The document reviews literature on karst features in southern Ontario, with a focus on the Niagara Escarpment. It summarizes the geological history and formation of the Escarpment between 400-500 million years ago. While karst features exist along the Escarpment, they are relatively underdeveloped due to the Wisconsin Ice Sheet removing existing features around 12,000 years ago, and the short timeframe for new features to form since. The most prominent karst occurs from Manitoulin Island to Grey County where conditions better enable feature development. Though immature, even small-scale features can impact local drainage, as seen in the 2000 Walkerton tragedy. More research is still needed on karst in southern Ontario and its

1. Reviewing Literature Concerning Karst in Southern Ontario with a
Specific Focus on the Niagara Escarpment
Skyler MacGowan, 250634552
Geo 3000Y
Term Paper due Nov 16, 2015

2. Geological History of the Niagara Escarpment
The Niagara Escarpment is a 725km long escarpment running from New York through
Ontario, Michigan and Wisconsin1
(figure 1). It formed 400-500 million years ago (mya)
during the Ordovician and Silurian Periodsi
at a time when a warm, shallow sea covered
southern Ontario, Michigan, and parts of Wisconsin and New York1
. The base layer of
the Escarpment is made up of shale deposited about 450mya and is the remnant of a
large, muddy delta that formed in the sea2
. It has a distinctly red colour due to the
presence of iron in the mud that was carried to the area by rivers flowing from the
uplifting Appalachian Mountains to the east whose rocks are rich in iron2
(figure 2).
Overlying the base layer of shale are mixed beds of sandstone, dolostone, limestone and
shale2
. Like the shale layer, the sediments in the sandstone layer came from rivers
flowing off the Appalachian Mountains2
. The limestone/dolostone layers were created
from marine coral and as we move north there are fewer mixed beds, reflecting a more
stable marine environment2
.
The top layer of the Escarpment was created approximately 420mya2
. It roughly indicates
the shoreline of the ancient sea, as along the especially shallow and warm waters of the
sea where it approached land there was constant deposition of marine organisms and
these deposited organisms mixed with sediment to form a limestone layer2
. During the
Silurian period some magnesium from the seawater mixed in with the limestone layer
causing the formation of the harder dolostone we see today2
. The shallow continental sea
eventually dried up about 250mya2
, opening up the layers deposited to erosional forces.
i
Ordovician Period: 485mya-445mya. Silurian Period: 445mya-420mya.

3. The layer of Queenston Shale is quite soft and has eroded faster than the dolostone
caprock, causing the steep face of the Escarpment we see today2
(figure 3).
Karst and The Niagara Escarpment
Although the dolostone caprock of the Escarpment is susceptible to the development of
karst features, landforms characteristic of a “typical” karst landscape (i.e. large cave
passages, sinkholes, sinking streams) are generally not well represented along the
Escarpment and those found are almost entirely postglacialii
and thus are generally under-
developed3
. However, although the Escarpment’s karst features are much less poignant
than in mature karst landscapes, that does not mean karst features along the Escarpment
are absent altogether. Furthermore, as will be discussed, even though karst features along
the Escarpment are relatively immature they can still profoundly impact the drainage
patterns of surrounding areas.
The most numerous and profound karst features in southern Ontario occur along the
section of the Niagara Escarpment running from Manitoulin Island through the Bruce
Peninsula down into Grey County4
. The increased prominence of this section results in
greater precipitation and steeper hydraulic gradients, important factors contributing to the
development of karst features3
. Additionally, there is minimal overburden along this
section of the Escarpment whereas 22-30 metres of overburden covers much of the rest of
the Escarpment3
. Water loses its acidity and hence its ability to form karst features when
it has to first percolate through sediment and thus the fact that there is minimal
overburden on this section of the Escarpment contributes to the proportionally high
number of karst features present there3
.
ii
The most recent ice sheet retreated roughly 12,000 years ago.

4. Why is the Karst on the Niagara Escarpment not More Developed?
As explained, there certainly are karst features on the Niagara Escarpment but as a whole
they are relatively underdeveloped. This is despite the fact that in many ways the
Escarpment and the section from Manitoulin Island down through Grey County in
particular is a prime site for the development of karst featuresiii
.
The primary reason for this has to do with the fact that the Wisconsin Ice Sheet only
retreated from southern Ontario about 12,000 years ago3
. The movement of this ice sheet
would have removed almost all of the Escarpment’s existing karst features, setting a
maximum timeframe of about 12,000 years for the current karst development to have
occurred3
. Mature karst features such as the caves found in south-central Kentucky
(which started forming 280mya5
) develop over millions of years and so the biggest single
reason why karst features on the Escarpment are not well developed is simply because
they have not had anywhere near the amount of time required for these features to
properly form. Furthermore, although the dolostone caprock of the Escarpment is prone
to karst development, dolostone is less soluble than limestone and thus karst features
typically take longer to form in dolostone than limestone3
.
Also, as described, between the caprock dolostone and the base layer of shale the
Escarpment contains mixed beds of shale, sandstone, limestone, and dolostone. These
mixed beds thin out as one moves northwards and are mostly absent on the portion of the
Escarpment north of Grey County2
. Shale is an aquitard meaning that development of
karst features can only occur within those materials that overlie the shale. Its presence
iii
I.E. it’s one of the largest dolostone plains in North America, local water acidity and erosive ability is
comparable to that of more southerly locations, it has high precipitation and hydraulic gradients, and in this
section of the Escarpment there’s little overlying sediment3
.

