NEW TRACE ELEMENT (SR, BA) DATA FOR PALEOECOLOGICAL RECONSTRUCTION AND EVALUATION OF ENAMEL DIAGESESIS FROM DIKIKA, ETHIOPIA

Isotopic ratios of carbon and oxygen from modern and fossil vertebrate tooth enamel have been used as a tool to reconstruct paleodiet, paleoecology, paleoenvioronment and paleoclimate. These data, however, do not uniquely distinguish the source of the diet and the trophic level of the animal. To this end, trace elemental ratio analysis of bioapatite (e.g., Sr/Ca and Ba/Ca) has been suggested as a source of information to differentiate dietary strategies and serve as a trophic level indicator within fossil food webs. The purpose of this research is to investigate the potential impact of diagenesis and to provide basis or a database to interpret paleoecology and trophic separation of early hominins, and other vertebrates in the Neogene of eastern Africa. We collected tooth enamel powder from Dikika, a Plio-Pliostocene paleontological site in Ethiopia. A total of 120 samples from seven mammalian families were analyzed for major, minor and trace elements using ICP-MS. Samples were pretreated to remove organic matter and secondary carbonates and digested by HF: HNO₃. Sr/Ca and Ba/Ca results indicate that mammals clearly discriminate differently against dietary strontium and barium, where grazers have a significantly higher Sr/Ca values than browsers (P<0.001). Carnivores and crocodiles have values intermediate between the two groups with wider range, which probably reflect a wide range of prey. The fact that trace element ratios reveal a similar distinction of the herbivores like δ¹³C_enamel into browser and grazer suggest that diagenesis has not obscured the relevant paleoecological signal. Moreover combining the trace element and isotopic analysis of tooth enamel would help to distinguish multiple aspects of paleodiet. Finally, in order to better interpret the fossil data and to determine whether diagenesis obscures paloecological information or not, analysis of modern tooth enamel is imperative.