Résumé
International audience
Understanding how environmental (geologic and climatic) dynamics shaped hominin dispersal before 1 Ma requires integrated reconstructions of the East African Rift’s evolving landscapes. In this study, we develop a time-continuous model of topographic and environmental change, accounting for tectonics, volcanism, mantle-driven dynamic topography, climate, vegetation and physiography. These reconstructions will then be used to constrain hominin dispersal and evolution using macro-ecological models.We present a new approach to reconstructing elevation changes through time by disentangling the contributions of dynamic topography (the deflections of the topography due to the vertical stresses imposed by the underlying mantle convection), isostatic adjustments (tectonic uplift and subsidence), and episodic volcanic activity that partially and episodically reshape the surface of the Earth. The dynamic component is obtained by comparing and electing the most appropriate model of global dynamic topography - albeit at a regional scale for this study. The isostatic component is reconstructed by a reasoned interpretation of the amplitude of tectono-volcanic events based on comprehensive compilations. These reconstructions form the foundation for an original regional elevation model that is continuous over time, and which will serve in our analysis of the climatic, physiographic and, more generally, environmental conditions likely impacting hominin dispersal across the region.Preliminary results highlight significant spatio-temporal variation in elevation and surface transformation, including phases of basaltic resurfacing, the formation of East African Rift shoulders and the Afar stratoid volcanic phase. Particular attention has been paid to the East African Rift System (EARS), in line with its central role in paleoanthropological research, although the study encompasses the entire African continent, with the aim of constraining and detecting the broader potential dynamics of hominin spatial occupation.References: [1] Prat, S., 2018. First hominin settlements out of Africa. Tempo and dispersal mode: Review and perspectives. Comptes Rendus Palevol. 17, 6–16. [2] Husson, L., Salles, T., Lebatard, A.- E., Zerathe, S., Braucher, R., Noerwidi, S., Aribowo, S., Mallard, C., Carcaillet, J., Natawidjaja, D.H., Bourlès, D., Aumaitre, G., Bourlès, D., Keddadouche, K., 2022. Javanese Homo erectus on the move in SE Asia circa 1.8 Ma. Scientific Reports. 12. [3] Faccenna, C., Glišović, P., Forte, A., Becker, T.W., Garzanti, E., Sembroni, A., Gvirtzman, Z., 2019. Role of dynamic topography in sustaining the Nile River over 30 million years. Nature Geoscience. 12, 1012–1017. [4] Rime, V., Foubert, A., Ruch, J., Kidane, T., 2023. Tectonostratigraphic evolution and significance of the Afar Depression. Earth- Science Reviews. 244, 104519. [5] Gibert, C., Vignoles, A., Contoux, C., Banks, W.E., Barboni, D., Boisserie, J.-R., Chavasseau, O., Fluteau, F., Guy, F., Noûs, C., Otero, O., Sepulchre, P., Souron, A., Ramstein, G., 2022. Climate-inferred distribution estimates of mid-to-late Pliocene hominins. Global and Planetary Change. 210, 103756