Structural correlation of the southern Transcaucasus (Georgia)-eastern Pontides (Turkey)
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The eastern Pontides (northeastern Turkey) and Transcaucasus (Georgia) belong to the same geological belt representing an active margin of the Eurasian continent. According to palaeotectonic-palaeogeographic reconstructions, based on regional geological, palaeomagnetic, palaeobiogeographical and petrological data, the eastern Pontides and the major part of the Transcaucasus, situated to the north of the North Anatolian-Lesser Caucasian ophiolitic suture, comprise island arc, forearc, back and interarc basins. The eastern Pontide segment of the belt consists of three structural units which, from north to south, are the northern, central and southern units. The northern unit, the southeastern Black Sea coast-Adjara-Trialeti Unit, represents a juvenile back arc basin formed during the Late Cretaceous (pre-Maastrichtian). This unit separates the southern and northern Transcaucasus zones. The central Artvin-Bolnisi Unit is also known as the northern part of the southern Transcaucasus and is characterized by Hercynian basement, unconformably overlying the Upper Carboniferous-Lower Permian molasse and Upper Jurassic-Cretaceous arc association. The southern unit is the imbricated Bayburt-Karabakh Unit and is known as the southern part of the southern Transcaucasus. This unit has a similar basement to the Artvin-Bolnisi Unit and also includes a chaotic assemblage; it unconformably overlies the Upper Jurassic-Cretaceous forearc association. The eastern Pontide system is interpreted as the product of interference between a spreading ridge and subduction zone during Late Jurassic-Cretaceous times. The North Anatolian-Lesser Caucasus Suture, comprising ophiolites, melanges and an ensimatic arc association, separates the overlying system from the Anatolian-Iranian Platform in the south. Maastrichtian-Lower Eocene cover rocks in the region unconformably overlie all the other units. Middle Eocene rifting resulted in the formation of new basins, some of which closed during an Oligocene-Early Miocene regression. Others, such as the Black Sea and Caspian Basins, have survived to the present day as relict basins.