Radiocarbon Geochemistry of Modern and Ancient Arctic Lake Systems, Baffin Island, Canada

The accuracy of Arctic lake chronologies has been assessed by measuring the¹⁴C activities of modern carbon sources and applying these isotopic mass balances to dating fossil lake materials. Small (<1 km²) shallow (<25 m) Arctic lakes with watersheds <12 km²have soil and peat stratigraphic sections with¹⁴C activities ranging from 98 to 51% Modern. The¹⁴C activity of particulate organic carbon, dissolved organic carbon, and dissolved inorganic carbon from lake and stream waters ranges from 121 to 95% Modern. The sediment–water interface of the studied lakes shows consistent¹⁴C ages of ∼1000¹⁴C yr, although the¹⁴C activity of living aquatic vegetation is 115% Modern. Radiocarbon measurements of components of the lacustrine carbon pool imply that the ∼1000¹⁴C yr age of the sediment–water interface results from deposition of¹⁴C-depleted organic matter derived from the watershed.