Evidence of climatic change from oxygen and carbon isotope variations in sediments of a small arctic lake, Canada

Radiocarbon dating of the organic-rich sediments of Lake Illisarvik in the outer Mackenzie Delta indicates that formation of the lake occurred approximately 9500yr BP, with maximum expansion around 6000 yr BP. Sedimentation rates have remained relatively constant at an average of 0.3mm/yr. 13C results on biogenic and inorganic carbonates and organics indicate a change from dominantly terrestrial organics (−27 to −28%0) to submerged aquatic vegetation or plankton (−18 to −23%0) upon formation of the lake (9500yr BP), and a dramatic return to dominantly terrestrial organics at 5800yr BP (δ13C = −27 to −30%0). This latter shift is accompanied by a drastic reduction in the macroflora and fauna populations. 18O results suggest that a warmer climate than today existed prior to the shift at 5800yr BP.