Sintesis biostratigrafica de la fosa de la Cerdanya (Pirineos orientales).

En el presente trabajo se describen las principales características estratigráficas y sedimentológicas del relleno de la fosa de la Cerdanya. A partir de éstas se han diferenciado dos unidades: la Unidad Neógena Inferior y la Unidad Neógena Superior que reflejan dos situaciones tectónicas diferentes. La Unidad Inferior corresponde al período de formación y posterior evolución de la fosa bajo el movimiento direccional de la falla NE-SW de la Tet, mientras que la Unidad Superior refleja una situación extensional generalizada. La revisión de los numerosos yacimientos de Mamíferos fósiles de la Unidad Neógena Inferior, expuesta en esta nota, permiten concluir que esta se sedimentó en el Vallesiense. Por contra, el hallazgo del nuevo yacimiento de Can Vilella, indican que la sedimentación de la Unidad Superior se inició en el Turoliense superior (MN 13

A Review of the current knowledge of the crustal and lithospheric structure of the Valencia Trough Basin

In this paper, we review the current geophysical knowledge of the Valencia Trough Basin, and the surrounding areas. For this purpose, we summarize the most significant regional geophysical datasets acquired since the seventies to investigate the trough (seismic, gravity, geoid and heat flow data). We then focus on the discussion regarding the geometry and physical properties of the present day crustal and lithospheric structure derived from seismic images, as well as combined potential field modelling and their relationships with the Alpine geodynamic evolution of the Valencia Trough. Finally, we discuss the differences in the results regarding the geometry of the lithosphere-asthenosphere boundary obtained by different modelling approaches and the features that, in our view, require further investigation to unravel the true nature of the Valencia Trough, including what could have caused the differences between the crustal structure observed in the SW region compared to the NE region, the asymmetric style of thinning across the trough; the origin of the changes in the lower crustal reflectivity across the basin; the fabric of the uppermost mantle, characterized by anomalously low P-wave velocities; and the physical properties of the lithosphere mantle (density, Pwaves velocity, thermal conductivity, temperature distribution, mineralogical composition, etc.)

Contexto estructural y paleogeográfico de los sistemas lacustres cenozoicos de España.

La evolución de los sistemas lacustres cenozoicos en España estuvo claramente influida por: l) la edificación de los orógenos pirenaico y bético y la intensa deformación interna que afectó la microplaca de Iberia. 2) l0s cambios de las condiciones paleogeogrlficas y paleoclimáticas generales que afectaron la región mediterránea occidental-atlántica oriental en la que se localizaba Iberia. Potentes sucesiones de carbonatos y evaporitas lacustres han sido reconocidas en la mayor parte de las cuencas cenozoicas españolas. Junto a estos depósitos se registra la presencia de otros menos frecuentes (carbón, devósitos bituminosos, diatomitas, arcillas especiales) también significativos desde un punto de vista geolimnolÓgico e interesantes desde una perspectiva económica. Los mayores y mis persistentes sistemas lacustres se ubicaron en las cuencas de antepaís, arealmente muy extensas. Los de menor entidad y mis corta evolución se formaron en cuencas limitadas por fallas de distintos tipos. En ambos casos los sistemas lacustres evolucionaron en estrecharelacióncon sistemas aiuviales y sus características hidroquírnicas estuvieron muy influidas por el reciclaje de depósitos de carbonatos, sulfatos y cloruros, fundamentalmente de edad mesozoica. Este reciclaje influyó tanto en la litologia de las sucesiones lacustres resultantes como sobre las caracteristicas de las asociaciones de organismos limnicos que se desarrollaron en los sistemas lacustres

Estructura geológica de las secuencias cretácico-cenozoicas en el extremo noroccidental de la Cuenca Vasco-Cantábrica (Pirineos Occidentales).

