Stratigraphy of the metamorphic rocks of Nigde Massif and new evidence of Triassic rifting of the Inner Tauride Ocean (Central Anatolia, Turkiye)

Metamorphites of Nigde Massif, which form the basis of study area covering the Nigde vicinity in Central Anatolia, are composed of Late Devonian Gumusler, Carboniferous-early Permian Kaleboynu late Permian Kizildag formation and unconformable Triassic-Late Cretaceous cover units from bottom to the top, which are separated from each other with unconformities. The Triassic succession (Sogutludere formation) of phyllite-marble-schist alternations with common amphibolite levels is first distinguished in this study, unconformably overlies the Paleozoic succession. Thick homogeneous marbles of Jurassic-Cretaceous period, is defined by quartzite at the bottom representing the unconformity at the base, is defined as the Kirtepe formation. The succession probably ends with the Late Cretaceous metaflysch (Kirkpinar formation) constituting metaophiolite blocks with unconformable contact relationships. Amphibolite sample of the Sogutludere formation gives 239 Ma (Middle Triassic) age, which is interpreted as the crystallization age of the primary basic magmatism. The youngest detrital zircon ages (223-224 Ma) obtained from the metaclastics of the same formation shows that the primary deposition age of the formation is probably Late Triassic, which is consistent with this data. Geochemical data indicate an extensional environment of the alkaline composition and anorogenic originated basic volcanism developed on the continental crust. When these results evaluated together with the regional data, the metabasites of the Sogutludere formation can be interpreted as the first phase products of rifting, which commenced with the rifting process of the Tauride-Anatolide Platform in the Triassic period and resulted in the opening of the Inner Tauride Ocean and the break off the Kirsehir Block.