An active oblique-contractional belt at the transition between the Southern Apennines and Calabrian Arc: The Amendolara Ridge, Ionian Sea, Italy

Abstract

High-resolution, single-channel seismic and multibeam bathymetry data collected at the Amendolara Ridge, a key submarine area marking the junction between the Apennine collision belt and the Calabrian subduction forearc, reveal active deformation in a supposedly stable crustal sector. New data, integrated with existing multichannel seismic profiles calibrated with oil-exploratory wells, show that middle to late Pleistocene sediments are deformed in growth folds above blind oblique-reverse faults that bound a regional pop-up. Data analysis indicates that~10 to 20 km long banks that top the~80 km long, NW-SE trending ridge are structural culminations above en echelon fault segments. Numeric modeling of bathymetry and stratigraphic markers suggests that three 45°dipping upper crustal (2-10 km) fault segments underlie the ridge, with slip rates up to~0.5 mm/yr. Segments may be capable with M~6.1-6.3 earthquakes, although an unknown fraction of aseismic slip undoubtedly contributes to deformation. The fault array that bounds the southern flank of the ridge (Amendolara Fault System) parallels a belt of M w < 4.7 strike-slip and thrust earthquakes, which suggest current left-oblique reverse motion on the array. The eastern segment of the array shows apparent morphologic evidence of deformation and might be responsible for M w ≤ 5.2 historic events. Late Pliocene-Quaternary growth of the oblique contractional belt is related to the combined effects of stalling of Adriatic slab retreat underneath the Apennines and subduction retreat of the Ionian slab underneath Calabria. Deformation localization was controlled by an inherited mechanical interface between the thick Apulian (Adriatic) platform crust and the attenuated Ionian Basin crust.

The Culmination of an Oblique Time‐Transgressive Arc Continent Collision: The Pollino Massif Between Calabria and the Southern Apennines, Italy

“…This unit is folded in an anticline (Ghisetti & Vezzani, ) on the hanging‐wall of the Raganello fault and may thus be interpreted as a thrust‐anticline related to that fault. This and other more external anticlines at the SE terminus of the Apennines, mostly in the submarine part, verge SW and are therefore symptomatic of antithetic “back‐thrusting” in the context of the NE vergence typical of the Apennines (Ferranti et al, ; Ghisetti & Vezzani, ; Mazzoli et al, ; Vitale & Ciarcia, ). Antithetic thrusting is not widely reported in the Apennines and the SW vergence of the Raganello fault is likely related to an unusual late‐stage circumstance such as the Pleistocene tectonic crisis of Calabria.…”

Lithospheric fault and kinematic decoupling of the Apennines system across the Pollino range

“…Active kinematic indicators (Figure d) and seismologic data suggest that the Pollino fault is not only young but it is still active, with kinematic discontinuity between the blocks on the two sides of the fault [ D ' Agostino et al , ; Palano et al , ; Orecchio et al , ]. Morphologic evidence of recent deformation at the submarine junction of the two blocks has been attributed to activity of an oblique fault consistent with an active discontinuity [ Ferranti et al , ]. Instrumental seismicity occurs on this submarine area in the Ionian offshore, as well as historical events.…”

“…Vertical slip rates of about 1 mm/yr found by trench studies [ Cinti et al , ] are consistent with those estimated by GPS data [ D ' Agostino et al , ], suggesting that the extension tectonics remains almost stationary over the Holocene. Recent studies evidenced that the area is still affected by the evolution of the Calabrian arc [ Ferranti et al , ; Orecchio et al , ].…”

InSAR Time Series Analysis of Natural and Anthropogenic Coastal Plain Subsidence: The Case of Sibari (Southern Italy)

“…In the Ionian Sea, in front of the SP an active oblique-contractional belt (the Amendolara Ridge) is recognized. The latter is due to the combined effects of subduction retreat of the Ionian slab underneath Calabria and stalling of Adriatic slab retreat underneath the Apennines [71]. The belt consists of the alignment of three anticlines (Amendolara, Rossano and Cariati) bounded by a main SW-verging back-thrust (Figure 5a).…”

“…[73]) shows the presence of three morphological highs (Amendolara, Rossano and Cariati highs). The main structural elements (thrusts and anticlines) are extracted from [71]. In the map is showed the hypocenters location of the earthquakes occurred between 2003 and 2010 (ISIDe [74]) with the relative magnitude and hypocentral depth.…”