Contrasting styles of fault reactivation in curved orogenic belts: Examples from the Central Apennines (Italy)

Abstract

The geometry of the Apennine fold-andthrust belt has been strongly infl uenced by the original architecture of the Adria paleo margin. In the Central Apennines, pre-thrusting normal faults (pre-orogenic Permian(?)/TriassicJurassic and synorogenic Neogene) were reactivated with compressional kinematics during the Neogene-Quaternary orogenesis.We present a study on the control of preexist ing extensional faults on thrust tectonics in the Central Apennines. We describe positive inversion geometries of some salient fold-and-thrust structures (Setteporte, the Sabini Mountains, the Sibillini Mountains, Montagna dei Fiori, the Gran Sasso range, Maiella Mountain, and Casoli-Bomba) by integrating surface geological data and seismic-line interpretation. In these structures, different styles of fault reactivation depend on their orientation with respect to the subsequent compressional NE-SW-trending stress fi eld. The NW-SE-and WNW-ESEtrending pre-thrusting normal faults in the backlimbs of the anticlines were displaced and passively translated in the hangingwall blocks of the thrust planes, thus exhibiting a classical shortcut geometry (shortcut anticlines). Differently, pre-orogenic normal faults in the N-S-trending anticlines were reactivated in a transpressive deformational context, as docu mented by the mainly dip-slip and strike-slip kinematics along the thrusts and back thrusts, respectively (reacti vation anticlines).The cases studied document differences in geometry in fold-and-thrust structures related to the trend of preexisting extensional faults, showing that different reactivation geom etries linked to the same inversion event can coexist at regional scale in curved foldand-thrust belts. The proposed inversion tectonic model and the resulting geometry of the fold-and-thrust belt could possibly be applied to analogous orogenic belts.

On the complexity of surface ruptures during normal faulting earthquakes: excerpts from the 6 April 2009 L'Aquila (central Italy) earthquake (<i>M</i><sub>w</sub> 6.3)

“…1). In the early Mesozoic the region was part of the African passive margin of the Tethys Ocean; it hosted large carbonate platforms and intervening pelagic basins that were subsequently broken up by E-W Triassic-Lower Jurassic extension (Calamita et al, 2011;Di Domenica et al, 2014). Since the Cretaceous, the region evolved within the framework of the convergent motion between the African and European plates; east-to northeastverging thrusts along with their associated foredeep/thrusttop basins progressed toward the Adriatic foreland up to the Middle Pleistocene (Patacca and Scandone, 1989) and were subsequently dissected by strike-slip and normal faulting.…”

Petroleum Geology and Hydrocarbon Potential of the Adriatic Basin, Offshore Croatia

“…In general this compression consisted of Pliocene inversion of pre-existing Triassic normal faults at the base of the carbonate succession, similar to Pliocene-Quaternary inversion structures in the Apennines (Calamita et al, 2011). Along the boundary between Croatia and Italy, a large anticlinorium displays evidence for several shortening phases from the Miocene to the Pliocene (Figs.…”

Defining a mid-Holocene earthquake through speleoseismological and independent data: implications for the outer Central Apennines (Italy) seismotectonic framework

“…The Apennines are a Neogene-Quaternary foreland-verging fold-and-thrust belt, showing a complex structural arrangement derived from the interaction between contractional structures and pre-existing extensional faults (e.g., Coward et al, 1999;Scisciani et al, 2002;Tozer et al, 2002;Butler et al, 2006;Calamita et al, 2011;Scisciani, 2009;Di Domenica et al, 2014a, b;Pace et al, 2014;Cardello and Doglioni, 2015). The orogenesis involved Triassic-toMiocene sedimentary successions related to different basin and platform paleogeographic domains of the Adria Mesozoic paleomargin (e.g., Ciarapica and Passeri, 2002;Patacca and Scandone, 2007).…”