Coexistence of fault‐propagation and fault‐bend folding in curve‐shaped foreland fold‐and‐thrust belts: examples from the Northern Apennines (Italy)

Abstract

Terra Nova, 24, 396–406, 2012 Abstract Fault‐bend and fault‐propagation folds have unique profiles in foreland fold‐and‐thrust belts that are caused by different fault‐related folding models and controlled by the mechanical characteristic of the multilayer and/or by reactivation of normal faults in a positive inversion tectonics context. In this work, NNE–SSW‐ and NW–SE‐trending anticlines, related to the Neogene curve‐shaped Olevano‐Antrodoco‐Sibillini thrust (Northern Apennines, Italy), are investigated to reconstruct fault‐related folding mechanisms. Geological and structural analysis allows us to interpret the NNE–SSW‐trending anticlines as fault‐bend reactivation folds and the NW–SE‐trending anticlines as fault‐propagation shortcut anticlines. The coexistence of fault‐bend and fault‐propagation folding processes involving the same multi‐layered succession in different arms of a curve‐shaped thrust is explained in an inversion tectonics context. This along‐strike variation of different folding mechanisms might be recognised in similar curve‐shaped orogenic thrust‐belts controlled by structural inheritance.

Complex Fault Geometry and Rupture Dynamics of the MW 6.5, 30 October 2016, Central Italy Earthquake

“…In particular, the portion that outcrops to the south of the Sibillini Mts. was interpreted as a transpressive thrust ramp resulting from tectonic inversion of a NNE‐SSW Jurassic normal fault system (i.e., the preorogenic Ancona‐Anzio fault; Castellarin et al, ; Calamita, Pace, et al, , and references therein; Di Domenica et al, ). This segment of the OAS shows a complex geometry: it is characterized by parallel splays defining a compound fault zone, up to 1 km wide; it presents fault‐bend folding structural style, with hanging‐wall ramp on footwall ramp relationships (Calamita, Satolli, et al, ).…”

Testing Different Tectonic Models for the Source of the Mw 6.5, 30 October 2016, Norcia Earthquake (Central Italy): A Youthful Normal Fault, or Negative Inversion of an Old Thrust?

“…Further faults are inferred only by stratigraphic relationships, such as thickness and facies variations across Mesozoic formations. The most representative of such inferred faults is indeed the NNE‐SSW Ancona‐Anzio lineament (Castellarin et al, ; Castellarin et al, ; Cavinato et al, ; Parotto & Praturlon, ), likely a regional paleogeographic feature that may have acted also as a lateral ramp or transpressional fault during the contractional phases (e.g., Calamita et al, ; Castellarin et al, ; Lavecchia, ; Tavarnelli et al, ).…”

Surface Faulting of the 30 October 2016 Mw 6.5 Central Italy Earthquake: Detailed Analysis of a Complex Coseismic Rupture

“…The axial zone of the central Apennines (Italy) is made of Meso‐Cenozoic carbonate and siliciclastic rocks that experienced NE thrusting during Miocene–Pliocene times (Vai & Martini, ). The Sibillini Mountains thrust (MST; Figure ) is one of the main resulting compressional structures in this region (Calamita et al, ). Since the Late Pliocene–Early Pleistocene, postorogenic extension started affecting the chain (Cavinato & De Celles, ; D'Agostino et al, ) with the present NE directed extension (Montone et al, ) reaching regional rates of 1–2.5 mm/year (D'Agostino et al, , ; Devoti et al, ).…”