Buried in ashes: Site formation processes at Lapa do Santo rockshelter, east-central Brazil

Abstract

Few archaeological sites in the Americas contain high concentrations of human burials dating back to the early Holocene. The tropical karstic region of Lagoa Santa, in central Brazil (state of Minas Gerais) is one of the richest bioanthropological records available to study the behaviors and funerary practices of early Holocene South Americans, with more than 200 skeletons found so far. One of the key locations to examine the history of human settlement in Lagoa Santa is the site of Lapa do Santo, a rockshelter known to contain the oldest rock art and the earliest evidence of funerary complexity in the continent. In this geoarchaeological investigation we focus on the early Holocene settlement at Lapa do Santo (7.9–12.7 cal kyBP) applying high-resolution geoarchaeological techniques, such as micromorphology, organic petrology and μFTIR, on both archaeological, modern reference and experimental samples. This is the first time that a micro-contextual approach integrated with experimental geoarchaeology has been applied to study the formation of rockshelter deposits in a tropical setting. Our results show that the stratigraphic sequence formed under the dual influence of anthropogenic sedimentation—through continuous combustion activities—and geogenic sedimentation in the form of oxisol aggregates which fell from above the limestone cliff into the rockshelter. Intact hearths and remobilized combustion debris, possibly hearth rake-out, are close to the graves suggesting repeated burning activities as part of the ritual behavior of early Holocene South Americans. Large amounts of ash are intermixed with heated and unheated oxisol aggregates. Heated termite mound fragments were also found mixed within the sediments. Post-depositional alteration of the site includes limited bioturbation and localized, low energy surface water and sub-surface concentrations of moisture, leading to precipitation of dense, secondary carbonates. The age inversions can be attributed to the human action of reworking the ashy sediments and not to post-abandonment processes. Despite this, the overall preservation of the sediments is good and most human burials can be considered to be in primary context.