The "Livello Raffaello" (Early Miocene) in the Umbria-Marche Apennines: stratigraphy, paleontology, mineralogy and geochemistry

A detailed stratigraphic and mineralogical-geochemical analyses were carried out on the Livello Raffaello of several sections throughout the Umbria-Marche Basin. The integrated biostratigraphic study shows that this clayey marker bed is mid-Aquitanian in age. The relative abundance of the bathymetric index forms within the assemblages suggests that the depth of the depositional environment is near to the lower limit of the upper bathyal zone. Whole rock composition was determined by diffraction and thermal methods in connection with other techniques. Unaltered samples are almost monomineralic being composed of more than 90% montmorillonite. It is possible to reconstruct the original grain size of the sediment by mineralogical determination, allowing some consideration about provenance. Based on compositional data, a volcanic genesis of the Livello Raffaello can be argued. It was probably linked to a high magnitude explosive event.