Geophysical Prospection of Yachay Archaeological Sites (Imbabura, Ecuador) to Improve Recovery of Ecuadorian Cultural Heritage

Abstract:

Ecuador has an extremely rich archeological history of pre-Hispanic cultures that still remains largely unexplored. This cultural heritage is under a constant threat due to illegal archeology and pressures of increasing population that needs new infrastructure and areas for farming etc. Yachay archeological sites surround the town of Urcuqui in Northwest Ecuador. This area has been settled in multiple periods of history resulting in an excessive concentration of archaeological remains: tolas (ceremonial burial mounds), tombs and ceramics. Geophysics is an extremely powerful tool for archeological prospection that can speed up the recovery by locating the suspected archeological targets for excavations. Here we present our comparative study of three non-invasive geophysical methods: GPR (Ground Penetrating Radar), ERT (Electrical Resistivity Tomography) and magnetometry combined with drone photography to test which methods are best suited for this particular archeological area dominated by volcanic ash. Three different test sites were chosen to cover the span of diverse archeological features, the first having both excavated and undetected tombs. There, resistivity models and GPR radargrams showed strikingly similar features in both shape and location, especially in the paleosol layer hosting the tombs, identified as potential graves. Magnetometry was not successful, likely due to the lack of buried metallic objects. The second site, a half-excavated tola with suspected burials gave inconclusive results. ERT indicates a homogeneous structure, whereas magnetometry detects internal features. Third target was unexcavated tolas. Large scale magnetometry showed that the tolas are magnetized in the direction of the existing Earth’s magnetic field with no internal structure. However, we also found two small size reversely magnetized anomalies requiring excavation. In conclusion, combining ERT and GPR is most promising for locating tombs, whereas magnetometry is more suitable for large scale search for rare buried metal objects in this area. This study confirms the effectiveness of geophysics in archeological prospection and highlights the potential of this little-explored archaeological area that can help strengthen the identity and cultural heritage of Ecuadorians.