Contributors: Laboratoire de paléontologie, évolution, paléoécosystèmes, paléoprimatologie UMR 7262 (Palevoprim Poitiers ); Université de Poitiers = University of Poitiers (UP)-Centre National de la Recherche Scientifique (CNRS); Biogéosciences UMR 6282 (BGS); Université de Bourgogne (UB)-Centre National de la Recherche Scientifique (CNRS); Plateforme Ezop (Ezop); ToxAlim (ToxAlim); Université Toulouse III - Paul Sabatier (UT3); Université de Toulouse (UT)-Université de Toulouse (UT)-Ecole Nationale Vétérinaire de Toulouse (ENVT); Institut National Polytechnique (Toulouse) (Toulouse INP); Université de Toulouse (UT)-Université de Toulouse (UT)-Institut National Polytechnique (Toulouse) (Toulouse INP); Université de Toulouse (UT)-Ecole d'Ingénieurs de Purpan (INP - PURPAN); Université de Toulouse (UT)-Université de Toulouse (UT)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Toulouse III - Paul Sabatier (UT3); Université de Toulouse (UT)-Université de Toulouse (UT)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE); Institut International de Paléoprimatologie, Paléontologie Humaine : Evolution et Paléoenvironnement (IPHEP); GeoZentrum Nordbayern; Friedrich-Alexander Universität Erlangen-Nürnberg = University of Erlangen-Nuremberg (FAU); Institut Terre Environnement Strasbourg (ITES); École Nationale du Génie de l'Eau et de l'Environnement de Strasbourg (ENGEES)-Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS); Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement (CEREGE); Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE); Corresponding OGRE fieldwork seasons were funded notably by the UMR 7262 PALEVOPRIM (Centre National de la Recherche Scientifique and University of Poitiers), the French Ministry of Europe and Foreign Affairs, the CNRS (grant SEEG Shungura), the French National Agency for Research, and the Fyssen Foundation. This work forms part of the PhD thesis of Axelle Gardin, who received financial assistance from the UMR 7262 (PALEVOPRIM, Centre National de la Recherche Scientifique and University of Poitiers), the ASAP project (grant no. 210724, Nouvelle-Aquitaine region, France, PI: Olga Otero), and the French Ministry of Higher Education, Research and Innovation.
نبذة مختصرة : International audience ; This study adopts a new approach describing palaeohydrology and palaeoclimates based on the interpretation of stable oxygen isotopes (δ18Op) recorded in fossil crocodilian teeth. They represent an archive of prime interest for tracking freshwater palaeoenvironmental change, applicable to many palaeontological localities in the world: crocodilian teeth are abundant in continental basins and have been widely distributed since their diversification during the Mesozoic; the enamel phosphate is resistant to diagenesis and retains its original isotopic composition over geological timescales; and their δ18Op mainly relies on that of the crocodilian's home waterbody (δ18Ow), which in turn reflects waterbody types, regional climate, and evaporation conditions. This study presents the first application of this theoretical interpretative model to the Shungura Formation (Lower Omo Valley, Ethiopia), a key witness of the important environmental change in eastern Africa during the Plio-Pleistocene that impacted the evolution of regional faunas, including humans. In this complex and variable environmental context, the δ18Op of coexisting crocodilians allows for the fingerprinting of the diversity of aquatic environments they had access to at a local scale. This study sheds light on two important results: the δ18Op of crocodilian teeth (1) indicates stable aquatic environments in the northern Turkana Depression from 2.97 to ca. 2.57 Ma but a decline in local waterbodies diversity after 2.32 Ma, suggesting increasing aridity, and (2) shows, like previous geochemical studies on palaeosols and bivalves in the area, a significant increase in δ18Ow from 2.97 to ca. 1.14 Ma, likely due to the shifting air stream convergence zones between the West African and Indian Summer Monsoons and/or reduced rainfall over the Ethiopian Highlands.
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