Türkiye Jeoloji Bülteni

Geologic Evolution of the Anatolian Segment of the Tethyan Belt

Abstract: The geological constraints presented in this paper show that the northern strand of Neotethys isnon-existent and the existing suture is actually of the Tethys (Paleotethys). Geologic and published paleomagneticevidence has been integrated to the conclusion that this ocean has persisted for the entire Palaezoic and Mesozoic andhas been consumed through periodically recessing northward subduction between the Triassic and Lutetian in westernand central Anatolia.Western Pontides has been rotated dextrally during the Permo - Triassie, contributing to upwarp of the Triassicarc, initiation of rifting of the western Black Sea and obduction of marginal ophiolites onto the active margin. Theenigma for the coeval Pontian and Gondwanian Karakaya formations is briefly discussed with emphasis on regressivenature of Triassic - Early Liassic sedimentation in Pontides versus the continuous fining - upward Mesozoic sequencesof the passive margin.The Jurassic (Late Triassic - Early Liassic) granitoids of the Pontides are suggested to correspond to thefractionated residue of the basic volcanism of the Triassic arc. These granites have intruded the Karakaya formation andhave been transgressed by a carbonate - flysch wedge of the southward onlapping back - arc basin, the Black Sea, inliaison with oceanward shift of the respective compressive and dilatational systems of the fore-arc and back-arc basinsdue to a presumable recess of subduction. The deposition in the extensional basins has started in troughs of earliercolapse and the intervening areas have been subject to progressive submergence between Portlandian - Berriasian andthe uppermost Cretaceous.There has been an incipient collision during the Cretaceous with intense shearing of the fore-arc and thepremontories of the passive margins of the intermediate and Arabian plates. A HP/LT deformation deletes all pre -Cretaceous deformations along the 50 km. wide Tethyan suture. The Cretaceous shear zones repeat with widening,towards the north, deformation being resticted to planes of movement when sufficiently away from the suture, enablingobservation of juxtaposed Cimmerian and Cretaceous deformations.Ophiolites have been obducted onto the passive margins of both Tethys and Neotethys during the early stages ofthe collisional period, uplifted by imbricate thrusting on the passive margin, finally gliding in foredeeps(exogeosynclines) that have been forming due to rotational processes.The Neotethys has sutured along immediate north of Bitlis/Puturge massives by Late Lutetian. However, thecompletion of colage has lasted until the Late Miocene in between these massives. The role of transform faults foracquisition of the fit of continental masses has been emphasised. Numerous left-lateral transforms are still active,aiming to push Western Anatolia southwards, onto the oceanic crust in the Eastern Mediterranean, the part of theNeotethys which has not completed its obliteration.