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Structure, Geochronology and Tectonic Evolution of the Ulukisla Successor Basin, South-Central Turkey

Abstract

The E-W-trending Ulukisla basin occurs between the Central Anatolian Crystalline Complex (CACC) and the Tauride carbonate platform (TCP) in south-central Turkey, and represents a successor basin that developed during and after the closure of the Inner Tauride Ocean in the latest Mesozoic–Cenozoic. It contains 2 to 5 km-thick, uppermost Cretaceous to Miocene-Pliocene strata and early middle Eocene mafic volcanic and intrusive rocks. The Maastrichtian–lower Paleocene sedimentary rocks in the bottom of the basin strata rest unconformably on an ophiolitic basement (Alihoca ophiolite) and contain abundant ophiolitic material and clasts derived from TCP. The overlying lower Paleocene–lower Eocene Halkapinar Formation consists of < 2-km-thick sandstone, mudstone, limestone and volcanic–volcaniclastic rocks with turbiditic sandstone intercalations, and includes clasts of marble and blueschist rocks derived from the exhumed TCP. It is laterally and vertically gradational into the lower–middle Eocene Ulukisla Formation (up to 1400 meter in thickness), composed mainly of submarine volcanic–volcaniclastic rocks, which are intruded by monzonitic dikes and stocks. The Halkapinar–Ulukisla Formations are unconformably overlain by the middle–Upper Eocene conglomerate and a 1-km-thick turbiditic sandstone-shale sequence (Hasangazi Formation), which is transitional upwards into a ∼200-300-m-thick mudstone-gypsum series (Kabaktepe evaporates). The Oligocene–lower Miocene fluvial and lacustrine rocks (∼450-m-thick) of the Aktoprak Formation unconformably cover the shallow marine Hasangazi rocks, and are in turn covered by the Upper Miocene–Pliocene fluvial and lacustrine rocks. The Eocene turbiditic and volcanic rocks of the Halkapinar–Ulukisla Formations are crosscut by NW-SE-striking normal faults, suggesting NE-SW–oriented tectonic extension. The Eocene and younger units are all deformed by WNW- and ENE-oriented transpressional and NNE-striking transtensional fault systems. This mainly sinistral strike-slip faulting also affected the ophiolitic rocks and the TCP extensively, as evidenced by large-scale strike-slip displacement within and across the platform carbonates. U-Pb zircon dating of the intrusive rocks in the Ulukisla Basin strata and in the TCP has yielded early-middle Eocene ages (52–48 Ma). U-Pb detrital zircon dating of sandstones from the Ulukisla and Halkapinar Formations revealed Precambrian, Mississippian and 53–48 Ma ages. The Eocene extensional deformation and the coeval magmatism within the Ulukisla Basin resulted from post-ophiolite emplacement and collision–induced slab breakoff. The Ulukisla Basin initially developed as a post-collisional relict depocenter between the CACC and TCP in the latest Mesozoic-early Cenozoic, and then evolved into a terrestrial basin in the late Tertiary. The extensive sinistral strike-slip deformation in and across the Ulukisla Basin resulted from the regional scale escape tectonics, driven by the middle Miocene–Present collision of Arabia with Eurasia.