Evolution géodynamique de la Mer d’Alboran par l’étude des bassins sédimentaires

The Alboran Sea is a back-arc basin located at the western end of the Mediterranean Sea, and has been affected by complex tectonic settings during its history. Based on a multidisciplinary "land-sea" approach, this work focuses on two major research topics: it aims (1) to better understand the opening and deformation processes of two key sedimentary basins during the Neogene, and (2) to study the effects and imprints of the Messinian Salinity Crisis onto the basins.Tectonic and stratigraphic analysis of the thickest sedimentary accumulation called Western Alboran Basin (WAB) led to build an original tectonic scenario in the Miocene. Inception of extension was triggered by major crustal shear zones favoring the exhumation of the metamorphic basement. Then, the subsidence became most probably controlled by the slab-pull effect of the underlying oceanic slab. In the Betic Cordilleras, a second generation of sedimentary basins, as the Sorbas Basin, developed along metamorphic core complexes exhumed during an extension regime. A set of paleogeographic maps proposes to explain the formation of the Alboran basins in relation with deep geodynamic processes.Field studies evidenced that peripheral basins bounding the Alboran Sea have been affected by a significant subaerial erosional phase in response to the Messinian Salinity Crisis. Stratigraphic analysis of seismic profiles demonstrated the onshore/offshore continuity of fluvial canyon morphologies recognized on land. A new scenario is then proposed to explain the reopening of the worldwide oceanic connection with the Mediterranean realm after more than 160.000 years of emersion.La Mer d'Alboran est un bassin arrière-arc situé à l'extrémité occidentale de la Mer Méditerranée ayant subi une évolution complexe. Basé sur une approche " terre-mer ", pluridisciplinaire, ce travail axé sur deux grandes thématiques de recherche vise à mieux comprendre les modalités d'ouverture et de déformation des bassins sédimentaires au cours du Néogène en étudiant notamment un événement majeur de l'histoire de la Mer Méditerranée, la Crise de salinité messinienne.L'étude tectonique et sédimentaire du bassin Ouest-Alboran, a permis de construire un nouveau schéma d'évolution tectonique et sédimentaire au cours du Miocène. L'initiation de la subsidence s'est effectuée au gré de grandes zones de cisaillement crustales affectant le socle métamorphique. La subsidence est ensuite contrôlée par la traction du panneau plongeant lithosphérique sous-jacent. Dans les Cordillères Bétiques, une seconde génération de bassins, dont celui de Sorbas, s'est développée le long de dômes métamorphiques exhumés au cours d'une phase d'extension. Des reconstitutions paléogéographiques montrent que la formation des bassins de la Mer d'Alboran est en relation avec la subduction sous-jacente.Des études de terrain ont mis en évidence une importante phase d'érosion des bassins périphériques de la Mer d'Alboran en réponse à la Crise de salinité messinienne. Cette érosion subaérienne eut pour conséquence le creusement de canyons fluviatiles à terre qui ont été suivis en mer par l'analyse fine de profils sismiques. Un nouveau scénario est alors proposé afin d'expliquer la réouverture de la connexion avec l'Océan Atlantique après plus de 160.000 ans d'émersion

From ductile to brittle, late- to post-orogenic evolution of the Betic Cordillera: Structural insights from the northeastern Internal zones

