MAGNETIC EXPLORATION AND DATA PROCESSING AT THE MITCHELL SPRINGS RUINS IN CORTEZ, COLORADO

In recent years, subsurface imaging techniques utilizing magnetic gradient and ground penetrating radar geophysical methods have been used to help survey large areas with potential archaeological significance. During the spring of 2001, detailed magnetic gradient surveys were collected along with 2-D and 3-D ground penetrating radar data and 2-D resistivity images at the prehistoric Mitchell Springs Ruins in Cortez, Colorado. The project objective was to test the usefulness of non-invasive geophysical methods for mapping suspected Anasazi ruins prior to archaeological excavation.

Several contour maps and digital images were produced from the magnetic data. Noise reduction and data processing were accomplished using matrix smoothing and various filtering techniques of the grid data. Results provided valuable insight into the archaeological information located in the shallow subsurface, and in addition were valuable in guiding subsequent excavations during summer field schools.

Some of the geophysical data have been verified by archaeological teams exposing several two meter by two meter test pits. Field verification of certain geophysical anomalies identified a pueblo with connecting rooms, several deep storage pits, and three burials. Using multiple geophysical methods and careful data processing decreases the ambiguity of anomalies, and increases the possibility of locating subsurface archaeological features.