Late Miocene-Early Pliocene Out-of-Sequence Thrusting in the Southern Apennines (Italy)

Stefano Vitale,Monia Sabbatino,Francesco D’Assisi Tramparulo,Rosa Di Maio,Jacopo Natale,Pasqualino Notaro,Sabatino Ciarcia,Claudio De Paola,Ester Piegari,Ernesto Paolo Prinzi

doi:10.3390/geosciences10080301

Abstract

We present a structural study on late Miocene-early Pliocene out-of-sequence thrusts affecting the southern Apennine orogenic belt. The analyzed structures are exposed in the Campania region (southern Italy). Here, thrusts bound the N-NE side of the carbonate ridges that form the regional mountain backbone. In several outcrops, the Mesozoic carbonates are superposed onto the unconformable wedge-top basin deposits of the upper Miocene Castelvetere Group, providing constraints to the age of the activity of this thrusting event. Moreover, a 4-km-long N-S oriented electrical resistivity tomography profile, carried out along the Caserta mountains, sheds light on the structure of this thrust system in an area where it is not exposed. Further information was carried out from a tunnel excavation that allowed us to study some secondary fault splays. The kinematic analysis of out-of-sequence major and minor structures hosted both in the hanging wall (Apennine Platform carbonates) and footwall (Castelvetere Group deposits and Lagonegro-Molise Basin units) indicates the occurrence of two superposed shortening directions, about E-W and N-S, respectively. We associated these compressive structures to an out-of-sequence thrusting event defined by frontal thrusts verging to the east and lateral ramp thrusts verging to the north and south. We related the out-of-sequence thrusting episode to the positive inversion of inherited normal faults located in the Paleozoic basement. These envelopments thrust upward to crosscut the allochthonous wedge, including, in the western zone of the chain, the upper Miocene wedge-top basin deposits.

Highlights

The study of the kinematics and structural style of thrust sheets, as well as dating their emplacement, is crucial for understanding the tectonic architecture and evolution of orogenic chains
Our study reports the occurrence of a regional tectonic event during the late Messinian-early
The main thrust, related to this event, is exposed along the N-NE flank of the carbonate ridges forming the mountain backbone of the Campania region. This out-of-sequence thrust juxtaposed the Meso-Cenozoic Apennine Platform carbonates onto its margin (e.g., Laviano and Mt Croce successions) or onto the Frigento unit (Lagonegro-Molise Basin unit), with the interposition, in both cases, of the upper Miocene wedge-top basin deposits of the Castelvetere Group (CVTG)

Summary

Introduction

The study of the kinematics and structural style of thrust sheets, as well as dating their emplacement, is crucial for understanding the tectonic architecture and evolution of orogenic chains. This task can be a challenge when the primary structures are not well exposed, such as the case of the southern. Many studies have provided temporal constraints to the fault activity in several fold-and-thrust belts worldwide through different geochronological methods.

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Discussion

Conclusion