USING OF GEOPHYSICAL TECHNIQUES TO DETERMINE BUILDING SYSTEMS AND MATERIALS PRESENT IN THE TUMULI OF THE FORMATIVE PERIOD IN THE AZAPA VALLEY, ARICA, CHILE

As a result of a joint research project between the Universidad Nacional Autonoma de Mexico and the Universidad de Tarapaca, Norte de Chile, a geophysical study, which included magnetic gradient and georadar techniques, was carried out for the first time in the Azapa Valley. This valley has been the origin of early human settlements linked to the Chinchorro tradition. Subsequently, in the last millennium BC, along with the initial development of agriculture, these populations built highly visible monuments, in which bodies and human remains were deposited, which were periodically removed for ceremonial purposes. Some previous archaeological excavations in the Az-80 archaeological site have revealed that most of the mounds were built using alternated layers of vegetation and sediments. The preservation of the organic materials in this environment of the Atacama Desert, one of the driest in the world, is remarkable. This has helped preserve the shape and size of the mounds and has allowed the use of geophysical techniques. From these techniques, we decided to use the gradiometer Geoscan FM36 and the georadar SIR 3000 from GSSI with 400 MHz antenna. Results of this first approach revealed that magnetic gradient detected the use of slightly magnetic stones in specific places during the building of the mounds. Most importantly, however, is that the radar reflections revealed previous building stages inside the mounds and in some cases what might be some burials and small funerary structures.