Through the support of the National Science Foundation, Dr. Lee Nordt and Mr. Steve Ahr at Baylor University will conduct the first systematic, regional-scale geoarcheological study to explore the age and origin of sandy-mantled uplands in Texas. This "sandy mantle" contains artifacts representing the last 10,000 years of human prehistory in North America, at depths of up to 4 meters, and in correct stratigraphic order. These sandy deposits rest on top of clay soil horizons that do not contain archeological remains. Often a point of strong disagreement between archeologists, geologists, and pedologists (soil scientists), the sandy mantle is a geoarcheological enigma, resulting in wholly disparate points of view as to its age, origin, and potential to contain preserved archeological sites. Two models explain how these sandy soils originated and how the archeological record became buried. The pedogenic model suggests the sharp boundary between the sandy mantle and clay horizons required thousands of years of soil weathering and downward movement of fine clay. The observed archeological stratigraphy is therefore a byproduct of artifacts shifting down through the soil profile over time, and such sites would exhibit minimal research value. In contrast, the geomorphic model suggests that the sandy mantle is a geologic unit that was deposited over the last 10,000 years, burying and preserving archeological sites soon after they were created. If correct, these archeological sites may be in their original depositional and cultural contexts and warrant investigation. Because archeological investigations are often mandated by various federal and state preservation policies, previous investigations have been limited to specific archeological sites. This problem has been compounded by a lack of regional-scale studies, and widely differing views from archeologists, geologists and pedologists.
This research will investigate five localities of similar topography, age, and soil parent material to assess whether the sandy soil horizons formed simultaneously with the underlying clay horizons, or if they were deposited some time later. Multiple analytical techniques will be used, including assessing parent material uniformity, identifying lithologic discontinuities, reconstructing gains and losses of mobile soil constituents, and optically stimulated luminescence dating.
The intellectual merit of this research is that it will represent a quantum leap toward unraveling the "sandy mantle mystery" and solving one of the most controversial aspects of geoarcheology within the Gulf Coastal Plain region of North America. Furthermore, this study will contribute significantly to understanding of the genesis of the sandy mantle and provide a much-needed context to evaluate buried archeological sites. Multiple analytical techniques applied to carefully selected soils promises to yield the most comprehensive understanding of this problem to date. Because legal protections and expenditure of public funds to investigate such sites is tied to their geologic integrity, this research may result in an overhaul of current archeological practice within the legal framework of cultural resources management.
The broader impacts of this project are that it will further dialogue between pedologists, geologists, and archeologists and will lead to significant new data regarding current models of sandy mantle formation. This research will facilitate graduate student training, and will result in conference presentations, a Ph.D. dissertation, and three peer-reviewed journal publications.