Autochthonous Upper Permian (Midian) Carbonates in the Western Sakarya Composite Terrane, Geyve Area, Turkey: Preliminary Data

Permian limestones occur widely within the clastic units of the "Karakaya Complex" and are interpreted as allochthonous bodies or olistoliths. In the Kadirler area to the south of Geyve, however, Upper Permian (Midian) quartz sandstones and carbonates with a rich foraminifer fauna disconformably overlie a crystalline basement complex. This basement complex comprises metaclastic rocks, recrystallised limestones, metacherts, and metadiabases, and is intruded by granodiorites. The overlying basal conglomerates and quartzitic sandstones are dominated by pebbles from the basement complex and are followed upward by medium- to thick-bedded dolomites, dolomitic limestones and limestones. The foraminiferal assemblage with Neoschwagerina haydeni Dutkevitch and Khabakov, Neoschwagerina ex. gr. ventricosa Skinner, Charliella rossae Altıner and Özkan-Altıner, Hemigordiopsis renzi Reichel, Yabeina sp., Pseudokahlerina sp. and Kahlerina sp. in these carbonates is indicative of deposition in a shelf-lagoon during the Midian stage of the Late Permian. This new finding constitutes further support for models that suggest a composite character for the Sakarya Terrane, and that the "Karakaya basin" in NW Anatolia opened above a Variscan-consolidated crustal basement and its Permian platform, whence the limestone olistoliths of the "Karakaya Complex" were mainly derived. Moreover, the Midian transgression and the foraminiferal assemblage in the studied successions are typical features of the northern Tauride-Anatolide Platform, indicating that the Sakarya Composite Terrane was attached to the latter prior to the opening of the İzmir-Ankara branch of Neotethys.