A Continuous Holocene Glacial Record Inferred from Proglacial Lake Sediments in Banff National Park, Alberta, Canada

Abstract

AbstractSediment cores from three proglacial lakes in northern Banff National Park, Alberta, preserve a record of Holocene glacial activity upvalley which is more continuous and better dated than available surficial records. Dating of the cores is based on tephrochronology and 16 AMS14C ages of terrestrial macrofossils. All cores contain a threefold sequence of lacustrine sediments overlying a late Pleistocene diamicton. Basal lacustrine sediments >10,10014C yr old contain little organic matter. Sediment composition indicates a large glacigenic contribution. A sharp increase in organic content marks the beginning of the Altithermal interval at all three lakes. This transition occurred abruptly at about 10,10014C yr B.P. at Crowfoot Lake and possibly more gradually at the other lakes. Altithermal sediments contain relatively little glacigenic material, and during most of the Altithermal, glaciers may have been absent above Crowfoot and Bow Lakes. Glaciers draining into Hector Lake appear to have persisted through the Altithermal. A subsequent decrease in organic content in each lake, reflecting increased clastic sedimentation, marks the end of the Altithermal and the onset of Neoglacial ice advances. The transition took place between about 5800 and 400014C yr B.P. and may be time-transgressive, beginning earlier in Hector Lake than in Crowfoot Lake. Changing Neoglacial clastic sedimentation rates through the Neoglacial interval indicate two main periods of increased glacier extent, between ca. 3000 and 1800 varve yr ago (ca. 2900–190014C yr B.P.) and during the last several hundred years. During the intervening period glaciers were less extensive, but much more extensive than during the recessions of the Altithermal interval.