The Cobequid Hills are the surface expression of a steep-sided, elongated fault block - a slice of Avalon crust - which forms a highland on the north side of the Minas Basin. It is a resistant massif surrounded by more easily eroded and low-lying Carboniferous and Triassic sediments (see Figure 19). The geology of the Cobequid Hills is dominated by metamorphosed sediments, granites, and volcanic deposits
which range in age from Precambrian to Devonian. These have been crushed, folded, and faulted. Geological complexity is manifest in the rapid changes of rock type within short distances.
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Precambrian Basement Rocks
The oldest rocks are those of the Bass River Complex, found from Economy River to Nuttby and in the Central New Annan area, and the Mount Thom Complex, exposed at Mount Thom. These rocks were originally sedimentary and volcanic deposits but have been metamorphosed to schists and gneisses. They form part of the Precambrian basement upon which deposition took place in the Silurian. Included in this basement are altered granites which were intruded during obscure early phases of crustal upheaval.
Overlying Sedimentary Rocks
There are no Cambrian strata in the Cobequid Hills, but deposition appears to have been continuous from the Silurian through the Devonian and Carboniferous. Many different rock types are present. The earlier, Silurian deposits of fossiliferous siltstone and shale are interleaved with various types of volcanic deposits such as ash (tuff) and flows (ignimbrites and lavas). These give way to younger (Devonian) non-fossiliferous red beds, which can be correlated to the Knoydart Formation in the Pictou-Antigonish area. The red beds were deposited in shallow, fresh water and are thought to represent the retreat of the sea prior to the Acadian crustal collision which led to the formation of Pangaea. Middle Devonian deposits include more volcanic rocks. Late Devonian strata include coarse sediments which continue into the Carboniferous.
The Acadian Orogeny caused the crushed and folded sediments to begin melting and mobilizing deep within the crust. The resulting granitic liquid rose and cooled, forming large intrusive bodies. These granites, together with their older counterparts, now represent more than 40 per cent of the bedrock underlying the Cobequid Hills.
Surface Exposure of the Fault Block
Although the Cobequid Hills have ancient origins, they did not become a topographic feature until after the Cretaceous. The block appears to have begun moving vertically upwards via fault movement during the Carboniferous, but was deeply covered by sediment at that time. Unlike other areas in the Avalon Uplands, it did not form an island in the Carboniferous Sea.
The block lies on the upper side of the uplifted planation surface and has remained as a resistant highland while the surrounding softer Carboniferous and Triassic sediments have been stripped away (see Figure 7).
The Cobequid Hills form a cigar-shaped block about 120 km long, 15 km wide, and on average 275 m high. The crest is a narrow, featureless plateau which ends abruptly at faulted margins on both the north and south
sides. The western extremity is the granite headland of Cape Chignecto (see Figure 9).
The southern boundary is the scarp of the Cobequid Fault, which is the westerly continuation of the Chedabucto Fault. This fault, which can be traced from Truro to Cape Chignecto, is obscure in the east, but in the
west it has a steep and prominent scarp slope. The fault zone is best exposed along the beach just west of Port Greville. It is also visible at Bass River as a 100-m band of crushed rock. East of Parrsboro it appears as a
series of high cliffs and steep hills that are skirted by the road. From Parrsboro to Diligent River, the highway follows the contact between the resistant older rocks on the north side and the Carboniferous lowlands to
the south. Beyond Fox River, the fault follows the north shore of the Minas Channel, becomes obscure around Advocate, and runs seaward off high cliffs at Cape Chignecto.
The northern boundary of the Cobequid Hills runs from Earltown to River Philip. Although there is an abrupt drop to the rolling northern plain, the slope descends more by a series of steps than as high cliffs.
The fault on the northern side is covered by Carboniferous deposits.
Within the Cobequid Hills, other east-west faults divide the block into long slices, but these have little topographic expression because they are juxtaposed rocks of similar hardness.
The crest of the Cobequid Hills is relatively even and undissected, except for two places where it is crosscut by major valleys: the Parrsboro and Folly gaps. The Parrsboro and Folly gaps are believed to be the
abandoned valleys of rivers which at one time may have flowed southwards from the Gulf of St. Lawrence. They were superimposed upon the massif as it rose and became exposed, and they cut deep channels across
its surface. The remnants of these rivers now flow northwards and may be represented by River Hebert and the Wallace River. The floors of the Parrsboro and Folly gaps are covered by glacial debris, including thick
deposits of gravel. Folly Lake has formed between dams of gravel at either end of the valley. Water seeps through on both sides to form the headwaters of the Wallace and Folly rivers.
