From paleoecology of crocodilians to paleoenvironments in the Shungura Formation (Plio-Pleistocene, Ethiopia), an interdisciplinary ballad using the oxygen stable isotopes

International audienceThe evolution of the Turkana Depression is geologically constrained by the East African Rift, but it is characterized by complex environmental, and more particularly hydrological, changes recently questioned by new sedimentological data. In the context of the Shungura Formation (Plio-Pleistocene, Ethiopia), these hydrographic changes are only documented by sedimentological studies and freshwater invertebrate assemblages, while terrestrial environments are by far more widely studied. However, aquatic environments retain information about water, an essential resource, and its interactions with climate, geodynamics and aquatic communities. The characterization of these humid areas, using freshwater organisms, is therefore essential to more accurately infer paleoenvironmental characteristics in this context. With an application in the Shungura Formation, we explore a new approach using the oxygen isotopic composition (δ18O) of fossil crocodilian teeth to describe environmental changes between 3 and 1 million years ago. This powerful geochemical tool is at the interface between the biology and geology, since it offers paleoecological information on crocodilians in their paleoenvironmental context. When most studies using δ18O to characterize paleoenvironments obscure paleoecological information (and vice versa), the integration of the two allows to go further and gain precision in paleoenvironmental interpretations. This contribution will present the results obtained on the crocodilians of the Shungura Formation from the article Gardin et al. (in prep) and will open the discussion on the interdisciplinary approach to the use of the δ18O to describe paleoenvironments.Gardin A., Pucéat E., Garcia G., Boisserie J.-R., Schuster M., Nutz A., Otero O. δ18O in crocodilian teeth apatite documents the diversity of aquatic environments and suggests their relative stability in the Turkana Depression between 3.0 and 2.6 Ma (Shungura Formation, Plio-Pleistocene, Ethiopia). In prep