La zona estudiada se localiza en el oeste de Cantabria, en el límite entre la Cordillera Cantábrica y los Pirineos Occidentales. Se presentan tres cortes geológicos de dirección N-S construidos a partir de datos de campo y de información sísmica. La estructura actual está dominada por cuencas mesozoicas extensivas delimitadas por fallas normales de dirección E-W, que fueron activas durante el Triásico y durante el periodo Malm-Barremiense y que posteriormente, durante la orogenia alpina, fueron parcialmente invertidas. La falla de Cabuérniga divide la zona de estudio en dos sectores. La región meridional está constituida por una estructura extensiva mesozoica bien preservada, a pesar de presentar una débil inversión tectónica. La región septentrional presenta una estructura compresiva de tendencia NS que separa la zona en otros dos sectores. El sector occidental presenta pliegues y cabalgamientos vergentes al sur formados durante la orogenia alpina, mientras que el sector oriental presenta estructuras diapíricas ocasionadas por arcillas del Keuper. En esta zona la Cuenca Vasco-Cantábrica fue transportada hacia el sur por un cabalgamiento profundo basculado 23º hacia el norte durante la orogenia alpina

The Basque - Cantabrian Pyrenees: report of data analysis

This contribution presents the analysis of a data set that was put together in the PhD thesis of Jordi Miró which is part of the OROGEN Project. The Basque - Cantabrian Pyrenees, that are the focus of this report, have been extensively studied over the last years. Several open debates in the Earth Science community aroused from this realm regarding the formation and reactivation of rift domains and formation of fold and thrust belts. This report summarizes the main tectonic models proposed to explain both the extension and reactivation history over this area and compile a series of data to consider for further discussions and interpretations. This report includes a thematic map of the Basque - Cantabrian Pyrenees showing an analysis of the tectono-stratigraphic evolution of the area. The map covers an area of more than 33 000 km2 and is a graphic representation of the geology of the region based on a large geodatabase including previous published maps and field observations. A composite reflection seismic line crossing the entire Basque - Cantabrian Pyrenees from the Ebro foreland basin to the offshore Landes High is also presented. This section enables to present a continuous dataset along the entire area with the projection of few drill holes, which are presented with the stratigraphic logs following the same tectono-stratigraphic legend obtained from the previous analysis. The main goal of this data report is to provide a coherent and complete dataset to the community, which enables to propose, discuss and test some of the new concepts related to the formation and reactivation of rifted margins. This data report is complementary to the contributions of Lescoutre and Manatschal (2020) and Cadenas et al. (in prep) that are part of the same special volume. Cette contribution présente l'analyse d'une compilation de données acquises par Jordi Miró lors de sa thèse de doctorat qui s'inscrit dans le projet OROGEN. Les Pyrénées Basco-Cantabriques, qui sont l'objet de ce rapport, ont été largement étudiées au cours de ces dernières années. Cette chaîne orogénique a alimenté de nombreuses discussions concernant la formation et la réactivation des domaines de rift ainsi que la formation des chaînes d'avant-pays (« fold-and-thrust belt »). Ce rapport résume les principaux modèles proposés dans la zone d'étude pour expliquer l'évolution tectonique de l'extension à la réactivation, et compile une série de données à prendre en considération pour les discussions et interprétations futures. Il comprend notamment une carte thématique des Pyrénées Basco-Cantabriques montrant les différentes unités tectono-stratigraphiques de la zone. La carte, qui couvre une superficie de plus de 33 000 km2, est une représentation graphique de la géologie régionale s'appuyant sur une large quantité de données comprenant des cartes publiées précédemment ainsi que de nouvelles observations de terrain. Un profile de réflexion sismique composite traversant la totalité des Pyrénées Basco-Cantabriques (du bassin d'avant-pays de l'Ebre au Haut des Landes) est également présentée. Cette section permet de présenter un ensemble de données continu sur toute la zone via notamment la projection des informations extraites des puits de forage tels que les logs stratigraphiques. L'objectif principal de ce rapport est de fournir à la communauté scientifique un ensemble de données cohérent et complet permettant de proposer, discuter et tester certains des nouveaux concepts liés à la formation et à la réactivation des marges hyper-étirées. Ce rapport de données fournit des informations complémentaires aux études disponibles dans cette publication spéciale du projet OROGEN

Geofluid behaviour in successive extensional and compressional events: a case study from the southwestern end of the Vallès-Penedès Fault (Catalan Coastal Ranges, NE Spain)

