Abstract
The Lewisporte/Loon Bay area is located within the Central
Volcanic
belt of Newfoundland. It contains rocks of (?)upper Cambrian to
Ordovician
in age. The most important group of rocks within this area is the
three
part Campbellton sequence. The oldest unit of the Campbellton
sequence
is the Loon Harbour Formation (500-1,000 m thick) composed of
mafic
volcaniclastics
that is conformably overlain by manganiferous cherts of the
Luscombe
Formation.
The Luscombe Formation (370 m thick) is composed of manganiferous
cherts
that grade upward into highly argillaceous chert. Conformably
overlying
the Luscombe Formation is the Riding Island greywacke that
represents
the
uppermost unit of the Campbellton sequence. Other units found
within
the
map area include the New Bay Formation, Dunnage melange, Burnt Bay
chert
- (new), Caradocian age black slate, Goldson Formation and the
Botwood
Group. The Campbellton sequence is interpreted to underlie the
Dunnage
melange with the Riding Island greywacke representing a member of
the
New
Bay Formation. The Burnt Bay chert (new) is inferred to directly
underlie
the Caradocian age black slate and overlie both the New Bay
Formation
and
Dunnage melange. Greywackes correlative with the Sansom/Point
Leamington
greywackes are not found within the map area.
The dominant structure of the Lewisporte/Loon Bay area consists of
a series; of moderate to steeply southeast -plunging inclined to
reclined,
close to tight, overturned macroscopic folds. Axial surface
cleavage of
these folds forms a regional penetrative cleavage that affects all
rocks
within the map area. These folds are interpreted to represent the
first
major phase of deformation that affected this area (Dl). Various
local
complications exist such as minor differences in style and
orientations
of the folds and associated lineations and cleavage. Some of the
minor
changes in fold orientations may be a result of a series of
north-northeast
trending sinistral faults that kink and offset cleavage. Important
non-penetrative
soft sediment structures pre-dating the major regional folding
episode
are found in several units.
The Carmanville melange may represent the accretionary prism of a
west
dipping subduction zone of the central volcanic belt of
Newfoundland
during
the late Cambrian to medial Ordovician. Deposition of the Luscombe
Formation
most likely occurred in the forearc basin of this arc system
during its
incipient development as nearby arc-related subsea volcanism
pumped
large
quantities of Mn, Fe and Si into the sea water to be precipitated
as
manganiferous
chert. Development of this arc system through time lead to the
deposition
of the New Bay Formation and Lawrence Head volcanics adjacent to
the
forearc
trough resulting in gravitational slope instabilities and the
olistotromic
deposition of the Dunnage melange in this forearc trough.
Livaccari, R.F., 1980. Geology of the Lewisporte/Loon Bay Area,
Newfoundland,
Canada. Unpublished MSc. thesis, State University of New York at
Albany.
135pp., +xi; 4 folded plates (maps).
University at Albany Science Library call number: SCIENCE
Oversize
(*) QE 199 L37X
MS thesis (scanned
text
pdf - 14 MB)
Plate 1 - Geologic
map
of
the
Lewisporte-Loon
Bay area, Newfoundland, Canada
(coloured geological outcrop map; scale
1:17,100, with pencil modifications) 14.8MB pdf file
(uncoloured geological outcrop map; scale
1:17,100, as
in original thesis) 3MB pdf file
Plate 3 - Stratigraphic
section
of
the
Luscombe Chert in the Loon Bay area
(uncoloured stratigraphic column; scale 1:120)
0.9MB pdf file
Plate 4 - Stratigraphic
section
of
the
Luscombe Formation in the Campbellton area (Old Mill
section)
(uncoloured stratigraphic column; scale 1:120)
0.8MB pdf file
Return to MS Theses completed in the
Geological
Sciences Program, University at Albany