Complex evolution of the Erzincan Basin (eastern Turkey)

Abstract

Two new tectonic models are presented to explain the pull-apart opening of the Erzincan Basin. Our field studies indicated that the Erzincan Basin is not a typical rhombic pull-apart basin; instead it has a rather complex, single- or two-stage pull-apart opening mechanism. The basin was initially formed as a result of a 4 km wide releasing stepover and a 15° divergence angle between segments 1 and 2 of the North Anatolian Fault Zone (NAFZ) along which the westward tectonic escape of the Anatolian Block has been taking place. The single stage model refers to the partitioning of the transtensional deformation by coeval normal and strike-slip displacements on parallel-trending faults which remained since their initiation. The two-stage model infers that the basin opening was modified later by the formation of the left-lateral Ovacik Fault which caused fragmentation of the Anatolian Block. The two-stage pull-apart basin opening mechanism accounts for the observed geometry of the Erzincan Basin. The present day geometry of the basin indicates that there had been 35 ± 5 km of right-lateral displacement along the NAFZ and 5 ± 2 km of left-lateral displacement along the Ovacik Fault.