Integration of sandstone petrography, sedimentology, stratigraphy, and structural and paleogeographic restorations of clastic sediments deposited in episutural basins has allowed us to unravel the collisional history of the Northern Apennines from middle Eocene to Holocene time, as illustrated in seven paleogeographic maps. The episutural successions were deposited in two types of basins.
1. Late Eocene–early Oligocene basins perched on deformed Ligurian units (ophiolites and their sedimentary cover) of the southwestern side of the Alps (i.e., part of the future northern Apennine accretionary wedge). In these basins, provenance evolved from an extrawedge north-to-south supply from the Austroalpine (Adriatic) continental block to an intrawedge supply with progressive unroofing of the collisional tectonic stack composed of Ligurian units plus minor high-pressure–low-temperature metamorphic units (Pennidic units). These basins developed after the middle Eocene continental collision between the Adriatic margin and the southern European margin, a period dominated by magmatism, uplift, and block faulting of the Pennidic-Ligurian orogen.
2. Late Oligocene–Holocene basins formed on top of the migrating Apenninic orogenic wedge, which was progressively thrust onto the Adriatic margin, where thick, turbiditic successions were being deposited on the foreland. Sandstone composition is characterized by an overall increase in detritus from Pennidic units both up-section and from south to north and by detritus recycled from older sedimentary units and their Ligurian substratum. These basins developed during continental subduction of the Adriatic plate toward the west underneath the Corsica-Sardinia block coupled with extension in the future western Mediterranean area.
Sedimentation patterns indicate that paleobathymetry and source rocks were markedly different north and south of the Val Secchia line, a structural lineament that does not correspond to a present-day observable structure across the Apennines.