Stops Of Interest: Trans-Labrador Highway
- Schist and quartzite, Smokey Mountain ski hill
- Iron minerals, Walsh River rapids
- Schist, Whiteway Drive, Wabush
- Julienne Lake iron deposit
- Javelin Road dolomite deposits
- Zoned pegmatite
- Proterozoic gabbro roadcut
- Granite and gabbro, Churchill River crossing
- Granite, Churchill Falls townsite
- Churchill Falls (Labrador) Corporation Ltd
- Sillimanite gneiss
- Road building and eskers
- Glacial features, Churchill River valley
- Lower Brook gneiss
- Granite, Muskrat Falls
- Lake Melville rift valley from Goose Bay
- Anorthosite quarry, Grand Lake road
1. Schist and quartzite, Smokey Mountain ski hill
Take the road to Smokey
Mountain ski hill on the north side of Labrador City, drive 3.2 km to
the end of the road and park. For safety and information, check in with
the manager before climbing the hill. The best exposures can be seen
under the farthest north of the ski tows. Warning! The top section of
the hill is very steep. For an easier route to the very top, follow the
service road around to the right where it crosses the tow line below the
steepest part of the hill.
The lower slope exposures are made of quartz_feldspar schist,
which also contains muscovite, kyanite, garnet, staurolite and biotite.
Some boulders in the debris from close by consist almost entirely of
biotite, although this material does not outcrop. These rock types
result from metamorphism of sandstone and shale during the Grenvillian
Orogeny. Farther up the hill, and on up to the top are large exposures
of white quartzite. This highly resistant rock can be seen on all of
the hilltops around, where it has been smoothed and scoured by glacial
action. You can feel with your hand the smooth grooves left by the ice.
On the way to the top, where the main track is joined by another
track leading downhill to the right, leave the track and walk a few
hundred metres up the low hill to the northwest. This hill is underlain
by oxide iron formation, here composed of hematite_magnetite_quartz
schist, similar to the material being mined by Iron Ore Company of
Canada. You can see folded banding, in which the colours indicate
different amounts of quartz. The iron formation overlies the white
quartzite, which caps the surrounding hills.
A few hundred metres farther northwest, across the small valley,
is an outcrop of gabbro on a low hill. The gabbro intruded the iron
formation in Middle Proterozoic time. It is composed of feldspar and
pyroxene, with some olivine, ilmenite, biotite and apatite.
At the top of the ski hill, there is an excellent view of the two
towns to the south, and of the IOCC open pit mine to the north.
Tailings from the processing of the iron ore are being deposited behind
a dam in the lake to the east. The company is gradually revegetating
the tailings; the green, grassed portion contrasts with the grey, newly
deposited tailings.
2. Iron minerals, Walsh River rapids
Drive outside Labrador City on the
road to Fermont. At 7.6 km west of the Circular Road turnoff, the
highway crosses the Walsh River. Park on the east side of the bridge,
and follow a trail up the east bank of the river 150 m to a small
waterfall.
A large outcrop of rusty, banded iron formation forms the falls
and yields a showy suite of metamorphic minerals. These include
(besides quartz) siderite (brown iron carbonate), grunerite (brownish
iron_magnesium silicate with radiating crystals), and ferrosilite (a
brownish-green, iron-bearing silicate). Deformation has formed wavy
folds in the outcrop. The bladed or radiating habit of grunerite can be
clearly seen on flat slabs on the small beach.
3. Schist, Whiteway Drive, Wabush
Drive into Wabush by the main road, and
turn left immediately on Whiteway Drive. The road curves around above
the town to where a large water tower is visible on the left. Park next
to the Anglican church and walk up the track to the tower.
A flat exposure of rusty schist can be seen at the top of the
roadway and you can see the strongly foliated nature of the rock. On
the north side of the fence surrounding the water tower are piled large
slabs of the same material.
The coarse-grained schist is composed of quartz, feldspar, white
and black mica, pink garnet, sparse bluish kyanite and small knots
composed mainly of quartz and feldspar. Darker garnet-bearing layers
show wavy folding and are broken apart.
