Stages of Development of the Northern Apennines Miocene Foredeep Basin: Insights from Facies Analysis and Structural Setting of the Marnoso-Arenacea Fm. (Umbria, Italy)

The Marnoso-arenacea basin (MaB) of the Northern Apennines represents one of the most significant lower–middle Miocene foredeep turbidite systems in the Mediterranean region. While the northern part of the basin (Emilia-Romagna Region) has been extensively investigated, the Umbrian portion remains less understood, particularly concerning high-resolution stratigraphic and structural frameworks. This study integrates detailed field mapping, physical stratigraphy, biostratigraphic data from calcareous nannofossils, and petrographic analyses of arenites and calcarenites to reconstruct the tectono-stratigraphic evolution of the MaB in the Umbrian portion of the basin. The basin is divided into three main tectono-stratigraphic units: Afra-Mt. Verde, Pietralunga–Gubbio–Valtopina and Mt. Vicino. The middle unit is detailed by means of stratigraphic architecture and sedimentary characteristics, which allow us to identify two distinct sub-units. Several carbonate and hybrid turbidite beds, including the Contessa megabed, serve as regional key markers, enabling robust stratigraphic correlations. Two mass-transport complexes (MTDs) have been identified and dated, revealing close relationships between sedimentation patterns and thrust propagation. Modal petrographic data indicate a mixed provenance, from the Alpine and Apennine regions, changing over time in response to tectonic segmentation. These findings enhance our understanding of the internal organization of the MaB and provide new insights into the foredeep’s paleogeography and tectono-sedimentary evolution during the Langhian–Serravallian stages.