Along the sides of the Parrsboro Gap are glaciofluvial gravel terraces and kames. Other kames and kame terraces in the centre of the valley cut off several small lakes.
Cobequid Hills form a drainage divide across northern mainland Nova
Scotia. Primary tributaries tend to run north-south. The Region
the headwaters for many watercourses draining to the Bay of
Fundy and the Northumberland Strait, including the Folly, Portapique,
Economy, and Chiganois rivers. The streams rise in the lakes and bogs
on the till-blanketed crest and then plunge down the scarp slopes in
waterfalls, cascades, and straight, steep-sided gorges. The falls and
gorges are most spectacular on the south side; e.g., along the
Economy, Moose, Bass, and Portapique rivers. On the north side, falls
can be seen east and west of New Annan. The valleys tend to be wider
on the north side. In some cases, a new channel has been cut in the
centre of a wider, shallow valley; e.g., along the Folly River where
the river occupies a central narrow gorge 20-30 m deep.
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The small headwater lakes, bogs, and swamps are relatively
infertile. Conductivity ranges between 16 and 62 micromhos/cm and pH
derived from the igneous and metamorphic rocks in this Unit are stony,
usually shallow, and extremely acidic, gravelly, sandy loams. Over
large areas the bedrock is within 0.5 m of the surface, and rock
outcrops are common. The Cobequid series covers most of the area. This
well-drained, sandy loam is an excellent forest soil, providing a
porous but solid rooting medium. The cool, moist climate is
responsible for the accumulation of colloidal organic matter in these
soils. Wyvern soils are found along the northern edge of the Cobequid
Hills. These soils are similar in many ways to the Cobequid series.
significant areas of Wyvern soils were accessible to early settlers who
cleared the land; some is now reverting to forest while the rest is
being used for blueberry production. Small areas of Hebert soils (well
to excessively drained gravelly, sandy loams) are found on glaciofluvial
sands and gravels around lakes.
top of the Cobequids now supports a Sugar Maple, Yellow Birch, and
American Beech forest interlaced on shallow soils with Balsam Fir and
Red and Black Spruce. The poorly drained depressions support Balsam
Fir and Black Spruce.
The northern part of the plateau has the purest stands of hardwoods.
Conifers become increasingly common to the south, especially Red
Spruce and Balsam Fir. The influence of the Bay of Fundy can be seen
towards the west where extensive stands of Red Spruce thrive up to 200
m above sea level. Parts of the plateau in Cumberland County that were
once cleared for agriculture are now blueberry fields. Other fields were
created recently by clearing woodlands. oldfields have come back in
coniferous stands dominated by White Spruce.
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Eastern Hemlock is common in ravines. White Spruce, Red Spruce, and
Balsam Fir form mixed woods with Sugar Maple, Yellow Birch, and Red
Maple on the slopes, becoming softwood forests of Black Spruce, White
Spruce, and White Pine in the valley bottoms.
Exposure to wind affects a large part of the Unit. Red Spruce and
Yellow Birch are particularly susceptible and may be stunted.
In 1912, C.D. Howe observed: "On the granite north of Advocate
bay [there is] a luxuriant forest which contains 75 percent red
spruce. The same type is found on the granite mass north of Greville
bay. From there, the outcrops of this group of rocks occur only in
small patches, until the Cobequid hills are reached, where they are
found in largest mass. The northern slopes of the Cobequid hills in
the neighborhood of Wentworth, for example, support at the base a
mixed forest of hardwoods and red spruce, fir and hemlock, in which
softwoods originally predominated. As one ascends the slopes the
forest becomes prevailingly of the hardwood type. In some places it is
two-thirds yellow birch; in other places it is about equally divided
between yellow birch, hard maple and beech. Near the top of the slopes
one often finds narrow ridges which are covered to the extent of ninety
percent with beech of inferior quality. In the higher levels
frequently immense hopper-like basins are found nearly enclosed by
ridges. In these, the forest is composed in nearly equal proportions
of balsam fir, red spruce and the hardwoods. In the narrow valleys of
the streams on the other hand, hemlock, spruce and fir prevail in the
order named, so that looking at the northern slopes of Cobequid from a
distance, one sees the green of the prevailing hardwoods interspersed
with black bands of coniferous softwood foliage."
