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Abstract: We present a new set of brittle microtectonic measurements carried out in the Pliocene and Quaternary rocks outcropping in several key sectors of the western Betic and Rif orogen, the so-called Gibraltar orogenic arc. This data set, along with available earthquake focal mechanisms and borehole breakouts, allowed us to compile the Pliocene and Quaternary stress map of this area. This map provides new constraints for tectonic models and the present-day tectonic activity of the proposed active eastward subduction of oceanic lithosphere beneath the Gibraltar Arc and roll-back. The horizontal maximum compressive stress (S Hmax) is NW-SE in the Betic Orogen and N-S/NNW-SSE in the southern Rif Cordillera. There is a significant consistency between S Hmax and the displacement field deduced from GPS measurements with respect to the African plate: both appear to reflect the NW-SE convergence between the African and the European plates that is perturbed in the Rif. We propose that part of the eastern Rif behaves as a quasi-rigid block welded to the stable African plate. This block is bounded by important faults that localized most of the deformation disturbing the stress and surface displacement field. Pliocene to Quaternary N-S to NW-SE Africa-Europe plate convergence seem to be associated to the reorganization of the remnant Early Miocene subduction system in a continental–continental collision framework. Three-dimensional reconstruction of available seismic tomography plotted against the intermediate seismicity shows that only part of the old subduction system, whose orientation ranges from N20°E to N100°E, remains active: the portion ranging from N30°E to N40°E, orthogonal to the regional convergence. [Copyright &y& Elsevier]

Abstract: The Ronda Depression constitutes a Neogene intramontane basin located in the external zones of the Western Betic Cordillera. Major deformation structures affect only the southwestern part of its sedimentary infill and consist of NNE–SSW and WNW–ESE box folds that developed simultaneously. New gravity data reveal two negative NNE–SSW elongated Bouguer anomalies, unrelated to basin depocenters, but corresponding to the accumulation of low-density ductile Triassic basement rocks in the core of antiforms or directly under the northwestern undeformed sedimentary infill. The Subbetic basement is also deformed by early-Burdigalian to Serravallian NNE–SSW folds and thrusts, although there is no clear continuity with those affecting the late-Miocene sedimentary infill. The aim of this contribution is to describe in detail the late-Miocene folds that deform the Ronda Depression, as well as to discuss the role of the basement nature on their reactivation. The reactivation of the pre-Tortonian folds, due to the heterogeneous distribution of evaporitic Triassic rocks in the basement as well as the presence of rigid limestones on the southwestern basin boundary, determined the simultaneous orthogonal fold development that only evidence local deformation. [Copyright &y& Elsevier]

Three crustal-scale sequentially restored cross-sections along the Central External Betic Cordillera enable us to pinpoint the role of extreme crustal thinning, tectonic inheritance and salt tectonics during the evolution of the South-Iberian paleomargin from Mesozoic rifting to Cenozoic continental subduction. This interpretation puts forward the existence of a former highly extended Mesozoic rift system, namely the Subbetic Basin. The basin comprises three main domains that coincide with the classical zoning of the External Betics: (i) The Intermediate units in the northern basin margin represent primary thick minibasins separated by salt walls; (ii) the External Subbetic units attest an inflated salt body in a central trough; and (iii) the Median and Internal Subbetic units in the southern basin margin are analogous to a group of primary minibasins with intercalations of submarine volcanic rocks overlying hyperextended crust. Shortening led to the extrusion of a salt canopy and the development of secondary minibasins. Furthermore, the tectonic inversion of the Subbetic Basin created two major thrusts sheets detached at the Upper Triassic evaporites, accommodating a shortening of ≈100–145 km at early Eocene-middle Miocene time. Compression reshaped the hyperextended domain into a subduction trench, and the former transfer faults into tear faults. Ongoing shortening led to the subduction of the South-Iberian paleomargin beneath the Alborán Domain lithosphere. Our results provide a new perspective on the inversion of segmented rift basins partly floored by mantle rocks and call for a major reconsideration on the tectonic architecture and evolution of the Betic-Rif Cordillera. [ABSTRACT FROM AUTHOR]

