NOAA/WDS Paleoclimatology - Devon Island Lake DV09 150 Year Varved Sediment Data

Sediments from a 3 ha lake (75deg. 34.34'N, 89deg. 18.55'W) from the coastal region of northern Devon Island, Nunavut, Canada, contain discrete laminations in the deepest part of the basin. The laminations are varves as indicated by the correspondence between counts and thickness measurements of the couplets and Pb210 dating. A 14cm. core representing 150 years of sedimentation contained laminated couplets consisting of a lighter inorganic layer with a higher percentage of calcium and magnesium, alternating with fine darker bands, typically more cohesive, and comprising higher proportions of silica and carbon. A reddish oxidation zone with higher iron and aluminum frequently separates the laminations. The dark layer represents a biogenic component deposited summer and is made cohesive by bacterial filaments among other the particles. The light inorganic layer represents clastic deposition from allochthonous sources. Deposition rates were relatively consistent through the core with an increase in varve thickness in the 1950's. Diatom concentrations in the sediments increased by two orders of magnitude in this century, with major increases in the 1920's and 1950's. The increase in varve thickness and diatom abundance coincides with an increase in summer melt percentage in an ice core from the Devon Island Ice Cap (Koerner 1997). The relatively high sedimentation rate (0.15 cm/yr) coupled with the consistency of deposition makes this lake a significant indicator for recent climate changes of the Canadian Arctic Archipelago.