4. Julienne Lake iron deposit
Drive 5 km east on the Trans-Labrador Highway
and turn north on Javelin Road. After 16 km, the road forks; to the
right, IOCC is mining dolomite, which is used in the iron ore
pelletizing process, and access is restricted. Take the left fork and
continue for about 6.5 km, taking the left fork at each option, to
arrive at the large open site of the Julienne Lake iron deposit. This
deposit was discovered and evaluated in the 1960s and early 1970s.
This is leached oxide iron formation, composed of quartzite
containing magnetite and specular hematite, and is similar to the
deposit being mined by Wabush Mines. During leaching, probably in the
Cretaceous, fluids passing through the rock dissolved iron and manganese
from some parts of the deposit, leaving cavities or vugs, and deposited
them as coatings of goethite and limonite in other areas.
Grey, leached and crumbling quartzite may be seen at the back of a
sandpit, 0.5 km south of the iron deposit, on the west side of the road.
This is the same formation as the hard, lustrous quartzite seen at the
top of the ski hill, but leaching has removed the material that used to
hold the quartz grains together.
5. Javelin Road dolomite deposits
Drive back 3.5 to 4 km south from the
Julienne Lake iron deposit, and watch for low, dirty whitish outcrops on
the east side of the road. This is the dolomitic marble being mined
nearby by IOCC for use as a flux in the preparation of iron-ore pellets.
The material is white to buff in colour and composed of dolomite, quartz
and amphibole. It is very soft, and weathers easily into a buff sand.
On one of the outcrops is a drillhole where material in and around the
hole has been further dissolved by rainwater.
6. Zoned pegmatite
There is a large roadcut on the north side of the Trans-
Labrador Highway, 1 km east of the 110 km post. Dark green gabbro is
intruded by a 7 m wide, light-coloured pegmatite dyke. The gabbro
intruded sedimentary rocks 1640 million years ago, and was itself cut by
the pegmatite about 1000 million years ago.
The dyke is zoned, meaning that the margins, which crystallized
first, contain different minerals from the centre. The centre is grey-
white quartz, and is 2 m wide. The marginal zones consist of creamy
white to pinkish feldspar studded with "books" of white mica
(muscovite) up to 6 cm in diameter. The feldspar has perfect cleavage,
particularly on the left hand side of the dyke, while the quartz has no
cleavage. The mica "books" have perfect cleavage parallel to the
"pages" and show the characteristic six-sided or hexagonal crystals.
7. Proterozoic gabbro roadcut
About 66 km west of Churchill Falls townsite
(5.8 km east of km 190), the highway passes through shiny black gabbro
roadcuts. On the freshly blasted surfaces, you can see medium- to
coarse-grained pyroxene (dark green to black) and feldspar (dark grey).
The gabbro intruded granite of the Trans-Labrador batholith about 1450
million years ago.
8. Granite and gabbro, Churchill River crossing
Stop by the bridge over the
Churchill River, 22 km west of Churchill Falls townsite, to view the
almost-dry river channel. Diversion of the Churchill River for
hydroelectric development allows access to spectacular exposures in the
dry riverbed. The more agile can scramble down the steep gravel by the
eastern bridge abutment, and examine the huge, water-worn blocks in the
channel. Warning! The river is occasionally used as a spillway for
excess water from the Smallwood Reservoir. Water has been released on
two occasions in the past 20 years.
The rocks that form the riverbed are granite and gabbro. Reddish
granite near the bridge has a slight foliation; upstream it contains
rounded masses of black gabbro. Rock deformation, which increases
upstream, occurred during the Grenvillian Orogeny, when these rocks were
being forced northward over the rocks that underlie the Smallwood
Reservoir. Potholes, rounded hollows in the rock of the riverbed, were
worn during the past few thousand years by pebbles being swirled around
in the river current.
The Churchill Falls waterfall, once a spectacular sight named the
Grand Falls of the Hamilton River, is now reduced to a mere trickle by
the demands of the power development. The waterfall can be viewed by
following a good trail downstream from the west end of the bridge. Park
in the open area just south of the highway. The waterfall, 76 m high,
is located at the head of the deeply cut Bowdoin Canyon, and flows over
a resistant buttress of granite. The canyon runs at right angles to the
river course above the waterfall, following the foliation direction of
the granite.
