Using the ¹⁴C Bomb Pulse to Date Young Speleothems

Abstract

Three modern speleothems were sampled at high resolution for radiocarbon analysis to identify their bomb-pulse signatures and to construct chronologies. Each speleothem exhibited a different 14 C response, presumed to be related to site characteristics such as vegetation, temperature, rainfall, depth below the surface, and water pathway through the aquifer. Peak 14 C activity for WM4 is 134.1 pMC, the highest cited thus far in the literature and suggestive of a lower inertia at this site. Dead carbon fractions for each stalagmite were calculated and found to be relatively similar for the 3 speleothems and lower than those derived from Northern Hemisphere speleothems. An inverse modeling technique based on the work of Genty and Massault (1999) was used to estimate soil carbon residence times. For each speleothem, mean soil 14 C reservoir ages differed greatly between the 3 sites, ranging from 2–6.5 to 32–46 yr.