Palaeoclimatic and palaeoenvironmental interpretations of the Late Oligocene, Late Miocene–Early Pliocene in the Çankırı-Çorum Basin

Abstract

Palaeoclimatic and palaeoenvironmental interpretations are reconstructed from the sedimentary sequences of the Late Oligocene and Miocene–Pliocene boundary in the Çankırı-Çorum Basin based on evidence obtained from palynofloras and ostracod and mammal faunas. Information on the main role of mixed mesophytic and broad-leaved evergreen forests was obtained from the Late Oligocene data from the Güvendik Formation. The pollen records of the formation showed a greater proportion of the hygrophytic forest communities. Thermophilic taxa and the taxonomic diversity of these forest communities developed mainly under dry subtropical climate conditions.Palynofloras and ostracods of the Latest Miocene and Earliest Pliocene were determined from coal bearing sediments of the Akaşdağı Formation in Central Turkey. The Latest Miocene palynoflora was represented by low diversity and abundance of spores and pollen, and it was characterized by mainly grassland species. The Earliest Pliocene palynoflora differs from that of the Latest Miocene through the presence of abundant and diverse palynomorphs. This palaeovegetation diversification from the Latest Miocene to Earliest Pliocene can be related to changes in temperature and precipitation in the southern part of the Çankırı-Çorum Basin. The identified ostracods, palynomorphs indicative of brackish environments, and a high abundance of gypsum crystals observed from the lower part of the Akkaşdağı Formation suggest brackish conditions during the Latest Miocene. Palynological evidence and results using the Coexistence Approach indicate that climate evolution in Central Turkey during this period can be referred to ongoing tectonic activity in this area and global climate change during the Neogene.