Constraining the Passive to Active Margin Tectonics of the Internal Central Apennines: Insights from Biostratigraphy, Structural, and Seismic Analysis

The polyphase structural evolution of a sector of the internal Central Apennines, where
the significance of pelagic deposits atop neritic carbonate platform and active margin sediments has
been long debated, is here documented. The results of a new geological survey in the Volsci Range,
supported by new stratigraphic constraints from the syn-orogenic deposits, are integrated with the
analysis of 2D seismic reflection lines and available wells in the adjacent Latin Valley. Late Cretaceous
syn-sedimentary faults are documented and interpreted as steps linking a carbonate platform to
the adjacent pelagic basin, located to the west. During Tortonian time, the pelagic deposits were
squeezed off and juxtaposed as mélange units on top of the carbonate platform. Subsurface data
highlighted stacked thrust sheets that were first involved into an initial in-sequence propagation with
top-to-the-ENE, synchronous to late Tortonian foredeep to wedge-top sedimentation. We distinguish
up to four groups of thrust faults that occurred during in-sequence shortening (thrusts 1–3; about
55–60 km) and backthrusting (thrust 4). During Pliocene to recent times, the area has been uplifted
and subsequently extended by normal faults cross-cutting the accretionary wedge. Beside regional
interest, our findings bear implications on the kinematic evolution of an orogenic wedge affected by
far-traveled units.