The Plio-Pleistocene succession between Trigno and Fortore rivers (Molise and Apulia Apennines): stratigraphy and facies characteristics

The Plio-Pleistocene succession forming the infill of the Southern Apenninic foredeep in Molise is described, for the first time, in terms of sedimentological characteristics, and is compared with the stratigraphic framework reconstructed from adjacent areas. The vertical stacking of facies between Trigno and Fortore rivers shows an obvious “regressive” tendency from open marine to alluvial depositional systems. Specifically, offshore deposits (Montesecco Clays) display vertical transition to overlying offshore-transition (lower Serracapriola Sands) and nearshore (upper Serracapriola Sands) facies. This shallowing-upward succession is unconformably overlain by alluvial deposits (Campomarino Conglomerates). Detailed facies investigation of Serracapriola Sands enables identification of a wide spectrum of littoral deposits, forming a peculiar progradational beach sequence. This includes, from bottom to top, lower shoreface, upper shoreface and foreshore facies associations, with local development of backshore deposits. River influenced deposits are identified close to the boundary with the overlying Campomarino Conglomerates. The Plio-Pleistocene succession described in this work displays strong similarities with the stratigraphic framework traditionally reported from the northern and central sectors of the Apenninic (periadriatic) foredeep. Particularly, the stratigraphic boundary between Serracapriola Sands and Campomarino Conglomerates is interpreted to reflect the boundary between depositional cycles Qm and Qc, recognized at more northern locations. Despite lack of reliable chronological data, facies analogies with the coeval units suggest that Serracapriola Sands might represent the southern equivalent of the “yellow sand” facies cropping out extensively along the Apennines foothills, between Emilia-Romagna and Marche.