Paleoclimatic interpretations of buried paleosols within the pre-Illinoian till sequence in northern Missouri, USA
Abstract Northern Missouri preserves shallow buried paleosols ranging in age from Early to Late Pleistocene that are developed in six pre-Illinoian tills beneath Illinoian (MIS 6) and Wisconsinan (MIS 4-2) loess. The morphology of these paleosols changes with age, reflecting a changing climate during the Pleistocene, and cosmogenic-nuclide burial dates of the respective sola provide age control on the timing of these changes. The depth to secondary calcium carbonate nodules within the weathering profiles increases with younger age, indicating a transition to moister conditions during the Pleistocene, and these nodules are absent entirely within the modern soils. After approximately 0.4 Ma, the sola became distinctly redder, even as the time available for pedogenesis became shorter, culminating in the bright red Sangamon Geosol (MIS 5). This trend is consistent with increasing interglacial temperatures and/or precipitation. Finally, erosion rates determined from cosmogenic-nuclide concentrations within the sola also increase systematically with younger age. This increase may be due to some combination of changing climate, more-frequent glaciations and the deposition of a thick cover of unconsolidated glacial sediment above the stable residuum-dominated preglacial landscape.