Micropaleontological, strontium isotopic characteristics and environmental interpretation of the Ayrancı basin miocene sequence (Karaman/Turkey)

This research was carried out by investigating the ostracod fauna in the Ayrancı Basin (South Turkey) in order to examine the Ayrancı Basin in detail from a stratigraphic, strontium isotope, and micropalaeontological point of view. Five stratigraphic sections and three isotopic samples were collected from the Ayrancı Basin, and a generalised stratigraphic section of the basin within the Neogene system was produced. Among the ostracod species found in the Mazı Formation, which are reefal limestone belonging to the studied sequences, a Neomonoceratina helvetica-Aurila soummamensis Zone and Carinocythereis initial level, as well as Praeorbulina glomerosa curva-Orbulina suturalis, were defined; Orbulina universa planktonic foraminiferal zone was also revealed. The Mazı Formation is a Miocene unit deposited over the Burdigalian-Langhian-Serravallian age range. A 87Sr/86Sr ratio of 0.708399 was analysed in the carbonate sample obtained from the formation. The age of the Mazı Formation was calculated as 20.9 Ma. Divlek Formation contains abundant fossils, clayish limestone, and marl intercalations, and the Initial Cyprideis Level was defined within it as having a late Miocene age. The age of the formation is late Serravallian-Tortonian and the Divlek-Kıraman regions of the Divlek Formation are rich in ostracod fauna, although the genera and species identified are not well preserved. The Ayrancı Basin stratigraphy highlights the development of a young reef that started in a Burdigalian shallow marine environment, deepened and shallowed in the middle Miocene, and ended with intermittent lagoonal inputs in the Tortonian. The 87Sr/86Sr ratios analysed from two carbonate samples obtained from the Divlek Formation revealed values ranging from 0.708926-0.708951. The age of the Divlek Formation was calculated as 7.1-8.4 Ma based on these isotope data.