Ground and shrub vegetation is usually varied and luxuriant. A
number of unusual arctic-alpine and Alleghanian plant species may be
found in cool, moist ravines and in rich Sugar Maple woods.
the accumulation of snow and the more-open deciduous forest forces
deer to migrate off the Cobequid Hills to the south-facing lower
slopes. The deer then return in May to mature hardwood habitats to
feed on spring flowers. The Cobequid Hills support good moose
populations year-round. Softwood forests on poorly drained soils are
used by moose for winter cover. It is thought that the winter
separation of moose and deer lessens the transfer of a
central-nervous-system nematode parasite from deer carriers to the
Animals and plants characteristic of fertile wetlands
are not abundant in this Region. Steep watercourses and small,
relatively unproductive headwater ponds and bogs disfavour their
establishment. Low-energy drainage systems on the crest are inhabited
by beaver, but sparse food and harsh climate usually limit
populations. Bobcats and, more recently coyotes, hunt the softwood
swamps for Snowshoe Hare.
Maple and Yellow Birch forests provide an excellent opportunity for
animals dependent on tree cavities and fallen logs. The erythristic
(all-red) colour phase of the Eastern Redback Salamander is commonly
found in the hardwood forest.
The scarcity of active farmland results in the virtual absence of
most open-country birds, and the predominance of hardwoods may
restrict the occurrence of some birds characteristic of softwood
forests. However, the Great Horned Owl is known to nest in the
softwoods on top of the hills and in the hardwood slopes below them.
Goshawk, Red-tailed Hawk, and Barred Owl also nest in this Unit. In
winter, bird life is relatively scarce except for possible sightings
of Common Raven, Pileated Woodpecker, and Ruffed Grouse in the
hardwoods. Grey Jay and chickadees proliferate in the softwoods. Many
species of warbler and other insectivorous birds can be seen here in
Brook Trout is the predominant fish species, but Brown Trout and
Atlantic Salmon are also found in many small headwater streams.
Unit 311 meets the coast at Cape Chignecto, where one sees various
marine birds and Grey Seal. Cliffs in this area are monitored as
possible nesting sites for Peregrine Falcon.
of the Cobequids Hills was logged in the early 1900s. A second wave of
forestry is now occurring with increasing construction of
forest-access roads and clearcuts. The new route for the Trans-Canada
Highway also passes through this Unit. Such activity may favour some
wildlife species and possibly negatively affect some other, old forest-dependent
species. Sugar Maple stands in the Cobequid Hills have also been used
for the commercial production of maple syrup. In some areas, such as
Mount Thom, forests were cleared for farmlands that are still in use.
Road construction has been challenged by the Cobequid Hills, with
passages like the Folly Gap providing important routing points. Tracts
of woodland have been cleared for commercial blueberry production.
Sites of Special Interest
- Road from Highway 104 to Lornevale - shallow iron deposits 800 m
north of Cobequid Fault
- Londonderry - iron-bearing carbonates formed the foundation of an
iron industry in the nineteenth century
- Folly Gap - U-shaped glaciated valley best seen near Wentworth is
a relic of the ancient drainage system
- Folly Lake - glacial lake
- Parrsboro Gap - the channel cuts Unit 311, draining the River
Hebert north and the Parrsboro River south; glacial terraces and
- Economy River, Bass River, Moose River, Tatamagouche - waterfalls
- Portapique River - cascades and gorge
- Nuttby Mountain - lookoff
- Bass River - Cobequid Fault zone of crushed rock
- Greville Bay and Cape Chignecto - cliff exposure of Cobequid
- Lynn Mountain - mature deciduous forest with characteristic flora
- Eatonville - junction of Units 311, 532,
Provincial Parks and Park Reserves
- Simpson Lake, Cape Chignecto
Proposed Parks and Protected Areas System includes Natural Landscape
23, and Candidate Protected Areas include 24 Economy River and 25
- Wentworth Valley, Sugarloaf Mountain, Parrsboro Valley, Greville
Bay, Five Islands Provincial Park, Portapique River, Economy River
(falls), Moose River (falls).
The Avalon and Meguma Zones
The Carboniferous Basin
Ancient Drainage Patterns
Terrestrial Glacial Deposits and Landscape Features
Rare and Endangered Plants
Birds of Prey
Plants and Resources
Freshwater Open-Water Lotic
Freshwater Bottom Lotic
Hardwood Forest (Sugar Maple, Yellow Birch, Beech Association)
Outer Bay of Fundy