Earth and Planetary Science Letters 395 (2014) 101–115 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl Far-field contractional polarity changes in models and nature Ioan Munteanu a,∗ , Ernst Willingshofer a , Liviu Matenco a , Dimitrios Sokoutis a,b , Sierd Cloetingh a a Utrecht University, Department of Earth Sciences, Budapestlaan 4, 3584CD Utrecht, The Netherlands b Department of Geosciences, University of Oslo, PO Box 1047 Blindern, N-0316 Oslo, Norway article info abstract Article history: Received 21 January 2013 Received in revised form 18 January 2014 Accepted 17 March 2014 Available online xxxx Editor: C. Sotin Keywords: contractional polarity changes analogue modelling far-field deformation Black Sea back-arc New Guinea–New Britain fore-arc A change in contractional polarity occurs when the direction of tectonic transport switches along strike. This switch is conditioned by lateral variations in rheology or inherited asymmetries, such as contrasts in structure or changes in the polarity of subduction zones. The parameters controlling contractional polarity changes are less understood in situations when the strain is transferred at large distances from indenters. Analysing this type of strain transfer is critical for understanding the mechanics of thrusting in fore- or back-arc settings of orogenic areas. Comparison of crustal-scale analogue modelling with the inversion of the Black Sea back-arc and the formation of the New Guinea–New Britain fore-arc suggest that far- field changes in contractional polarity are related to rheological contrasts across inherited normal faults. The initial extension creates rheological weak zones that localize the subsequent far-field contractional deformation along groups of thrusts with opposite vergence along the strike of the system. The largest amount of far-field contractional deformation is recorded in the transfer zone located between the two indenters moving in opposite directions and is particularly high when inverting oblique extensional systems.  2014 Published by Elsevier B.V. 1. Introduction The inversion of extensional structures observed in rift-, fore- arc- or back-arc basins has been documented by numerous obser- vational studies that have demonstrated the key role of inherited strength variations in crust and/or lithosphere during deformation (e.g., Roure, 2008; Ziegler et al., 1998). The kinematics and struc- tural style of inversion is controlled by many parameters, such as the angle between the directions of extension and compression or the distance between the source of compression and the area of strain localization in weakness zones (Brun and Nalpas, 1996; Flottmann and James, 1997). In particular, lateral variations in rhe- ologies commonly inherited from previous extensional times ap- pear to play a critical role during the subsequent inversion (Aanyu and Koehn, 2011; Buiter et al., 2009; Ziegler and Cloetingh, 2004). These observations have been generally confirmed by other numer- ical modelling studies that have also underlined the critical role played by the increasing crustal strength during post-rift thermal relaxation (e.g., Beekman et al., 1996; Buiter et al., 2009; Cloetingh et al., 1995; Hansen and Nielsen, 2003; Mike, 1999). These results are in general agreement with analogue modelling studies (e.g., * Corresponding author. Tel.: +34915456322. E-mail address: ioan.munteanu@gmail.com (I. Munteanu). Aanyu and Koehn, 2011; Bonini et al., 2000; Dubois et al., 2002; Marques and Nogueira, 2008; Panien et al., 2006; Sokoutis and Willingshofer, 2011; Willingshofer and Sokoutis, 2009) that have suggested a number of additional parameters controlling the inver- sion of extensional structures, such as the presence of oblique to transversal basement ramps (e.g., Konstantinovskaya et al., 2007; Michon and Sokoutis, 2005; ter Borgh et al., 2011, and refer- ence therein) or syn-kinematic sedimentation (Pinto et al., 2010; Smit et al., 2010). The along-strike variability of the mechanics of inversion may also be the result of the contraction transmitted by two different indenters moving in the same direction, but with different velocities, such as in the case of Pamir–Hindu Kush defor- mation (Burtman, 2000; Mohadjer et al., 2010; Reiter et al., 2011; Smit et al., 2013). A change in contractional polarity occurs during inversion when the direction of tectonic transport switches along strike to an opposite one, the indenters (or backstops) deforming the former extensional basin from two sides. The most frequent type of con- tractional polarity change is observed in orogenic areas, when contraction during subduction and/or collision inverts the former passive continental margin and its buried continental rift. Such changes are observed in New Guinea–New Britain, Taiwan, New Zealand, Pyrenees, or the Alps–Dinarides system (Luth et al., 2010, 2013; Molli and Malavieille, 2011; Tregoning and Gorbatov, 2004; Reyners et al., 2002; Sibuet and Hsu, 2004; Sinclair et al., 2005; http://dx.doi.org/10.1016/j.epsl.2014.03.036 0012-821X/ 2014 Published by Elsevier B.V.