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

Abstract

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. Continuation of LATINMAG Special Issue #4, Stud. Geophys. Geod., 54 (2010) M.A. Rada Torres et al. 718 Stud. Geophys. Geod., 55 (2011)

Testing lake-level reconstructions based on rock magnetic proxies for the sediment record of Laguna Cháltel (Patagonia, Argentina)

“…For analysis of IRM curves, a direct signal analysis (DSA) was applied to the experimental IRM. The DSA method has been widely described by Aldana et al (1994, 2011) and has been used to analyse IRM curves obtained from archaeological samples (Rada Torres et al, 2011), sedimentary rocks (Costanzo-Álvarez et al, 2012, 2019), soils (Costanzo-Álvarez et al, 2017a), and synthetic samples (Costanzo-Álvarez et al, 2017b). Figure 3A and B shows the experimental and fitted curves for the shallow sample of core CH04/2, as well as the spectral histogram obtained.…”

Microbial activity and studies on excavated megalithic micaceous potsherds from Peninsular India

“…Researchers have used many analytical techniques for estimating the firing temperature of the potsherds. Firing temperature has been estimated through thermal expansion and dilation of ceramics [20], measurement of the coercive field and saturation magnetization [21,22], interlayer spacing in illite mineral by X-ray diffraction [23], Mossbauer spectroscopy, and thermal analysis [24]. Besides, the parameters like heating rate, duration of firing, atmospheric condition, cooling rate, and refiring events have often been used in ceramic investigations [25].…”