Deformed Pleistocene marine terraces along the Ionian Sea margin of southern Italy: Unveiling blind fault‐related folds contribution to coastal uplift

Abstract

Morphotectonic analysis and fault numeric modeling of uplifted marine terraces along the Ionian Sea coast of the Southern Apennines allowed us to place quantitative constraints on middle Pleistocene‐Holocene deformation. Ten terrace orders uplifted to as much as +660 m were mapped along ~80 km of the Taranto Gulf coastline. The shorelines document both a regional and a local, fault‐induced contribution to uplift. The intermingling between the two deformation sources is attested by three 10 km scale undulations superimposed on a 100 km scale northeastward tilt. The undulations spatially coincide with the trace of NW‐SE striking transpressional faults that affected the coastal range during the early Pleistocene. To test whether fault activity continued to the present, we modeled the differential uplift of marine terraces as progressive elastic displacement above blind oblique‐thrust ramps seated beneath the coast. Through an iterative and mathematically based procedure, we defined the best geometric and kinematic fault parameters as well as the number and position of fault segments. Fault numerical models predict two fault‐propagation folds cored by blind thrusts with slip rates ranging from 0.5 to 0.7 mm/yr and capable of generating an earthquake with a maximum moment magnitude of 5.9–6.3. Notably, we find that the locus of predominant activity has repeatedly shifted between the two fault systems during time and that slip rates on each fault have temporally changed. It is not clear if the active deformation is seismogenic or dominated by aseismic creep; however, the modeled faults are embedded in an offshore transpressional belt that may have sourced historical earthquakes.

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

“…Since middle Pleistocene, the coastal sector of the Apennines abutting the Ionian Sea has experienced vigorous uplift (~1 mm/a and locally more) [ Westaway , ; Cucci and Cinti , ; Ferranti et al ., ; Santoro et al ., , ; Caputo et al ., ]. Uplift is manifested by staircases of raised paleoshorelines, whose deformed profiles embeds both a long‐ and a short‐wavelength component.…”

“…Boxes are thrust segments derived from dislocation modeling by Santoro et al . []. Amendolara Fault System (AFS) and Valsinni Fault System (VFS) from this work.…”

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

“…Alternatively, Calabrian subduction and possibly Apennine collision are continuing, though at a much reduced rate (D'Agostino et al, 2011). Not surprisingly, therefore, thrusting on the SE flank of the Pollino Massif is at least as young as Mid-Pleistocene (Caputo et al, 2010;Ferranti et al, 2009) and thrust-folding may be ongoing in the submerged portion of the boundary SE of the massif (Sibari-Corigliano Basin; Santoro et al, 2013;Ferranti et al, 2014).…”

Active mountain building along the eastern Colombian Subandes: A folding history from deformed terraces across the Tame anticline, Llanos Basin

“…Most of these studies (Lavé and Avouac, 2000;Thompson et al, 2002) focused primarily on planar fault-related folds, because they obey a wellknown formulation that relates fold geometry to fault slip and horizontal shortening (Hardy and Poblet, 2005;Mitra, 1990;Suppe, 1983;Suppe and Medwedeff, 1990). Some other kinematic models have been put forward for understanding blind thrust faulting, including trishear (Gold et al, 2006), fault-propagation folding (Santoro et al, 2013), and listric faults (Amos et al, 2007). Most of these models were developed for regions with little to no constraint on the subsurface fold geometry.…”