Fossil carbon in coastal sediments

Fossil carbon, as present in coal, oil and their derivatives, is free from radioactive 14 C and its presence in even small concentrations within sedimentary materials can lead to anomalously old radiocarbon ages. For example, Erlenkeuser et al. 1 have noted artificially high 14 C ages in the upper 20 cm of Baltic Sea sediments in correlation with enhanced heavy metal concentrations. Both findings are consistent with the growth of industrial activity in this location, and the radiocarbon age increase has therefore in the past been regarded as an approximate measure of the extent of pollution of sediment organics by industrial fossil fuels. The results presented here will indicate that the latter interpretation is not always valid and that in studies of coastal marine sediments the incorporation of natural fossil carbon in the samples can introduce considerable error.