Une étude multidisciplinaire a été réalisée sur les dépôts néogènes (alluviaux, lacustres et marins) du sud-est du bassin de Valdelsa (Italie centrale). Ces sédiments, datés du Tortonien supérieur-Messinien inférieur, sont surmontés, en discontinuité, par des sédiments du Messinien supérieur-Pliocène. Cette étude suggère que ces dépôts résultent de l'interaction de phénomènes locaux tels que la surrection et la dénudation des reliefs ainsi que l'eustasie plutôt que du changement drastique dû à la transgression du Zancléen inférieur sur le Lago-Mare, enregistrée en Méditerranée. Ces sédiments, déposés à la transition du Mio- Pliocène correspondent au synthème de Borro Strolla (qui comprend trois sub-synthèmes). Il a été daté Messinien supérieur- Zancléen inférieur grâce à l'analyses de coupes, d'études sédimentologiques (étude de faciès), et de la biochronologie établie sur les associations de faunes non-marines, montrant elles-mêmes de nouveaux éléments. La découverte, dans la partie inférieure du synthème de Borro Strolla, du gerbillidé Debruijnimys sp. et du muridé Stephanomys aff . S. donnezani (Depéret, 1890) à affi nité pliocène est un élément nouveau dans cette association faunistique qui correspond par ailleurs à celle observée en Italie dans les sites du Messinien supérieur. D'autre part, la présence de mollusques terrestres dans ces mêmes sédiments permet aussi d'attribuer le synthème de Borro Strolla au Messinien supérieur-Zancléen inférieur. Les attributions stratigraphiques établies pour le synthème de Borro Strolla sont corrélées aux événements locaux et régionaux enregistrés à la limite Messinien-Pliocène.
A multi-disciplinary study has been carried out on a Late Neogene succession exposed in the SE portion of the Valdelsa Basin (Strolla Creek, Central Italy). Th e succession consists of upper Tortonian-Messinian sediments, unconformably overlain by uppermost Messinian-Pliocene deposits, accumulated in alluvial, lacustrine and marine environments. Previous studies on this succession hypothesized a sudden marine fl ooding of the upper Messinian Lago-Mare realm in the earliest Zanclean in apparent agreement with the Mio-Pliocene transition recorded elsewhere in the Mediterrranean Basin. Data from this study suggest a more complex stratigraphy recording a local depositional evolution possibly driven by interference between uplift, relief denudation and eustacy. Th e sediments encompassing the Mio-Pliocene transition have been included into the Borro Strolla synthem, furtherly subdivided into three sub-synthems. Th e Borro Strolla synthem has been dated as uppermost Messinian-earliest Zanclean based on the integration of physical stratigraphy, facies analysis and biochronology of non-marine fossil assemblages in part documented for the fi rst time. Th e occurrence in the lower Borro Strolla Synthem of the gerbil Debruijnimys sp. and the murid Stephanomys aff . S. donnezani (Depéret, 1890) with Pliocene affi nity represents the most important novelty in the composition of a mammal fauna otherwise similar to other Italian late Messinian sites. Th e co-occurrence of terrestrial molluscs from the same sediments gives further biochronologic constrains supporting the calibration of the Borro Strolla synthem to the latest Messinianearliest Zanclean. Th e Borro Strolla stratigraphic section then is discussed in the framework of local to regional events which marked the transition from the Messinian to Pliocene.
The end of the Lago-Mare time in the SE Valdelsa Basin (Central Italy): interference between local tectonism and regional sea-level rise.
Esu D;
2008
Abstract
A multi-disciplinary study has been carried out on a Late Neogene succession exposed in the SE portion of the Valdelsa Basin (Strolla Creek, Central Italy). Th e succession consists of upper Tortonian-Messinian sediments, unconformably overlain by uppermost Messinian-Pliocene deposits, accumulated in alluvial, lacustrine and marine environments. Previous studies on this succession hypothesized a sudden marine fl ooding of the upper Messinian Lago-Mare realm in the earliest Zanclean in apparent agreement with the Mio-Pliocene transition recorded elsewhere in the Mediterrranean Basin. Data from this study suggest a more complex stratigraphy recording a local depositional evolution possibly driven by interference between uplift, relief denudation and eustacy. Th e sediments encompassing the Mio-Pliocene transition have been included into the Borro Strolla synthem, furtherly subdivided into three sub-synthems. Th e Borro Strolla synthem has been dated as uppermost Messinian-earliest Zanclean based on the integration of physical stratigraphy, facies analysis and biochronology of non-marine fossil assemblages in part documented for the fi rst time. Th e occurrence in the lower Borro Strolla Synthem of the gerbil Debruijnimys sp. and the murid Stephanomys aff . S. donnezani (Depéret, 1890) with Pliocene affi nity represents the most important novelty in the composition of a mammal fauna otherwise similar to other Italian late Messinian sites. Th e co-occurrence of terrestrial molluscs from the same sediments gives further biochronologic constrains supporting the calibration of the Borro Strolla synthem to the latest Messinianearliest Zanclean. Th e Borro Strolla stratigraphic section then is discussed in the framework of local to regional events which marked the transition from the Messinian to Pliocene.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
