Добірка наукової літератури з теми "Balearic promontory"

AbstractA special type of coastal settlement, promontory forts defended by inland-facing walls, appeared in the Balearic Islands in an imprecise time during the Bronze Age. A research project was initiated in 2011 to study one of these sites on each of the two major islands of the archipelago. The first one, Es Coll de Cala Morell (north Menorca), is a walled promontory with a relatively large plateau, with 13 horseshoe-shaped houses (navetes). The second, Sa Ferradura (east Mallorca), is a smaller coastal cape, with a different spatial planning, with only two large built-up areas, both attached to the enclosure wall. Two of the navetes have been excavated at Es Coll de Cala Morell, showing a domestic space with a central hearth in both cases. The occupation has been dated to around 1600–1200 cal BC. At Sa Ferradura seven hearths have been recorded in a large, open-air area. Their chronology falls within the interval of approximately 1200/1100–900 cal BC. From a chronological point of view, fortified settlements in coastal promontories are not, as was expected, a unitary phenomenon in Menorca and Mallorca and have to be related to different cultural periods.

Abstract Two major types of kinematic models have been proposed to explain the opening of the western Mediterranean basins (Liguro-Provençal and Algerian basins, and Valencia trough). In one type of models, all continental blocks bounding the basins drift to the southeast, driven by the rollback of the Tethys subduction slab. In the other type of models, the Alboran domain drifts to the southwest, implying a westward rollback of the broken subducting slab and a NE-SW opening of the Algerian basin. In most models, however, the structure of the Balearic promontory was not taken into account, despite its key location at the boundary of the three major basins. We used the interpretation of a large seismic database coupled to gravity and magnetic anomaly analyses to characterize the nature and structure of the South Balearic margin. The constraints brought by the new analyses allow us to suggest a new scenario for the opening of the Algerian basin. Seismic profiles show that the South Balearic margin is composed of four segments with different morphologies and crustal structures. Two segments, the Mazarron and the Emile Baudot escarpments, are characterized by steep scarps and sharp crustal thinning. Two other segments, the South Ibiza and South Menorca margins, have a smoother bathymetry and crustal thinning. We interpret the former in terms of transform margins, and the latter as divergent margins. The distribution of faults on the passive margin segments suggests that they have recorded at least two phases of deformation. A first phase of opening, probably in a NW-SE direction, affected the south Balearic margin, and possibly created some oceanic floor. The existence of the transform margin segments and the prominent NW-SE orientation of the magnetic lineations in the eastern Algerian basin suggest that most of this basin opened in a NE-SW direction, in different oceanic corridors. The two eastern corridors formed by the southwestward drift of the Kabylies. The western corridor, bounded by the transform segments of the South Balearic margin and the Algerian margin, results from the southwestward drift of the Alboran domain, as suggested by previous studies.

This article presents new radiometric data from archaeological layers of the inhabited structures adjacent to the cyclopean monument of Cap de Forma (Mahon, Menorca). The archaeological site is located on a narrow isthmus that links a 30-m-high coastal promontory to the mainland. It is next to an excellent natural harbor on the south coast of the island. The protohistorical complex consists of a cyclopean monument surrounded by a necropolis of rock-cut tombs (cuevas) that are dug into the cliff. The monument is an atypical example of Talayotic architecture. The excavations carried out since 1997 have discovered three living spaces. These lean against the southern wall of the cyclopean structure. The artifacts are almost all pan of a chronological horizon that corresponds to the beginning of the Talayotic period. This study uses radiometric data to help interpret the recent findings from the three living spaces that flank the wall of the central monument.

This article presents new radiometric data from archaeological layers of the inhabited structures adjacent to the cyclopean monument of Cap de Forma (Mahon, Menorca). The archaeological site is located on a narrow isthmus that links a 30-m-high coastal promontory to the mainland. It is next to an excellent natural harbor on the south coast of the island. The protohistorical complex consists of a cyclopean monument surrounded by a necropolis of rock-cut tombs (cuevas) that are dug into the cliff. The monument is an atypical example of Talayotic architecture. The excavations carried out since 1997 have discovered three living spaces. These lean against the southern wall of the cyclopean structure. The artifacts are almost all pan of a chronological horizon that corresponds to the beginning of the Talayotic period. This study uses radiometric data to help interpret the recent findings from the three living spaces that flank the wall of the central monument.