International audienceRelations between Alpine detachment-bounded metamorphic domes, crustal-scale strike-slip fault zones and sedimentary basins in the Internal zones of the Betic cordillera are still matter of debate. Current tectonic interpretations of these basins vary from late-orogenic extensional structures to compressional ones associated with strike-slip motions along major still active faults. Structural investigations including new field mapping, meso-scale faults recognition, palaeostress analysis of brittle small-scale faults systems were performed in the sedimentary cover of the Almanzora corridor and the Huércal-Overa basins, located either in the hanging wall unit of the Filabres extensional shear zone or at the termination of the Alhama de Murcia sinistral fault zone. In parallel, a detailed study of the ductile and the ductile-brittle deformation was carried out in the footwall unit of the Filabres extensional shear zone, in the Nevado-Fílabride complex. Three main brittle events were recognised in the basin cover including two extensional events that occurred prior to a weak tectonic inversion of the basin during a third, still active event. The first one, D1b is characterized by the development a first stress regime consistent with ~NW-SE extensional tectonics. Besides, the consistency between the latest ductile and the brittle kinematics for the Filabres extensional shear zone and the activity of meso-scale fault systems that primarily control the main SW-NE depocentres allow concluding to a top-to-the-NW continuum of strain during the final exhumation of the Nevado-Filábride complex. The resulting overall half-graben architecture of the basins is then related to the combination of the formation of the metamorphic domes that added a local control superimposed on the regional deformation. Indeed, after a consistent top-to-the-west shearing prevailing during most of the Nevado-Filábride exhumation, final exhumation stages were in turn, characterised by important kinematics changes with a subordinate top-to-the-NW sense of shear (D1b). The onset of sedimentation in the basins occurred shortly after the crossing of the ductile-brittle transition in the underlying metamorphic domes at ca. 14 Ma into SW-NE fault-bounded troughs. Tectonic subsidence was then maintained during D2b while extensional kinematics changed to N-S or even locally to SSW-NNE. Extensional tectonics then lasted most of the Tortonian during the final tectonic denudation increments of the Sierra de los Filabres achieved at ca. 9-8 Ma. Intramontane basins are therefore genuinely extensional and clearly related to the latest exhumation stages of the Nevado-Filábride complex in the back-arc domain. Conversely, at ca. 8 Ma, basins started to record a ~N-S to NNW-SSE compressional stress regime (D3b) and ceased to be active depocentres while shortening within the Internal zones then recorded only the Iberia/Africa convergence. The weak inversion of the basins however resulted either in the reactivation of originally extensional faults such as the Alhama de Murcia fault or the basin individualisation and a progressive water exchange reduction with the Atlantic ocean and is thus proposed to be directly responsible for the Late Miocene salinity crises

Origin and age of carbonate clasts from the Lusi eruption, Java, Indonesia

Deep stratigraphic constrains below the Indonesian Lusi mud eruption are currently lacking due to the absence of deep wells and good quality seismic data. A collection of carbonate clasts has been sampled from the Lusi site, active since its birth in 2006. These specimens are part of a large variety of lithotypes erupted from the main crater. The carbonates analysed comprise scleractinian coral and bivalve shell fragments, probably shallow-water in origin, and clasts consisting of planktonic foraminifera- bearing mudstone, from pelagic deposits. Selected rocks were analysed using planktonic foraminifera and 87Sr/86Sr dating with the aim to constrain their age and to improve the understanding of the, so far unknown, sequence of limestone deposits inferred at this site. Based on biostratigraphy using planktonic foraminifera, one group of samples reveal to belong to the Planktonic Foraminifera Zone M5b, with an age comprised between 16.29 and 15.10 Ma (Miocene, Latest Burdighalian to Langhian). The Sr isotope-based ages of clasts analysed for 87Sr/86Sr cover a larger time window spanning from Pliocene (Zanclean and Piacenzian), Miocene (Messinian) down to Eocene (Priabonian). The Pliocene and Messinian ages are unreasonably young from what is known of the local geology and one sample provided an 87Sr/86Sr age that is ∼8 My younger compared to that obtained from the planktonic foraminifera assemblage occurring in that sample. The discrepancy suggests that this and the other unduly young samples have possibly been contaminated by geological materials with radiogenic Sr isotope composition. The minimum age of 37.18 Ma obtained by 87Sr/86Sr from a well-preserved oyster shell indicates that some of the clasts can be attributed to the deep seated Ngimbang Formation. The dating has been combined with the interpretation of seismic profiles to investigate the stratigraphy of inferred carbonates below Lusi and the PRG-1 well located some kilometres to the north east. PRG-1 borehole data are also integrated and discussed in this study. The obtained results reveal multiple implications: a) the Tuban and Kujung Formations are overlapping at Lusi site; b) the Lusi feeder conduit brecciated and mobilized to the surface carbonate lithologies buried as deep as possibly ∼3.8 km as well as even older and deeper seated lithotypes from the Ngimbang Formation; c) since the deeper carbonate samples erupted in 2006 belong to the typically not overpressured Kujung Formation, an additional overpressure generated from deeper units (Ngimbang Formation) would be required to force these fragments to surface

