Michelle Ferrandini

Le Miocène du bassin de Saint-Florent(Corse): Modalités de la transgression du Burdigalien supérieur et mise en évidence du Serravallien

The Miocene series of Corsica deposited after the anti clockwise rotation of the Corsica-Sardinia block,between 18 and 21 Ma (Rehault 1981; Rehault et al. 1984). The study of the Saint-Florent basin (NW corsica) allows to document the conditions of the Miocene transgression and the evolution of the basin. The Saint-Florent sedimentary serie consist of 3 marine formations lying between 2 continental ones. At the base, the continental formation of Fium Albino (150 m) in the northern part of the basin, stratigraphically lies on the Upper Nebbio alpine nappe. It consists of well stratified, red, colluvial deposits from local origin, with interbedded palaeosoils remains. We have very few paleontological evidences, however from geometrical evidence, these series are clearly post nappe and ante Upper Burdigalian. This formation is described here for the first time. At the upper part, the continental formation of Saint-Florent, characterized by well rounded pebbles of rhyolites, lies with an erosional surface truncating different terms of the marine series. It is probably of Lower Tortonian age. The 3 lithostratgraphic units of the marine series are, from the base to the top: the Torra formation (50 m) is characterized by coastal deposits (conglomerate, siltstone, sandstone layers, with debris of oyster, sands with scutella) with sparse micro-fauna and - flora, suggesting an Upper Burdigalian (upper N7/lower N8 Blows zones); the Monte San Angelo Formation (250 m) is a white calcarenite with rhodophytes, its different components - fine and coarse terrigenous detritus, benthic or planktonic bioclasts-having built hydraulic dunes under the action of varying currents in a low water environment. Planktonic foraminifera - rich levels indicate a Langhian age (from N8 to the upper part of the N9 Blows zones); the Farinole Formation (100 m), described here for the first time, is observed only in the northern part of the basin. It consists of marls and clayey sandstones deposited in circalittoral environment. Rich microfauna of benthic and planktonic foraminifera, and rich calcareous nannoplankton evidence the Serravallian (NN7-NN6, Martinis zones). To the east, the basin is limited by a meridian normal fault. On the one hand, synsedimentary deformations in the Torra formation and in the lower part of the Monte San Angelo Formation are located to the north of the basin near the fault. On the other hand, thick subtidal environment deposits of the Torra Formation occure in a shallow water. Thus the subsidence of this Formation is probably controled by the syn-sedimentary activity of the meridian normal fault. Extensional fractures indicating a NE-SW direction of extension.

Pliocene deformation of the north-Ligurian margin (France): consequences of a south-Alpine crustal thrust

The Oligo-Miocene extension phase of the Mediterranean basins rifting (30-25 Ma) [Jolivet and Faccenna, 2000] followed by the Ligurian basin oceanic crust formation (21-18 Ma) [Le Pichon et al., 1971 ; Rehault et al., 1984 ; Carminati et al., 1998 ; Gueguen et al., 1998] occurred during the western Alps compression phase. The deformations were characterised during the Miocene by the southwestward structuration of the Castellane Arc [Fallot and Faure-Muret, 1949 ; Laurent et al., 2000] and during the Mio-Pliocene by the southward structuration of the Nice Arc. This latter arc is bounded on its western side by a dextral strike-slip fault and on its southern side by a thrust inducing an uplift of this arc [Ritz, 1991 ; Guglielmi and Dubar, 1993 ; Clauzon et al., 1996 ; Guardia et al., 1996 ; Schroetter, 1998]. Fission tracks thermochronology data [Bigot-Cormier et al., 2000] suggest a general uplift at ~3.5 Ma of the Argentera massif. Stratigraphical [Irr, 1984 ; Hilgen, 1991 ; Hilgen and Langereis, 1988, 1993] and geomorphological studies [Clauzon et al., 1996 b ; Dubar and Guglielmi, 1997] show evidences for an uplift of the Ligurian coast increasing east of the Var river. The analysis of 70 seismic-reflection profiles allows us to better characterise and quantify the deformation from Antibes to Imperia (fig. 1). We then reconstruct vertical motions in space and time since the Messinian crisis in order to propose a deformation model of the margin related to crustal thickening.

La formation conglomératique du Vazzio près d'Ajaccio (Corse-du-Sud), un témoin des dépôts du Chattien supérieur continental synrift en Méditerranée occidentale

Abstract Evidence of Oligocene deposits was for the first time described in Corsica (near Ajaccio) within the Vazzio Formation. The succession is composed of a continental sedimentary sequence, mainly conglomerate, with a thickness of 250 to 300 m. Such conglomerates were deposited in torrential and lacustrine environments. Pollinic association and mammal data date the formation from Late Oligocene age (MP 29). The Vazzio Oligocene formation was deposited in a half-graben upon Hercynian granites. Within the Corsica-Sardinia block, the Vazzio Formation can be considered as an equivalent of the Ussana Formation of Sardinia. A Late-Oligocene palaeogeographic reconstruction is attempted, prior to the rotation of the Corsica-Sardinia block.

Définition et datation de la Formation de Venaco (Corse) : dépôt d’origine gravitaire d’âge Priabonien

Priabonian age is highlighted for the first time in Corsica in the Venaco Formation using the presence of specific microfauna (in particular some representatives of Turborotalia cerroazulensis lineage). This silicoclastic formation is mainly represented by coarse facies. It is composed of three members from south to north and from oldest towards youngest: member of Uboli, Cardo and Orsu. The sedimentologic analysis reveals a gravity depositional environment, involving different type of currents. Sedimentologic and chronologic characteristics make the Venaco Formation and the Annot Formation (p.p.) equivalent. Dating the Venaco Fm. brings confirmation that the green schist metamorphism of the Variscan batholith and the related deformation are from the pre-Priabonian period.

Stratigraphie, sédimentologie (Paléoenvironnement)Définition et datation de la Formation de Venaco (Corse) : dépôt d’origine gravitaire d’âge PriabonienDefinition and dating of the Venaco Formation (Corsica, France): A Priabonian gravity flow deposit

Priabonian age is highlighted for the first time in Corsica in the Venaco Formation using the presence of specific microfauna (in particular some representatives of Turborotalia cerroazulensis lineage). This silicoclastic formation is mainly represented by coarse facies. It is composed of three members from south to north and from oldest towards youngest: member of Uboli, Cardo and Orsu. The sedimentologic analysis reveals a gravity depositional environment, involving different type of currents. Sedimentologic and chronologic characteristics make the Venaco Formation and the Annot Formation (p.p.) equivalent. Dating the Venaco Fm. brings confirmation that the green schist metamorphism of the Variscan batholith and the related deformation are from the pre-Priabonian period.

Présence de Pomelomeryx boulangeri (Artiodactyla, Mammalia) dans l’Oligocène supérieur de la région d’Ajaccio (Corse) : étude paléontologique et conséquences

Abstract The Vazzio basin (Ajaccio, Upper Corsica) is made up of a set of continental sedimentary deposits of the torrential type, generally equated to temporary fresh water environments. This set of deposits, which rests on the Hercynian granitic substratum, is locally covered by the marly Pliocene. An examination of upper jugal tooth tracks allowed us to identify a specimen of Pomelomeryx boulangeri and thus to date the deposits to the Upper Chattian stage. This mammal was part of the massive invasion of Moschidae in Europe originating from Asia during the Upper/Late Oligocene. The youngest samples correspond to the MN3 biozone. The Corsican specimen examined is morphologically very similar to that of Moissac-II, which corresponds to MP29. Thus, during the Upper Oligocene, the separation of Corsica from the continent was either only partial or very recent.