Geoarchaeology, Paleoenvironments, and Hunter-Gatherer Land-Use Intensification in the Caprock Canyonlands of Northwest Texas, USA

Abstract

The eastern Escarpment Breaks or “Caprock Canyonlands” are an ecological and physiographic boundary in northwest Texas, USA, between the Southern High Plains to the west and the Central Lowlands to the east. The canyonlands are defined by the steep Ogallala caprock escarpment, remnant mesas, and co-alluvial fans, and have experienced episodes of severe erosion during the late Quaternary. 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. This dissertation examines the relationship between late-Quaternary geomorphic processes, paleoenvironments, and hunter-gatherer land-use intensification in the canyonlands compared to adjacent regions. New pedologic, lithologic, radiocarbon, and multiple-proxy paleoenvironmental data (i.e. stable carbon isotopes, phytoliths, and diatoms) are presented from the soil and sediment archives from landforms of different ages. Results show that the canyonlands offered a landscape with a more diverse plant community and more effective moisture compared to western Texas, Oklahoma, and Kansas. Intensive erosion has mostly removed sedimentary deposits and cultural materials dating to the late Pleistocene and early Holocene, with the exception of co-alluvial fans. However, the eroding slopes near the edge of the caprock escarpment exposed a record of in situ Archaic to Protohistoric-aged materials at the surface, specifically fire-cracked rock (FCR) features (n=385). With prehistoric hunter-gatherer land-use intensification and population estimates tied to site discovery and numerical dating, it is critical to measure erosion bias and correct human population estimates based on potential sites lost. Thus, the impacts of intensive erosion on FCR-feature preservation were modeled using the Revised Universal Soil Loss Equation (RUSLE). A method for calculating prehistoric demographic changes is presented, where archaeological preservation bias is accounted for after determining the density of hearth features from landform surfaces of known ages. When we understand geomorphic processes, paleoenvironments, and the extent to which the archaeological record has been affected by erosion, we can make more substantiated conclusions about the archaeological patterns that inform us about human behavior.