Sediment chemistry and diatom stratigraphy of two high arctic isolation lakes, Truelove Lowland, Devon Island, N.W.T., Canada

Abstract

Three sediment cores from two lakes, Fish Lake and Phalarope Lake, in Truelove Lowland, Devon Island, N.W.T. were analyzed for diatoms and chemical composition. Multivariate statistical techniques using a range of chemical variables successfully isolated three sediment groupings in the cores. Allochthonous and autochthonous chemical components in the sediments have been used to reconstruct paleoenvironmental conditions. The two lakes began approximately 10 600 years ago as shallow marine lagoons that were isolated from the sea as a result of glacio-isostatic rebound. Based on the presence of distinctive diatom assemblages, the three stratigraphic zones are identified as a basal marine zone, an intermediate and transitional brackish/marine zone and an upper freshwater zone. Following isolation from the sea, the lakes were flushed with freshwater produced by snow and ice melt. In Fish Lake, the period of transition from marine to freshwater, which began approximately 7000 years ago, lasted approximately 800 years. In Phalarope Lake, which was isolated from the sea approximately 5 000 years ago, flushing by fresh water was completed only within the last 300 years. Fe, Cr, and Mo in the sediments are associated with the isolation phase when lake sedimentation is sensitive to the presence of brackish water and erosion within the lake catchments. In particular, the precipitation of Mo as MoS 2 reflects the presence of hypolimnetic anoxia associated with lake isolation. During the early post-isolation phase the response of lake biota to an influx of nutrients is reflected in an increase in biological silica and organic carbon in the lake sediments. On the other hand, the generally low organic content of the sediments indicates that sedimentation in these lakes has been largely determined by variations in non-biogenic factors through time. During the mid Holocene the progressive stabilization of surface materials within the lake catchments is marked by decreasing Cr, As and Na in the sediments. At the same time, an increase in allochthonous Mn and Fe is attributed to progressive soil development. During the last 2500 years the catchments have experienced decreased erosion resulting in a decrease in both allochthonous clastic input and lake productivity.

A palaeolimnological record of diatom-community dynamics and late-Holocene climatic changes from Prescott Island, Nunavut, central Canadian Arctic

“…This is in contrast to other studies of lake sediment cores from the Canadian Arctic Islands where diatoms are absent, poorly preserved, apparently present at low levels of diversity or show few changes during the Holocene (eg, Young and King, 1989;Perren et al, 2003). Currently it is not well understood how various factors interact to produce lakes with well-preserved, diverse diatom assemblages showing responses to climatic changes, although elevated pH and salinity may contribute to diatom dissolution (Hamilton et al, 2000).…”

Isolation of Lacustrine Basins and Marine Regression in the Kuujjuaq Area, Northern Québec, as Inferred from Diatom Analysis

“…Density stratification, and subsequent anoxic conditions at depth, appear to be features typical of certain lakes isolated from the sea (e.g. Kjemperud, 1981;Young and King, 1989). The combined effect of this situation with pronounced changes in sediment input, seems to have created favourable conditions for the preservation of sediment laminae.…”

Changes in diatom assemblages in Lake C2 (Ellesmere Island, Arctic Canada): response to basin isolation from the sea and to other environmental changes

“…For example, Williams (1990a) documented a marine transi-* This is the eighth in a series of papers published in this issue on the Taconite Lakes Project. These papers were collected by Dr R. S. Bradley. tion of two lakes on Baffin Island, and Young & King (1989) reported on a similar study from Devon Island. Other arctic paleolimnological studies do not show this transition (e.g., Wolfe 1994;Smol 1983;Lemmen et al, 1988), as these lakes were either located above the marine limit or because sediment coring did not penetrate the marine sediments.…”