Formation of the Late Palaeozoic–Early Mesozoic Karakaya Complex and related ophiolites in NW Turkey by Palaeotethyan subduction–accretion

Abstract

Several pre-Jurassic tectonic units in NW Turkey are crucial to the current debate regarding the timing and direction of subduction of Palaeotethys, a major ocean that separated Eurasia and Gondwana in Late Palaeozoic–Early Mesozoic times. The most critical unit is the Karakaya Complex, a deformed, low-grade assemblage of oceanic origin which comprises a NW-verging, SE-dipping stack of tectonostratigraphic units, here interpreted as a Palaeotethyan accretionary complex. The units display lithologies consistent with origins in seamount, trench, abyssal and rifted carbonate platform settings. Clastic basin sequences developed on top of the complex. Other relevant tectonostratigraphic units in the area include ultrabasic rocks of supra-subduction zone affinity, which tectonically overlie Permian carbonate platform units with intervening metamorphic soles and mélanges. Restored structural trends suggest the presence of a southward-dipping Palaeotethyan subduction zone bordering Gondwana-related units during the Late Permian–Triassic. This was probably additional to more important regional northward subduction along the southern margin of Eurasia from the Eastern Mediterranean to the Himalayas.

Triassic blueschists and eclogites from northwest Turkey: vestiges of the Paleo-Tethyan subduction

“…The Upper Triassic high-pressure metamorphic rocks in northwest Turkey constitute part of a much larger Triassic mafic magmatic complex, the Nilüfer unit, which has been variously interpreted as a former oceanic island (Pickett and Robertson, 1996), an oceanic plateau (Okay, 2000) or an ensimatic forearc sequence (Göncüoglu et al, 2000). These oceanic edifices were accreted during the latest Triassic to the active continental margin of Laurasia (Fig.…”

“…The metabasic rocks of the Nilüfer unit represent fine-grained mafic tuffs, pyroclastic rocks and pillow lavas. The geochemistry of the metabasic rocks and the mineral chemistry of the relict igneous pyroxenes suggest a within-plate tectonic setting (Pickett and Robertson, 1996). The marbles within the sequence have yielded Lower and Middle Triassic conodonts (Kaya and Mostler, 1992).…”

Late Cretaceous–Early Eocene tectonic development of the Tethyan suture zone in the Erzincan area, Eastern Pontides, Turkey

“…The oldest unmetamorphosed sedimentary unit in the area is a coherent Upper Carboniferous clastic succession ('molasse'), which crops out ∼ 50 km north of Erzincan in the Pulur region (Okay & Leven, 1996). The Upper Palaeozoic units are regionally overlain by a mélange known as the Karakaya Complex that is widely interpreted as a Triassic accretionary complex related to northward subduction of Palaeotethys (Pickett & Robertson, 1996, 2004Okay, 2000), although other interpretations exist (see Okay & Göncüoglu, 2004). All of the metamorphosed and deformed units are unconformably overlain by a Lower-Middle Jurassic succession that includes abundant volcanogenic rocks (e.g.…”

Tethyan oceans

“…(see Kozur 1997b) but they represent a Marianatype marginal ocean developing south of the Sakarya margin. During the Cimmerian collision event, the Late Permian-Early Triassic Karakaya-K0re back-arc ocean subducted southwards ($eng6r et al 1980;T0ysiiz 1990;Pickett & Robertson 1996) Afghanistan (Boulin 1988) and in the Pamirs (Khain 1994a, b;Leven 1995 For the opening and oceanization of the Meliata Rift, the main geodynamic factor used is the thermal subsidence, which affected the whole Austro-Alpine domain and other internal parts of the Alps since the Permian-Triassic boundary, implying a rifting phase just before that time (Fig. 7).…”