EDXRF study of Tupi-Guarani archaeological ceramics

A set of Indian Brazilian pottery fragments belonging to Tupi-Guarani tradi tion has been studied by EDXRF. The main objective was to characterize the ceramic paste, as well as the superficial layer of the ceramic fragments, i n order to get qualitative information about the pigment composition of the plastic decoration. Energy Dispersive X-ray Fluorescence (EDXRF) methodolo gy was employed to obtain the ceramic paste composition, as well as the sup erficial layer of the ceramic fragments. The experimental set-up consisted of 238Pu, 55Fe and 109Cd radioactive sources, a X-ray tube (at 15 kV, 40 mA , Me target and Zr filter), a Si(Li) detector (30 min(2), with a Be window) and a multichannel analyzer. X-ray spectra were analyzed using the AXIL pr ogram. A program based on the graphic polygonal representation method was d eveloped and used to correlate the representative intensity data of each fr agment. A low Ca content and a systematic presence of relatively high conce ntrations of Fe can characterize the ceramic pastes. Ti and Zr are also alw ays present at high levels, and Ni, Cu and in some cases Zn at level of tra ces; Rb, Sr, Ba and Y are also present at low concentration. The black pigm ent in the pottery plastic decoration is due to the presence of Mn, the red pigment is due to the presence of Fe, while the white pigment is character ized by the presence of Ba. For the eleven fragments studied, the polygonal representation method points that the same materials were employed in the pottery production, and the pigments in the plastic decoration were obtaine d from different inorganic materials. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.