Brittle‐ductile shear zones along inversion‐related frontal and oblique thrust ramps: Insights from the Central–Northern Apennines curved thrust system (Italy)

High‐strain deformation within the Earth’s crust often occurs in localized, narrow, and sub‐parallel wall‐sided zones known as shear‐zones, which accommodate differential movement during the deformation of the lithosphere. They may be related to any tectonic regime (compression, extension, or strike–slip), varying in width from microns/millimeters (grain‐scale) to kilometers (mega‐shears). The heterogeneous character of natural deformation in shear zones produces characteristic fault rocks as mylonites and cataclasites, developedunder deep‐seated (10–25km deep) ductile (viscous) or shallow‐crustal (0–15km deep) brittle–ductile (frictional–viscous) deformation regimes, respectively (e.g. Ramsay and Graham 1970; Sibson 1977, 1983; Ramsay 1980; Alsop and Holdsworth 2004). The analysis of brittle–ductile and ductile shear zones exhumed and/or extruded and exposed at the surface through a variety of approaches and across a range of scales is essential for unraveling deformation histories. Deciphering the kinematic significance of deformation fabrics within fault rocks and reconstructing the regional tectonics contribute profoundly to understand how localized crustal deformation occurs (e.g. Casas and Sàbat 1987; Alsop et al. 2004; Carosi et al. 2004; Iacopini et al. 2008; Mukherjee 2007, 2010a,b, 2011, 2013a, b, c, 2014a, b; Mukherjee and Koyi 2010a,b; Calamita et al. 2012a; Tesei et al. 2013). In this chapter the geometric and kinematic characteristics of shear deformation fabrics associated with frontal and oblique ramps belonging to curve‐shaped thrusts are described. A detailed mesoscale structural and kinematic analysis is presented by examining some remarkable examples of brittle–ductile thrust shear zones related to regional‐scale frontal and oblique thrust ramps in the Central–Northern Apennines of Italy.