Cretaceous and Triassic subduction-accretion, high-pressure-low-temperature metamorphism, and continental growth in the Central Pontides, Turkey

Okay, A. I.
Tuysuz, O.
Satir, M.
Altıner, Sevinç
Altıner, Demir
Sherlock, S.
Eren, R. H.
Biostratigraphic, isotopic, and petrologic data from the Central Pontides document major southward growth of the Eurasian continental crust by subduction-accretion during the Cretaceous and Triassic Periods. A major part of the accreted material is represented by a crustal slice, 75 km long and up to 11 km thick, consisting of metabasite, metaophiolite, and mica schist that represent underplated Tethyan oceanic crustal and mantle rocks. They were metamorphosed at 490 degrees C and 17 kbar in mid-Cretaceous time (ca. 105 Ma). The syn-subduction exhumation occurred in a thrust sheet bounded by a greenschist facies shear zone with a normal sense of movement at the top and a thrust fault at the base. A flexural Foreland basin developed in front of the south-vergent high-pressure-low-temperature (HP-LT) metamorphic thrust sheet; the biostratigraphy of the foreland basin constrains the exhumation of the HP-LT rocks to the lbronian-Coniacian, similar to 20 m.y. after the HP-LT metamorphism, and similar to 25 m.y. before the terminal Paleocene continental collision. The Cretaceous subduction-accretion complex is tectonically overlain in the north by oceanic crustal rocks accreted to the southern margin of Eurasia during the latest Triassic-earliest Jurassic. The Triassic subduction-accretion complex is made up of metavolcanic rocks of ensimatic arc origin and has undergone a high pressure, greenschist facies metamorphism with growth of sodic amphibole. Most of the Central Pontides consists of accreted Phanerozoic oceanic crustal material, and hence is comparable to regions such as the Klamath Mountains in the northwestern United States or to the Altaids in Central Asia.


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The configuration and evolution of subduction zones in the Eastern Mediterranean region in Cretaceous time accommodating Africa-Europe convergence remain poorly quantitatively reconstructed, owing to a lack of kinematic constraints. A recent palaeomagnetic study suggested that the triangular Central Anatolian Crystalline Complex (CACC) consists of three blocks that once formed an similar to N-S elongated continental body, underthrusted below ophiolites in Late Cretaceous time. After extensional exhumation a...
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In northern Turkey, the Intra-Pontide suture zone represents one of the first-order tectonic structures located between the Istanbul-Zonguldak and the Sakarya continental terranes. It consists of an E-W-trending assemblage of deformed and variably metamorphosed tectonic units, including sedimentary rocks and ophiolites derived from a Neo-Tethyan oceanic basin, known as the Intra-Pontide oceanic basin. One of these units is represented by the Daday Unit that consists of a block-in-matrix assemblage derived f...
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Yılmaz, İsmail Ömer (2008-04-01)
The study areas located near the towns of Goynok, Muclurnu and Nallihan in the central northwestern part of Turkey lie on the 'Sakarya Continent', which is one of the tectonic entities of the Cretaceous geology of Turkey. Measured stratigraphic sections comprise the Aptian pelagic carbonates and the overlying Albian-Coniacian turbiditic sequences, which are all capped by a Late Santonian red pelagic succession. Lower and Upper Aptian, Upper Albian and Cenomanian/Turonian marine black shales recognized in th...
Cretaceous black shales (Oceanic Anoxic Events) in Turkey:collaboration of tectonics, sea level and oceanographic changes
Yılmaz, İsmail Ömer (null; 2017-08-26)
Cretaceous oceanic anoxic events are recorded as black shale deposits in Mid-Barremian, Aptian, Cenomanian/Turonian stages in different basins in Turkey. The Mid-Barremian black shales (MBE) have been recorded within a turbidite succession in a deep marine setting in central Sakarya zone of Pontides (YILMAZ et al., 2012). 2 ‰ shifts in the carbon isotope curve are recorded in parallel with European basins, but with low TOC values. The Aptian black shales (OAE1a) are recorded in pelagic carbonate slope envir...
Citation Formats
A. I. Okay et al., “Cretaceous and Triassic subduction-accretion, high-pressure-low-temperature metamorphism, and continental growth in the Central Pontides, Turkey,” GEOLOGICAL SOCIETY OF AMERICA BULLETIN, pp. 1247–1269, 2006, Accessed: 00, 2020. [Online]. Available: