Successful application of geophysics at the aganoa archaeological site, Island of Tutuila, American Samoa

GPR and magnetometry were used at a site on the SE shore of Tutuila in search of the deepest, relatively undisturbed occupation level. The general purpose of the archaeological research was to further elaborate the nature of Ancestral Polynesian Culture and to obtain datable materials representative of the oldest habitation of this island. This was also to serve as another data point toward determining the nature of Polynesian origins; whether it was an in situ cultural evolution from the earliest colonists, or possibly due to outside cultural influences much later, as some would now suggest. The several-hectare site occupies a re-entrant into the otherwise steep shoreline of the island. Magnetometry was used to attempt to locate buried basalt blocks (walls or tools) encased in nonmagnetic coral sands. GPR in the form of long, shore-perpendicular transects was able to show the accretionary history of this beach and ridge area. Surprisingly, it revealed that the earlier ridges were directly below the modern ridge, ie, progradation of this geomorphic feature had not occurred. Hence, exploration was re-directed to the modern topographic high (between modern houses of the village), and resulted in the GPR discovery of a 5m x 5m compacted floor at 1.5m depth, containing numerous and datable artifacts.