Oxidation states of iron as an indicator of the techniques used to burn clays and handcraft archaeological Tupiguarani c
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Oxidation states of iron as an indicator of the techniques used to burn clays and handcraft archaeological Tupiguarani ceramics by ancient human groups in Minas Gerais, Brazil D. L. Floresta · J. D. Ardisson · M. Fagundes · J. D. Fabris · W. A. A. Macedo
Published online: 31 January 2013 © Springer Science+Business Media Dordrecht 2013
Abstract Ceramics of the Tupiguarani Tradition typically have in common the burning characteristics, their forms and decoration motifs. Dating such ceramic pieces with the radiocarbon method indicate that these artifacts were probably handcrafted between 1,500 and 500 years before the present. Fragments ceramic utensils were collected in the archaeological site of Beltrão, in the municipality of Corinto, state of Minas Gerais, Brazil. A fragment of about 50 mm in diameter and 15 mm thick, with a color gradation across the ceramic wall ranging from red, on one side, grayish, in the middle, and orange, on the opposite side, was selected for a more detailed examination. The fragment was transversely cut and a series of subsamples were separated from different points along the piece wall, in layer segments of ∼3 mm. All subsamples were analyzed with Mössbauer spectroscopy at room temperature and 80 K. Results reveal that hematite is the magnetically ordered phase. A Fe2+ component (relative spectral area, 50 %) appears for the grayish subsample. According to these first results, the red subsample seems to be the side that had direct contact with fire used to burn the precursor clay in air. The grayish middle layer is probably due to the clay mixed with some ashes. Mössbauer data reveal that the orange layer, corresponding to the opposite side of the ceramic relatively to the direct fire, does contain about the same Fe2+ :Fe3+ ratio but much lower proportion of α-Fe2 O3 than the red layer. Keywords Tupiguarani ceramics · Archaeometry · Iron oxides
Thirteenth Latin American Conference on the Applications of the Mössbauer Effect, LACAME 2012, Medellín, Columbia, 11–16 November 2012. D. L. Floresta (B) · J. D. Ardisson · W. A. A. Macedo Laboratory of Applied Physics, Development Center of Nuclear Technology (CNEN/CDTN), 31270-901 Belo Horizonte, Minas Gerais, Brazil e-mail: [email protected] M. Fagundes · J. D. Fabris Laboratory of Archaeology and Landscapes Studies, Federal University of Jequitinhonha and Mucuri Valleys (UFVJM), Diamantina, 39100-000 Minas Gerais, Brazil
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1 Introduction Ceramics of the Tupiguarani Tradition are found in many parts throughout the Brazilian territory. They typically have many similarities mainly concerning the primitive technique of burning conditions, their forms and decoration motifs. Data on selected pieces obtained with the radiocarbon method indicate that these artifacts are dated from between 1,500 and 500 years before the present [1, 2]. Fragments of a Tupiguarani pottery found in the archaeological site known as Beltrão (location map, Fig. 1), in the municipality of Corinto, state of Minas Gerais, were identified and collected b
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