Les formations Cénozoïques dans le sud-Est de la France (région entre Grasse et Nice)

National audienceLes formations Cénozoïques dans le sud-Est de la France (région entre Grasse et Nice

Les formations Cénozoïques dans le sud-Est de la France (région entre Grasse et Nice)

National audienceLes formations Cénozoïques dans le sud-Est de la France (région entre Grasse et Nice

The Upper Miocene fossil fish locality of Pecetto di Valenza (Piedmont, Italy): a multidisciplinary approach

Pecetto di Valenza is the first Upper Miocene fossil fish locality of Piedmont to have been studied and the only one in which fossils are embedded in a diatomitic sediment. Sturani & Sampo (1973) considered that it is Messinian in age. However, as a preliminary examination of the diatomflora from this locality by one of us (Elisabeth Fourtanier) suggested a late Tortonian age, it was decided to complete a more thorough micropalaeontological study in order to clarify the stratigraphical question. A comprehensive study of the diatom flora confirmed the preliminary results. Later; the study of the calcareous nannoplankton also concluded a late Tortonian age for the fossiliferous diatomaceous sediment. However, the examination of the planktonic foraminifera supports a Messinian correlation. Such a contradiction is puzzling and is hitherto not understood, even when making reference to a possible reworking. The composition of the fish fauna from Pecetto di Valenza is very similar to that observed in the two other marine Upper Miocene fish faunas of Piedmont, as myctophids predominate in all of them with more than 50% of the total number of specimens, whereas clupeids belonging to the species Alosa elongata comprise about 20% of the fauna. Except for the two species of the genus Lepidopus which, together; reach almost 8%, each one of the other identified taxa is below 5% of the fish fauna. The occurrence of upwellings, which is indicated by the abundance of the diatom Thalassionema nitzchioides in every diatomaceous sample, may have been responsible for the rather significant percentage of Lepidopus in the fish fauna. However, the upwelling environment did not exert any notable influence on the overall composition of the fish fauna from Pecetto di Valenza, relatively to those of the Tortonian of the Tanaro River and of the pre-evaporitic Messinian of Roddi, two localities in which diatoms are missing

Paleontologie du gisement de poissons fossiles di Messinien pr\ue9\ue9vaporitique de Roddi, pr\ue8s d'Alba (Pi\ue9mont, Italie).

Palaeontology of the preevaporitic Messinian fossil fish locality of Roddi, near Alba (Piedmont, Italy). The palaeontological excavations carried out by the Museum "F. Eusebio" during the construction of the housing estate Roddi Cadonia have produced several hundred more or less complete fish skeletons and some molluscs. The Messinian age of this locality was determined using the nannoplankton. Like in the Tortonian fish fauna of Tanaro, Myctophids are, together with the Clupeid species Alosa elongata Agassiz, the dominant taxa. This association is indicative of an environment of moderate depth which, probably, did not exceed 200 metres, as suggested by the occurrence of a school of the epipelagic species Alosa elongata Agassiz in the lower part of the fossiliferous strata. Like for the fish fauna, the malacofauna is strongly reminiscent of that from the Tortonian of Tanaro, especially if we take also into consideration the molluscs found in the levels directly overlying the strata which has yielded the fishes

Paleontologie des marnes tortoniennes affleurant dans le lit du Tanaro pres d'Alba (Pi\ue9mont, Italie)

Palaeontology of the Tortonian marl outcropping in tbe bed of the Tanaro river, near Alba (Piedmont, Italy). During field work made by the museum "F. Eusebio" in the marls of Tortonian age outcropping in the bed of the Tanaro river, near Alba, a rich material of fish articulated skeletons was collected. Additionally, the skeleton of a marine turtle, some echinoderms and molluscs were also found. The study of the nannoplankton has made possible a precise age determination of the fossiliferous strata. Myctophids are, together with Clupeids, the main components of the fish fauna. This association is indicative of an environment of moderate depth which was probably less than 200 metres, as confirmed by the study of the malacofauna. The predominance of the mesopelagical components in the fish fauna was probably produced by marine currents which are supposed to have been active in the west\uacern part of the Paduan gulf