Triassic limestone, turbidites and serpentinite–the Cimmeride orogeny in the Central Pontides

Abstract

The basement of the Central Pontides, and by implication that of Crimea, consists of pre-Permian low-grade metaclastic rocks intruded by latest Permian – Early Carboniferous (305–290 Ma) granitoids. Further up in the stratigraphic sequence are Triassic limestones, which are now preserved as olistoliths in the deformed Upper Triassic turbidites. New conodont and foraminifera data indicate an Anisian to Carnian (Middle to Late Triassic) age for these hemi-pelagic Hallstatt-type limestones. The siliciclastic turbidites surrounding the Triassic limestone contain the Norian (Late Triassic) bivalve Monotis salinaria; the same species is also found in the Tauric series in Crimea. The Upper Triassic flysch in the Central Pontides is locally underlain by basaltic pillow lavas and includes kilometre-size tectonic slices of serpentinite. Both the flysch and the serpentinite are cut by an undeformed acidic intrusion with an Ar–Ar biotite age of 162 ± 4 Ma (Callovian–Oxfordian). This indicates that the serpentinite was emplaced into the turbidites before Middle Jurassic time, most probably during latest Triassic or Early Jurassic time, and that the deformation of the Triassic sequence pre-dates the Middle Jurassic. Regional geological data from the circum-Black Sea region, including widespread Upper Triassic flysch, Upper Triassic eclogites and blueschists of oceanic crustal affinity, and apparent absence of a ‘Cimmerian continent’ between the Cretaceous and Triassic accretionary complexes indicate that the latest Triassic Cimmeride orogeny was accretionary rather than collisional and is probably related to the collision and accretion of an oceanic plateau to the southern active margin of Laurasia.

Late Cretaceous infant intra-oceanic arc volcanism, the Central Pontides, Turkey: Petrogenetic and tectonic implications

“…The _ Istanbul Zone is represented by Neo-Proterozoic crystalline basement (Chen et al, 2002) and overlying Lower Ordovician to Devonian sedimentary sequences (Boztug, 1992;Dean et al, 2000). The Sakarya Zone consists of Permo-Carboniferous crystalline basement and Upper Triassic distal turbidites with dismembered ophiolitic rocks (Nzegge et al, 2006;Okay et al, 2015;Ustaömer and Robertson, 1993. Middle Jurassic granitoids and related LP/HT metamorphic rocks form part of a magmatic arc within the Sakarya Zone (Okay et al, 2014;Yılmaz and Boztug, 1986).…”

Petrology, Geochronology and Tectonic Setting of Early Triassic Alkaline Metagabbros From the Eastern Pontide Orogenic Belt (NE Turkey): Implications for the Geodynamic Evolution of Gondwana's Early Mesozoic Northern Margin

“…In the far south part of the orogenic belt, the same time span is represented by Alaskan‐type mafic‐ultramafic intrusions whose source is interpreted to be subcontinental lithospheric mantle that was metasomatized during the subduction of Paleotethyan oceanic lithosphere (Eyuboglu et al, ; Eyuboglu, Dudas, Santosh, Xiao, et al, ). Late Paleozoic granitoids are also widespread in the central and western Pontides, with ages clustered between 320 and 250 Ma (e.g., Gücer et al, ; Nzegge et al, ; Okay et al, ; Okay & Topuz, ; Şahin et al, ; Sunal et al, ).…”

Facies Associations and Microfossils From the Middle-Upper Triassic Limestones of the Transilvanian Nappes (Perșani Mountains, Eastern Carpathians, Romania)

“…6a-d). Meandrospira dinarica is known mainly form the Anisian deposits (Premoli Silva, 1971;Zaninetti et al, 1972;Bucur et al, 1994;Kobayashi, 2008;Okay et al, 2014;Lehrmann et al, 2015). The first occurrence of Endotriadella wirzi is at the Olenekian-Anisian boundary (Zaninetti, 1976;Dağer, 1980).…”