Entre 5.97 et 5.33Ma, à la fin du Miocène, un événement géologique exceptionnel aux conséquences majeures a affecté le bassin méditerranéen : la Crise de Salinité Messinienne (CSM). Cet épisode, dont le scénario exact reste encore énigmatique, est responsable du dépôt d’un volume considérable d’évaporites connu sous le nom de Géant Salifère de Méditerranée (GSM). Aujourd'hui, plus de 90 % des dépôts évaporitiques du MSG sont situés dans les bassins profonds de la Méditerranée et sont enfouis sous une épaisse couche de sédiments Plio- Quaternaire. Ces évaporites ont donc été étudiées principalement par imagerie sismique. Dans ce mémoire, nous nous intéressons aux dépôts de la crise enregistrés sur Promontoire des Baléares (BP), un haut topographique situé dans bassin de la Méditerranée occidentale. Du fait qu’il contient une succession de bassins en position intermédiaire stratégique, étagés entre les bassins marginaux du pourtour Méditerranéen et les bassins profonds, le BP se révèle un lieu unique avec des dépôts évaporitiques variés, ubiquistes et peu déformés tectoniquement, permettant d’accéder à une vision complète de l’enregistrement de la crise et pouvant mener à un scénario global cohérent.Cette thèse de doctorat a été réalisée dans le cadre d’un projet transdisciplinaire : « European Training Network (ETN) SaltGiant », dont l'objectif est de comprendre le GSM. Une approche pluridisciplinaire a été appliquée sur la zone d’étude choisie pour apporter des contraintes afin de répondre à certaines des nombreuses questions encore sans réponses sur la crise de salinité messinienne. Le travail de base a consisté en l'interprétation d'un large ensemble de données de sismique réflexion en Méditerranée occidentale, particulièrement concentré sur les dépôts messiniens du BP. Ceci a permis de préciser la cartographie des unités messiniennes de cette région et de définir leurs inter-relations géométriques. Une comparaison détaillée de ces unités évaporitiques avec celles du bassin messinien sicilien de Caltanissetta a été menée afin de reconstituer l'histoire de leur dépôt pour la confronter au modèle chrono-stratigraphique « consensuel » à trois phases. Pour reconstituer la paléo-bathymétrie de la dépression centrale de Majorque (CMD), le bassin le moins déformé situé dans sa partie centrale du BP, une interprétation structurale a permis d’identifier les principaux mouvements tectoniques post-MSC, modérés et localisés dans des corridors de décrochement. L'analyse par backstripping 2D et pseudo-3D, en collaboration avec d’autres collègues du projet SaltGiant, a alors permis de restaurer la paléo-bathymétrie de la CMD. Enfin, ces résultats ont été utilisés comme contraintes bathyétriques et de volumes pour modéliser le dépôt des évaporites observées, par des modèles physiques basés sur la théorie du contrôle hydraulique des détroits. Les résultats montrent que les unités messiniennes de la CMD pourraient constituer un analogue non déformé de celles qui affleurent à terre dans le bassin sicilien de Caltanissetta. Ils démontrent aussi qu'une baisse générale du niveau marin de grande amplitude (>850m) est nécessaire pour précipiter le volume de halite observé dans la CMD. Ces résultats, très bien contraints par ces études précises, remettent en cause certaines idées parfois encore largement acceptées. Ces doutes concernent en particulier l'apparition synchrone du sel à l'échelle du bassin méditerranéen, la profondeur maximale de dépôt du gypse inférieur primaire (PLG) et le moment de la formation du gypse inférieur resédimenté (RLG). En conclusion, ce mémoire montre la nécessité de réviser le scénario consensus actuel de la CSM, et l’importance de réaliser des forages en mer dans la région clef du BP, ce qui permettrait de révéler de nombreux mystères encore enfouis sous le géant salifère de Méditerranée
