GEOARCHAEOLOGY AND THE BASKETMAKER COMMUNITIES PROJECT: PRELIMINARY RESULTS

Under investigation are four Basketmaker III (1250-1500 BP) sites in the Central Mesa Verde region of the Colorado Plateau (5MT10647, the Dillard site; 5MT10709; 5MT10736, the TJSmith site; and 5MT2032, the Switchback site). As these sites record occupation by sedentary farmers, geoarchaeological investigations focus on the soils’ development and tilth, but also include examination of local soil and rock as potential material resources. This work takes place under the auspices of the Basketmaker Communities Project (BCP), a multiyear effort focused on better understanding the Basketmaker III Period, as well as the organization and development of Early Pueblo communities.

We profiled and sampled at each archaeological site in both on- and off-site contexts. Soil profiling included classification of color, texture, horizonation, structure, root density, and precipitate accumulation. Though uniformly aridisols with Mesa Verde Loess parent material (originally deposited in the Late Pleistocene-Early Holocene), soils vary in degree of B-horizon formation. In most on-site locations, caliche is present within 1 m of the surface, while in most off-site locations it is not. Soils have a blocky structure and mineral accumulation appears to begin along aggregate surfaces in veins that thicken over time, forming a hardpan. We are currently analyzing soil samples for mineralogy, micromorphology, ion content, pH, and conductivity.

As pan accumulation limits agricultural productivity, the rate of pore closure and soil hardening is an important factor with implications for site choice and long-term soil use-life. Additionally in Basketmaker III and other prehistoric and modern Pueblo cultures, farmers do not practice irrigation, despite arid conditions. Paleoclimate, cultural practice, and pedogenesis are, therefore entwined within this geocultural record, the deciphering of which will aid in BCP archaeological interpretation. Additional soil testing in virgin piñon-juniper forest (a hypothesized paleoecology for the region) and in modern non-irrigation farming contexts serves to elucidate this record.