Geology and Structural Evolution of the Region between the Upper Kelkit Basin and Munzur Mountains

The purpose of this study is to analyse the structural evolution of the region where the Eastern Pontides and the Eastern Taurides are closest to each other. The main tectonic units in the area, from north to south, are the Kelkit Paraautochthonous Unit, Çimendağ Nappe, Erzincan Nappe and Munzurdağ Limestone Unit. The pre-Jurassic basement of the tectonic units consists of heterogeneous rock units in different areas. Since the relationships between these units cannot be established in the study area, it is not possible to create a model for the pre-Jurassic period with the evidence from this locality. Therefore, the tectonics, tectono-stratigraphic and structural evolution of the study region were evaluated only for the Jurassic-Quaternary interval. The Jurassic-Early Cretaceous Kelkit Paraautochthonous Unit and Çimendağ Nappe represent the genesis of rifting and then deposition of platform-type carbonates in the Eastern Pontides. The Jurassic-Early Cretaceous Munzurdağ Limestone Unit represents the northernmost part of the Eastern Taurides and also has features of platform-type carbonates. During this period, a mid-oceanic ridge and ensimatic arc were active together along the North Anatolian Ophiolitic Belt. Therefore, it is possible to suggest a model representing passive continental margins to the north and south, with the mid-oceanic ridge in the north and the ensimatic arc in the south along the intervening oceanic environment in the Jurassic-Early Cretaceous periods. In the Late Cretaceous-Palaeocene, all evidence shows that the extensional regime completely converted to a compressional regime. In this time interval, an ensialic arc-forearc occurred along the Eastern Pontides and an ensimatic arc with subduction complex occurred along the North Anatolian Ophiolitic Belt. In the south, pelagic carbonates were deposited along the Munzur Mountains. It seems inevitable that the existence of two different north-dipping subduction zones should be accepted in this time interval. The Eocene and Oligo-Miocene units overlie older structural units with a polygenic conglomerate and angular unconformity. These units underwent intense deformation and the entire study area first became a shallow marine and then a terrestrial environment. Eocene volcanism indicates a post-collisional phase in the Eastern Pontides. The Pliocene-Quaternary rocks, reflecting continental deposits, unconformably overlie the older units, with an approximately horizontal layered structure. Considering this unconformity and the intense deformation before the Pliocene, it is possible that the North Anatolian Fault (NAF) developed during the Pliocene and had dextral movement with at least 25 km offset. In this context, the annual slip value for the fault may be 4.7 cm/year.