The structural position of the Upper Jurassic-Lower Cretaceous carbonates located in the central part of the Catalan Coastal Ranges corresponds to the southwestern end of the Vallès-Penedès Fault. This fault was reactivated at different times during successive extensional and compressional events and several generations of fractures and cementations were formed

Geology of the Eastern Prebetic Zone at the Jumilla region (SE Iberia)

This article presents a geological map and cross-sections at 1:50,000 scale covering an area of 609 km2 of the Eastern Prebetic Zone (SE Iberia). The structure of the studied area is characterized by an NW-directed fold-and-thrust belt and inactive salt diapirs that are parallel to the ENE- to NE-regional trend of the eastern Betic Cordillera. This regional trend is locally disrupted by the NW-trending Matamoros Basin, which is flanked by the active Jumilla and La Rosa diapirs. The geological map, the cross-sections and the outcrop observations support the hypothesis that the major Mesozoic rifting phase affecting the Eastern Prebetic Zone occurred during the Upper Jurassic to Santonian times coeval to the development of extensional basins in the Western Tethyan area. The proximal part of this passive margin was subsequently incorporated into the external part of the Betic thin-skinned fold-and-thrust belt. The Upper Cretaceous to Cenozoic tectonic evolution of the study area encompassed the following stages: a Campanian to Aquitanian NW-directed contraction; a Burdigalian to upper Miocene extensional reactivation of the main subsalt faults; and a Serravallian NWdirected contractional reactivation. In this scenario, the combined effect of the previous contractional reactivation of pre-existing salt structures together with the Miocene subsalt extension triggered passive salt extrusion of the La Rosa and Jumilla diapirs

Paleomagnetic constraints on the kinematics of inverted passive margins with salt diapiric structures. Preliminary results from syndiapiric overburden rocks of the northern margin of the Basque-Cantabrian extensional Basin.

Salt levels deposited prior to deformation in either passive margins or orogenic settings generate a decoupling in deformation, with differential deformation in layers above and below the salt detachment. Distribution of salt detachments controls differential shortening and formation of orogenic arcs; and widespread diapirism can generate isolated minibasins which may record vertical axis rotations during their development. Our study aims to unravel the kinematics of salt diapiric structures by means of a paleomagnetic study of a portion of the Basque Arc, in the northern margin of the Basque-Cantabrian extensional Basin, where the salt overburden appears compartmentalized by several salt walls (Bakio, Bermeo, Guernica and Mungia diapirs). In this setting, 65 paleomagnetic sites from the overburden sequence have been analyzed. Predominant anticlockwise rotations with some clockwise and anticlockwise rotations in opposing flanks of the salt walls are observed. Fold tests reveal that some of the sites are clearly remagnetized, whereas some other sites show a prefolding magnetization. These observations are confirmed by magnetic hysteresis and back-field experiments in part of the studied rocks. Although further analyses will be necessary to explain the origin and distribution of the remagnetization, a preliminary kinematic model for the suprasalt deformation together with the underlying decoupled autochtonous materials can be established

Distinguishing the effect of diapir growth on magnetic fabrics of syn-diapiric overburden rocks: Basque-Cantabrian basin, Northern Spain

An analysis of Anisotropy of Magnetic Susceptibility was done on Aptian-Albian sediments from the Basque-Cantabrian basin. Samples were collected from 39 sites in the halokinetic sequences of the Bakio, Bermeo, Guernica and Mungia diapirs; 28 sites were sampled close to diapirs, and 11 sites were far from the diapir edges. The magnetic foliation is parallel to bedding, suggesting it reflects depositional and compaction processes, whereas the orientation of magnetic lineation varies. Far from the diapir edges, the magnetic lineation is interpreted as being related to the regional Pyrenean compression. Close to diapir edges, the observed behaviour shows that diapirs, predominantly formed by rigid ophites, have acted as buttresses, with shadow areas at their northern faces being protected from the Pyrenean compression. The high sensitivity of AMS makes it a very useful tool to distinguish deformation in halokinetic sequences related to diapir growth from that related to subsequent compression