The integrated analysis of largely unpublished seismic reflection profiles (commercial lines and a reprocessed segment of the CROP-04 deep crustal line), exploratory well logs and geologic-structural relations among the lithostratigraphic units of the west-central Campania-Lucania Apennines (Italy), shed light on the structural architecture and tectonic evolution of this region. Pre-orogenic, Mesozoic-Neogene carbonate platform, margin-slope and basinal units that frame the Picentini, Marzano and Alburni mountain ranges and the Irpinia hills were imbricated during Miocene thrusting. The imbrication led to the formation of an heterogenous multilayer that controlled style and localization of both the late-orogenic Pliocene thick-skinned thrusting in the underlying Apulia platform and of the Quaternary transtension and extension. We reinterpreted five exploratory well logs (Acerno, Contursi, San Fele, San Gregorio Magno and Taurasi) based on surface constraints and on the modern understanding of regional lithostratigraphy. Using velocity data from sonic logs, the well stratigraphy and the seismic signature were correlated through an accurate wellto-seismic tie, which, together with literature data, allowed to build a local velocity model for depth conversion of seismic profiles. Seismic facies analysis calibrated by the well-to-seismic tie led to identification of seven seismic units with distinctive reflections attributes, which were assigned to as many lithostratigraphic units logged in wells. The analysis documents the stratigraphic-structural thickness and the depth distribution of the thin-skinned thrusts sheets that form the Apennines fold-thrust belt. The Liguride Basin succession is characterized by a ~900 m thickness and is highly fragmented by later high-angle strike-slip and normal faults. The Apenninic Platform shows lateral thickness changes in correspondence with shelf (~3 km), margin (~2-2.5 km) and margin-to-slope (~1.5 km) facies successions that form as many imbricates within a coherent thrust sheet. The Lagonegro-Molise Basin rocks shows dramatic changes in structural thickness because of detachment of the Upper Mesozoic section (~500 m) from above the main Mesozoic section (~1-1.5 km). The underlying Apulian Platform is characterized by a regional anticlinorium (~30-50 km wavelength) that, based on our new reconstruction, extends further to the west in the hinterland than previously known. The anticlinorium exhibits shorter-wavelength (<10 km wavelength) anticlines limited by NNE-verging thrust ramps. The ramps have a typical high (~45°) dip, suggesting they root in the crystalline basement of Apulia, and accommodate the thrust envelopment of the previously imbricated thrust sheets. Analysis of the last ~15 years’ seismicity reveals that most of the upper crustal seismicity falls within a crustal volume localized in the Apulia basement and broadly limited by the Irpinia fault and by its antithetic fault, both of which slipped during the Mw 6.9 1980 earthquake.
Structural architecture and tectonic evolution of the west-central Campania-Lucania arc (Southern Apennines, Italy): constraints from seismic reflection profiles, well data a nd structural-geologic analysis
Ferranti L.;Carboni F.;Bello S.;Brozzetti F.;
2023-01-01
Abstract
The integrated analysis of largely unpublished seismic reflection profiles (commercial lines and a reprocessed segment of the CROP-04 deep crustal line), exploratory well logs and geologic-structural relations among the lithostratigraphic units of the west-central Campania-Lucania Apennines (Italy), shed light on the structural architecture and tectonic evolution of this region. Pre-orogenic, Mesozoic-Neogene carbonate platform, margin-slope and basinal units that frame the Picentini, Marzano and Alburni mountain ranges and the Irpinia hills were imbricated during Miocene thrusting. The imbrication led to the formation of an heterogenous multilayer that controlled style and localization of both the late-orogenic Pliocene thick-skinned thrusting in the underlying Apulia platform and of the Quaternary transtension and extension. We reinterpreted five exploratory well logs (Acerno, Contursi, San Fele, San Gregorio Magno and Taurasi) based on surface constraints and on the modern understanding of regional lithostratigraphy. Using velocity data from sonic logs, the well stratigraphy and the seismic signature were correlated through an accurate wellto-seismic tie, which, together with literature data, allowed to build a local velocity model for depth conversion of seismic profiles. Seismic facies analysis calibrated by the well-to-seismic tie led to identification of seven seismic units with distinctive reflections attributes, which were assigned to as many lithostratigraphic units logged in wells. The analysis documents the stratigraphic-structural thickness and the depth distribution of the thin-skinned thrusts sheets that form the Apennines fold-thrust belt. The Liguride Basin succession is characterized by a ~900 m thickness and is highly fragmented by later high-angle strike-slip and normal faults. The Apenninic Platform shows lateral thickness changes in correspondence with shelf (~3 km), margin (~2-2.5 km) and margin-to-slope (~1.5 km) facies successions that form as many imbricates within a coherent thrust sheet. The Lagonegro-Molise Basin rocks shows dramatic changes in structural thickness because of detachment of the Upper Mesozoic section (~500 m) from above the main Mesozoic section (~1-1.5 km). The underlying Apulian Platform is characterized by a regional anticlinorium (~30-50 km wavelength) that, based on our new reconstruction, extends further to the west in the hinterland than previously known. The anticlinorium exhibits shorter-wavelength (<10 km wavelength) anticlines limited by NNE-verging thrust ramps. The ramps have a typical high (~45°) dip, suggesting they root in the crystalline basement of Apulia, and accommodate the thrust envelopment of the previously imbricated thrust sheets. Analysis of the last ~15 years’ seismicity reveals that most of the upper crustal seismicity falls within a crustal volume localized in the Apulia basement and broadly limited by the Irpinia fault and by its antithetic fault, both of which slipped during the Mw 6.9 1980 earthquake.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
