Tectonic evolution and paleogeography of the Kırşehir Block and the Central Anatolian Ophiolites, Turkey

Abstract

In Central and Western Anatolia two continent-derived massifs simultaneously underthrusted an oceanic lithosphere in the Cretaceous and ended up with very contrasting metamorphic grades: high pressure, low temperature in the Tavşanlı zone and the low pressure, high temperature in the Kırşehir Block. To assess why, we reconstruct the Cretaceous paleogeography and plate configuration of Central Anatolia using structural, metamorphic, and geochronological constraints and Africa-Europe plate reconstructions. We review and provide new 40 Ar/ 39 Ar and U/Pb ages from Central Anatolian metamorphic and magmatic rocks and ophiolites and show new paleomagnetic data on the paleo-ridge orientation in a Central Anatolian Ophiolite. Intraoceanic subduction that formed within the Neotethys around 100-90 Ma along connected N-S and E-W striking segments was followed by overriding oceanic plate extension. Already during suprasubduction zone ocean spreading, continental subduction started. We show that the complex geology of central and southern Turkey can at first order be explained by a foreland-propagating thrusting of upper crustal nappes derived from a downgoing, dominantly continental lithosphere: the Kırşehir Block and Tavşanlı zone accreted around 85 Ma, the Afyon zone around 65 Ma, and Taurides accretion continued until after the middle Eocene. We find no argument for Late Cretaceous subduction initiation within a conceptual "Inner Tauride Ocean" between the Kırşehir Block and the Afyon zone as widely inferred. We propose that the major contrast in metamorphic grade between the Kırşehir Block and the Tavşanlı zone primarily results from a major contrast in subduction obliquity and the associated burial rates, higher temperature being reached upon higher subduction obliquity.

The discovery of a low-angle normal fault in the Taurus Mountains: the İvriz detachment and implications concerning the Cenozoic geology of southern Turkey*

“…There is no need for a subduction under the CACC to explain igneous activity as previous studies suggested (e.g., Lefebvre, 2011;van Hinsbergen et al, 2016). During the core complex formation, delamination of the lithosphere can create synand postexhumation magmatic activity (e.g.…”

“…40 Ar/ 39 Ar dating of 72.11 ± 1.46 Ma andesite has been reported in the basin fill of the AyhanBüyükkışla basin, which is related to the exhumation of the CACC's Hırkadağ massif (Advokaat et al, 2014;Lefebvre et al, 2015) (location 5 in Figure 1). Recent studies using paleomagnetic reconstructions suggest that the CACC experienced nearly E-W extensional exhumation above an eastward-dipping subduction during late Cretaceous times (Lefebvre, 2011;Lefebvre et al, 2013Lefebvre et al, , 2015Nairn et al, 2013;van Hinsbergen et al, 2016).…”

Kinematics of Late Cretaceous subduction initiation in the Neo‐Tethys Ocean reconstructed from ophiolites of Turkey, Cyprus, and Syria

“…The ophiolites analyzed in this study are distributed south of the İzmir‐Ankara suture zone and form the highest structural unit of a dominantly continental crust‐derived orogen known as the Anatolide‐Tauride belt [e.g., Şengör and Yilmaz , ; Okay , ; Okay and Whitney , ; Plunder et al , , , van Hinsbergen et al , ]. These ophiolites have a SSZ geochemical signature and crustal ages that are consistently clustered around 95–90 Ma (see reviews in, e.g., Robertson [], Moix et al [], and van Hinsbergen et al []). These ophiolites are underlain by thin and disrupted metamorphic soles with Ar/Ar cooling ages that are comparable to those of the ophiolitic crust [ van Hinsbergen et al , , ].…”

“…These ophiolites have a SSZ geochemical signature and crustal ages that are consistently clustered around 95–90 Ma (see reviews in, e.g., Robertson [], Moix et al [], and van Hinsbergen et al []). These ophiolites are underlain by thin and disrupted metamorphic soles with Ar/Ar cooling ages that are comparable to those of the ophiolitic crust [ van Hinsbergen et al , , ].…”

“…SSZ ophiolites are widespread in the eastern Mediterranean and Middle East region and form thousands of kilometers long ophiolitic belts running from Serbia to Greece and from Turkey to Oman. These ophiolites formed within the Neo‐Tethys Ocean, a vast oceanic domain with intervening microcontinents separating Gondwana and Eurasia continents [e.g., Şengör and Yilmaz , ], during two major subduction initiation events in the Middle Jurassic (~170 Ma [ Schmid et al , ; Robertson , ; Bortolotti et al , ; Maffione et al , , ]) and Late Cretaceous (~95–90 Ma [e.g., Searle and Cox , ; Robertson , , ; Çelik et al , ; Chan et al , ; Karaoğlan et al , ; van Hinsbergen et al , and references therein].…”