Holocene paleohydrology of a hypersaline lake in southeastern Alberta

Analyses of pollen, plant macrofossils, sediment mineralogy, geochemistry, and lithology of cores from Chappice Lake, southeastern Alberta, provide an outline of paleohydrological changes spanning the last 7300 radiocarbon years. Situated near the northern margin of the Great Plains, Chappice Lake is currently a small (1.5 km²), shallow (<1 m), hypersaline lake. Results of this study suggest that the lake has experienced significant changes in water level and chemistry during the Holocene.From 7300 to 6000 BP the lake oscillated between relatively high stands and desiccation. From 6000 to 4400 BP it was smaller than present and ponded highly saline water. Although extreme water level variations of the preceding period had ceased, pronounced seasonal fluctuations persisted. Between 4400 and 2600 BP, lake level was more stable but gradually rising. Carbonates were a major component of the sediments deposited during this interval. A large, relatively fresh lake existed from 2600 to 1000 BP. Illite was the dominant mineral deposited during this period, but since then has been a minor constituent in a mineral suite dominated by detrital silicates. A series of low-water, high-salinity stands occurred between 1000 and 600 BP, although these low stands were not as pronounced as low-water intervals in the middle Holocene. Relatively high water levels were sustained from 600 BP until the late 1800s. The lake declined significantly in the last one hundred years, notably during the historically documented droughts of the late 1800s, 1920s, 1930s, and 1980s.The timing of paleohydrological events at Chappice Lake corresponds closely with well documented Holocene climatic intervals, such as the Hypsithermal, Neoglaciation, Medieval Warm Period, and Little Ice Age. In addition, historic lake-level fluctuations can be related directly to climate. As a result, the Chappice Lake sedimentary succession offers a rare opportunity to obtain a high-resolution, surrogate record of Holocene climate on the northern Great Plains, and to observe the response of lake chemistry and biota to significant environmental change.Geological Survey of Canada Contribution No. 45191, Palliser Triangle Global Change Contribution No. 2This publication is the first of a series of papers presented at the Conference on Sedimentary and Paleolimnological Records of Saline Lakes. This Conference was held August 13–16, 1991 at the University of Saskatchewan, Saskatoon, Canada. Dr. Evans is serving as Guest Editor for this series.