The role of orogen-transversal tectonic structures on the “syn” and “post” depositional evolution of a foredeep succession: The case of the Cervarola Sandstones Formation, Miocene, Northern Apennines, Italy

In collisional belts, foredeep turbidites are tracers of the evolution of the orogenic wedge. Syn-depositional tectonics affects the sedimentary facies distribution of the turbidite deposits, while post-depositional tectonics generates the major structures that deform the foredeep basins. The Aquitanian to Burdigalian Cervarola turbiditic succession is one of the main Oligo-Miocene foredeep units that characterize the northwestern portion of the Northern Apennines. The reconstructed syn and post depositional evolution of the Cervarola succession reveals that orogen-transversal tectonic structures strongly and persistently controlled this turbiditic succession, from the time turbidites were infilling the foredeep basin (Aquitanian-Burdigalian) to the time this foredeep deposits became a major and complex thrust sheet of the Northern Apennines orogenic wedge (post-Burdigalian-Present). The syn-depositional history of the Cervarola turbiditic succession has been defined through a detailed facies analysis that has allowed the basin morphology to be accurately constrained. Then, the post-depositional history has been addressed to define the multi-scale deformations preserved in the Cervarola succession through the following approaches: 1) analysis of published geological maps, 2) detailed field mapping, 3) construction of geological cross sections across the major folds, 4) analysis of meso-scale structures and 5) analysis of a seismic reflection profile. The study has outlined that the foredeep basin morphology was tectonically controlled and segmented by compressive structures transversal to the NW-SE basin elongation. The same structures were also present during the post-depositional compressive phases that built up the orogenic wedge and they have been even reactivated in the latest extensional events that have dismembered the mountain range. These orogeny-transversal and long-lasting (~23Myrs) lineaments cross-cut the entire tectonic stacking of the Northern Apennines, affecting tectonic units which suffered different amount of translation during the mountain building, making the reconstruction of the geological evolution possible only with an integrated approach as performed in this work.