Composite structures resulting from negative inversion; an example from the Isle of Favignana (Egadi Islands)

Many structures produced under one given deformation regime, namely extensional, contractional or strike-slip, exhibit remarkable geometrical analogies when analysed at different scales. By contrast, field examples that illustrate the scale effects on structures resulting from superimposed deformations are rare. Yet, the change from contraction to extension, known in the literature as negative tectonic inversion, occurs often in the most thickened portions of the continental crust and lithosphere. The Apennine-Maghrebide fold-and-thrust belt of Sicily and adjacent minor islands shows many examples of post-orogenic extensional deformation. Composite structures, resulting from late normal faults that offset folds and thrusts, are observed at two different scales, from macroscopic to mesoscopic, in the Isle of Favignana, the major island of the Egadi group. The analogies recognised in the geometry of these composite structures may provide a key for the interpretation of the features of macroscopic structures, whose deep geometry is often poorly constrained. Moreover, comparison of normalised displacements accommodated by contractional and extensional faults of different scales indicates that self-similarity is not unique to structures produced under single tectonic regimes.