A Potential Tool for Groundwater Dating

Every radioactive isotope detected in groundwater serves as a potential tool for dating. The half-life of 36C1 — 3 x 105 years—is especially promising because it fills in a most important time span, that is, beyond the limits of groundwater dating by radiocarbon. 

Marcel Dekker, Inc. 270 Madison Avenue, New York, New York 10016 

The flux of cosmic rays varies with sunspot activity and other parameters, and the flux reaching the Earth s surface varies with latitude and altitude. Furthermore, reactions with 35C1 produce some 36C1, which causes a dependence in the distance from the ocean. Altogether, the production of 36Cl varies spatially by a factor of up to five. Hence, the 36C1 production rate is site specific and has to be determined for each study site, as outlined later. 

2 Evapotranspiration Affecting the Cl and 36CI Concentration in Recharged Groundwater 

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