THE PLEISTOCENE-HOLOCENE TRANSITION IN SOUTHEASTERN WASHINGTON: AN EXAMINATION OF SEDIMENT AND PALEOSOL ISOTOPE GEOCHEMISTRY FROM THE MARMES SITE (45FR50)

Recent studies have shown relationships between environmental trends and soil isotope geochemistry to be systematic. This paper focuses on the analysis and interpretation of stable isotope geochemistry from the latest Quaternary sediments at the Marmes archaeological site (45FR50), located at the confluence of the Palouse and Snake Rivers in southeastern Washington. Pollen is the most common late Quaternary climate proxy in the Columbia Plateau, but is mostly limited to the uplands. In the southern Columbia Plateau, a riverine human settlement pattern is assumed to have been established by 10,000 ¹⁴C BP, and thus reliable models of cultural evolution require local, lowland paleoenvironmental data. The Marmes Site contains a well-dated sedimentary sequence for which non-isotope biophysical properties have already been obtained. Here, analysis of d¹⁸O and d¹³C from organic matter and secondary carbonate rhizoliths is used to infer plant community composition, prehistoric climate, and changes therein. The construction of a stable isotope chronology at the Marmes Site provides the direct association between paleoecological data and archaeological materials necessary for the utilization and development of cultural evolutionary diet-breadth and optimal foraging models for the southern Columbia Plateau.