Late Eocene evolution of the Çiçekdaǧi Basin (central Turkey): Syn-sedimentary compression during microcontinent-continent collision in central Anatolia

The Central Anatolian Crystalline Complex (CACC) exposes metasediment rocks overlain by Cretaceous ophiolites and intruded by granitoids. Following late Cretaceous exhumation of its high-grade metamorphic rocks, the CACC started to collide with the Central Pontides of southern Eurasia in the latest Cretaceous to Paleocene. Here, we present the sedimentary, stratigraphic and tectonic evolution of the Çiçekdaǧi Basin, located in the northwest of the CACC. Magnetostratigraphic dating, supported by ⁴⁰Ar/³⁹Ar geochronology, shows a late Eocene basin age. The basin fill unconformably overlies metamorphic basement in the south and ophiolites of the CACC in the north. It consists of red conglomerates, sandstones and siltstones, which overlie a sequence of nummulitic limestones. In the south, these limestones are ~10m thick, are underlain by a few meters of conglomerate unit unconformably covering the CACC metamorphics. In the north, the limestones are underlain by a ~200m thick sequence of volcanics and fine-grained clastics intercalating with shallow marine black shales. The upper Eocene sediments of the Çiçekdaǧi Basin were deformed into a syn-anticline pair. Progressive unconformities in the northern flank and a rapid and persistent ~180° switch in paleocurrent directions from southward to northward in the southern flank of the anticline demonstrate syn-sedimentary folding. We interpret the folding to result from a southward progression of the Çankiri foreland basin as a result of ongoing collision between the CACC and the Pontides.