The role of the Early Tertiary Ulukısla Basin, southern Turkey, in suturing of the Mesozoic Tethys ocean
Robertson, Alastair H F
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The Maastrichtian–Late Eocene Ulukısla Basin is representative of the tectonic and sedimentary evolution of prominent Early Tertiary basins in central Anatolia, including the Tuzgolu and S arkısla basins. The Ulukısla Basin overlies an ophiolitic melange of Late Cretaceous age between the Bolkar Carbonate Platform to the south and the Nigde–Kırsehir 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 Ulukısla 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 Ulukısla Basin formed after Late Cretaceous ophiolite and melange emplacement and ended with Late Eocene emergence, deformation and onset of Oligo-Miocene non-marine deposition. We propose that Late Cretaceous ophiolite and melange 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 Ulukısla 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.