Sorgun-Yıldızeli basin is an east-west trending asymmetric marginal foreland (peripheral foreland basin) formed as a result of the consumption of oceanic crust of the northern branch of Neotethys due to the collision of Sakarya continent in the north and Kırşehir Block in the south. It provides much information about the geodynamic evolution of the region. The basement of the study area consists of Late Palaeozoic-Mesozoic Akdağmadeni Massif. Akdağmadeni Massif was intruded by CenomanianMaastrichtian granitoids and is overlain tectonically by Late Cretaceous Artova ophiolitic melange within the İzmir-Ankara-Erzincan suture zone and by Cenomanian-Maastrichtian Darmik Formation. The uppermost section of the sequence which consists of generally clastic and coarse clastics is named the Konacı member. When the sedimentation and volcanism continued in the basin, gabbroic intrusions occurred as sills and laccoliths cutting the Boğazköy Formation. These gabbroic rocks were named the Yaycılar Gabbro. The age of 51.0 ± 0.7 Ma was found for the Yaycılar Gabbro with the 40 Ar/ 39 Ar geochronologic method. As a result of slab breakoff, the relicts of the consumed oceanic crust and the released massif were uplifted rapidly and the units of Middle-Late Eocene Tokuş Formation were deposited transgressively on the Boğazköy Formation and on outcropping basement rocks in the basin which was controlled by an extensional tectonic regime. Upper Miocene-Pliocene (İncesu Formation), Pliocene and Quaternary terrestrial sediments were deposited unconformably on all older units.

Sorgun-Yıldızeli basin is an east-west trending asymmetric marginal foreland (peripheral foreland basin) formed as a result of the consumption of oceanic crust of the northern branch of Neotethys due to the collision of Sakarya continent in the north and Kırşehir Block in the south. It provides much information about the geodynamic evolution of the region. The basement of the study area consists of Late Palaeozoic-Mesozoic Akdağmadeni Massif. Akdağmadeni Massif was intruded by Cenomanian-Maastrichtian granitoids and is overlain tectonically by Late Cretaceous Artova ophiolitic melange within the İzmir-Ankara-Erzincan suture zone and by Cenomanian-Maastrichtian Darmik Formation. The volcano-sedimentary sequence deposited in Sorgun-Yıldızeli foreland basin developed on the relicts of the İzmir-Ankara-Erzincan Suture Zone along the northern margin of Kırşehir Block and was named the Boğazköy Formation. The pelitic, clastic and coarse clastic levels of Upper Palaeocene-Middle Eocene Boğazköy Formation including İzmir-Ankara-Erzincan Suture Zone slices and olistostromes are differentiated as the Dolak member. Toward the inner part of the basin, a turbiditic sequence of conglomerate, sandstone, claystone including rare limestone beds was deposited, consisting of conglomerate, sandstone, claystone, rarely limestone and alternations of three different volcanic rocks (acidic, basic and intermediate) related to subduction and/or collision. Calc-alkaline lava and pyroclastics of basaltic and basalt-andesite composition were differentiated as the Pazarcık volcanic member, with lava and pyroclastics of dacitic and rhyolitic composition called the Sarayözü volcanic member and calcalkaline lava and pyroclastics of andesitic, trachyandesitic and dacitic composition called Kiremitlik volcanic member in Sorgun-Yıldızeli basin. According to the 40 Ar/ 39 Ar geochronologic method, the ages of 57.2±2.0 Ma and 56.7±1.8 Ma were obtained for Pazarcık volcanics, 48.8±1.5 Ma for Sarayözü volcanics and 45.1±1.3 Ma and 47.3±0.6 Ma for Kiremitlik volcanics. The reefal limestones which are not thick and occur in higher parts of the Boğazköy Formation were called the Limestone member. The uppermost section of the sequence which consists of generally clastic and coarse clastics is named the Konacı member. When the sedimentation and volcanism continued in the basin, gabbroic intrusions occurred as sills and laccoliths cutting the Boğazköy Formation. These gabbroic rocks were named the Yaycılar Gabbro. The age of 51.0 ± 0.7 Ma was found for the Yaycılar Gabbro with the 40 Ar/ 39 Ar geochronologic method. As a result of slab breakoff, the relicts of the consumed oceanic crust and the released massif were uplifted rapidly and the units of Middle-Late Eocene Tokuş Formation were deposited transgressively on the Boğazköy Formation and on outcropping basement rocks in the basin which was controlled by an extensional tectonic regime. Upper Miocene-Pliocene (İncesu Formation), Pliocene and Quaternary terrestrial sediments were deposited unconformably on...

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Orta Anadolu’da Niğde dolaylarını kapsayan inceleme alanının temelini oluşturan Niğde Masifi’ne ait metamorfitler alttan üste doğru Geç Devoniyen yaşlı Gümüşler, Karbonifer-erken Permiyen yaşlı Kaleboynu, geç Permiyen yaşlı Kızıldağ formasyonu ile bunları uyumsuz olarak üzerleyen ve birbirlerinden uyumsuzluklarla ayrılan Orta Triyas-Geç Kretase topluluğundan yapılıdır. İlk kez bu çalışmada ayırtlanan, yaygın amfibolit düzeyli fillit-mermer-şist ardalanmalı Triyas istifi (Söğütlüdere formasyonu) Paleozoyik istifi uyumsuz olarak üzerlemektedir. Tabanda uyumsuzluğu tanımlayan kuvarsitle başlayan Jura-Kretase yaşlı kalın homojen mermerler Kırtepe formasyonu olarak tanımlanmıştır. İstif yine uyumsuz dokanak ilişkilerine sahip, metaofiyolit blokları içeren, olasılı Geç Kretase yaşlı metafiliş (Kırkpınar formasyonu) ile sonlanmaktadır. Söğütlüdere formasyonundaki amfibolit örneğinden ilksel bazik magmatizmanın kristalizasyon yaşı olarak yorumlanan 239 my (Orta Triyas) yaş elde edilmiştir. Aynı formasyona ait metakırıntılılardan elde edilen en genç detritik zirkon yaşları (223-224 my) bu veri ile uyumlu olacak şekilde formasyonun ilksel çökelim yaşının olasılıkla Geç Triyas olduğunu göstermektedir. Jeokimyasal veriler söz konusu alkali bileşimli ve anorojenik kökenli bazik volkanizmanın kıtasal kabuk üzerinde gelişen bir genleşme ortamını işaret etmektedir. Bölgesel verilerle birlikte değerlendirildiğinde Söğütlüdere formasyonuna ait metabazitler, Torid-Anatolid Platformu’nun Triyas döneminde parçalanması ile başlayıp İç Toros Okyanusu’nun açılması ve Kırşehir Bloku’nun koparılması ile sonuçlanan riftleşmenin ilk evre ürünleri olarak yorumlanabilir.