Electrical and GPR joint prospecting at the Palo Blanco archaelogical site, NW Argentina. A Case History

MARTINO, LUIS; BONOMO, NÉSTOR; LASCANO, EUGENIA; OSELLA, ANA; RATTO, NORMA

GEOPHYSICS

SOC EXPLORATION GEOPHYSICISTS

Año: 2005 vol. 71 p. 193 - 199

0016-8033

We conducted a geophysical survey at the Palo Blanco archaeological site located in Catamarca, Argentina. Age estimates from radiaocarbon dating indicate first occupation of the site around 1500 years ago. The first description of the site was done in 1960. At that time, five residential units with different architectural arrangements were reported. These structures had different levels of deterioration due to exposure and human activities. Some of these original structures have become completely covered by sediments. To aid in the design of efficient excavation plans  detailed maps are required to locate the buried walls. For this purpose we conducted geophysical surveys over one of the structures. We only had poor documentation about the structure at the time of the survey, only one of the walls described in the earlier report was partially visible. We used two geophysical methods: ground penetrating radar (GPR) and electrical resistivity. We performed two-dimensional inversion of the resistivity data, together with numerical GPR simulations. These helped distinguishing the expected reflection events from others aiding a correct interpretation of the data. Finally we made a complementary interpretation of the resistivity and GPR data to compile a detailed map of the selected structure. We found that considering the two methods independently would have led to an incomplete map. We delineated a much more complex structure than that originally expected, and designed an excavation plan which was carried out. The layout of the rooms of the structure fully matched the predictions based on the interpretation in detecting the walls and their depths. In this way the geophysical forecasts were confirmed after excavation.