Journal of Geodynamics 55 (2012) 1–17 Contents lists available at SciVerse ScienceDirect Journal of Geodynamics j ourna l ho me page: http://www.elsevier.com/locate/jog Restraining stepover deformation superimposed on a previous fold-and-thrust-belt: A case study from the Mt. Kumeta–Rocca Busambra ridges (western Sicily, Italy) Giovanni Barreca ∗ , Francesco Emanuele Maesano Department of Geological Science, University of Catania, Corso Italia 57, 95129 Catania, Italy a r t i c l e i n f o Article history: Received 24 May 2011 Received in revised form 25 October 2011 Accepted 25 October 2011 Available online 3 November 2011 Keywords: Sicilian Apennines Western Sicily Strike-slip tectonics Meso-structural analysis Pop-up Restraining stepover a b s t r a c t The western segment of the Sicilian Apennines (southern Italy) is affected by poly phase deformation characterized by non-coaxial structural associations. In particular, this study is focused on two nar- row ∼E–W oriented structural and topographic culminations of the fold and thrust belt (Mt. Kumeta and Rocca Busambra ridges), resulting from the exhumation of a deep-seated tectonic unit. A detailed field mapping and meso-structural analysis reveals that since Pliocene time the region was tectonically controlled by the propagation of two major NW–SE oriented right-lateral shear zones and associated structures that often propagated along inherited discontinuities. In particular, the left-stepping geome- try and the sense of motion of these regional strike-slip fault systems produced in the overlapping area a wide rhomboidal-shaped contractional region characterized by the occurrence of double-verging ∼E–W striking compressive structures. These bound the Mt. Kumeta and Rocca Busambra carbonate ridges, forming a pair of pop-up structures which link the coeval transcurrent boundary faults. Field data show that contractional structures are affected by significant bending along strike that increases close to the major shear zones. Structural rotations around the vertical axis allowed the carbonate ridges to develop a typical sigmoidal shape. The topographic expression and the internal structural architecture, compared with experimental models describing deformations associated with segmented strike-slip faults, suggest that the analyzed segment of Sicilian fold and thrust belt can be interpreted as a restraining stepover in which crustal shortening, exhumation and vertical axis rotation occurred. Moreover, field data, compared to the subsurface setting imaged by the analysis of available geophysical data (e.g. gravimetric maps and available/interpreted seismic profiles), reveal that, since Pliocene times, the restraining stepover deformation was transversally superimposed on a pre-existing NE–SW oriented thrust and fold system related to the Miocene Africa–Europe collision. © 2011 Elsevier Ltd. All rights reserved. 1. Introduction Restraining bends or stepovers occur along transform bound- aries or in intraplate, intracontinental strike-slip and transpres- sional settings (e.g. Barka and Kadinsky-Kade, 1988). They mostly develop, from the scale of major mountain ranges to sub-crop-scale examples, along bent strike-slip fault planes (restraining bends) or in contractional sectors between overlapping en-echelon seg- ments (restraining stepovers). In both cases, the involved structures show complex kinematic relationships depending mostly on spa- tial arrangements and the rate of displacement of the bounding wrench faults (Cunningham and Mann, 2007). Contraction in the ∗ Corresponding author. Tel.: +39 095 7195739; fax: +39 095 7195712. E-mail addresses: g.barreca@unict.it (G. Barreca), framae80@gmail.com (F.E. Maesano). overlapping areas generally produces topographic highs related to crustal shortening, uplift and exhumation (Segall and Pollard, 1980; Mann and Gordon, 1996; McClay and Bonora, 2001). Push-up or palm-tree structures usually develop (Harland, 1971; Sanderson and Marchini, 1984; Naylor et al., 1986; Woodcock and Schubert, 1994; Wilcox et al., 1973; Sylvester and Smith, 1976; Harding, 1974; Sylvester, 1988) and consist of a series of anastomos- ing convex-upward reverse faults which steepen progressively at depth. In addition, three-dimensional strain in overstepping strike-slip settings typically involves vertical-axis rotations (e.g. Jackson and Molnar, 1990). Accordingly, orogenic systems affected by wrench tectonics can provide suitable field examples for understanding the deformation mechanisms associated with the development of segmented strike-slip faults. As documented by abundant literature, the Sicilian Chain in southern Italy (Fig. 1) experienced a long tectonic history which produced multi-deformed rocks. In particular, many investigators 0264-3707/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jog.2011.10.007