5. south of Grey County is therefore a big part of the reason why karst features along the
Escarpment become less common south of Grey County. Finally, as explained, south of
Grey County the Escarpment is overlain by up to 30 metres of glacial till which
substantially reduces the water’s ability to dissolve the dolostone layer3
.
Moving Forward
The karst features on the Niagara Escarpment are almost all very young and with time
they will become more profound and influence drainage patterns to a greater degree,
especially along the section of the Escarpment running from Manitoulin Island down
through the Bruce Peninsula and into Grey County. In a 1976 study by Cowell on karst in
the Bruce Peninsula, Cowell hypothesized that eventually almost all drainage into
Georgian Bay from the Bruce Peninsula will take place underground3
. However, it will
be a very long time before a situation like this occurs because as mentioned mature karst
features and landscapes develop over a very long time.
Having said this, just because the Niagara Escarpment and southern Ontario do not have
many well-developed karst features that does not mean these areas cannot exhibit
drainage patterns similar to what one would expect to see in a mature karst landscape.
Once conduits are 1mm or greater in diameter they can become significant in the
karstification process4
and southern Ontario, including the Niagara Escarpment has quite
a few features like this that have developed in the past 12,000 years since the last ice
age6
. This has important implications for groundwater protection strategies in southern
Ontario and along the section of the Escarpment running from Manitoulin Island down to
Grey County in particular7
.

6. A tragic example of what can happen when karst features and their impact on local
drainage patterns are not well understood and appreciated is the Walkerton tragedy of
2000 in which E.coli contaminated Walkerton’s water supply, causing seven fatalities.
Subsequent tracer tests found that water moves very quickly (200-500m daily) through
the thin overburden and karst features in the carbonate bedrock underlying Walkerton8
.
These karst features allowed runoff from nearby farms to rapidly enter the community’s
wells without having undergone the normal filtration process that would typically take
place in an area void of any karstic features.
So, even though the Niagara Escarpment and southern Ontario more generally may not be
a mature karst landscape, karst features certainly are present in these areas and
consequently at times they can exhibit drainage patterns characteristic of mature karst
environments. In conducting my research for this paper I found a general paucity in
research of karst in southern Ontario as there have only been a few researchers who have
looked into this topic and most of their literature has focused exclusively on the Bruce
Peninsula. Therefore, going forward, more research on karst in southern Ontario is
required as karst areas are highly susceptible to groundwater contamination and as we
saw with the Walkerton tragedy, a failure to understand such drainage systems can have
dire consequences for human health.

7. Figure 1: Map of the Niagara
Escarpment
Figure 2: Stripped Por0on of Queenston Shale
at Cheltenham Badlands
Note: red colour of the shale is due to presence of iron which was transported here by
rivers flowing from the Appalachian Mountains whose rocks are high in iron.

8. Figure 3: Cliff Face of the Escarpment
Close to Ra9lesnake Point (Milton)

9. References
1) The Niagara Escarpment | Bruce Trail. Retrieved November 6, 2015, from
http://brucetrail.org/pages/about-us/the-niagara-escarpment
2) Gilhespy, B. (2015, April 15). Escarpment Geology: Another part of our
Living Landscape. Bruce Trail Magazine, 22-29.
3) Cowell, D. (1976). Karst Geomorphology of the Bruce Peninsula,
Ontario. Hamilton, Ont., Ontario: McMaster University.
4) Brunton, F., & Dodge, J. (2008). Karst of Southern Ontario and
Manitoulin Island. Sudbury, Ontario: Queen's Printer for Ontario.
5) Wagoner, J., & Cutliff, L. (1985). Mammoth Cave. Arlington, Va.,
Virginia: Interpretive Publications.
6) Brunton, F. (2013). Karst and Hazards Lands Mitigation: Some
Guidelines for Geological and Geotechnical Investigations in Ontario Karst
Terrains. Sudbury, Ontario: Queen's Printer for Ontario.
7) Harvey, D. (2003). Grey and Bruce Counties Groundwater Study.
Waterloo, Ontario.
8) Worthington, S., Smart, C., & Ruland, W. (2001). Karst hydrogeological
investigations at Walkerton. Dundas, Ontario.