Pliocene–Quaternary tectonic evolution of the Gulf of Gökova, southwest Turkey

Abstract

Evolution of the east–west-trending Gökova Graben structure is related to the north–south extension of the Aegean segment of the Aegean–Anatolian Microplate. The Pliocene–Quaternary successions surrounding the onland portion of the Gökova Graben as well as coeval successions within the marine portion of the graben are cut by at least three families of faults that strike northwest–southeast, east–west and east-northeast–west-southwest. These orientations are inconsistent with a simple north–south extensional regime. Interpretation of seismic reflection profiles, multibeam bathymetry and GPS vectors indicates that the Gökova Graben developed as a lazy-S-shaped graben in the back-arc setting north of the Hellenic Arc. A counterclockwise rotation of the Aegean segment of the Aegean–Anatolian Microplate is the suggested mechanism for this geometry, as subduction zone rolled back occurred during the Pliocene–Quaternary. The Gulf of Gökova is the youngest of a series of basins that developed within this large back-arc system, including the Nisyros, Karpathos, and Kamilonisi basins, collectively named to as the Gökova–Nisyros–Karpathos Graben. It is proposed that this graben experienced a scissor-like opening initiating from the west during the Pliocene and progressing eastward during the Quaternary. Faults that are seemingly un-correlated onland and in the marine areas become remarkably aligned when the Marmaris-Rhodes Block is progressively rotated by 6° counterclockwise relative to the Muğla Block using a pole position located within the Gulf of Gökova. The scissor-like opening of the westernmost regions of the Gökova Graben likely occurred during the late Pliocene, whereas the central and eastern portions of the graben developed during the early–middle Pleistocene and late Pleistocene–Holocene, respectively. The onset of the opening of the westernmost segment of the Gökova–Nisyros–Karpathos Graben occurred at a time earlier than the late Pliocene.