A commemorative plaque at the viewing point is mounted on a large
boulder of hornblende granite. This boulder is what is known as a
glacial erratic; well rounded by glacial transport, it has probably been
carried a great distance because this rock type is not found locally.
9. Granite, Churchill Falls townsite
The town is built on granitic rocks of
the Trans-Labrador batholith. The granite exposed around the hotel is
weakly foliated, but in some places has been changed to a gneiss by
deformation and metamorphism.
The granite outcrops northeast of the hotel show smooth, strongly
grooved surfaces from the passage of glaciers. The grooves are oriented
roughly east_west, and can easily be felt by running your fingers across
them. There are also large, crescent-shaped gouges, made when rocks
held in the base of the glacier scraped against the bedrock, and chipped
off fragments. The ice moved from west to east in this region. High
hills around the townsite are metamorphosed gabbro intrusions.
10. Churchill Falls (Labrador) Corporation Ltd
The town of Churchill Falls
was established by the company to build and service the hydroelectric
project that required the diversion of the Churchill River and the
flooding of the Smallwood Reservoir. The town is still owned and
operated by the company. The plant at Churchill Falls generates
5,428,000 kW of power, most of which is sold to Quebec. The tunnels and
chambers of the powerhouse were hollowed out of grey gneissic granite to
a depth of over 300 m.
Tours of this impressive hydroelectric facility are free of
charge, and can be arranged through the Churchill Falls Inn, (709) 925-
3211. It is advisable to book in advance to avoid disappointment.
11. Sillimanite gneiss
East of the Metchin River, as the road rises over the
Red Wine Mountains, rock exposures appear more frequently than in the
sandy esker terrain to the west. The main rock type in this area is
sillimanite gneiss, formed during the Labradorian Orogeny about 1650
million years ago. Sillimanite is a mineral that grows at high
temperatures during metamorphism. In this area, it formed at around
900¡C, when the rocks were buried at least 35 km below the surface.
This extreme metamorphism produces very erosion-resistant rocks,
accounting for the rugged character of the Red Wine Mountains. These
rocks were brought to the surface by faulting during the Grenvillian
Orogeny about 1000 million years ago.
Sillimanite gneiss occurs in flat, smooth outcrops on the north
side of the road between the Metchin River and Middle Brook. The rock
also contains feldspar, biotite, hornblende and magnetite. The gneissic
banding is extremely folded and contorted.
12. Road building and eskers
For much of its route across central Labrador,
the Trans-Labrador Highway is built on top of eskers. This is
especially notable from about 12 km east of the Cache River bridge to 9
km west of the bridge over Bob's Brook. The road in these stretches is
relatively level with sinuous curves, and there are often small lakes or
ponds on both sides simultaneously. The top of the esker, which has
been used for the roadbed, stands 10 m or more above the surrounding
level sandy terrain, and the sides slope steeply down (see Glacier
panel).
Eskers are an important source of coarse gravel for road
construction, and many pits have been dug along the highway to obtain
it. To avoid having to transport their road building material, the
engineers selecting the route often bring the road to the material by
routing it along the course of eskers. For this lower grade of road,
the gravel is used directly from the source without sorting it.
Therefore the road surface includes many rounded boulders, such as those
you see piled along the edge, making the surface uneven and bumpy to
travel!
13. Glacial features, Churchill River valley
About 90 km west of Goose Bay
the road descends from the uplands of central Labrador eastward down a
long steep hill (Pope's Hill) into the Pinus River valley, and then
emerges into the broad sweep of the Churchill River valley. Stop near
the top on any rise that offers a good view east down the valley. The
U-shaped profile of the valley is characteristic of glacial erosion and
was formed during the last ice age, which began about 25,000 years ago
(see Glacier panel). When the ice age drew to a close about 8,000 years
ago, the glaciers melted rapidly and a river of meltwater partly filled
the valley with sand. As the land surface rebounded, the sand was
eroded by the Churchill River into terraces and bluffs.
As you drive along the Churchill River valley east of the Pinus
River, you may see low, crescent-shaped ridges, at right angles to the
road and visible along thinly wooded sections. These are sand dunes
built by the wind from loose sand deposits.
