Significance of Ba-rich zeolitic sediments of the Oligomiocene sequences near Voghera (PV-AL provinces), Italy

The sediments are thick from a minimum of 2cm to a maximum of 180cm with average values about 30-40cm and affect the pelitic-arenaceous sequences for a thickness of 80-100m. The zeolitic layers are normally grey pink coloured and clearly distinct from the pelites by showing both higher hardness and a defined boundary. They show sedimentary textures as fine bedding, bio-turbations, slumps, cylindrical concentrations of pure green smectite and dispersed hexagonal crystals of biotite. The chemical and mineralogical data obtained might serve to define the type of magmatism that characterized the Oligo-Miocene boundary in a large area of the northern Apennines.