Transtensional deformations and oblique-slip fault propagation: an example from the Lucanian Apennine, southern Italy

Faults and fractures are the dominant modes by which the upper brittle crust accommodates deformation, and an extensive documentation of their geometrical and kinematic features is critical for a better understanding of how these structures enucleate and evolve through time. The map distribution and cross-sectional profile of macroscopic normal faults suggest that these structures enucleate as smaller isolated segments, and that individual segments are linked to produce larger faults as their tips propagate laterally and down-dip. By contrast, documentation of these relationships in outcrop-scale examples is relatively less abundant, and mesoscopic information on the modes of linkage of isolated fault segments is quite rare: yet, minor structures are often well exposed, thus allowing for a detailed determination of the processes responsible for their development. In this study we document a situation from the Potenza Basin (Southern Apennines, Italy) where a mesoscopic transtensional fault array grew by linkage of smaller isolated fault segments. Observations of the zones of fault segment overlap provide the basis for a kinematic deformation model of stepped ramp-flat fault surface development. Because of the need of investigating at the early stages of faulting, we restricted our analysis to very small structures, where the overprinting relationships among minor fabrics are particularly clear. The present investigation represents the methodological continuation of two earlier contributions and aims at comparing the results from fault analysis in the Potenza Basin with those recently obtained for the high Agri Valley.