Epikarst – the shallow, surficial part of a karstic massif – has a significant influence on the spatio-temporal variability of recharge and the hydrodynamic functioning of many karst aquifers. In the Mediterranean morphoclimatic zone, the average thickness of a well-developed epikarst is around ten metres, but the spatial patterns of its degree of development are very heterogeneous due to the complex interaction of a number of different factors such as lithology, fracturing, weathering, soil and vegetation. In addition, direct field observation is difficult because good outcropping conditions are restricted to particular locations, some areas are not accessible and the size of the study area is often too large for exhaustive field surveys. Satellite-based remote sensing, however, provides a complete coverage of an entire area with spectral resolutions that detect variability in features that can define image textures related to the development of the epikarst. This paper describes a quantitative methodology for epikarst mapping using satellite images and field data. The proposed method comprises an unsupervised classification to define the spectral signature of each of three epikarst development categories in a high-resolution satellite image followed by a supervised classification of the terrain into one of the three categories on a low spatial resolution scale. The training areas in the field are assigned to the three categories by a panel of experts using the Delphi method. Geophysical data are used for validation to overcome any bias that may be introduced by the panel. The proposed methodology has been applied to the Sierra de las Nieves karstic aquifer (Málaga, southern Spain). The outcome is a map of estimated epikarst development that is an approximation to reality and which can be improved as more experimental data become available. [ABSTRACT FROM AUTHOR]

Highlights: [•] A large magnetic dipole characterizes the southwestern part of the Iberian Peninsula. [•] Monchique Alkaline Complex, that extends eastwards hundreds km, is the responsible of the anomaly. [•] The dipole has a N-S sharp discontinuity across the Guadiana River. [•] A depth crustal fault, The Guadiana Fault, conditions the sharp step of the body. [ABSTRACT FROM AUTHOR]

Abstract: The Volubilis Basin is located between two structural arcs formed by the Prerif Ridges that developed during and after sedimentation. The arcs correspond with W- to WSW-verging anticline culminations, limited, to the north by a NE-SW strike-slip lateral ramp. Sedimentary infill took place during two stages of ridge formation and propagation. The first stage occurred in the Middle Miocene-early Tortonian and was determined by the deposition of the Nappe Prérifaine in the northern part of the basin, and continental and marine sediments over the Prerif Ridges. The second one, Late Miocene in age (Tortonian–Messinian), corresponds to the sedimentation of calcarenites and bioclastic limestones at the basin edges, with a lateral transition to white and blue marls toward the center of the basin. There is clear evidence of synsedimentary deformation, suggesting the interaction of sedimentation and tectonics. Geophysical data allow us to characterize the stratigraphic architecture of the Volubilis Basin and the geometry of the top of the Paleozoic basement. An approximately N–S Tortonian–Messinian asymmetric depocenter is located close to the front of the eastern arc. This research illustrates the nucleation, progressive thrust bending and segmentation, and the propagation of folds interacting with sedimentation. Thrust nucleation agrees with Paleozoic basement highs under the detachment surface. The progressive development of these tectonic structures conditioned the formation, segmentation and final continentalization of the Volubilis Basin, which can be considered as a piggy-back basin. [Copyright &y& Elsevier]

Abstract: The Oulmès granite is a NE–SW elongated stock intruded in Ordovician metasedimentary rocks which crop out at the core of a regional anticlinorium of the Moroccan Variscan Meseta. The stock, dated at around 300Ma, is made up of peraluminous two-mica granite, with subordinate amounts of muscovite leucogranite. Mineral composition and textural features of both the granite and the thermal aureole enable us to constrain the P–T conditions during magma intrusion in ≈250–300MPa and ≈600°C at the contact between the granite and its host rock. Emplacement of the Oulmès granite postdates the main regional structures and is coeval with the late stages of Variscan compression. Prior to granite intrusion, the host rocks were affected by a main deformation phase responsible for the development of a penetrative slaty cleavage and regional-scale folds. Granite emplacement gave way to a 2km-thick strain aureole, which includes both the uppermost part of the stock and the surrounding host rocks. The strain aureole is characterized by a gently-dipping planar-linear fabric with a generally weak N–S oriented stretching lineation. In the granite, the fabric of the strain aureole consists of a solid-state, locally mylonitic, foliation. In the host rocks, a secondary foliation develops which crenulates the older regional foliation. Magmatic structures, mainly consisting of steeply dipping N–S oriented magmatic foliation, are preserved in the central part of the pluton. The 3D shape of the granite has been modelled from gravity data and, together with the observed magmatic flow along subvertical planes and the strain recorded in the aureole, leads us to envisage a diapiric-dominated mechanism for the emplacement of the Oulmès granite. Drawing on the petrogenesis of peraluminous granites, the diapiric ascent of the granite probably has not exceeded 10km. [Copyright &y& Elsevier]