Chedabucto Bay is the largest bay on the Atlantic Coast and was formed by the drowning of part of an ancient river system. The river developed on the erodable Carboniferous sediments, which can now be seen on the lowland margins of the bay. Various soils have developed on deep tills and include
extensive clay areas. This part of the Atlantic Coast Region is more sheltered, but the coastal forest still dominates. Freshwater habitats are more productive than elsewhere in the Region. Water temperatures are warmer in the summer than on more exposed coasts and support some southern marine fauna species.
Geology and Landscape Development
Chedabucto Bay lies immediately to the east of the Horton sandstone Rolling Upland (District 570) of the Carboniferous Lowlands. It is dominated by sedimentary rocks deposited during and after the formation of Pangaea in the late Devonian and Carboniferous periods.
Apart from slices of Precambrian Fourchu volcanics, which have been faulted up against younger rocks on Isle Madame, the oldest deposits in the District are coarse conglomerates, including some volcanics. These were deposited during the unsettled period from Late Devonian to Early Carboniferous
when major crustal movement and adjustment was taking place in Nova Scotia. These conglomerates and related deposits are extensively exposed in eastern Guysborough County, on Isle Madame, and between L'Ardoise and Loch Lomond.
The succeeding deposits are salts (Windsor Group), reddish siltstones (Canso Group), and fine sandstones (Riversdale Group). All these
rocks are relatively soft and erodable, and they have formed a rolling lowland which slopes towards Chedabucto Bay and the Strait of Canso.
Chedabucto Bay owes its origin and shape to a number of factors. Its southern boundary marks the position of the Chedabucto Fault,
which extends across central Nova Scotia from the Bay of Fundy to the Canso peninsula. This fault line, the Strait of Canso, and Chedabucto Bay itself
were probably part of a major river system which rose on the continental shelf and flowed northwards into the Gulf of St. Lawrence during the Triassic
and Cretaceous periods. Later tilting and submergence drowned the valley, creating both the bay and the strait.
Glacial ice moving into Chedabucto Bay from the northwest and from local ice caps deposited a locally derived red-brown sandy till across
the Carboniferous rocks. Drumlins are entirely absent on the northwest side of the bay but are common in the eastern part where they have an east-west
(Isle Madame) or northwest-southeast orientation. Consequently, rivers rising in the uplands flow southwards across the Carboniferous Lowland
into Chedabucto Bay. River Inhabitants, the largest in the District, rises in the Maple Brook area south of the Creignish Hills and empties into the bay
through a drowned valley. Marine erosion provides abundant coastal sediment for numerous small gravel beaches. The beaches often enclose small lagoons
or salt marshes.
Many small to medium-sized lakes are scattered throughout the District, and pH ranges between 6.0 and 7.0. Bogs are particularly common
on Isle Madame, and large wetland areas can be found along the Inhabitants River.
The soils in this area have developed for the most part from sandstones, slates, and shales, giving tills ranging in texture from sandy loam to
shaly clay loam. In Guysborough County, mottled, imperfectly drained clay loam Millbrook soils are common. The better-drained Westbrook sandy loam
is found around the town of Guysborough. Riverport (imperfectly drained shaly loam) and Kirkhill (sandy loam) soils have both developed from shales.
On Cape Breton Island the western section of this District has more Millbrook soils, imperfectly drained Diligence and Queens clay loams, and
poorly drained Kingsville soils. Further east, including much of Isle Madame, soils have developed from stony tills derived from hard sandstones and
angular metamorphic rocks. They are the same as those found in the Louisbourg area; i.e., Thom and Arichat soils, with extensive peat deposits.
Along the River Inhabitants the soils are a complex mix of peat; alluvial fine sandy loams known as Kingsville, Cumberland, and Bridgeville
soils; and the coarse Hebert series which has developed on outwash gravels.
