Applying Geophysics and Geochemistry to Understand Middle Woodland Site Spatial Organization At the Northwood Site, Vigo County, Indiana

Abstract

The Northwood site (12Vi194) in northern Vigo County is attributed to the Late Middle Woodland culture known as Allison-LaMotte. Previous studies at other Allison-LaMotte sites are inconclusive regarding the village structure of this culture. While some studies identify a habitation zone surrounding a circular plaza, other Allison-LaMotte sites lack an observable spatial layout to the site. Magnetometry studies completed at the Northwood site in 2005 reveal a possible semi-circular community pattern with a central plaza. This study employed the 2005 magnetometer survey data, magnetic susceptibility, ground penetrating radar (GPR), and geochemical analyses to confirm the hypothesized site organization. Magnetic data from the magnetometer survey and magnetic susceptibility of artifact classes were compared to identify sources of magnetic anomalies. The map produced by magnetometry was compared with the GPR map to identify overlaps in possible pit features and the plaza zone. Excavating in locations identified as magnetic anomalies allowed for ground truthing survey results and collecting magnetic susceptibility measurements and soil samples for geochemical analysis. Geochemical analyses included detailed phosphorus geochemistry, total organic matter content, and organic carbon enhancement of soils collected from the site. Finally, determination of the source and strength of feature magnetic signals were analyzed using magnetic susceptibility and magnetometer data. These investigations provide better estimates of site spatial structure at the Northwood Site.