Radiocarbon dating of marine sediments

Abstract

Radiocarbon dating techniques have not been as widely applied as they might be to the analysis of marine sediments because of the generally low carbon content in these sediments. Thus, a method to date sediments with low carbon content by means of dilution of the sample carbon dioxide with carbon dioxide having low radiocarbon activity was developed and tested on samples from the Cariaco Basin and the Mississippi Delta. The results show that the method yields valid dates with a slight increase in their statistical error. The method limits the range in age to approximately half the normal range of 30,000 years before present, but this range is sufficient to reach the Recent Pleistocene boundary in marine sediments. The samples analyzed from the Cariaco Basin indicate a continuous sedimentation rate of about 25 cm/1000 years or greater. Cores from the basin deeps have higher total sediment accumulation rates because of localized post-deposition movement of sediment masses, either down the basin slopes or as a result of fault movement, as well as the continuous accumulation. The sediment emplaced in this manner can be detected as isochronous layers within the age versus depth profile. Only one Cariaco Basin sediment sample required the dilution method. This sample provided a check on the validity of the dilution procedure due to its close proximity to undiluted samples.