Diatoms of the Sturgeon Lake Marl, Saskatchewan

Abundant diatoms were found in two exposures of a fresh-water carbonate (marl) deposit along the shore of Sturgeon take, Saskatchewan. The diatoms from various stratigraphic intervals were washed, cleaned, mounted on microscope slides, and then identified as to kind. The valves of the different species recognized were counted for each sample. An examination of the diatomaceous flora as a whole yielded a total of 94 different diatoms, or which 72 were assigned to existing species and 13 to varieties, all together belonging to 28 different genera. In addition, seven diatoms were identified only as to their generic position, and two were categorized only as to Order. Most of the "fossil" diatoms are fresh-water species whose counterparts live in water containing less than 5,000 p.p.m. total dissolved solids. A few are living in brackish water. By extrapolating the ecological tolerance limits of living species back to late glacial and postglacial time, it was possible to reconstruct the changes in salinity, pH, alkalinity, and trophic type of the water of Sturgeon Lake during the time, from about 9,000 to 5,000 years ago when the marl was deposited. It was found that pH remained almost constant throughout the period, and that the water was eutrophic. Salinity and alkalinity varied as fresh-water conditions changed to brackish water and back to fresh-water. There seems to have been a period of drying of part or whole of the lake, indicated by unconformities and extinction of diatoms. This drying is believed to have taken place during the hypsithermal interval of time, about 8,000 years ago When higher temperatures prevailed in western North America. These interpretations appear to corroborate those based on a study of the ostracode fauna, and allow the tentative correlation of three stratigraphic sections with each other. Note:This thesis contains maps that have been sized to fit the viewing area. Use the zoom in tool to view the maps in detail or to enlarge the text