Climat et niveau de l’océan Atlantique restitués en Espagne du Sud-Ouest de 6,3 à 5,2 Ma. Implications sur la Crise messinienne en Méditerranée

The Mio-Pliocene succession of Andalusia on the Atlantic coast (Guadalquivir Basin) is known as one of the former stratotype candidate for the Andalusian Stage, proposed during the seventies as the last stage of the Miocene. Its type section is located in Carmona, east of Seville. Our investigation includes the drilling of three cored boreholes, which provide bio- and magnetic-stratigraphic data in complement to preexisting industrial information, and a high-resolution palynological analysis (pollen grains, spores and dinoflagellate cysts). The pollen flora and its climatic quantification provide the mean to correlate the section to the oxygen isotope curve from the Montemayor-1 borehole, located about 80 km to theWest of Carmona. The variations in the ratio between dinoflagellate cysts and pollen grains are used to identify high and low oceanic levels, consistently with a recent paleobathymetric reconstruction based on foraminifera: the two lowest levels being successively marked by the deposit of a littoral calcarenite (the Calizza Tosca Formation) then by a subaerial erosive episode. Based on the correlation with the Montemayor-1 regional drilling, the two major lowerings in oceanic level observed at Carmona are linked with the two episodes of the Messinian Crisis. The interlocking position of the high-energy sandstone deposits inscribed in the Messinian valley leads to an assessment of a drop in the global oceanic level of about 114m at the beginning of the paroxysm of the Messinian Crisis, amplitude to be moderated with respect to the potential effect of isostatic readjustements due to the Messinian Crisis. Comparisons are discussed with the amplitude of the Messinian Erosional Surface in theWest-Alboran Basin which potentially remained suspended and fed with Atlantic waters during the height of the crisis and isolated from the rest of the almost totally dried Mediterranean Basin. The quantified climate constructed from the pollen records confirms that dry conditions existed before the Messinian Crisis in Southern Mediterranean latitudes including the Atlantic side, making the Mediterranean Sea climatically predisposed to desiccation. Atlantic sea-level variations observed in the Guadalquivir region and measured at Carmona suggest that global glacio-eustatism somewhat facilitated the onset and completion of the Messinian Crisis in the Mediterranean Basin. At last, this work allows to discriminate two regional erosive events: the first one, dated at 5.60 Ma, of fluvial origin in relation with global eustasy; the second one, submarine, occurred just before 5.33 Ma, and referred to the strain exerted by the Guadalquivir olistostrome.La succession mio-pliocène d’Andalousie atlantique (bassin du Guadalquivir) est connue comme ancienne candidate pour le stratotype de l’Andalousien, proposé comme dernier étage du Miocène dans les années 70. Sa coupe-type est située à Carmona, à l’est de Séville. Nos travaux comprennent notamment la réalisation de trois forages carottés où furent acquises des données bio- et magnéto-stratigraphiques complémentaires aux informations connues des recherches industrielles et, surtout, une analyse palynologique (grains de pollen et kystes de dinoflagellés) à haute résolution. La flore pollinique et la quantification climatique autorisent des corrélations climatostratigraphiques avec la courbe d18O du forage Montemayor-1 implanté près de Huelva. Les variations du rapport entre kystes de dinoflagellés et grains de pollen permettent d’identifier les hauts et bas niveaux océaniques en accord avec une récente estimation paléobathymétrique basée sur les foraminifères, les deux plus bas niveaux étant successivement marqués par le dépôt d’une calcarénite littorale (Formation de la Caliza Tosca) puis par un épisode érosif subaérien. Après corrélation avec le forage Montemayor-1, ces deux baisses du niveau océanique sont respectivement mises en correspondance avec les deux temps de la Crise messinienne. L’emboîtement des dépôts gréseux à haute énergie inscrits dans la vallée messinienne conduit à évaluer une chute du niveau atlantique d’environ 114m lors du paroxysme de la Crise messinienne, amplitude à modérer toutefois compte tenu du possible effet des rebonds isostatiques liés à la Crise messinienne. Des comparaisons sont discutées avec l’ampleur de l’érosion messinienne dans le bassin ouest-Alboran potentiellement resté suspendu et alimenté en eaux atlantiques pendant le paroxysme de la crise et isolé du reste du bassin méditerranéen quasi-totalement asséché. Les restitutions quantifiées du climat comparées entre la province atlantique et le domaine méditerranéen confirment les conditions xériques des latitudes sud-méditerranéennes s.l. et ainsi la prédisposition climatique de la Méditerranée à la dessiccation. Les variations du niveau atlantique observées dans la région du Guadalquivir et mesurées à Carmona suggèrent que le glacio-eustatisme global a quelque peu contribué au déclenchement et à l’achèvement de la Crise messinienne en Méditerranée. Ce travail permet enfin de discriminer deux événements érosifs régionaux : le premier à 5,60 Ma, d’origine fluviatile en relation avec l’eustatisme global, le second intervenu peu avant 5,33 Ma, sous-marin, lié aux contraintes exercées par l’olistostrome du Guadalquivir.CNRS-INSU, Total and Elf-Aquitaine companie

