Synopsis of the Study Lakes
The northern Great Plains region of North America contains an estimated 4 million lakes and another 6-8 million sloughs and wetlands. Most of these water bodies are saline. In large areas of the Canadian Prairies these high salinity lacustrine brines are the only permanent surface water present.
Historically, this semi-arid region has been affected by episodic drought and anthropogenic stresses, resulting in well documented imbalances in water supply and demand. Notwithstanding the agricultural importance of this ‘breadbasket of the continent’, there is a profound lack of knowledge of long-term historic and Holocene perturbations in hydrology, climate, and environmental setting. Until just a decade ago, the Great Plains region had the lowest density of paleolimnological sites in North America, despite the presence of millions of extant lakes and Quaternary lacustrine basins.
The modern lacustrine environments in the Great Plains are extremely diverse in size, basin morphology, hydrochemistry, and sediment character. Although many of today’s lakes are small, shallow and ephemeral, the region also contains several of North America’s largest and deepest lakes. The four lakes targeted for study in this proposal are relatively small (8-80 km2), perennial (maximum depths 5-50 m), saline to hypersaline (35-80 ppt TDS), and dominated by Na, Mg, and SO4. Except for Deadmoose Lake, all have been extensively used by the public for recreation, and have popular Provincial Regional Parks and extensive cottage development on the shores. However, use of these lakes has suffered in recent years due to water level fluctuations (low water in Manito and Antelope; high water/flooding in Waldsea and Deadmoose). Low water levels in Manito and Antelope have significantly increased salinity in these closed basins, further deteriorating their attractiveness for recreational, commercial, and agricultural uses.
Waldsea/Deadmoose Lakes: Waldsea Lake is probably one of the most intensively sampled and studied salt lakes in western Canada. It has been the subject of 8 M.Sc. theses, 3 Ph.D. theses, and at least 5 honours B.Sc. theses; a total of more than thirty scientific reports have been published on this lake. The basin is clearly attractive for study because of its small size, simple morphology, excellent accessibility, and interesting meromictic character. The larger Deadmoose Lake, located about one kilometer from Waldsea, is comparatively poorly studied. In many respects the geolimnology of the two lakes is quite similar. Both are saline to hypersaline and meromictic; both contain phototrophic bacterial plates; both precipitate aragonite and contain finely laminated stratigraphic sequences. However, other aspects of the basins are different. The Deadmoose basin is larger and much more complex in terms of morphology, modern sedimentary facies, and processes than Waldsea. The Holocene history of Deadmoose also appears to be less straight-forward than that of Waldsea.
Antelope Lake: Antelope Lake is a saline lake located on the eastern margin of the Great Sand Hills in southwestern Saskatchewan. Like Manito Lake, Antelope has experienced a dramatic decrease in lake level over the past three decades. High water levels during the 1960's prompted the construction of extensive Regional Park facilities and the lake was routinely stocked with fish. Since the mid-1970's levels have steadily decreased, with concomitant increase in salinity from less than 10 ppt to over 30 ppt. During the summer of 1994 the lake became chemically stratified. Presently the lake water is strongly supersaturated with respect to aragonite and protodolomite and near saturation with respect to gypsum.
Reconnaissance coring during the early 1990’s gave encouraging results and the basin was included as part of the GSC’s IRMA project (Vance and Last, 1994). A preliminary 210Pb chronology was established for the sediment in the offshore area of the basin (Turner, 1994; Turner and Delorme, 1996). Unfortunately, similar to the situation for Waldsea and Deadmoose, preservation of diatoms and other microfossils is very poor (Vance, 1997b) so little further paleolimnological effort has been devoted to the lake.
Manito Lake: Manito Lake, located about 100 km west of Battleford, Saskatchewan, is a relatively large deep hypersaline lake. Because of the significant water level decrease over the past several decades, the lake is now 15% of its mid-20th century volume and 46% of its former area. The salinity has increased from 10 ppt to about 50 ppt TDS. This decrease in water level has exposed large areas of nearshore microbialites (mainly thrombolites and stromatolites) that range in size from several cm to over a meter (Ginn et al., 2007). Preliminary subaerial and subaqueous mapping of these features has revealed large biohermal structures several meters high. To date, the offshore sediments have not been sampled.