Late Palaeozoic extensional volcanism along the northern margin of Gondwana in southern Turkey: implications for Palaeotethyan development

Alastair H F Robertson,Osman Parlak,Timur Ustaömer

doi:10.1007/s00531-021-02051-7

Abstract

The Late Palaeozoic–Early Mesozoic Tethyan development of the Eastern Mediterranean region remains debatable, especially in Turkey, where alternative northward and southward subduction hypotheses are proposed. Relevant to this debate, new whole-rock geochemical data are provided here for early Carboniferous (Late Tournaisian-Late Visean; c. 340–350 Ma) tuffaceous sedimentary rocks within the Çataloturan thrust sheet (Aladağ nappe), eastern Taurides. The tuffs accumulated from evolved alkaline volcanism, variably mixed with terrigenous and radiolarian-rich sediments. In addition, Late Palaeozoic meta-volcanic rocks, c. 150 km farther NE, within the Binboğa (= Malatya) metamorphics (a low-grade high-pressure unit), are indicative of a within-plate setting. An impersistent geochemical subduction signature in these volcanics may represent an inherited, rather than contemporaneous, subduction influence, mainly because of the absence of a continental margin arc or of arc-derived tuff. Both the Binboğa metamorphics and the Çataloturan thrust sheet (Aladağ nappe) restore generally to the north of the relatively autochthonous Tauride carbonate platform (Geyik Dağ), within the carbonate platform bordering north-Gondwana. The Çataloturan thrust sheet is interpreted, specifically, as a c. E–W, deep-water, volcanically active rift that progressively infilled. Regional geological evidence suggests that melange units (Konya Complex, Afyon zone), Teke Dere unit, Lycian nappes), and Chios–Karaburun melange, E Aegean) accreted to the north-Gondwana continental margin during the late Carboniferous; this was coupled with localised calc-alkaline granitic magmatism (Afyon zone of Anatolide crustal block). We propose an interpretation in which Late Devonian–Carboniferous alkaline intra-plate volcanism relates to extension/rifting along the north-Gondwana margin. In contrast, the melange accretion and granitic magmatism could relate to short-lived late Carboniferous southward subduction that accompanied the diachronous closure of Palaeotethys.

Highlights

The geological development of the northern margin of Gondwana, in Turkey, during the Late Palaeozoic is critical to an understanding of the wider Tethyan region
Model 1 Palaeotethys existed since Early Palaeozoic (Fig. 1ai) and later, during Devonian-Carboniferous, subducted southwards beneath the northern margin of Gondwana (Fig. 1aii)
Late Carboniferous melanges and related units within the Anatolides (Konya Complex) and the Taurides (Lycian nappes), and in the Karaburun Peninsula (E Aegean) are interpreted as fragments of a regional subduction complex that accreted to the northern margin of Gondwana (Robertson and Ustaömer 2009a)

Summary

Introduction

The geological development of the northern margin of Gondwana, in Turkey, during the Late Palaeozoic is critical to an understanding of the wider Tethyan region. Model 1 Palaeotethys existed since Early Palaeozoic (Fig. 1ai) and later, during Devonian-Carboniferous, subducted southwards beneath the northern margin of Gondwana (Fig. 1aii) This process led to the construction of the Sakarya magmatic arc. The northward-moving Cimmerian continent collided with the southward-migrating Eurasian continental fore-arc fragment during the latest Triassic, closing Palaeotethys in Turkey This interpretation is based on the tectonic models of Stampfli et al (2001), Stampfli and Borel (2002), Eren et al (2004), Stampfli and Kozur (2006), Stampfli et al (2013), Moix et al (2008, 2013). Late Carboniferous melanges and related units within the Anatolides (Konya Complex) and the Taurides (Lycian nappes), and in the Karaburun Peninsula (E Aegean) are interpreted as fragments of a regional subduction complex that accreted to the northern margin of Gondwana (Robertson and Ustaömer 2009a). We use the IGC International Chronostratigraphic Chart (Cohen et al 2020)

Methods and materials

Findings

Conclusions