The Messinian Salinity Crisis in the Dacic Basin (SW Romania) and early Zanclean Mediterranean-Eastern Paratethys high sea-level connection

International audienceNew field observations and fossil analyses complete and clarify the strong impact of the Mediterranean sea-level changes linked to the peak of the Messinian Salinity Crisis on the Dacic Basin in southwestern Romania. In addition to the Gilbert-type fan delta already evidenced along the Danube River in the area of Turnu Severin, a new Gilbert-type fan delta is described northward. Early Zanclean bottomset beds are evidenced and dated based on nannofossils at the junction of the two coalescing Gilbert-type fan deltas. A clear sedimentological, morphological and chronologic differentiation is established in the area between the Carpathians Late Miocene piedmont alluvial fans and the early Zanclean Gilbert-type fan deltas. The early Zanclean age of the Hinova clays, where the bottomset beds of the Gilbert-type fan deltas are mostly developed, is confirmed by the occurrence of nannofossil markers of Subzone NN12b and a Bosphorian mollusk macrofauna. Early Zanclean inflow of Mediterranean marine waters into the Dacic Basin is also supported by the record of planktonic foraminifers. In the Dacic Basin, the Messinian Salinity Crisis resulted in the cutting of the Iron Gates by a Carpathians river. Fluvial erosion also affected the residual Pannonian Basin and probably catched the paleo-Tisza River which contributed to the erosion of the Iron Gates and to the fluvial drainage of the partly desiccated Dacic Basin. Arguments are reinforced in favor of a marine gateway between the Mediterranean and Dacic Basin through the Balkans before and after the Messinian Salinity Crisis

Lago Mare and the Messinian Salinity Crisis: Evidence from the Alboran Sea (S. Spain)

International audienceThis paper provides a new environmental, sedimentological and stratigraphic context of the Lago Mare deposits from the North Alboran region and clarifies their chronologic location with respect to the Messinian Salinity Crisis. We present new micropaleontological data (dinoflagellate cysts, calcareous nannoplankton, planktonic foraminifers), correlated with field observations and offshore seismic interpretations. We show that the Lago Mare event known in three onshore localities (Río Mendelín near Malaga, Zorreras near Sorbas, Gafares near Níjar) follows the marine reflooding of the Mediterranean Basin which ended the Messinian Salinity Crisis. Chronologically, these Lago Mare deposits last from the latest Messinian to the early Zanclean. In fact, the first influx of Paratethyan- organisms is revealed by the dinoflagellate cyst record from near Malaga within a Gilbert-type fan delta overlying the Messinian Erosional Surface. Invading molluscs and/or ostracods may have persisted in lagoonal coastal areas more or less affected by discontinuous marine influxes (Sorbas and Níjar). The Malaga area is convenient for a paleogeographic and sedimentary reconstruction which shows the prevalent forcing of sea level changes during the time-interval 5.600-5.332 Ma at the difference of the usually solicited prevalent tectonics. The studied Lago Mare event is the third episode resulting in such a paleobiological assemblage in the Mediterranean region and corresponds to the final two-way water exchange at high sea level between the Mediterranean and the former Paratethys. It documents the onset of the modern marine circulation in the Mediterranean after the reflooding ending the Messinian Salinity Crisis

