Late Eocene evolution of the Çiçekdağı 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 Çiçekdağı 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 ~ 10 m thick, are underlain by a few meters of conglomerate unit unconformably covering the CACC metamorphics. In the north, the limestones are underlain by a ~ 200 m thick sequence of volcanics and fine-grained clastics intercalating with shallow marine black shales. The upper Eocene sediments of the Çiçekdağı 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 Çankırı foreland basin as a result of ongoing collision between the CACC and the Pontides.

► The Çiçekdağı basin folded during the late stages of Kırşehir Block–Pontide collision. ► Magnetostratigraphy provides a late Eocene (~ 38–35 Ma) age for this folding. ► Foreland basin deposition and deformation moved southward from the Çankırı to the Çiçekdağı basin.