Archaeometric studies in pre-colonial guarani ceramic production (Taquari, Brazil)

The archeological site RS-TQ-141 is located in Rio Grande do Sul (Brazil) and belongs to the pre-colonial Guarani Tradition (between fifth and seventeenth century). The site extends to the bank of the Taquari River. About 200 small fragments of ceramic from the site present internal and/or external coating surfaces. Archaeometry analyses were applied in order to understand coating application mechanism. X-ray Fluorescence (XFR) analyses revealed that the main elements are iron, titanium, potassium, and calcium. Applying the micro Fourier Transform Interferometer (ATR-FTIR) method it was possible to differentiate white and red coatings produced with different types of (ocher) clays. ATR-FTIR was applied in order to try to distinguish the vessels use. The coatings were produced with the same groups of clays used for the manufacture of ceramics. The presence of at least two groups of clay is recorded: montmorillonite-like and kaolinite-like. The white coatings can be distinguished in the FTIR spectra by the presence of a carbonate peak. From this research, there does not seem to be any difference between internal and external coatings. Carbonyl materials were detected, both in the coating and in the production of the ceramics; the latter is probably related to pyrolysis.