EARLY PLIOCENE ENVIRONMENTS AT GONA, ETHIOPIA

The western margin area of the Gona Paleoanthropolgical Research Project in Afar, Ethiopia, is composed of both fluvial and lacustrine sediments, and contains abundant fossils, including those of Ardipithecus ramidus. We use the carbon and oxygen isotopic composition of paleosol carbonates, fossil teeth and aragonitic shell from these sediments to characterize early Pliocene (4.3-4.5 Ma) environments at Gona. δ¹³C values of paleosol carbonates and tooth enamel indicate environments with a mix of C₃ and C₄ vegetation wherein the majority of large mammals had C₄-dominated diets. δ¹⁸O values of paleosol carbonates, fossil teeth and aragonitic shell are too low to have formed under the present climate conditions at Gona and likely indicate more rainfall and different circulation patterns in the early Pliocene.