Five sites in the Palouse Loess of the Columbia Plateau, that each span the last 75,000 yr (the last glacial cycle through the current interglacial), will be mapped in exposures, described, and sampled. The sequence of sites will form a bioclimatic transect from about 200 mm to 700 mm precipitation, warm to cool temperature, and shrub-steppe to forest. Tephrochronology, soil stratigraphy, and thermoluminescence dating will provide chronological control and correlation among sites. The stable isotope geochemistry and abundances of opal phytoliths and the stable isotope geochemistry of soil-formed calcium carbonates will yield information about fluctuations in plant cover, plant community type, and temperature through time. Site stratigraphy and the micromorphology (soil microscopy), physical, and chemical properties of paleosols will yield interpretations of loess aggradation and erosion cycles, of soil development, and of relationships of changing vegetation and climate to soil-forming processes and landscape evolution. Measurement of magnetic susceptibility of paleosols and loess will serve as a critical test of the climate proxy model developed from Chinese loess. The sub projects above will be synthesized into a quantitative descriptive model of change in 5,000 to 10,000 year time slices through the last 75,000 yr. Two longer stratigraphic sections that date back to 175,000 yr B.P. then will be sampled and analyzed using the same techniques to reconstruct the record of the penultimate glacial-interglacial cycle Project goals are to provide direct information on changes in climate and vegetation, to quantify region-wide responses of the pedologic, sedimentologic, and hillslope-geomorphic systems to those changes, to further document a losess-based proxy record of activity of the Cordilleran Ice Sheet, and to test several climate proxy records.
