia versus Eurasia, or (2) strike-slip motion followed by orthogonal extension, both favoring hyperextensionrelated heating, and (3) scissor-style opening of the Bay of Biscay coupled with subduction in the Pyrenean realm, favoring the slab break-off hypothesis. We test these kinematic scenarios for Iberia against a newly compiled paleomagnetic dataset and conclude that the scissor-type scenario is the only one consistent with a welldefined ~35 degrees counterclockwise rotation of Iberia during the early Aptian. We proceed to show that when taking absolute plate motions into account, Aptian oceanic subduction in the Pyrenees followed by late Aptian- early Albian slab break-off should leave a slab remnant in the present-day mid-mantle below NW Africa. Mantle tomography shows the Reggane anomaly that matches the predicted position and dimension of such a slab remnant between 1900 and 1500 km depth below southern Algeria. Mantle tomography is therefore consistent with the scissor-type opening of the Bay of Biscay coupled with subduction in the Pyrenean realm. Slab break-off may thus explain high-temperature metamorphism and alkaline magmatism during the Albian-Cenomanian in the Pyrenees, whereas hyperextension that exhumed Pyrenean mantle bodies occurred much earlier, in the Jurassic.
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Recognizing and interpreting features attributable to tidal influence in the sedimentary record may be difficult in certain settings, such as fluvial-tidal estuaries or deltas and protected inland tidal embayments, because marine fossils and classic tidal features, such as bi-polar current indicators or tidal bundles, may be absent. Deposits of the central area of the Oncala Group, from the Cameros Basin (Early Cretaceous, N Spain), represent one of these cases in which the lack of several classic tidal features makes the recognition of tidal influence difficult. These deposits were developed at the terminus of a fluvial system and pass laterally to coeval, shallow, carbonate-evaporitic laminated deposits, which do not contain any definitive sedimentary feature or fossil remains that clearly indicate a marine depositional setting. The central area of the Oncala Group is characterized by laterally very continuous deposits, which can be followed along tens or hundreds of metres, predominance of non-channelled facies over channelled bodies and ubiquitous subaerial exposure evidence, such as desiccation cracks and vertebrate footprints. Although these characteristics might indicate deposition in a continental sandy-muddy flat, additional sedimentary features lead to interpret these deposits as formed in broad, low-gradient, tidal flats, traversed by meandering channels. These features include: (1) presence of meander loop bodies displaying low angle, inclined heterolithic stratification; (2) repetitive alternation of mudstone and siltstone/sandstone laminae both in meander loop bodies and non-channelled facies; (3) rhythmic vertical variations in the type of bedding (lenticular-wavy-flaser-wavy-lenticular) and in the thicknesses of the couplets; (4) presence of desiccation cracks at the top of numerous, consecutive, mudstone laminae or couplets. As a result, the Oncala Group represents a good example of tide-influenced deposits that lack several typical tidal features, such as marine fossils or common bi-polar current indicators, and thus yields criteria for recognition of tide influence in similar ancient sediments.
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Stromatolites associated with ooids are often described in the literature, both in marine and continental environments. However, a lateral relationship between them does not necessarily entail that ooids are trapped within the stromatolites. For example, present-day stromatolites that trap ooids (agglutinated oolitic stromatolites) are only found in tidal environments of the Bahamas and Shark Bay, whereas non-agglutinated stromatolites laterally related with oolitic facies are common in different modern and fossil environments. The Leza Fm carbonates (Cameros Basin, N Spain) were formed in a system of coastal-wetlands during Barremian-Aptian times (Early Cretaceous) and they offer an opportunity to elucidate the role of tides in ooid-trapping processes because they contain examples of both agglutinated and non-agglutinated stromatolites associated with oolitic facies. Agglutinated stromatolites are found in tide-influenced oolitic facies from the eastern Leza Fm and they show very scarce calcified microbial filaments. Non-agglutinated stromatolites are found in freshwater-dominated oolitic facies from the western Leza Fm and these stromatolites contain calcified filamentous microfabrics (i.e. skeletal stromatolites) without significant ooids trapped in them. The textural and sedimentological differences between both stromatolites suggest that water chemistry and hydrodynamics were different during their formation. The carbonate saturation state of the water might have been low enough to prevent intense microbial calcification of the tide-influenced stromatolites, developing soft microbial mats; moreover, the cyclic hydrodynamic changes of tides allowed the periodic supply of grains to be trapped by the soft mats. In contrast, the higher carbonate saturation of meteoric waters, which passed through and dissolved the Jurassic carbonate substrate of the basin, probably led to the stronger mat calcification of skeletal stromatolites from the western Leza Fm, without tidal influence. This together with the lower hydrodynamic changes of the environment prevented ooids from being trapped within these stromatolites. The Leza Fm example is therefore a step forward for understanding the processes involved in the development of stromatolites in tidal oolitic depositional environments. Moreover, its study together with a review of the literature suggests that conditions for ooid-trapping by stromatolites may be preferentially achieved in tidal environments.
