Late Holocene sedimentology paleohydrology and isotope geochemistry of three saline lakes in south-central Saskatchewan, Canada
Read, Jeffrey T.
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Waldsea, Deadmoose, and Lenore lakes are three saline lakes located in the Lenore Basin drainage complex north of the town of Humboldt in south-central Saskatchewan, Canada. Waldsea Lake and Deadmoose Lake are both meromictic, with anoxic, saline to hypersaline (~30-45 g L-1 TDS) Na-Mg-SO4 –rich monimolimnion waters underlying hyposaline to saline mixolimnions. Lenore Lake water shows similar ionic ratios but is less saline (~4 g L-1 TDS) and does not exhibit meromixis. Water levels in these closed-basin lakes have historically fluctuated dramatically. Present-day high levels in the basins have lead to considerable social, economic, and environmental disruptions and problems. Short sediment cores (~1 m length) were collected from deep-water offshore locations in each basin in order to study sedimentological and hydrological changes that have occurred over the past several millennia and to place the current high water levels into a longer-term perspective. The late Holocene stratigraphic sequences recovered from Waldsea and Deadmoose lakes are roughly similar: both comprise overall well-bedded, fine-grained, organic-rich sediment dominated by endogenic gypsum and detrital clay minerals, with associated quartz, plagioclase and carbonate minerals. They both contain laminae composed of endogenic aragonite. Two lithostratigraphic units are identified in each sequence on the basis of bedding, grain size, organic matter content, geochemistry, mineralogy, and δ18O and δ13C characteristics. Although chronostratigraphic control is limited, AMS 14C dating of plant remains in the cores indicate that the recovered sequence from Waldsea spans approximately 1500 years whereas the Deadmoose sequence covers about 3500 years. The recovered Lenore Lake sequence is mainly non-bedded and largely composed of fine to coarse-grained siliciclastics and detrital carbonate minerals. Like Waldsea and Deadmoose, two lithostratigraphic units are identified, however efforts to establish chronostratigraphic control for the section recovered from Lenore Lake were not successful. The short cores recovered from each of these basins show a clear change from shallow water deposition at the base to deep(er) water conditions further up the section. This change was likely a result of the development of a more positive hydrologic budget in each of the basins. The lack of chronological synchrony of the interpreted hydrologic changes, however, suggest that the effects of regional climatic fluctuations are masked by various intrinsic sedimentological, geochemical, and biological processes operating within each basin.