LATE PERMIAN UNCONFORMITY AROUND ANKARA AND NEW AGE DATA ON THE BASEMENT ROCKS, ANKARA, TURKEY

Abstract

At southwest of Gölbaşı (Ankara) there are two different sequences in tectonic contact. The one at the bottom with low-degree metamorphism is represented by phyllite, metabasite, crystallized limestone, schist and quartz porphyry veins. Above them are early Carboniferous-late Permian neritic and pelagic carbonates which are unconformably overlain by late Permian clastics and carbonates. Samples collected from neritic carbonates yielded early Carboniferous (Visian-Serpuhovian) to middle Carboniferous (Bashkirian- Moskovian) ages. These carbonates of shallow facies character are overlain by radiolarite- bearing pelagic deposits of middle Carboniferous-Permian age. Fossils from the upper most neritic carbonates gave Kubergandian-Murgabian age. This Permo-Carboniferous sequence is unconformably overlain by a sequence consisting of clastics and carbonates. Basal conglomerates and sandstones contain abundant quartz and fewer amounts of carbonated-cemented metamorphic rock fragments and they change to medium-thick bedded dolomitic limestone and limestones to the top. The age of these carbonates of shallow marine character is found Murgabian-Dorashamian. It is suggested that late Paleozoic carbonate basement was deposited in a neritic environment during early-middle Carboniferous, in a pelagic environment during middle Carboniferous-Permian and again in a neritic environment during Kubergandian-Murgabian. Following a deformation stage, it was accreted onto the Variscan basement at north and carbonate deposition took place as a result of late Permian transgression and finally some of exotic blocks within the upper Karakaya Complex were derived from this basement.