Climate change drove Late Miocene to Pliocene rise and fall of C 4 vegetation at the crossroads of Africa and Eurasia (Anatolia, Türkiye)

Abstract. Life on Earth has been capitalizing on the C3 photosynthetic pathway for 2.8 billion years. However, in the world’s grasslands that emerged since the Paleogene, C4 vegetation expanded dramatically between 8 and 3 Ma in response to climatic changes. Here we present the first comprehensive Late Miocene to Holocene δ13C soil carbonate record from the Eastern Mediterranean region (Anatolia) to reconstruct long-term geographic distributions of C3 and C4 plants, a region with patchy records compared to parts of Africa and Asia. Our results show a colonization of Anatolian floodplains by C4 biomass by 9.9 Ma, similar to regions in NW and E Africa, followed by a transition from this mixed C3-C4vegetation to C4 dominance between ca. 7.1 Ma and 4.9 Ma. The transition coincides with a similar shift from C3 to C4 vegetation in southern Asia and is generally attributed to the Late Miocene Cooling in response to decreasing atmospheric pCO2. However, the Anatolian paleoecosystem patterns are unique due to a rapid and permanent return to C3 dominance in the Early Pliocene, which is not observed elsewhere and occurs simultaneously with the disappearance of the open environment-adapted large mammal Pikermian chronofauna. We propose that this return to C3 vegetation was caused by paleoclimatic processes that regionally shifted precipitation from the warm to the cool season, resembling the modern Mediterranean climate. In conclusion, changes in rainfall seasonality under subhumid climate, rather than increased aridity, drove the demise of C4-dominated floodplains and the open-environment adapted Pikermian chronofauna at the Eurasian-African crossroads.