To move or not to move? Manganese oxide procurement during the Archaic period in the Atacama Desert

This paper investigates the possible sources of manganese (Mn) acquisition for the Chinchorro population of Arica, in northern Chile. To accomplish this, we analyse Mn distribution using digital geological map data and SEM/EDX and XRD analysis to chemically characterize twenty-five samples. Of these, eighteen were taken from geological sediments and seven from black pigments related to the Chinchorro mummification tradition (ca. 6950–2950 BP) from the archaeological sites of Maestranza 1, Morro 1, and Playa Miller 8. In contrast with previous highland Mn acquisition hypotheses, our results show that the lowland and coastal geological sediments near the Lluta river mouth have high Mn concentration, with a granular form that was easy to mine and process. The archaeological samples show that the Chinchorro used a high-grade Mn, without the need to use large mining tools (e.g. hafted hammers). This supports the proposition that there was a local (lowland and coastal) acquisition of good quality Mn, minimizing long-distance travel to the highlands for Mn procurement. The abundance of local finely-ground Mn sources can explain the cultural centrality of this pigment for several millennia during the Archaic period.