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

Abstract

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.