Author(s)

D.M. Bonotto

Abstract

Some constraints on the modelling using the uranium isotopes ^U and ^U for dating groundwaters from Guarany aquifer, South America D.M. Bonotto Institute de Geociencias e Ciencias Exatas, UNESP, Brasil. Abstract Groundwaters from the Guarany aquifer located at the South American continent and sampled at four wells with described geological sections in Sao Paulo State, Brazil, were chemically and isotopically analysed with two aims: to evaluate the quality of this important hydrological resource and to investigate the possibility of using the natural uranium isotopes ™U and ^*U as a chronological tool, since the ^U/^U activity ratio and dissolved U content data in groundwater systems have generated models for dating purposes. Introduction The natural radioelement uranium is widely distributed in crustal rocks, and under conditions present at the earth's surface, it tends to be a mobile element. ^*U is the principal isotope of natural U (99.3% abundance) and is the

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