The role of the Early Tertiary Ulukisla Basin, southern Turkey, in suturing of the Mesozoic Tethys ocean

Abstract

The Maastrichtian–Late Eocene Ulukisla Basin is representative of the tectonic and sedimentary evolution of prominent Early Tertiary basins in central Anatolia, including the Tuzgölü and Şarkışla basins. The Ulukisla Basin overlies an ophiolitic mélange of Late Cretaceous age between the Bolkar Carbonate Platform to the south and the Nigde–Kırşehir metamorphic massif to the north. The basin stratigraphy records successive phases of transgression, subsidence, volcanism, evaporite deposition, deformation and uplift. Subsidence curves are consistent with an extensional (or transtensional) basin origin terminated by uplift. The Ulukisla Basin includes a thick succession ( c . 2 km) of Upper Paleocene–Lower Eocene basaltic to andesitic submarine pillow lavas, lava flows, volcaniclastic rocks and intercalated limestones. Whole-rock XRF chemical analysis indicates a within-plate origin, with a marked subduction influence, believed to be inherited rather than contemporaneous. The Ulukisla Basin formed after Late Cretaceous ophiolite and mélange emplacement and ended with Late Eocene emergence, deformation and onset of Oligo-Miocene non-marine deposition. We propose that Late Cretaceous ophiolite and mélange emplacement reflect initial ocean basin closure. This was followed by a long period ( c . 30 Ma) of microcontinental adjustment, including possible strike-slip, palaeorotation and suture tightening, during which the Early Tertiary Ulukisla Basin developed. Possible driving forces were regional slab pull (of a relict subduction zone) or oblique (diachronous) convergence. Suture tightening was complete by Late Eocene time marked by collisional deformation and regional uplift.