Possible subsurface production of carbon-14

A subsurface origin of 14C is rarely considered by researchers interested in dating groundwater. Theoretically, nuclear reactions induced by emissions from U and Th nuclei can produce measurable concentrations of 14C in groundwater. Under very special conditions, calculations indicate that subsurface production might cause significant errors in dates of less that 1 x 104 years, although normally such errors showld not be important until after 5 x 104 years. However, some anomalous 14C concentrations reported recently for deep groundwater may possibly be caused in part by subsurface production of 14C