Synsedimentary deformation in Upper Cretaceous– Lower Paleogene limestones within a thrust anticline of the Umbria-Marche Apennines, Italy

The geometry of collisional mountain belts, which were formed at the expense of passive continental margins, is often complex because orogenic structures, such as thrusts and related folds, commonly interfere with pre-orogenic extensional struc- tures, namely, normal faults, resulting in kinematically complex, composite struc- tural assemblages. In these settings, analysis of the relationships between depositional and structural features may provide very useful tools to correctly unravel the local sedimentary and deformational history and relative ages of structures. Analysis of the relationships between minor normal faults and slumps near Frontale in the Umbria- Marche Apennines of Italy made it possible to correctly unravel the local chronology of events and hence to infer the depositional and deformation history of a part of the Upper Cretaceous–Paleogene Scaglia Rossa Formation pelagic basin. The results of this investigation made it possible to ascribe the normal faults to events that predate the construction of the Umbria-Marche mountain belt. Therefore, the normal faults at Frontale are distinct from those that overprint the main compressional structures responsible for the present-day seismicity of central Italy.