Meaning of the Küçuk Menderes graben in the tectonic framework of the central Menderes metamorphic core complex (western Turkey)

Abstract

Unusually steep, high-angle south-dipping normal faults, that separate the metamorphic rocks of the Menderes massif from the Neogene sedimentary deposits, occur in the northern Küçük Menderes graben in western Turkey. These faults probably reached their current position as a result of the special tectonic framework of the central Menderes metamorphic core complex. This area experienced further exhumation along with the rolling hinges of faults limiting Alasehir and Büyük Menderes grabens, giving rise to a huge syncline in the region. This regional structure would be most likely responsible for the present position of the high-angle graben bounding normal faults that rotated along a horizontal axis. However, recent studies in the same area claim for the development of reverse faulting between the metamorphic basement and the Neogene sedimentary units, and present this observation as evidence for a supposed Miocene–Pliocene regional contractional regime in western Turkey. Even if these reverse faults or other post-Miocene contractional structures existed in the central Menderes massif, they would not afford evidence of regional contraction since its generation could be related to the contractional area that would have developed along the axial zone of the huge syncline in the central Menderes massif, in its turn resulting from a regional extensional process that took place during the further exhumation stage.