Carbon and oxygen stable isotopes on Choique (Pterocnemia pennata) egg-shell: A palaeoenvironment indicator?

PANARELLO, H.O.; FERNANDEZ, J.; DUCOS, E.I.

Cordoba, Argentina

Simposio; II South American Symposium on Isotope Geology; 1999

The South American ratite birds (Fam. Rheidae) are widely spread in different environments of Argentina. One of its species is the choique. This work deals with the egg-shells corresponding to this species. Fresh choique eggs were collected in the Puna, province of Jujuy (P. pennata garleppi); in Northwestern Patagonia, provinces of Neuquen and Rio Negro; and in Southern Patagonia, province of Santa Cruz (P. pennata pennata). Fragments of choique egg-shells found between layers of carbon-14 dated charcoal in the Haichol cave, province of Neuquen were also sampled for this experiment.The first results of this study on the isotopic composition of choique egg-shells show the existence of good correlations between delta O-18 and delta C-13. Despite the few isotopic pairs available, it can also be suggested that each regression line could represent the isotherm of a given region for the egg-laying period. The position of the lines defined for the four areas under study was found to vary according to the respective temperature. Due to the low humidities and high evaporation rates found in the regions under study, delta O-18 in water (drinking water and in food) reach rather constant values, which are almost independent of the original meteoric water composition. Therefore delta O-18 of the egg-shell cannot be used as a temperature indicator. Taking into account the above-given data, we believe that the carbon and oxygen isotopic composition of the choique egg-shell is a tool worth considering in palaeoenvironmental studies in Quaternary Geology and in Archaeology, at least for the environments described in this paper.