The salt lakes of western Canada: A paleolimnological overview

The northern Great Plains of western Canada contain many saline and hypersaline lakes. Deadmoose and Waldsea Lakes in south-central Saskatchewan are meromictic, with saline Mg-Na-SO₄-Cl waters overlying denser brines of similar composition. Mineralogical, chemical, palynological, and stable isotope analyses of the sediments in the Waldsea basin indicate the lake was much shallower about 4 000 years ago in response to a warmer and drier climate. Since that time water levels have generally increased in the basin giving rise to higher organic productivity and greater inorganic carbonate precipitation. Within this overall trend there is also evidence of several lower water stages during the last 3 000 years. The stratigraphy preserved in the Deadmoose basin suggests considerably lower water levels about 1 000 years ago.Ceylon Lake, located about 350 km south of the Waldsea-Deadmoose area, is presently a shallow, saline playa. The basin originated about 15 000 years ago as a glacial meltwater spillway. Stratigraphic variation in evaporite and carbonate mineralogy shows that the basin evolved from a relatively low salinity, riverine lake to one in which initially Na-rich and then Mg-rich hypersaline brines dominated.Lake Manitoba is a large, hyposaline lake located in the eastern Great Plains about 700 km from the Deadmoose-Waldsea area. Stable oxygen and carbon isotope analyses of the endogenic carbonates in the basin indicate gradually increasing levels of organic productivity but decreasing temperatures between 9 000 and 5 000 years B.P. Between about 4 000 and 2 000 years ago the isotope ratios suggest relatively stable temperatures followed by a strong decrease during the most recent 2 000 year period.