Abstract

In the Spoleto and Valnerina areas (Umbria), the average trend of Miocene thrusts and strike-slip faults differs from that recognised elsewhere in the Northern Apennines, and is parallel to that of the Olevano-Antrodoco line. The faults have major strike azimuth changes. Structural relations between folds and faults suggest that strike variations are due to at least two mechanisms: 1) formation and linkage of en-echelon segments above a major basement reverse-dextral fault; 2) folding of thrust surfaces. The curved shape of the fault surfaces constrained the directions of transport of reactivated faults during the initial part of the subsequent Plio-Pleistocene extensional tectonic event. The transport directions of folded fault surfaces were top-to-northwest, i.e. parallel to the hinges of the antiformal fault surfaces.

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