Pollen, ostracod and stable isotope records of palaeoenvironment and climate: Upper Miocene and Pliocene of the Çankırı Basin (Central Anatolia, Turkey)

Abstract

An integrated stratigraphic study of Neogene lacustrine succession in the Çankırı Basin (Central Anatolia), combining pollen analysis, biostratigraphy and isotope analysis records variations in vegetation and depositional environment. The palynological analysis of the upper Miocene interval of the studied section reveals the existence of a coniferous forest. This flora reflects warm-temperate, humid climatic conditions. The pollen changes observed at the onset of the Pliocene are related to climatic changes. In the early Pliocene the vegetation changed to a mixed coniferous forest dominated by meso-microthermic trees (Cedrus and Cathaya) with a widespread herbaceous understory (Poaceae) sparcely interspersed with open areas occupied by Asteraceae whereas Abies and deciduous trees (Quercus, Carya, Juglans, Ulmus, Carpinus, Acer, etc.) are represented by lower percentages. This flora reflects a warm-temperate, relatively arid climate, reflecting the global warm climate of the Early Pliocene. The fluctuations in abundance of Tsuga may represent fluctuations in temperature. Climate analysis using the Coexistence Approach (CA) shows the presence of precipitation oscillations within the Pliocene. The identified ostracod assemblage indicates a dominance of fresh water conditions during the early late Miocene and of brackish water conditions during the late late Miocene while minor salinity oscillation is present throughout the section. The δ18Osulfate and 87Sr/86Sr isotopic ratios of non-marine gypsum are indistinguishable from the marine evaporites. This suggests recycling of older marine evaporites which is also supported by intense replacement of ostracods by gypsum.