Contraintes sur la dispersion des roches pyroclastiques du Mont Vulture, sud de l’Italie : implications des conditions climatiques de l’avant-fosse au Pléistocène moyen

Abstract

Mt. Vulture volcano is located on the thrust front of the southern Apennines. Its mid-Pleistocene products are spread southeastward in the adjacent Bradano foredeep basin. The stratigraphic record of the volcano within the Quaternary sedimentary successions helps to better understand the paleo-environmental setting of the foredeep. Volcaniclastic deposits cropping out close to the edifice, tephra levels and associated paleosols recovered from the southernmost sector of the foredeep are of key importance in reconstructing the Pleistocene morpho-climatic conditions in which they formed, using a multiproxy approach. Geomorphological observations and stratigraphic sampling come from the Venosa lacustrine-alluvial basin and from the areas of Irsina and Pomarico villages, where pumice fall levels and related paleosols are present at the top of the lower-middle Pleistocene sedimentary succession. Geochemical and mineralogical analyses of paleosols and pyroclastic rocks have indicated that the Pomarico pumices, reworked and deposited in an alluvial environment, could be likely correlated to the Fara d'Olivo ignimbrites (39Ar/40Ar age < 687 ± 8 ka) present in the basal unit of the Mt. Vulture volcanic succession. The presence of a 7A halloysite phase in the paleosols from two different sites suggests that the Pleistocene weathering likely developed in a dry-humid climate with an alternation of rainy seasons and dry periods.