Radiocarbon dating of porewater - Correction for diffusion and diagenetic processes

Two simple algorithms are suggested here to correct for the effect of diffusion and diagenetic sulfate reduction on radiocarbon age determination of marine porewater. The correction algorithms were developed from mass balances of sulfate, dissolved inorganic carbon (DIC), and ¹⁴C of the DIC (¹⁴C_DIC) in vertical concentrations profiles in porewater starting from the sediment water interface. The algorithms were tested on data collected during our recent study of sediment porewaters extracted from the deep Eastern Mediterranean. The real ages of these porewaters varied from present (top of the core) to approximately 30 ka BP (bottom of the core) covering most of the dynamic range of the ¹⁴C method (approximately 5 half lives). These ages were markedly older than the ages calculated from ¹⁴C_DIC analyses by the regular age equation. It is clearly demonstrated that in this case the correction of the apparent age for diffusion across the sediment/water interface is overwhelmingly larger than the correction for the effect of sulfate reduction. The correction for the effect of ¹⁴C diffusion alone results in a perfect match between the calculated apparent ¹⁴C ages and the real ages of porewater and therefore is the preferred algorithm for correcting apparent ages of porewater.