USING SOIL AND GEOMORPHOLOGY STUDIES TO UNDERSTAND PREHISTORIC LAND USE IN PETRIFIED FOREST NATIONAL PARK: IMPLICATIONS FOR LANDSCAPE HISTORY AND RESOURCE MANAGEMENT

The Petrified Forest National Park in northeastern Arizona contains extensive Quaternary-age sand sheets and dunes. While the Quaternary deposits have not been a major focus of previous studies, archaeologists have long recognized the importance of the eolian landscape for prehistoric agricultural groups. Archaeological sites dating from c. 200-1400 A.D. seem to be correlated with eolian landscape features, and archaeologists have hypothesized that the landscape was heavily used for dry-farmed dune agriculture.

This paper uses soil geomorphology, soil chemistry, Optically Stimulated Luminescence (OSL) dating, and micromorphology to better understand the Quaternary landscape history. I document the relative quality of eolian soils for prehistoric agriculture, as well as the geologic conditions that made agriculture possible, and perhaps even productive, in a marginal landscape.

Results demonstrate high eolian activity in the late Holocene, as well as multiple, distinct periods of deposition throughout the Holocene. This chronology correlates regionally with other eolian landscapes. Soil geomorphic studies demonstrate high clay content and weak soil development, and suggest that clay in the dunes and sand sheets is due to inputs from local sources. It is hypothesized that the high clay content contributed to increased water holding capacity, improving sediment conditions for prehistoric agriculture. Soil chemistry has shown mixed results: some areas are only marginal for agriculture, with low soil productivity, but other areas may have been relatively more productive.

In addition to understanding prehistoric land use patterns, these results have implications for current resource management in the park, including managing a semi-stabilized eolian system in the face of future climate changes, as well as for understanding archaeological site preservation in the eolian landscape.