The Western Pontides of northern Turkey are a tectonic mosaic formed as a result of progressive welding of continental and oceanic fragments during the Palaeozoic and Mesozoic. In this region, three approximately east–west trending zones can be distinguished: the Pontide Zone representing the Pontides sensu stricto; the Sakarya Zone which is regarded as the southerly continental fragment; and the Armutlu–Ovacık Zone which is viewed as a tectonic mixture of the two zones.
The Pontide Zone records development of an ensimatic island arc which are emplaced upon a continental fragment of Laurasian origin prior to the development of the Ordovician sediments. On top of this amalgamated basement, association thick sediments were deposited during the Palaeozoic and Early Mesozoic. During the Dogger, Palaeotethyan ophiolites were obducted onto the Pontides. The thick pile of cover sediments and the ophiolite slab were exhumed along a detachment surface while the underlying rocks were elevated to form a metamorphic core complex during the Early Cretaceous. The metamorphic rocks are exposed along the Ballıdağ, Sünnice, Almacık and Armutlu mountain ranges. This east–west trending structural high separated two coeval basins, the Ulus Basin and the Boyalı Basin, which are located to the north and south respectively. During the Late Cretaceous, collision occurred between the Sakarya continent and the Pontide Zone. The continental convergence affected the region until the late Early Eocene. The present tectonic style of the region was established during this phase. From the Middle Eocene onwards only structural rearrangements have occurred. Copyright © 1999 John Wiley & Sons, Ltd.