The Messinian Salinity Crisis (MSC; 5.97– 5.33 Ma) is one of the most controversial geological events that influenced the evolution of the Mediterranean Basin in the late Miocene, leaving behind an immense volume of evaporites known as the Mediterranean Salt Giant (MSG). Today, more than 90% of the MSG evaporitic deposits are located offshore, buried below thick sediments that are Pliocene to Quaternary in age, and have thus been studied mainly by marine seismic reflection imaging. The Balearic Promontory (BP), a prominent topographic high in the Western Mediterranean basin, contains a unique and tectonically poorly deformed MSC record that resembles the evaporitic record of other peri-Mediterranean marginal and intermediate basins.This PhD thesis was performed in the framework of the SaltGiant European Training Network (ETN), a cross-disciplinary project whose objective is to understand the formation of the MSG. The work of the thesis is focused on the MSC deposits of the BP. Multi-disciplinary approach was applied to answer some of the still open questions concerning the MSC event. As a first step, seismic interpretation of a wide seismic reflection dataset in the Western Mediterranean in general and in the BP in particular was performed, with the aim of refining the mapping of the Messinian units covering the area. To restitute the depositional history of the MSC evaporites of the BP, a detailed comparison with the Messinian evaporitic units of the Sicilian Caltanissetta Basin was carried out, in which a discussion on how this history matches the existing 3-stages chrono-stratigraphic ‘consensus model’ is illustrated. The next step consisted in the restoration of the paleo-bathymetry of the BP at the beginning of the MSC, focusing on the relatively less-deformed basin located in the central part of the BP and called the Central Mallorca Depression (CMD). To achieve this restoration, structural interpretation in the CMD area was done where the main post-MSC tectonic-related vertical movements that altered the MSC paleo-bathymetry were identified. Then 2D and pseudo-3D backstripping analysis were applied in collaboration with other colleagues from the SaltGiant project, to restore the paleo-bathymetry. In the final step, the paleo-bathymetry was used to model the deposition of the MSC evaporite volumes observed in the CMD using physics-based models built on strait hydraulic-control theory. The results show that the MSC units of the CMD could constitute an undeformed analog of those outcropping on-land in the Sicilian Caltanissetta Basin. Moderate post-MSC deformation acted along MSC strike-slip corridors in the CMD following the MSC evaporites deposition, thus altering only locally the paleo-bathymetry. A high amplitude drawdown (>850m) is required during the halite stage of the MSC. The results rise a series of doubts about the current consensus model, still widely accepted. Doubts concern the synchronous onset of salt at the basin scale, the maximum depth of deposition of the Primary Lower Gypsum (PLG) and the timing of formation of the Resedimented Lower Gypsum (RLG). All the results and discussions hint to the need of revision of the current MSC consensus model, as well as the importance of initiating drillings offshore over the BP area, which would help revealing many of the mysteries still buried with the MSG

Abstract Submarine landslides can entail a substantial hazard for offshore infrastructure as they are capable of triggering tsunamis and may develop into highly mobile turbidity currents capable of breaking seabed cables. Despite considerable research activity, the trigger mechanisms for such landslide events cannot be clearly defined. Recently, marine gas occurrence has been investigated as a possible trigger mechanism. The behaviour of a fine-grained gassy soil is influenced by a variety of micromechanical processes; amongst destructuring due to fracture formation or gas bubble expansion, and bubble flooding with subsequent cavity collapse. Capturing and modeling these processes in order to assess the destructive potential of enclosed gas bubbles in submarine slopes is to date a considerable scientific challenge. With the help of a large number of Finite Element Limit Analyses (FELA), which are based on laboratory tests on a gravity core from the western Mediterranean Sea, submarine slope stability in the respective region was evaluated. Based on these analyses, gassy soil can be defined as a preconditioning factor but not as a capable trigger mechanism for submarine landsliding.