Deciphering the inorganic chemical record of ancient human activity using ICP-MS: a reconnaissance study of late Classic soil floors at Cancuén, Guatemala

Inorganic chemical analysis of soil floors using inductively coupled plasma-mass spectrometry (ICP-MS) was undertaken to provide information on the nature and location of past human activity in the ancient Maya city of Cancuén, Guatemala. The use of ICP-MS to detect trace and ultra-trace elemental enrichment of two excavated soil floors from the late Classic period is the first study of its kind in Mesoamerican archaeology. Geochemical background of the site was established by the analysis of palaeosols and nearby undisturbed ‘off-site’ soil profiles. Robust statistical methods used in the study clearly distinguished the level of anthropogenic enrichment across the former floors. Many elements measured showed only minor departures (10–20%) from the site's background soil chemistry. The greatest levels of elemental enrichment were detected in the rare earth elements, mercury, and gold. The latter is of particular interest considering the consensus that gold was absent from the world of the Classic-period Maya. Comparisons of the spatial pattern of mercury enrichment with lithic and archaeological data show strong linkages to past industrial and ritual activities. Elevated rare earth element concentrations were recorded broadly across both soil floors and are considered to be related to concentrated human occupation in antiquity.