The southern coast of the gulf of Corinth exhibits syn-rift deposits, giving insights into the first stages of continental extension as well as the geodynamic evolution of the surrounding Aegean region. The stratigraphy (relative position, 3D geometry, dating) of these deposits is still subject to controversies. The syn-rift evolution of the central part of the southern coast of the Corinth rift is revisited, based on new sedimentological and paleontological data. While ostracods analysis provides precise information about the paleoenvironments, recent advances in palynology supply a more accurate chronology.For the first time, we document marine evidences and Pleistocene evidences below the well-known giant Gilbert-type fan deltas of the Corinth rift. The syn-rift fill records a three-phase history: (1) the Lower Group corresponds to continental to lacustrine environments passing up progressively to brackish environments with occasionally marine incursions from before 1.8 Ma to some time after 1.5 Ma, (2) the Middle Group corresponds to giant alluvial fans and to Gilbert-type fan deltas prograding in an alternating marine and lacustrine environment from around 1.5 Ma to some time after 0.7 Ma, and (3) the Upper Group corresponds to slope deposits, Gilbert-type fan deltas and marine terraces indicating the emergence of syn-rift sediments along the southern coast from at least 0.4 Ma to the present day, with alternating marine and lacustrine deposition controlled by the position of the Mediterranean sea level relative to the Rion Strait sill. Age et évolution paléoenvironnementale du remplissage syn-rift de la marge sud du golfe de Corinthe (Grèce)Mots clés. -Sédimentologie, Palynologie, Ostracode, Pléistocène, Rift de Corinthe, GrèceRésumé. -Le remplissage sédimentaire qui affleure sur la marge sud du golfe de Corinthe a enregistré les premiers stades d'une extension continentale mais aussi des éléments de l'évolution géodynamique de la région égéenne. La stratigraphie (position relative, géométrie 3D, datation) de ces dépôts est toujours sujette à controverse. Une nouvelle étude sédimentologique et paléontologique permet de proposer un modèle d'âge plus précis à l'aide d'une étude palynologique et une reconstitution paléoenvironnementale des dépôts basées sur les faciès sédimentaires et les assemblages d'ostracodes. Ce travail présente pour la première fois des indices marins et des évidences d'âges pléistocènes sous les fameux Gilbert-type fan deltas du golfe de Corinthe. Le remplissage syn-rift enregistre trois grandes phases : (1) le Groupe inférieur (Lower Group) correspond à des environnements continentaux à lacustres qui évoluent progressivement vers des environnements saumâtres avec des incursions marines ponctuelles à partir d'au moins 1,8 Ma jusqu'à 1,5 Ma, (2) le Groupe intermédiaire (Middle Group) correspond à des cônes alluviaux géants et des Gilbert-type fan deltas progradants dans une étendue d'eau alternativement marine et lacustre de 1,5 Ma jusqu'à au moins 0,7 Ma, et (3) le Groupe supérieur (Upp...
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 reassert 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;
Mapping thick conglomerates in the subalpine chains around Digne allows reconstruction of a deeply incised Messinian-Pliocene paleo-drainage network. It shows that the main rivers (Bléone, Bès, Mardaric, Eaux-Chaudes) have existed since at least the Messinian. Pollen analysis reveals that the Pliocene-Early Quaternary continental infill of these canyons did not start at 5.3 Ma, like in the Zanclean rias, but in the Late Pliocene (between 3.4 and 2.6 Ma). This 2 m.y. delay results in part from the timing of the retrogradation of the alluvial wedge, and in part from the inland shift of the river mouths that accompanied the Zanclean flooding of Messinian canyons. This shift corresponds to a shortening of hundreds of kilometers of the river profiles that caused the river to gain more erosive energy. This strong Zanclean erosion is contemporaneous with the main infill of the rias downstream.We describe sections of paleo-canyons that were uplifted, tilted, overthrusted or truncated by strike-slip faults. The geometry of this dissected drainage network provides new constraints on the tectonic evolution of the southern subAlpine chains. An about 2.3 km strike-slip separation of the Bléone river paleo-canyon confirms that the front of the Digne nappe is an oblique ramp of the south-verging thrust system of the 'Arc de Castellane'. This nappe moved south-southwestward along the N015 trending tear fault. Fault striation analysis in the Late Pliocene-Quaternary conglomerates shows that this displacement was characterized by ENE-WSW compression, along the Digne oblique ramp, consistent with its dextral slip. Most of the Digne nappe displacement (~20 km) occurred prior to the Late Pliocene as shown by the La Bonnette section of the Bléone paleo-canyon that incises a block of the overthrusted "residual basin". It was followed by~2.3 km southward displacement along out-of-sequence faults during the Late Pliocene and the Quaternary. This out-of-sequence reactivation of the Digne nappe is contemporaneous with the formation of the Barles half-window nappe anticline as shown by the 345 m uplift of the l'Escuichière paleo-canyon. The reconstructed paleo-drainage network attests for the tectonic activity of the Barles nappe anticline, the Bès tear fault, the Saint Benoît tear faults and the Digne nappe during the Pliocene and the Quaternary. Canyons messino-zancléens à remplissage continental dans la nappe de Digne (Alpes du Sud). Implications tectoniquesMots-clés. -Evénement messinien, Canyons messiniens, Réseau hydrographique, Tectonique quaternaire, Nappe de Digne, Barles.Résumé. -Dans les chaînes subalpines de Digne, la cartographie de conglomérats qui ont rempli de profonds canyons permet de reconstruire un réseau hydrographique attribuable au Messinien et au Pliocène. On met ainsi en évidence que les principales rivières (Bléone, Bès, Mardaric, Eaux-Chaudes) existent depuis au moins le Messinien. L'analyse de pollens provenant du fond de ces canyons révèle que leur remplissage Pliocène-Quaternaire n'a pas commencé à 5,3 Ma com...
Since the discovery of calcareous nannofossils, dinoflagellate cysts and planktonic foraminifers in deposits from the Dacic Basin, intensive research has been performed in order to evidence which gateway this microplankton used to connect Paratethys and the Mediterranean prior and after the Messinian Salinity Crisis (MSC). Such a gateway is also to be regarded at the origin of successive influxes of Paratethyan organisms (molluscs, ostracods, dinoflagellates) into the Mediterranean Basin ("Lago Mare" events). Observing that the İ stanbul area, usually proposed for this purpose, was inefficient, we examine the succession of marine well-dated pre-MSC and post-MSC deltaic deposits through the Balkans, from northern Greece to southern Romania, that constitutes a reliable candidate for such a marine corridor, the origin of which was caused by the regional tectonic extension. The reconstructed palaeogeography for high sea level episodes that encompassed the MSC clarifies the context of the so-called North Aegean Lake. This marine gateway probably evolved as a powerful river during the peak of the MSC, contributing to the deposition of clastics in the hydrocarbon Prinos Field. A tectonically controlled subsidence to the north and south of the Skopje region caused the closure of such a gateway.
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