The present valley follows the route of a much older rift valley
formed in Late Proterozoic times. The cliffs that form the walls of the
present valley follow the boundary faults of the ancient rift valley,
which was filled in Late Proterozoic time by sandstone and conglomerate.
Most of these ancient sedimentary rocks have been removed by erosion, or
covered by the new Quaternary sand deposits.
14. Lower Brook gneiss
In the Churchill River valley, 3.3 km west of Lower
Brook, a long roadcut exposes banded gneiss. Originally the gneiss was
an Early Proterozoic granite intrusion, about 1650 million years old.
The granite was intruded by diabase dykes, and then metamorphosed to
form the gneiss during the Grenvillian Orogeny, about 1000 million years
ago. The light-coloured bands consist of quartz, feldspar, biotite and
hornblende and are derived from the granite. The dark bands, which are
the remains of the dykes, are composed almost entirely of hornblende.
15. Granite, Muskrat Falls
At Muskrat Falls on the Churchill River, a high
knob of Early Proterozoic pink gneissic granite has resisted the
erosional force of the post-glacial river, and severely restricted the
course of its flow. Instead of easily wearing a way through soft sand
and gravel, as is the case in most of the broad lower channel, the river
hurls itself through a gap 100 m wide, and drops over a 20-m shelf in an
impressive cascade.
To reach the falls, take the turnoff for Muskrat Falls, and drive
3.25 km toward the river, to the intersection where there is a concrete
cistern on the corner. A short distance straight ahead, there is a
lookout point high above the river. To reach the falls, turn right at
the cistern, drive a short distance, park, and walk 1 km over a wet and
rough, but well-used trail, keeping on the up-river side of the high
hill. You will come out at the edge of the falls, onto red granite
outcrop and large jumbled blocks.
16. Lake Melville rift valley from Goose Bay
Goose Bay and Happy Valley are
built on the amalgamated sandy deltas of the Goose and Churchill
rivers, where they enter Lake Melville. Park on the east side of the
road opposite the end of the main airport runway in Goose Bay, and look
northeast across Lake Melville, which is actually an arm of the sea.
The broad valley, much of which is occupied by the lake, was
formed as a rift valley in Late Proterozoic time, but was carved into
its present shape by glaciers during the last three million years. At
the end of the ice age, the lake was larger than it is now and the area
where you stand was then a beach. The lowlands around the shore are
covered by sand that was washed into the lake as the ice sheet melted
and retreated. The fault on the northwest side of the rift valley is
the line of cliffs extending into the distance on the left. The
southeast boundary is the escarpment of the Mealy Mountains on the south
side of the lake. The highlands on both sides of the valley are
composed mainly of anorthosite.
The Lake Melville rift valley is a widened extension of the
Churchill River rift valley (Stop 13) and is a branch of the huge rift
system that split the continents apart in the Late Proterozoic and
formed the Iapetus Ocean (see Plate Tectonics panel).
17. Anorthosite quarry, Grand Lake road
Take the paved road toward North
West River, cross the Goose River bridge, turn left on the Grand Lake
forest access road, and drive for 3.4 km to a small quarry on the right.
The quarry has been excavated in Early Proterozoic anorthosite which
underlies the high ground seen from Stop 16 in Goose Bay.
The anorthosite is about 1640 million years old and may be
continuous at depth with the much larger intrusions south of Lake
Melville. The rock in the quarry is typical of the large anorthosite
intrusions found in many parts of Labrador.
Here, it is composed of grey labradorite feldspar crystals up to
40 cm long, intergrown with large black pyroxene crystals and smaller
crystals of magnetite, apatite and pyroxene. When wet, some of the
labradorite crystals show the play of colour (iridescence) for which the
mineral is noted. Many of the pyroxene crystals have rims of needle-
like brown and green amphibole, intergrown with flakes of black mica.
The rims formed when hot fluids, which were pumped through the
anorthosite during the Grenvillian Orogeny, reacted with the edges of
the pyroxene crystals.
This series of web pages provides an introduction to the publication
below, which can be ordered from the
Geological Association of
Canada 
Newfoundland and Labrador Traveller's Guide to the Geology
Edited by: S. Colman-Sadd and S.A. Scott, 91 pp. + map, 1994
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