Paolo Giannandrea

Pliocene to Quaternary evolution of the Ofanto Basin in southern Italy: an approach based on the unconformity-bounded stratigraphic units

The Ofanto Basin is an actively evolving intra-chain basin of the Southern Apennines, Italy. It has an elongated shape, about 7 km large and 45 km long, and is E-W striking, representing a marked bend in the NW-SE regular orientation of the south-Apennines morphostructures.The basin is filled up by Pliocene to Quaternary clay, sandstone, and conglomerate, deposited in both marine and continental environments. The main sedimentary deposits are grouped into six units bounded by stratigraphic discontinuities marked by unconformities and abrupt lithological variations. Three of those discontinuities are recognisable on a regional scale and represent the physical boundaries of three supersynthems, in turn subdivided into synthems and subsynthems by basin-scale unconformities. The sedimentary evolution of the basin is herewith reported. Facies analyses and architecture of the sedimentary bodies revealed that each unit formed different alluvial and deltaic depositional systems located on the southern and northern margins of the basin. The morphology of the northern slope was probably steeper than the southern one. The oldest units were deposited in the Western sector of the Ofanto basin. Starting from the late Zanclean to the early Gelasian, the sedimentary bodies underwent an Eastward shift in their deposition, suggesting a basinward relocation of the depositional systems. Such variations in time and space seem to reflect relevant changes in accommodation space and sedimentary supply during the tectonic evolution of the basin. Eventually, correlations among adjacent basins and the meaning of the discontinuities as former erosional surfaces have been pointed out.

Morphometric analysis of fluvial network and age constraints of terraced surfaces of the Ofanto basin, Southern Italy

The Ofanto basin is an intermontane depression located in an intermediate position between the axial zone and the thrust front of the southern Apennines, Italy, filled by Pliocene to Quaternary sediments of both marine and continental origin. This basin presents some peculiarities such as the orientation of the elongation axis with regard to the strike of the chain, marked anomalies of the drainage network, and the asymmetric distribution of the terraced surfaces. Our paper focuses on the morphotectonic evolution of such a complex intermontane basin and tries to explain all those characteristics. The results obtained from both quantitative and morphostructural analyses allowed us to reconstruct the Quaternary evolution of the basin, particularly referred to the ancient land surfaces and the younger fluvial terraces. The hypothesis of a long-term process driven by the differential tectonic behaviour of the two basin flanks instead of a pure litho-structural control responsible for the fluvial network asymmetry of the Ofanto River catchment is here presented and discussed.

Geological map of the eastern sector of the Gorgoglione Basin (southern Italy)

In this paper we report new stratigraphic data related to a new geological map of the Miocene Gorgoglione Basin of southern Italy, traditionally considered as a piggy-back or wedge-top basin filled by a turbidite-like succession. Well exposed outcrops in the study area (eastern sector of the basin) show four unconformities in the Castelmezzano-Pietrapertosa area. Two of these unconformities pass to paraconformities southeastward, in the Cirigliano-Gorgoglione area. Based on new stratigraphic data the succession of the Gorgoglione Flysch can be divided into different informal units: Val Miletta formation and Gorgoglione supersynthem. The latter can be subdivided into the Cirigliano and Castelmezzano synthems. The previously established Cirigliano synthem is here divided into three subsynthems. The lowermost sediments of the Gorgoglione Flysch on the eastern sectors correspond to a complex unit (Val Miletta formation) including Numidian-like quartzarenites, Gorgoglionelike sandstones, and, at the top of the formation, an olistostrome of varicoloured clays, belonging to the Argille Variegate Group. The stratigraphic analyses and the biostratigraphic results based on calcareous plankton assemblage, improve the reconstruction of the geometries of the sedimentary bodies and the time-space facies evolution of the synthems. Sedimentologic and petrographic characters of the upper part of the Castelmezzano synthem show a clear fining and thinning upward trend. Medium- and fine-grained arenites, varying in composition from quartz sandstones to siltstones and shales, are locally marked by abundant planktonic foraminifera and are interpreted as contourites. Moreover, the relationships between tectonics and sedimentation are analyzed. The data are used to propose a scheme of the Burdigalian to Tortonian tectono-stratigrafiphic evolution of the eastern sector of the basin.