Radiocarbon Dating of Alkenones from Marine Sediments: II. Assessment of Carbon Process Blanks

Abstract

We evaluate potential process blanks associated with radiocarbon measurement of microgram to milligram quantities of alkenones at the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility. Two strategies to constrain the contribution of blanks to alkenone 14C dates were followed: 1) dating of samples of known age and 2) multiple measurements of identical samples. We show that the potential contamination associated with the procedure does not lead to a systematic bias of the results of alkenone dating to either younger or older ages. Our results indicate that alkenones record ∆14C of ambient DIC with an accuracy of approximately 10. A conservative estimate of measurement precision is 17ppm for modern samples. Alkenone 14C ages are expected to be reliable within 500 yr for samples younger than 10,500 14C yr.