|dc.description.abstract||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.||en_US