Geology Reference
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measured for loss of mass over a 5-year period, limestone and dolomite disks weathered
much fastest than granite disks (Thorn et al., 2002). This is not surprising. It is also not
surprising that poor drainage (increasing wetness) and decreasing PH (increasing acidity)
correlate with weathering of the dolomite disks. Elsewhere in northern Sweden, post-
glacial rates of mechanical weathering are not only relatively slow (André, 1995a, 1996,
2002) but also dependent on rock type. Again, as might be expected, rates of general
surface lowering on carbonate rocks are an order of magnitude greater (
∼
5 mm/ka) than
on homogeneous crystalline rocks (
0.2 mm/ka) (André, 2002).
Apart from these investigations in northern Sweden, there is little systematic data
available on the absolute and relative rates of chemical weathering processes in cold polar
latitudes. Several data sets from mid-latitude alpine regions (Caine and Thurman, 1990;
McCarroll, 1990 ; Williams et al., 2006) suggest that chemical weathering is of importance.
The one defi nitive conclusion that can be made is that the limitation to chemical weather-
ing in cold climates relates primarily to moisture rather than to cold temperature (Balke
et al., 1991).
∼
4.6.2. Solution and Karstifi cation
A chemical weathering process that always attracts attention from geomorphologists is
that of limestone solution. This refl ects the solubility of calcium carbonate (CaCO
3
) in
water. Because the solubility of CaCO
3
in water increases with a decrease in temperature,
it has been suggested that solution in cold regions is higher than in other regions. For
example, Rapp (1960a) concluded that solution loss was by far the most important agent
of denudation at Kärkevagge (see earlier). Yet studies in other cold environments suggest
that solution activity is no greater than elsewhere. For example, in the central Canadian
Arctic, solution rates are actually smaller than in low latitudes, carbonate concentrations
in standing water bodies are of the same order of magnitude as those of temperate regions,
and elevated concentrations of carbon dioxide in snow banks do not always exist (Smith,
1972). Some typical limestone solution values and rates of denudation are listed in Table
4.5. Other factors being equal, precipitation controls the solution rate. We might conclude,
therefore, that the generally low rates of limestone solution denudation that typify many
cold environments probably refl ect the relative aridity of these areas rather than any
“weakness” of solution activity.
Where hard and relatively pure limestone outcrops over large areas, solution processes
that are concentrated along joints, bedding planes, and other discontinuities may assume
special importance. The result is cold-climate “karst” terrain. Initially, it was thought that
permafrost inhibited solution activity and karst terrain. Thus, D. A. St-Onge (1959)
remarked upon the absence of solutional effects in terrain developed in gypsum on Ellef
Ringnes Island, and J. B. Bird (1967, pp. 257-270), in a detailed account of the limestone
scenery of the central Canadian Arctic, concluded that solution effects were weak.
However, recent studies by D. C. Ford now suggest that a “sub-cutaneous karst” model is
applicable to limestone terrain in areas of permafrost. The model asserts that groundwater
circulation and solution are limited to the seasonally-active zone, favoring the develop-
ment of spreads of shallow karren (i.e. solution-pitted) ground at the expense of sinkhole
and cavern topography.
A number of relationships between karst terrain and glaciation have been considered
(Ford, 1984, 1987, 1996) in the context of northern Canada. The fi rst is where continuous
permafrost exists. Here, bedrock has remained frozen, initially beneath Pleistocene ice
and subsequently during deglaciation. Thus, karst development is postglacial in age and
restricted to the active layer, and mostly along the edges of bedrock outcrops. Today, minor
