LATE HOLOCENE PALEOHYDROLOGY AND PALEOLIMNOLOGY OF TWO ADJACENT MEROMICTIC LAKES, NORTHERN GREAT PLAINS OF WESTERN CANADA

Waldsea and Deadmoose lakes, located at the northern fringe of the prairies in central Saskatchewan, are among the best studied meromictic lakes in western Canada. Recent water level fluctuations in these and other lakes in the area have resulted in considerable property damage and environmental degredation. Clearly, the water chemistry, hydrological balance, and overall geolimnological characteristics of these closed-basin saline lakes are strongly influenced by both short-term (seasonal and annual) weather conditions and longer term climate fluctuations, as well as anthropogenic modifications to the landscape. The late Holocene stratigraphic records of Waldsea and Deadmoose are undergoing detailed investigation in an effort to better understand the nature of past water level and limnological changes.

The late Holocene offshore sediments in these lakes comprise finely laminated, organic-rich calcareous clay, with lesser amounts of authigenic pyrite and gypsum, and detritial quartz and feldspars. The irregularly spaced laminae are composed of well-sorted, micron-sized subhedral to euhedral aragonite crystals and are likely the result of aperiodic rapid whiting events in the mixolimnions. The lithostratigraphy, overall mineralogy, and δ¹³C and δ¹⁸O signatures of the endogenic carbonates confirm the long-term saline and closed hydrologic setting of the basins, but exhibit little consistent variation over the past several millennia. The C/N, δ¹³C and δ¹⁵N stratigraphic data from the organic matter, however, provide detailed information about fluctuations in the trophic status, source of the organics, and water levels. Although the lakes are currently experiencing historically high water levels, the late Holocene stratigraphy suggests that these conditions are within the range of natural variation observed during the past several millennia.