THE IMPACT OF HOLOCENE ICE MARGINAL CHANGES ON THE SEDIMENTARY RECORD IN HIGH ARCTIC PROGLACIAL BEAR LAKE, DEVON ISLAND, NUNAVUT

Combined catchment, subbottom acoustic and sedimentology studies of High Arctic, proglacial Bear Lake, Devon Island, were carried out to identify the impact Holocene catchment evolution and glacier changes have had on the sedimentary record. The south, proximal basin of the lake contains laminated sediments that we interpret as varves, primarily due to the sedimentology, highly seasonal inflow of meltwater, persistent summer lake ice, and the depth (maximum 100 m). In shallower locations of the proximal basin, accumulation is approximately 1-4 mm/year and results from homopycnal distribution of fines throughout the proximal basin, resulting in a simple varve couplet. Although there is an absence of organic material suitable for radiocarbon dating, acoustic and core evidence indicates we have the entire Holocene lacustrine sequence. Varves in the early Holocene change to massive mud near the middle of the core record, which we interpret as ice retreating from the catchment. In the late Holocene, the varves return, becoming progressively thicker and suggesting that ice returned into the headwaters of the basin. This record provides the first direct evidence for ice margin changes of the Devon Island Ice Cap and should prove valuable for interpreting the terrestrial and ice core proxy records.