New discoveries in the Piramide Naranjada in Cahuachi (Peru) using satellite, Ground Probing Radar and magnetic investigations

摘要

The detection of buried earthen structures by using remote sensing techniques is still an open issue and a strategic challenge as crucial as it is complex. It is crucial because earthen archaeological remains are widely present thoughtout the world (in South America, Asia, Africa) and it is complex due to the subtle physical contrast between earthen remains and the surrounding subsoil. This paper presents the results from investigations based on Very High Resolution (VHR) satellite imagery (2002, 2005, 2008), geomagnetic surveys (November 2008) and Ground Probing Radar (GPR) (April 2008), we conducted on a mound named Piramide Naranjada. It is located in Cahuachi (Nasca, Southern Peru), the largest adobe Ceremonial Centre in the World. The studies were performed on two sides of this pyramid: (i) North-Eastern side, not yet excavated, using satellite data and magnetic prospection; (ii) and Eastern side using GPR to support the ongoing excavation activity. In the North-eastern side, results from the analysis of satellite images allowed the identification of shallow and outcropping adobe (earthen material) walls related to terraced platforms which compose the trunk-pyramidal structure of the Piramide Naranjada. These archaeological features were further investigated by high resolution geomagnetic surveys. The gradiometric maps enabled the identification of magnetic anomalies with different shapes: (i) linear shape features linked to buried, shallow and outcropping walls (the latter two already detected from the optical dataset); (ii) and circular shape anomalies linked to tombs and ceremonial offerings. In the Eastern side, where the excavations are in progress, radargrams allowed the discovery of a rich ceremonial offering made up mainly of ceramics, textiles, and painted pumpkins.