Multi-technique investigation of potshards of a cerrito (earthen mound) from southern Brazil

The physicochemical investigation of ceramics crafted and managed by ancient humans allows a better understanding of their social, technological, economical, routine and artistic activities. The Brazilian State of Rio Grande do Sul presents the biggest number of registered archaeological sites in the country, and many of them are earthen mounds, locally known as cerritos de indios. This kind of archaeological site is of utmost importance to understand the social development of the biome Pampa - including areas from Brazil, Argentina and Uruguay - and almost nothing is known about the physicochemical composition of the artifacts from the Brazilian portion. In this work we investigated the mineral phases present in archaeological ceramics from the cerrito Pavão I (PSG-20) by means of white light microscopy (petrography), Raman micro-spectroscopy, XRD and XRF spectroscopies, and FTIR-ATR. Different minerals were identified and allowed to propose a firing temperature of ca. 500-650 °C. It was also suggested that the makers used both oxidizing and reducing atmospheres, that more than one clay source was used to prepare the ceramics, and that trace elements are present in different shards. Regarding the multi-analytical technique approach, the results highlight the importance of complementary investigations and underline the role of Raman micro-spectroscopy for these objects.