Intraspecific variability in the d13C and d15N values of archaeological samples of Zea mays cobs (northeastern argentinean Puna)

Abstract

The aim of this article is to present the results of δ13C and δ15N on a sample of Zea mays cobs from the Río Doncellas Collection (Department of Cochinoca, Jujuy), obtained in archaeological excavations conducted between 1973 and 1975. This study includes the analysis of various races, therefore it will also contribute to the reconstruction of the isotopic ecology of the North Puna. Furthermore, it will also assess whether this diversity is accompanied by an equally variable isotopic correlation, including whether possible sources of this variation might be physiological responses to environmental factors (differential cultivation at different altitudes) or genetic influences. Likewise, we straightforwardly discuss the pertinence of the values from archaeological samples in the reconstruction of human paleodiets, taking into consideration the digenetic influences that degrade the primary isotopic signature of archaeological these samples. In an attempt to generate a frame of reference for possible explanations of the Zea mays values obtained, we also present here the first results of present-day studies from the micro-region of Antofagasta de la Sierra (Catamarca, Southern Argentine Puna). Here we sampled three cultivated fields located at different altitudes, types of irrigation and use of fertilizers. In the assemblage (n=6) we noted a lower variability in the δ13C values and a higher range in the δ15N values, which indicates the importance of the use of fertilizers in arid environments and the its implications in isotopic enrichment given that the most enriched values occurred in those field with the least access to water. In an attempt to strenghten our conclusion, these values have been compared to the extant isotopic data for Zea mays from the larger Andean context.