EARLY PLIOCENE PALEOSOLS OF THE BARINGO BASIN, KENYA

The Pliocene Epoch is a high priority for understanding climatic and geomorphic responses to rising CO₂ levels, yet the majority of paleoclimate records from this interval are from marine basins. Paleosols (fossil soils) preserve in situ archives of terrestrial paleoclimate, paleovegetation, and surface processes, and therefore offer invaluable insights into landscape responses to Earth System changes. This presentation will showcase macromorphologic, sedimentologic, and stratigraphic relationships for paleosols preserved in the Chemeron Formation of the Baringo Basin in central Kenya. A high-resolution geochronologic framework based on Ar-Ar ages of tuffs previously linked lacustrine-alluvial cycles within the stratigraphy to precession-dominated orbital control. This study focuses on the interval of approximately 5.0-4.1 Ma, during a globally warm interval but prior to the mid-Pliocene. Paleosols tend to be Vertisols formed in lowland marsh to alluvial plain settings on a mixture of fluvial to lacustrine parent materials. Poor drainage is indicated by the presence of hydromorphy, including redox mottling, FeMn nodules, and drab colors, though some profiles are more oxidized and contain pedogenic carbonate masses. Other paleosols in the stratigraphic interval include Entisols, Inceptisols, and possible Alfisols. Our continuing efforts include analyses of pedogenic carbonate formation temperatures from clumped isotopes (Δ₄₇), development of paleovegetation records from δ¹³C analyses on pedogenic carbonates and organic matter, and mass-balance analysis of major and minor elemental oxides to track silicate weathering.