Structural trend line pattern and strain partitioning around the Gibraltar Arc accretionary wedge: Insights as to the mode of orogenic arc building

Mediterranean tectonics results in tight orogenic arcs enclosing back-arc basins of oceanic or thinned continental lithosphere. The Gibraltar Arc cannot be explained solely by the Europe-Africa plate convergence; therefore complementary mechanisms have been proposed. Most of them imply a westward motion of the arc and a general transpressive regime on both branches (Betic and Rif chains). A structural revision made along the western Gibraltar Arc allows us to generate a detailed kynematic map and to introduce new constraints on the possible arc formation mechanisms. Our results suggest that the strain partitioned into two main types of structures: structures accommodating suborthogonal shortening (folds and thrusts) and structures accommodating arc-parallel stretching (normal faults, conjugate strike-slip faults, and distributed minor structures). On the basis of the fan pattern depicted by the slip direction of contractional structures and the homogeneous distribution of arc-parallel stretching, an arc formation mode close to the piedmont glacier type is suggested.Peer reviewe