Date

2015-10-07

Author

Okay, Aral
Altıner, Demir
Sunal, Gursel
Aygul, Mesut
Akdogan, Remziye
Altıner, Sevinç
Simmons, Mike

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Before the Late Cretaceous opening of the Black Sea, the Central Pontides constituted part of the southern margin of Laurasia. Two features that distinguish the Central Pontides from the neighbouring Pontide regions are the presence of an extensive Lower Cretaceous submarine turbidite fan (the Cag.layan Formation) in the north, and a huge area of Jurassic-Cretaceous subduction-accretion complexes in the south. The Central Pontides comprise two terranes, the Istanbul Zone in the west and the Sakarya Zone in the east, which were amalgamated before the Late Jurassic (Kimmeridgian), most probably during the Triassic. The basement in the western Central Pontides (the Istanbul Zone) is made up of a Palaeozoic sedimentary sequence, which ends with Carboniferous coal measures and Permo-Triassic red beds. In the eastern Central Pontides, the basement consists of Permo-Carboniferous granites and an Upper Triassic forearc sequence of siliciclastic turbidites with tectonic slivers of pre-Jurassic ophiolite (the Kure Complex). The Kure Complex is intruded by Middle Jurassic granites and porphyries, which constitute the western termination of a major magmatic arc. Upper Jurassic-Lower Cretaceous shallow-marine limestones (the Inalti Formation) lie unconformably over both the Istanbul and Sakarya sequences in the Central Pontides. Two new measured stratigraphic sections from the I.nalti Formation constrain the age of the I.nalti Formation as Kimmeridgian-Berriasian. After a period of uplift and erosion during the Valanginian and Hauterivian, the I.nalti Formation is unconformably overlain by an over 2 km-thick sequence of Barremian-Aptian turbidites. Palaeocurrent measurements and detrital zircons indicate that the major part of the turbidites was derived from the East European Platform, implying that the Black Sea was not open before the Aptian. The Cag.layan turbidites pass northwards to a coeval carbonate-clastic shelf exposed along the present Black Sea coast. In the southern part of the Central Pontides, the Lower Cretaceous turbidites were deformed and metamorphosed in the Albian. Albian times also witnessed accretion of Tethyan oceanic crustal and mantle sequences to the southern margin of Laurasia, represented by Albian eclogites and blueschists in the Central Pontides. A new depositional cycle started in the Late Cretaceous with Coniacian-Santonian red pelagic limestones, which lie unconformably over the older units. The limestones pass up into thick sequences of Santonian-Campanian arc volcanic rocks. The volcanism ceased in the middle Campanian, and the interval between late Campanian and middle Eocene is represented by a thick sequence of siliciclastic and calciclastic turbidites in the northern part of the Central Pontides. Coeval sequences in the south are shallow marine and are separated by unconformities. The marine deposition in the Central Pontides ended in the Middle Eocene as a consequence of collision of the Pontides with the Kirsehir Massif.

Subject Keywords

Geology, Ocean Engineering, Water Science and Technology

URI

https://hdl.handle.net/11511/48959

Collections

Department of Geological Engineering, Conference / Seminar