High-elevation western Anatolian topography delayed faunal migration during the Early Miocene

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Abstract
Anatolia has been a major thoroughfare for faunal migration, and its paleogeography impacted faunal dispersal among Africa, Europe, and Asia. Delays in faunal migration from Africa into and through Anatolia and differences in faunal populations between Europe and Anatolia are evident in the Early Miocene record despite the prior closure of seaways separating the continents. We suggest that high elevations in western Anatolia posed migration barriers, leading to the observed delays. To test this hypothesis, we calculated paleoelevations based on hydrogen isotopic ratios of 12 volcanic glass samples and oxygen isotopic ratios of 25 new and 117 published carbonate samples. We constrained new sample ages to 19–16 Ma based on detrital and volcanic zircon U-Pb geochronology. Volcanic glass samples yielded δDpaleowater values ranging from −113.7‰ to −67.5‰, and alluvial paleosol carbonates yielded δ18Opaleowater values ranging from −13.7‰ to −7.5‰. The δ18Opaleowater value (−4.7‰) from an Oligocene marginal marine paleosol sample is consistent with the δ18O values (−5.6‰ to −4.3‰) of precipitation from Global Network of Isotopes in Precipitation (GNIP) stations on the SW Anatolian coast and provides a low-elevation baseline for paleoelevation calculations. Application of a thermodynamic Rayleigh distillation lapse rate to the mean values of the most negative quartile of δ18Opaleowater (−9.6‰) and δDpaleowater values (−75.5‰) yielded 19–16 Ma paleoelevations for western Anatolia of 3.6 ± 0.5 km and 3.9 ± 0.5 km (1σ), respectively. We conclude that the Early Miocene topography in western Anatolia was ~2 km higher than the current topography, consistent with the hypothesis that high Early Miocene paleoelevations in western Anatolia hampered faunal dispersal.

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