Possible subsurface production of carbon‐14

Abstract

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 than 1 × 104 years, although normally such errors should not be important until after 5 × 104 years. However, some anomalous 14C concentrations reported recently for deep groundwater may possibly be caused in part by subsurface production of 14C.

Using in situ produced cosmogenic isotopes to estimate rates of landscape evolution: A review from the geomorphic perspective

“…Other Sources of "Cosmogenic" Isotopes production of 3He is minimal in most rocks and that radiogenic 3He can be corrected for during analysis. In situ production of appears to be inconsequential [Zito et al, 1980;Fabryka-Martin, 1988;Raisbeck and Yiou, 1990].…”

Dating Groundwater

“…Third, a minute but significant amount of 14 C is probably produced in the subsurface. Although not important in dating water less than a few thousand years old, 14 C produced in the subsurface may limit accurate dating to water which is 50,000 to 80,000 years old or less [25].…”

“…Theoretical studies [25,42] have shown that significant amounts of a number of radionuclides usually assumed to be derived only from the atmosphere may actually be produced in the subsurface, largely through interactions with secondary neutrons produced by alpha capture reactions. The alpha particles are derived mostly from normal decay of natural U and Th.…”

In-Situ Cosmogenic 14C: Production and Examples of its Unique Applications in Studies of Terrestrial and Extraterrestrial Processes

“…Cosmogenic 14 C can be produced in several exothermic or low-energy nuclear reactions (cf. Zito et al 1980;Lal 1988a). We list below some exothermic nuclear reactions which can produce 14 C:…”

“…Nuclear transformations, ternary fission (cf. Vorobyov et al 1972), and anomalous decay of heavy nuclei (Sandulescu et al 1980;Rose and Jones 1984;Price 1989) lead to formation of 14 C. Several nuclear reactions produced by radiogenic particles arising from U and Th series nuclides, due to α-decay, and neutrons produced by α-particle induced nuclear reactions, also lead to production of 14 C (Zito et al 1980;Jull et al 1987;Lal 1988a). However, the last of the three mechanisms, namely the continuous production of 14 C in diverse materials by nuclear interactions of primary and secondary cosmic ray particles, is by far the most important source of 14 C on the earth (Lingenfelter 1963;Lal and Peters 1967;Lal 1992a).…”