The type of rock underlying a lake is important in determining the chemical character of a lake. Lakes found entirely on Precambrian
rocks are more sensitive to acid rain and have less of a capability to adjust to changes in acidity (pH). They may also be
very low in calcium making it difficult for fish and other organisms to thrive. Lakes found entirely on carbonacious rocks (limestone,
calcite) are better at maintaining a pH balance (buffering capacity), but are usually higher in calcium content making them more
likely to provide suitable habitat for invasive species such as the zebra mussel. White Lake falls into the latter category.
The geological map (reproduced below), which was part of the above cited report, clearly shows the nature of
the rocks underlying White Lake. White Lake can be seen on this map in the upper right hand corner. The map legend indicates that
the entire western shore of the lake is composed of granites, granite gneiss and syenite. These rocks we associate
with Precambrian Shield. The map also shows that the lake itself and it's eastern shore is entirely underlain by sedimentary
rocks such as crystalline limestone, including dolomite. Indeed, the Tatlock calcite mine is only a few kilometers from White Lake.
White Lake only abuts on shield type rocks and the chemical composition the lake water is not appreciably affected by this
A more recent description of the geological setting for White Lake can be found in the 1988 Ontario Geological Survey
Open File 5693: R. M. Easton, Geology of the Darling Township Area, Lanark and Renfrew Counties, pp. 265. The download link can be
Because White Lake is in contact with both granites and sedimentary rocks, the lake has developed a unique character.
It has good buffering capabilities guarding against changes in acidity while at the same time has a relatively high content of calcium
measured at about 35 parts per million. Click HERE
for additional information on the geology of White Lake and a coloured geological
map. The full version of the map showing greater detail and adjoining areas can be viewed and downloaded HERE.
Geological Setting of White Lake