Although this part of the Atlantic coast is more sheltered, the coastal forest is still manifest, with the predominant forest association being
White Spruce and Balsam Fir with maple and birch. On the clay Queens soils of Cape Breton sections of this District, Balsam Fir and Black Spruce are
the dominant species, with scattered shade-intolerant hardwoods. Some aspen also occur, especially in disturbed areas. Barren and bog vegetation
are common, particularly on Isle Madame. Old farmland is found mainly on the clay soils and is mostly regenerating in pure White Spruce. The low
coastal relief and abundance of sediment give areas of salt marsh, but significant local winter ice action restricts the growth of seaweeds.
Chedabucto Bay is not a productive area for waterfowl or seabirds because there are few undisturbed islands, and winter sea ice restricts
feeding from open water. However, salt marsh and estuary areas do provide some wading bird habitat (herons and shorebirds).
Warm water temperatures in summer permit the reproduction and survival of some more southerly marine species. Many of them are
also found in the Gulf of St. Lawrence but are no longer able to interact freely with those in Chedabucto Bay because of the presence of the Canso
Causeway. The diversity and populations of epifauna are restricted by ice action. Whales are sometimes seen in Chedabucto Bay.
The River Inhabitants provides rich aquatic habitat and is important for nesting Wood Turtles. Freshwater lakes on Isle Madame
contain interesting relict fauna with a more continental distribution, including a species of freshwater clam.
Scenically, this District is dominated by Chedabucto Bay and its extension into the Strait of Canso. Localities adjacent to both higher relief
and the ocean (i.e., around Guysborough Harbour and the eastern end of Canso Strait) are of high scenic quality, particularly where farming adds a
human element to the landscape. Isle Madame, though flat, has salt marshes and much of human interest, with characteristic Acadian village forms.
Inland, scenic values are generally low to medium because there is little settlement or relief, and only a few lakes (almost none in Inverness County). There
is added scenic value, however, where this lowland abuts the Avalon Uplands (Region 300), notably along the upper reaches of River Inhabitants.
Nicholas Denys established a fur trading and fishing post at St. Peters in 1636. During the eighteenth century, Isle Madame was an
important Acadian settlement in close communication with Louisbourg. In general, small-scale farming, fishing, and forestry have been the resource use of the
land and sea in this area. Shipbuilding was once common and, today, shipbuilding and maintenance industries continue. An industrial base established
along the Strait of Canso is strategically located to make use of the shipping lane connecting the Gulf of St. Lawrence with the Atlantic Ocean.
Forestry exploitation yields pulpwood, which supplies a sulphite mill and a newsprint mill at Point Tupper. A coal-fired, steam-turbine
electrical plant is also located at Point Tupper. St. Peters Canal is an important link to the Bras d'Or Lake, facilitating recreational boating. Prior to the
completion of the canal, small vessels were pulled by oxen over the narrow strip of land on skids, and thus the area was referred to on Admiralty charts of the
time as "Haulover Isthmus." In 1970 the Greek tanker
Arrow, carrying 16,200 tons of bunker C oil to a pulp mill at Point Tupper struck Cerberus Rock
in Chedabucto Bay, creating a massive oil spill which polluted half of the bay's 600-km coastline. Twenty years later, Bedford Institute of
Oceanography scientists studying Chedabucto Bay concluded that little evidence of this oil spill remained.
Sites of Special Interest
- Loch Lomond - exposed conglomerates and deposits
- Janvrin Island - exposed red and purplish strata
Provincial Parks and Park Reserves
- Mast Cove
- Ragged Head
- Dorts Cove
- Kempt Road
- Lennox Passage
- Cap La Ronde
- Pondville Beach
- Cove Road
Proposed Parks and Protected Areas System includes Natural Landscape 47.
- Guysborough Harbour (both sides)
- River Inhabitants (tidal reaches)
- Salt marshes between Isle Madame and Janvrin Island
- Arichat Provincial Park (Arichat Harbour)
- St. Peters Canal
The Carboniferous Basin
Post-glacial Colonization by Animals
Amphibians and Reptiles
Freshwater Open-Water Lentic
Freshwater Bottom Lentic
Freshwater Water's Edge Lentic
Mixed Forest (White Spruce, Fir-Maple, Birch Association)
|Associated Offshore Regions|
|916 Bras d'Or Lake