Evolution of sedimentary environments in an axial rift system: the Lower Omo Valley (Turkana Depression, Ethiopia) for the past four million years

The time interval between 4 Ma and 0.8 Ma is pivotal for the evolutionary history of hominids in eastern Africa, and particularly in the Turkana Depression (East African Rift System, Kenya / Ethiopia). It coincides with a number of major evolutionary events, including the evolution and disappearance of the genus Australopithecus, the appearance of the genus Homo, the first expansions to Eurasia, and many technological innovations, especially the Lomekwian, Oldowayan and Acheulean lithic industries. This period is also marked by pronounced environmental changes, relatively well constrained at the global scale using marine records, but still poorly documented on the continents. Indeed, little information exists on their impact on landscapes, whose configuration, dynamics, spatial expansion are inevitably intertwined with other factors at play at the regional and local scale.

In this contribution, we aim at reconstructing the evolution of sedimentary environments and landscapes in the Lower Omo Valley (Ethiopia) for the past four million years to provide a better understanding of the physical environments in which local biological and cultural evolutions took place. To do so, we investigated the evolution of sedimentary systems and landscape dynamics in the Lower Omo Valley combining a Landscape Evolution Model (Landlab) to constrain the input sediment flux with a stratigraphic forward model (DionisosFlow, Beicip-Franlab). To assess the consistency of model reconstructions, we compare model outputs to sedimentary architectures, volumes of eroded and deposited sediments and facies distribution derived from field observations and seismic data. Subsequently, we will present and discuss the roles of the different forcings, such as changes in precipitation and tectonic uplift, that drove the evolution of the sedimentary system.