A COMPARISON OF LATE QUATERNARY C4 PLANT PRODUCTIVITY USING BURIED SOIL DATA FROM THE GREAT PLAINS, USA: IMPLICATIONS FOR ARCHAEOLOGICAL RESEARCH

Stable carbon isotope data are presented from late Quaternary soil and sediment archives of tributaries of the South Fork of the Double Mountain Fork of the Brazos River in northwest Texas, USA. The study area falls within the Caprock Canyonlands, an ecological and physiographic boundary between the Southern High Plains to the west and the Central Lowlands to the east. In stark contrast to the flat, featureless Southern High Plains surface, the canyonlands contain abundant springs, lithic resources, shelter, and plant and animal food sources that attracted hunter-gatherer groups. A series of laterally inset alluvial and palustrine fills span ca. 22,000-3000 ¹⁴C yr B.P., and buried soils in lacustrine and co-alluvial deposits range from ca. 10,300-8900 ¹⁴C yr B.P. Stable carbon isotopes, along with phytoliths and diatoms, from these soils and sediments indicate that a cool/moist environment was prevalent at the Pleistocene-Holocene transition, followed by a slight increase in aridity with seasonal wetting and drying. Late Holocene buried soils in alluvial fills along the South Fork reveal that a mixed C₃/C₄ plant community persisted, with only slight increasing aridity over time. Overall, C₄ plant productivity increased since the Last Glacial Maximum, but a C₃ and mixed C₃/C₄ plant community persisted in Holocene microenvironments. These results are in contrast to previously published stable carbon isotope data for the surrounding regions of the Great Plains, USA. Through comparisons of δ¹³C values from short-grass prairie modern soils and buried soils from archaeological contexts in Texas, Oklahoma, Kansas, and North Dakota, the canyonlands offered a landscape with a more diverse plant community and more effective moisture. Because of the increased recognition of the importance of buried soils and soil science applications to the interpretation of archaeological landscapes, we are now in a position to use these growing data sets to develop models and test claims about hunter-gatherer adaptions. In particular, this study has implications for advancing our understanding of hunter-gather adaptations to microenvironments by testing the relationships between paleoenvironmental data from soils and sediments with archaeological and zooarchaeological data.