Abstract

The upper Miocene S. Bartolomeo Formation is a significant turbidite succession filling a collisional basin of the southern Apenninic chain and outcropping between Sannio and Daunia Mountains. Based on geological mapping, an updated lithostratigraphic scheme of this formation has been proposed; moreover, on the basis of sedimentological analyses and measurement of several stratigraphic sections, the main and characteristic gravity flow lithofacies have been described and interpreted, and the stratigraphic architecture of the whole turbidite succession has been reconstructed, showing the correlation between the main lithostratigraphic units and stratigraphic-depositional ones. The typical diagenetic concretions of this formation have been described and interpreted: the main lithofacies types are elongate bed-parallel concretions (costole), irregularly distributed and spheroidal concretions (cogoli) and joint/fault parallel concretions. A basin model has been proposed, on the basis of geologic-structural mapping, of the collected stratigraphic and sedimentologic data, and of the petrographical and biostratigraphical data derived from literature; in this model three fundamental phases of late Miocene, basin evolution have been described: (i) late Tortonian onset of the basin and deposition of the lower turbidite units (stages of growth I-II), with aggradational to retrogradational stacking patterns; (ii) early Messinian initiation of out-of-sequence thrusting and coeval deposition of the mainly pelitic deposits of basin closure (turbidite stage III); (iii) from the late Messinian to the early Pliocene, integral dislocation of the basin fill and definitive incorporation in the thrust-belt, with fairly good preservation potential of Miocene stratigraphic features. In general, the stratigraphic record of the basin is related to tectono-eustatic control; the tectonic control is dominant and its effects depend on the variations of the thrusting propagation regime; the eustatic control is subordinate, but it can be enhanced during tectonic quiescence. Finally, the studied basin has been framed within the southern Apenninic chain, which represents a complex accretionary prism related to continental subduction, with Miocene history characterized by onset, rapid tectono-sedimentary evolution, following closure and dislocation of two types of basins: thrust-related basins (for example S. Bartolomeo) and deformed peripheral foredeep basins.

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