Preliminary dielectric and rock magnetic results for a set of prehistoric Amerindian pottery samples from different Venezuelan Islands

Abstract

Potsherds from 7 Venezuelan islands have been studied using a two-fold magneto/dielectric technique in order to identify clay sources and characterize different stages of pottery craftsmanship. This is the first study of archeological material using this technique. Petrographic analyses appear to agree with the clusters of data identified in scatter plots of initial magnetic susceptibility versus saturation isothermal remanent magnetization (SIRM), and natural remanent magnetization (NRM). Thus, these magnetic parameters appear to be suitable for describing clay source characteristics. Effective magnetic grain sizes, investigated via stability analyses of SIRM and anystheretic remanent magnetization (ARM) upon alternating field (AF) demagnetization, and SIRM acquisition and AF demagnetization crossover plots, seem to be related to different steps of pottery craftsmanship, namely clay preparation, finishing and firing. Thermomagnetic curves might also provide valuable information about original firing conditions. A scatter plot of SIRMs intersections versus maximum current depolarization temperatures and average activation energies, shows a coarse correlation due perhaps to the fact that these rock magnetic and dielectric data are both associated to pore-related features.

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

“…Petrographic analyses were carried out previously (Costanzo-Álvarez et al, 2006 andRada et al, 2008) for some representative samples of each ceramic group.…”

“…In this study we attempt to completely characterize, via petrographic, rock magnetic and dielectric analyses, a set of potsherds, from some Venezuelan islands, with ages between 1060 AD and 1530 AD. This group includes those samples previously studied in Costanzo-Álvarez et al (2006) and Rada et al (2008). The potsherds analyzed in these studies (Table 1) were excavated in archeological sites in Los Roques Archipelago (Dos Mosquises, Cayo Sal and Domusky Norte), Las Aves de Sotavento Archipelago (Curricai and Isla del Tesoro), La Orchila (Los Mangles) and La Blanquilla (Cuevas de la Cabecera) islands ( Fig.…”

“…Mooney et al (2003) used magnetic susceptibility and isothermal remanence in provenance studies at archaeological ochre quarries in Australia. In Venezuela, Costanzo-Álvarez et al (2006) and Rada et al (2008) have formerly carried out provenance studies for a collection of potsherds from some Venezuelan islands.…”

“…In Costanzo-Álvarez et al (2006) it was employed, for the first time, a two-fold magneto/dielectric technique (i.e. rock magnetic properties and thermally stimulated depolarization currents technique or TSDC).…”

“…In this fashion, the irreversibility parameter of thermomagnetic curves (IP), previously used as an indicator of the amount of organic matter burnt during original pottery firing for three representative samples of the Dos Mosquises (Rada et al, 2008), is applied here to the whole set of samples. In Costanzo-Álvarez et al (2006) the ceramic samples were dielectrically characterized, in this study this technique is employed on the whole set of samples. The IRM curves of all the studied samples are analyzed here using an alternative approach to decompose them (Aldana et al, 2011).…”