Terrestrial paleoclimate and paleoenvironments from the Pliocene: case studies from the Meade Basin, Kansas, USA and 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. This presentation showcases ongoing efforts to leverage paleosols from Pliocene deposits in North America and eastern Africa to develop quantitative estimates of mean annual precipitation (MAP), temperature (MAT) and paleovegetation (C₃ vs. C₄ biomass). We use a previously published random-forest recursive partitioning model (RF-MAP) that reconstructs MAP values using 10 major and minor elemental oxides from paleosol B horizons as input variables and is applicable on most soil types in most climate regimes. Our work in the Meade Basin of Kansas, USA, shows evidence of expanding and contracting wetlands during the Pliocene, with paleosols consisting of Vertisols to Aridisols depending on geomorphic position. Average paleoprecipitation totals appear to be near the semi-arid to subhumid boundary (~500 mm, similar to modern values) and remain steady across the Pliocene through early Pleistocene. Pliocene deposits of the Baringo Basin of central Kenya consists of orbitally-controlled lacustrine-alluvial cycles. Paleosols tend to be Vertisols in lowland marsh to alluvial plain settings, however localized Andisols and Inceptisols are also present. 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 application of the RF-MAP model on Baringo Basin paleosols.