New insights on the Sorbas Basin (SE Spain): the onshore reference of the Messinian Salinity Crisis

International audienceThe Sorbas Basin is the land reference of the Messinian Salinity Crisis (MSC) that affected the Mediterranean Sea in the latest Miocene. Its stratigraphy has been re-visited using calcareous nannofossils and planktonic foraminifers, which provide a reliable biostratigraphic frame and lead to particularly specify the relationships between the Sorbas and Zorreras members with Yesares evaporites.The evaporites overlie a shallowing upward sequence ending with the deposition of the Reef Unit and Terminal Carbonate Complex (TCC) on the periphery of the basin. The reefal carbonates of the TCC are overlain by clastic deposits that are foreset beds of post-MSC Gilbert-type fan deltas developed on the northern edge of the basin. These sedimentary structures are separated from reefal carbonates and the Reef Unit by the Messinian Erosional Surface (MES). The various facies of the Sorbas Member have been correlated with the bottomset beds of the Gilbert-type fan deltas despite some differences in palaeobathymetry. In the southeastern periphery of the basin, the MES separates the Sorbas Member from the Yesares gypsums. In the central part of the basin, a hiatus characterizes the contact between these members. The Zorreras Member postdates the MSC and entirely belongs to Zanclean. Its white “Lago Mare” layers are lagoonal deposits, the fauna of which is confirmed to result from Mediterranean–Paratethys high sea-level exchange after the post-MSC marine reflooding of the Mediterranean Basin.This study allows to re-assert the two-step scenario of the MSC (Clauzon et al., 1996) with the following events:- at 5.971–5.600 Ma, minor sea-level fall resulting in the desiccation of this peripheral basin with secondary fluctuations;- at 5.600–5.460 Ma, significant subaerial erosion (or lack of sedimentation) caused by the almost complete desiccation of the Mediterranean Sea;- instantaneous marine reflooding, accepted at 5.460 Ma, followed by continuing sea-level rise

New Insights on the Sorbas Basin (SE Spain): the onshore reference of the Messinian Salinity Crisis

The Sorbas Basin is the land reference of the Messinian Salinity Crisis (MSC) that affected the Mediterranean Sea in the latest Miocene. Its stratigraphy has been re-visited using calcareous nannofossils and planktonic foraminifers, which provide a reliable biostratigraphic frame and lead to particularly specify the relationships between the Sorbas and Zorreras members with Yesares evaporites. The evaporites overlie a shallowing upward sequence ending with the deposition of the Reef Unit and Terminal Carbonate Complex (TCC) on the periphery of the basin. The reefal carbonates of the TCC are overlain by clastic deposits that are foreset beds of post-MSC Gilbert-type fan deltas developed on the northern edge of the basin. These sedimentary structures are separated from reefal carbonates and the Reef Unit by the Messinian Erosional Surface (MES). The various facies of the Sorbas Member have been correlated with the bottomset beds of the Gilbert-type fan deltas despite some differences in palaeobathymetry. In the southeastern periphery of the basin, the MES separates the Sorbas Member from the Yesares gypsums. In the central part of the basin, a hiatus characterizes the contact between these members. The Zorreras Member postdates the MSC and entirely belongs to Zanclean. Its white "Lago Mare" layers are lagoonal deposits, the fauna of which is confirmed to result from Mediterranean-Paratethys high sea-level exchange after the post-MSC marine reflooding of the Mediterranean Basin. This study allows to re-assert the two-step scenario of the MSC (Clauzon et al., 1996) with the following events: - at 5.971-5.600 Ma, minor sea-level fall resulting in the desiccation of this peripheral basin with secondary fluctuations; - at 5.600-5.460 Ma, significant subaerial erosion (or lack of sedimentation) caused by the almost complete desiccation of the Mediterranean Sea; - instantaneous marine reflooding, accepted at 5.460 Ma, followed by continuing sea-level rise

