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Isotope geochemistry of lacustrine carbonate represents a powerful tool to reconstruct paleoclimatic and paleoenvironmental conditions. Here, we present a comprehensive set of long-term oxygen (delta O-18) and carbon (delta C-13) stable isotope records from 5 Chattian to Burdigalian lacustrine sequences distributed over the Central Anatolian Plateau. Field relationships combined with stable isotope geochemistry indicate a relatively humid subtropic Late Oligocene climate with an environment characterized by large, temporally open freshwater lakes. Approximately during the middle Aquitanian, a 4 parts per thousand-5 parts per thousand increase in lake delta O-18 values indicates changes in regional climate including more arid conditions and an increasing dominance of closed saline lake conditions in the central plateau region. This time period was also characterized by frequent climatic fluctuations such as short-lived humid periods, possibly recording the influence of seasonality, topography, and the waxing and waning of aridity. In general, relatively high Oligo-Miocene delta O-18 lake water values within the modern plateau interior, even for the least evaporative sequences, suggest the absence of significant orographic barriers at both the northern and southern plateau margins prior to 20-16 Ma.