Rock magnetic, petrographic and dielectric characterization of prehistoric Amerindian potsherds from Venezuela

• Published in: Studia geophysica et geodaetica Vol. 55; no. 4; pp. 717 - 736
• Main Authors: Torres, Myriam Andrea Rada, Costanzo-Álvarez, Vincenzo, Aldana, Milagrosa, Suárez, Nery, Campos, Corina, Mackowiak-Antczak, Maria Magdalena, Brandt, María Carmela
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.10.2011; Springer Nature B.V
• Subjects: Atmospheric Sciences; Ceramics; Earth and Environmental Science; Earth Sciences; Geophysics; Geophysics/Geodesy; Magnetism; Petrology; Prehistoric era; Structural Geology; TSDC; Amerindian pottery; rock magnetism; dielectric; petrographic
• ISSN: 0039-3169; 1573-1626
• DOI: 10.1007/s11200-010-9021-1

Rock magnetic, petrographic and dielectric analyses were carried out, in a number of archeological ceramic potsherds, in order to characterize the different manufacturing techniques used by Prehistoric Venezuelan Amerindian potters. Samples were excavated in 7 Venezuelan islands and ascribed to distinct cultural groups on purely stylistic grounds (i.e. Valencioide, Ocumaroide, Dabajuroide and Unknown). Mean coercivity values were determined through a direct signal analyses (DSA) applied to isothermal remanent magnetization (IRM) acquisition curves. Logarithmic plots of these mean coercivities are the best quantitative means to classify diverse ceramics. The mean coercivity values seem to group the samples according to the manufacturing development. These values also seem to discriminate the samples provenance, indeed, this plot displays a good grouping of data for samples presumably manufactured by the same culture but excavated at different locations. Thermomagnetic cycles supply helpful information about original ceramic firing conditions. The irreversibility parameter (IP) for thermomagnetic curves (heating and cooling), serves as an indicator of the amount of organic matter burnt during original pottery firing. The IP for a number of pottery samples from Venezuelan islands and mainland, with ages ranging between 300 BC to 1500 AD, might suggest a possible increasing trend in time towards the complete reversibility line of IP = 0. Most samples, independently of age and cultural group, have IP values that suggest that most open fires, used by primitive Venezuelan Amerindian potters, had enough ventilation and oxidizing atmospheres. A scatter plot of maximum current depolarization temperatures versus natural remanent magnetization (NRM) suggests a complex non-linear relationship between these two parameters most likely due to the fact that both, dielectric and rock magnetic data, are linked to pore-related features.