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High-quality images provided by 3D seismic surveys have transformed the interpretations of salt geometries in passive margins. Complementary field studies are needed to expand the ideas derived from seismic image interpretation. The Cotiella Basin exposes middle Coniacian–early Santonian basins developed by post-rift gravity-driven extension and passive diapirism in the proto-Atlantic Ocean. Salt-related sedimentary and structural features were preserved during the subsequent Pyrenean Orogeny, but the diapirs were squeezed to such a degree that they were completely destroyed. As a result, their influence on the development of the Cotiella Basin remains unclear. This paper presents a 3D geometric reconstruction of the extensional faults, the stratigraphic surfaces and the associated salt structures with the main objective of discussing the role of extension versus salt withdrawal. Our results indicate that the main Cotiella Basin was dominated by extensional faulting combined with along-strike salt migration, whereas the smaller Armeña, Mediodía and Seira basins were mainly dominated by salt withdrawal, involving the growth of passive diapirs, salt pillows and transfer faults. This is relevant because the described structures constitute an almost unique example to study in outcrop the structural style and kinematics of structures usually found offshore.
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The distribution and structure of the Mesozoic and Cenozoic cover within the central part of the North Iberian Margin (Bay of Biscay) is analyzed based on a dense set of 2D seismic reflection lines and logs. The integration of well data allows the recognition of seven seismostratigraphic units and the construction of a surface that illustrates the 3D morphology of this area at the time of the Jurassic rifting. The study zone comprises what is known as Le Danois Bank, a basement high, and the Asturian Basin, one of the sedimentary basins originated during the Iberian rifting at the end of the Paleozoic. Its development continued with the oceanization of the Bay of Biscay as a failed arm of the Atlantic rift; later, during the Cenozoic, a drastic change in tectonic regime induced the partial closure of Biscay and building up the Cantabrian-Pyrenean chain along the northern border of Iberia. This compressional period left its imprint in the Asturian Basin sediments in the form of a mild inversion and general uplift. The geometry of the basin bottom appears as an asymmetric bowl thinning out toward the edges, with a main E-W depocenter, separated by E-W striking faults from a secondary one. Those bounding faults show twisted trends in the north, interpreted as a consequence of the compressional period, when a transfer zone in a N-S direction formed between the two E-W striking deformation fronts in Biscay. This study shows that the transfer zone extends further to the west, reaching the longitude of Le Danois Bank. The maximum thickness of the filling within the Asturian Basin is estimated in more than 10 km, deeper than assessed in previous studies. The recognition of frequent halokynetic structures at this longitude is another observation worth to remark. Based on this study, it is suggested that the basin formed on top of a distal basement block of stretched crust limiting with the hyperextended rifted domain of Biscay. This location largely conditioned its deformation during the late compression. This article is protected by copyright. All rights reserved.
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The upper Albian to middle Cenomanian unconformity-bounded megasequence, recorded in three different tectonic-sedimentary settings (Prebetic, Iberian, and Albacete domains), reflects a large-scale transgressive-aggradational progradation episode. Three major evolutionary episodes can be distinguished: a poorly developed lowstand systems tract (fluvial clastics at the base of the sequence), followed by a major transgressive systems tract (marked by the development of four successive carbonate ramps showing a progressive retrogradational pattern), and finally by a highstand systems tract. -from Authors
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