Paleo-environmental landscape evolution on the Eastern Caprock Escarpment of the Southern High Plains, Texas

Extensive geomorphologic research describing soils and depositional environments of late-Quaternary age was conducted to add to the existing archaeological database of the ecological boundary of the Southern High Plains (Llano Estacado) and Central Lowlands (Rolling Plains), defined by the Eastern Caprock Escarpment in West Texas. The escarpment provides a landscape record that illustrates local and regional climatic conditions, and relationships between environmental change and past human occupation. This research is a detailed exploration of soil stratigraphic units to characterize buried soils (mostly A-horizons) and reflects processes of soil formation, depositional environments, and relative and absolute soil-age relationships. The objectives were designed to build upon the knowledge of soil-landscape interactions and record accurate soil associations based upon topographic settings and the nature of the sediments through their chemical, physical, and isotopic characteristics. High rates of erosion and geological controls determine the preservation of soils and sediments along the South Fork of the Double Mountain Fork of the Brazos River (South Fork). Very near the headwaters of the South Fork River, the UU Ranch localities are composed of eroding slopes and terrace remnants of late Pleistocene/early Holocene sediments, preserved due to low gradients and vertical incision into the underlying geology. Moving downstream to the Macy Ranch localities, the South Fork River channel broadens with more lateral incision to become a more dynamic and erosive landscape. Soils and sediments are preserved in stream terraces of late Holocene age (~2000-1000 years) with several periods of landscape stability and soil formation. Soils and sediments of older ages are either truncated or deeply buried due to extensive erosion. Eolian sediments blanket the entire landscape and reveal conditions of increased eolian activity beginning ~1000 years ago. Comparisons of the findings are to be expanded to relate to other well-known local and regional environments.