Sinistral transport along the Trans-European Suture Zone: detrital zircon–rutile geochronology and sandstone petrography from the Carboniferous flysch of the Pontides

Abstract

The Lower Carboniferous flysch of the Istanbul Zone in Turkey is an over 1500 m thick turbiditic sandstone-shale sequence marking the onset of the Variscan deformation in the Pontides. It overlies Lower Carboniferous black cherts and is unconformably overlain by Lower Triassic continental sandstones and conglomerates. The petrography of the Carboniferous sandstones and the geochronology and geochemistry of the detrital zircons and rutiles were studied to establish the provenance of the clastic rocks. The sandstones are feldspathic to lithic greywackes and subgreywackes with approximately equal amounts of quartz, feldspar and lithic clasts. The amount of quartz and lithic fragments decreases upwards in the sequence at the expense of feldspar. The lithic fragments are dominated by intermediate volcanic rocks, followed by metamorphic and sedimentary rock fragments. Coarse lithic fragments are generally granitoidic. In the discrimination diagrams, sandstone samples lie mainly in the field of dissected arc. A total of 218 detrital zircons and 35 detrital rutiles from four sandstone samples were analysed with laser ablation ICP-MS. The detrital zircons show a predominantly bimodal age distribution with Late Devonian to Early Carboniferous (390 to 335 Ma) and Cambrian-Neoproterozoic (640 to 520 Ma) ages. The remaining 9 % of the analysed zircons are in the 1700-2750 Ma range; zircons of the 700-1700 Ma age range are absent. The REE patterns and Th/U ratios of the zircons are consistent with a magmatic origin. With one exception (Neoproterozoic), the rutile ages are Late Devonian-Early Carboniferous and their geochemistry indicates that they were derived from amphibolite-facies metamorphic rocks. Sandstone petrography and detrital zircon-rutile ages suggest one dominant source for the Lower Carboniferous sandstones: a Late Devonian to Early Carboniferous magmatic and metamorphic province with overprinted Neoproterozoic basement. Late Devonian-Early Carboniferous magmatic and metamorphic rocks are unknown from the Eastern Mediterranean region. They are, however, widespread in central Europe. The Istanbul Zone is commonly correlated with the Avalonian terrranes in central Europe, which collided with the Armorican terranes during Carboniferous times, resulting in the Variscan orogeny. The Carboniferous flysch of the Istanbul Zone must have been derived from a colliding Armorican terrane, as indicated by the absence of 700-1700 Ma zircons and by Late Devonian-Early Carboniferous magmatism, typical features of the Armorican terranes. This suggests that during Carboniferous times the Istanbul terrane was located close to the Bohemian Massif and has been translated by strike-slip along the Trans-European Suture Zone to its Cretaceous position north of the Black Sea.

Early Cretaceous sedimentation and orogeny on the active margin of Eurasia: Southern Central Pontides, Turkey

“…In contrast to the East European Craton, Neoproterozoic granitoids are widespread in the Gondwana‐derived terranes, including the Istanbul Zone, which has a basement dominated by late Neoproterozoic granitoids [590–560 Ma; Chen et al ., ; Ustaömer et al ., ; Bozkurt et al ., ]. Late Neoproterozoic clastic zircons (640–520 Ma) also form a dominant population in the Paleozoic sediments of the Istanbul Zone including the Carboniferous and Ordovician sandstones [Figure ; Okay et al ., ; Ustaömer et al ., ]. The sediments in the Lesser Caucasus are also characterized by predominantly late Neoproterozoic zircon populations [Figure ; Vincent et al ., ].…”

LA-ICP-MS U–Pb dating of detrital rutile and zircon from the Reynolds Range: A window into the Palaeoproterozoic tectonosedimentary evolution of the North Australian Craton

“…U-Pb age dating of detrital rutile is a new approach in provenance studies and has, until now, only been applied in Phanerozoic sediments (e.g. Okay et al, 2011;Meinhold et al, 2011;Bracciali et al, 2013;Rösel et al, 2014). This contribution is the first to describe a U-Pb age study of detrital rutile in Palaeoproterozoic sediments and highlights its potential for other weakly metamorphosed Palaeoproterozoic sedimentary sequences.…”

Petrostratigraphic evolution of the Thrace Basin (Bulgaria, Greece, Turkey) within the context of Eocene-Oligocene post-collisional evolution of the Vardar-İzmir-Ankara suture zone

“…(2) Located at the southwestern margin of the Black Sea, the İstanbul Zone is a continental fragment about 400 km long and 70 km wide. It comprises a Precambrian crystalline basement and a fairly complete Ordovician-Carboniferous sedimentary cover which was deformed during the Variscan orogeny (Görür et al, 1997;Okay, Zack, Okay, & Barth, 2011). Its stratigraphic, palaeobiogeographic, and palaeomagnetic characters show a marked Laurasian affinity.…”