Search

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.

A basin-scale, integrated approach, including sedimentological, geomorphological and soil data, enables the reliable reconstruction of the infilling history of the southern Apenninic foredeep, with its subsequent inclusion in the wedge-top of the foreland basin system. An example is shown from the Molise-Apulian Apennines (Southern Italy), between Trigno and Fortore rivers, where the Pleistocene tectono-sedimentary evolution of the basin is framed into a sequence-stratigraphic scheme. Specifically, within the traditional subdivision into Quaternary marine (Qm) and Quaternary continental (Qc) depositional cycles, five third-order depositional sequences (Qm1, Qm2, Qc1, Qc2 and Qc3) are identified based upon recognition of four major stratigraphic discontinuities. The lower sequence boundaries are represented by angular unconformities or abrupt facies shifts, and are generally associated with distinctive pedological and geomorphological features. Three paleosols, observed at top of depositional sequences Qm2, Qc1 and Qc2, represent pedostratigraphic markers that can be tracked basinwide. The geomorphological response to major tectono-sedimentary events is marked by a series of paleosurfaces with erosional, depositional and complex characteristics. Detailed investigation of the relationships between stratigraphic architecture and development of unconformities, paleosols and paleosurfaces suggests that the four sequence boundaries were formed in response to four geomorphological phases/tectonic events which affected the basin during the Quaternary. The first three tectonic events (Lower-Middle Pleistocene), marking the lower boundaries of sequences Qm2, Qc1 and Qc2, respectively, are interpreted to be related to the tectonic regime that characterized the last phase of thrusting recorded in the Southern Apennines. In contrast, sequence Qc3 does not display evidence of thrust tectonics, and accumulated as a result of a phase of regional uplift starting with the Middle Pleistocene.

Integrated sedimentological and micropalaeontological analyses of Montesecco Clays cropping out along the Molise Apennines foothills allow to reconstruct the depositional setting and major palaeoenvironmental changes within the Molise Periadriatic Basin (Apenninic foredeep) during the Late Pliocene and Early Pleistocene. Sedimentological and palaeocological data from four reference stratigraphic sections document an overall shallowing-upward tendency within Montesecco Clays, which is also confirmed by compositional data analysis of microfaunal assemblages. Lower Montesecco Clays (Ururi and Trigno sections) accumulated from the middle epibathyal/bathyal to lower circalittoral zone, while upper Montesecco Clays (Guglionesi and Colle Favaro-Petacciato sections) contain a microfauna indicative of an outer circalittoral to infralittoral environment. As documented by previous subsurface data, the palaeoecological analysis suggests increasing depths in the Molise Periadriatic Basin from NW to SE.