4-8 Paleosols and interpreted landscapes associated with Pliocene hominins from Woranso-Mille, Ethiopia

Session: Recent Advances in Soil and Paleosol Science

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The Woranso-Mille paleontological research area in the Afar region of Ethiopia has yielded fossils of several species of Pliocene hominins (Australopithecus) closely related in space and time. Associated with these fossil localities are successions of paleosols that provide critical information about the landscapes that these early hominins inhabited. Within Woranso-Mille, nine primary pedotypes, interpreted as various Entisols, Inceptisols, and Vertisols, occurred in association with fluvial sandstones and floodplain pond deposits. The environments in which these paleosols formed included levee, proximal floodplain, clastic wetland, seasonal wetland, and distal floodplain. A general trend was found toward the occurrence of lower levels of pedogenic development and locally high moisture content in older paleosol successions with an increase in the occurrence of paleosols with high levels of development in the younger sections. This observation records a change in soil-forming processes and environments driven by shifts in parent material, sedimentation rate, landscape stability, soil moisture, and soil drainage likely associated with changes in fluvial style. Related to landscape changes, ichnofossils within the paleosols suggest a shift from predominantly patchy, early successional vegetation and early shrublands to more laterally expansive shrublands, wooded shrublands, and grasslands higher in the section. The paleosols early in the depositional history of Woranso-Mille suggest the occurrence of a mosaic of poorly developed soils with patchy, fast-growing weedy vegetation. Paleosols changed to reflect a more stable but still heterogenous landscape, characterized by expansive grasslands and shrublands growing on well-developed soils. Hominin fossils are found throughout this succession, highlighting these groups’ ability to occupy a variety of landscapes, and their diversity may be related to this heterogenous environment.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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