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

Metamorphites of Niğde Massif, which form the basis of study area covering the Niğde vicinityin Central Anatolia, are composed of Late Devonian Gümüşler, Carboniferous-early PermianKaleboynu late Permian Kızıldağ formation and unconformable Triassic-Late Cretaceous coverunits from bottom to the top, which are separated from each other with unconformities. The Triassicsuccession (Söğütlüdere formation) of phyllite-marble-schist alternations with common amphibolitelevels is first distinguished in this study, unconformably overlies the Paleozoic succession.Thick homogeneous marbles of Jurassic-Cretaceous period, is defined by quartzite at the bottomrepresenting the unconformity at the base, is defined as the Kırtepe formation. The successionprobably ends with the Late Cretaceous metaflysch (Kırkpınar formation) constituting metaophioliteblocks with unconformable contact relationships. Amphibolite sample of the Söğütlüdere formationgives 239 Ma (Middle Triassic) age, which is interpreted as the crystallization age of the primarybasic magmatism. The youngest detrital zircon ages (223-224 Ma) obtained from the metaclastics ofthe 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 thealkaline composition and anorogenic originated basic volcanism developed on the continental crust.When these results evaluated together with the regional data, the metabasites of the Söğütlüdereformation can be interpreted as the first phase products of rifting, which commenced with the riftingprocess of the Tauride-Anatolide Platform in the Triassic period and resulted in the opening of theInner Tauride Ocean and the break off the Kırşehir Block.