AN EARLY MONUMENTAL SITE AT LOS MORTEROS, PERU REVEALED BY GROUND-PENETRATING RADAR

Archaeological excavations in the 1970s at Los Morteros in the Salinas de Chao of northern coastal Peru identified a pre-ceramic-age site dating to ca. 4000 radiocarbon years BP., containing the remains of small, rock-walled structures, marine fauna, numerous groundstone mortars, and evidence of human burials. The archaeological material was found at the top of a large geomorphic feature, identified by the excavator as a sand dune, located on a raised marine shoreline, 4.7 km [2.81 mi] from the present day shoreline. At present, the landform is the largest, non-bedrock feature in the area. Smaller barchan dunes are common below the raised marine shoreline.

In July 2006, the University of Maine field party conducted a reconnaissance ground-penetrating radar survey of the landform in an effort to understand the formation processes associated with this anomalous feature. This work produced evidence of large, highly reflective material inconsistent with the fine-grained, aeolian deposits associated with sand dunes, and not related to an underlying bedrock feature. The placement and orientation of these reflectors is consistent with walls and stairs that are characteristic of other pre-ceramic monumental structures identified in coastal Peru. This work suggests that the Los Morteros site is located on the apex of a large, human-constructed mound, not a sand dune or bedrock-cored feature. Construction of the mound pre-dates the age of the archaeological material sampled from the mound surface, placing the building of this feature at the very beginning of monumental architecture in Peru.