Geodynamic evolution of the Alboran sea by the study of the sedimentary ponds

La Mer d'Alboran est un bassin arrière-arc situé à l'extrémité occidentale de la Mer Méditerranée ayant subi une évolution complexe. Basé sur une approche " terre-mer ", pluridisciplinaire, ce travail axé sur deux grandes thématiques de recherche vise à mieux comprendre les modalités d'ouverture et de déformation des bassins sédimentaires au cours du Néogène en étudiant notamment un événement majeur de l'histoire de la Mer Méditerranée, la Crise de salinité messinienne.L'étude tectonique et sédimentaire du bassin Ouest-Alboran, a permis de construire un nouveau schéma d'évolution tectonique et sédimentaire au cours du Miocène. L'initiation de la subsidence s'est effectuée au gré de grandes zones de cisaillement crustales affectant le socle métamorphique. La subsidence est ensuite contrôlée par la traction du panneau plongeant lithosphérique sous-jacent. Dans les Cordillères Bétiques, une seconde génération de bassins, dont celui de Sorbas, s'est développée le long de dômes métamorphiques exhumés au cours d'une phase d'extension. Des reconstitutions paléogéographiques montrent que la formation des bassins de la Mer d'Alboran est en relation avec la subduction sous-jacente.Des études de terrain ont mis en évidence une importante phase d'érosion des bassins périphériques de la Mer d'Alboran en réponse à la Crise de salinité messinienne. Cette érosion subaérienne eut pour conséquence le creusement de canyons fluviatiles à terre qui ont été suivis en mer par l'analyse fine de profils sismiques. Un nouveau scénario est alors proposé afin d'expliquer la réouverture de la connexion avec l'Océan Atlantique après plus de 160.000 ans d'émersion.The Alboran Sea is a back-arc basin located at the western end of the Mediterranean Sea, and has been affected by complex tectonic settings during its history. Based on a multidisciplinary "land-sea" approach, this work focuses on two major research topics: it aims (1) to better understand the opening and deformation processes of two key sedimentary basins during the Neogene, and (2) to study the effects and imprints of the Messinian Salinity Crisis onto the basins.Tectonic and stratigraphic analysis of the thickest sedimentary accumulation called Western Alboran Basin (WAB) led to build an original tectonic scenario in the Miocene. Inception of extension was triggered by major crustal shear zones favoring the exhumation of the metamorphic basement. Then, the subsidence became most probably controlled by the slab-pull effect of the underlying oceanic slab. In the Betic Cordilleras, a second generation of sedimentary basins, as the Sorbas Basin, developed along metamorphic core complexes exhumed during an extension regime. A set of paleogeographic maps proposes to explain the formation of the Alboran basins in relation with deep geodynamic processes.Field studies evidenced that peripheral basins bounding the Alboran Sea have been affected by a significant subaerial erosional phase in response to the Messinian Salinity Crisis. Stratigraphic analysis of seismic profiles demonstrated the onshore/offshore continuity of fluvial canyon morphologies recognized on land. A new scenario is then proposed to explain the reopening of the worldwide oceanic connection with the Mediterranean realm after more than 160.000 years of emersion

La géothermie : une énergie ubiquiste, sous différentes formes

International audienceLa géothermie (ou chaleur de la Terre) fait partie des nouvelles formes d'énergies souvent évoquées depuis l'avènement de la transition énergétique qui presse l'humanité à changer ses modes de production et de consommation énergétiques. L'utilisation de la géothermie est une pratique qui est néanmoins connue depuis des siècles avec l'utilisation notable des sources thermales, et qui a connu ces dernières décennies un essor tout particulier. La Programmation Pluriannuelle de l'Energie (PPE) en France vise à augmenter la part des énergies renouvelables dans la consommation de chaleur qui reste aujourd'hui nettement dépendante des centrales thermiques fonctionnant au gaz. Malgré le fait que 99 % du volume de la Terre soit à une température supérieure à 100 °C, la chaleur est répartie de manière inégale à la surface du globe. Les grands mouvements tectoniques aux frontières et à l'intérieur des plaques tectoniques, le volcanisme, ou encore l'hydrothermalisme sont autant de facteurs favorisant la circulation de chaleur depuis les profondeurs. Faisons le point sur cette ressource aux différentes facettes, et qui reste malgré tout encore mal connue. Les évènements des dernières années, faisant état de sismicité en lien avec l'exploitation géothermale de certains sites, ont participé à ternir l'image de la géothermi