Download `lhe Martin Group in the Greater Beaverlodge Area by F. F. Langford

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'lhe Martin Group in the Greater Beaverlodge Area
by F. F. Langford*
'Ihe Martin Lake Series was first defined by
(1957, 1959) in the area arm.md Martin
Lake, Before that these rocks had been
incltrled with the Athabasca Series lying
south of Lake Athabasca (Alcock, 1936;
Christie, 1953), Fahrig (1961) proposed the
narre Martin Formation, and Tremblay (1972)
was the first to sub:iivide the formation
beyond rrerely recognizing the presence of
basaltic lavas in the central part.
GusS<M
In relating various outlying elastic sequences to the rocks in the Martin Lake area,
the author encountered a greater variety of
Table l.
rocks than had been anticipated, leading to
the establish.Trent of the Martin Group made up
of four formations. Table 1 sha,,,s the new
stratigraphic sequence COT!l")ared to Tremblay's
(1972) classification and Fig. l the approximate distribution.
In this paper the term "arkose" will be used
only to signify a elastic sedirrent with rrore
than 10 percent alkali feldspar. Since the
sedimmts in this area are practically all
arKosic, it seens rrore useful to use the terms
sandstone and siltstone which carry a size
designation and are thus rrore descriptive.
Stratigraphic column of the Martin Group
This report
Tremblay (1972)
(Table XXX and Fig.
4)
M2lville
Lake
Formation
Siltstone and argillite
(as described by Tremblay)
Siltstone M:!mber: "Mainly thinbedded chocolate-red siltstone
interbedded with thin beds of
arkose ••. "
Seaplane
Base
Formation
Bright pink sandstone and
conglOTIErate; includes upper
3/4 of Trerrblay' s Upper Arkose
Upper Arkose Member: "Mainly
orange-red to salnon-pink arkose;
locally includes thick lenses of
conglorrerate; ... "
Gillies
01.annel
Forrnation
Sandstone Menber: heterogeneous,
buff and red, pebbly sandstone
and pebble conglOTIErate; central
portion interlayered with maf ic
fl CMS
Basalt and Andesite M:!mber:
" .••• Basalt and Andesite interbedded with arkose .•.. "
:Lower Arkose !>Ember:
Boulder Conglarerate M2rrber
Beaverlodge
Fonnation
Red-bro..m Sandstone M2mber:
mainly uniform fine-grained sandstone ranging to siltstone, very
well indurated
Basal Conglarerate !>Ember
"M:iinly orange-red to salrron-pink
arkose; includes locally sane
thinly bedded chocolate-red siltstone and/or thick lenses of
conglorrerate; ... "
Basal Conglarerate: " •.. includes
up to 1000 feet of siltstone."
*oepart:rrent of Geological Sciences, University of Saskatchewan, Saskatoon. This study is
funded by grants from NSER:. The Saskatchewan Department of Mineral Resources supported the
project by the loan of field equif(l"eilt.
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LEGEND
§
ATHABAS CA GROU
•
MART1N GROUP
~ THLUICHO GROUP
/ /
FAUlT
flaggy partings are present. On good exposures , graded bedding, cross-bedding and a
vari ety of scour channels are evident , which
suggests they are widespread a l though not
easily seen.
the southwest shore of Beaverlodge Lake
near Hansen Bay, there is a large zone of
rrediun-grained, f eldspathic, yellow and
greenish grey sandstone. r-bst of the sandstone is well laminated, and as sorre beds are
rather fr i able, the rock forms l edgy outcrops .
Although very conspicuous along the road to
Lodge Bay, this unit seems to be a l ocal facies within the reddish brc,;.m sandstone, but
detailed mapping v.0uld be required to establ ish the strati graphic relationships .
On
Gillies Channel Fonnation:
Lake
Alhahosco
O
:5
IO lun
Fig. l - Geo l ogical map of the s ubdivisions of
t he Marti n Gr oup at Beaverlodge Lake
Martin Lake Area
Beaverlodge Fornation:
'Ihe base of the Beaverlodge Fonnation rests
unconfornably an Tazin granites, orthogneisses
and paragneisses. Over much of the area thi s
contact is marked by a basal conglarerate well
described by Trenblay (1972, see parti cularl y
Plates 17 and 18). Good exposures occur near
the Fay shaft at Eldor ado , and around the old
I.orado mill. Trenblay (1972) dem:mstrated
that the fragirents were derived fran the
underl ying rocks and that transport has been
l imited to a few rretres . 'Ihickness of the
oonglarerate is highly variable; in parts of
the area, Trerrblay (1972) sh<:Jv,ej it to be as
rruch as 700 rn thick, and in pl aces it is
absE11t. MJch of the variation in thickness
is due to irregul arities of the surface of
the unweathered baserrent.
'Ihe Gillies Channel Formation extends around
the main body of M:lrtin Lake and inclu::l.es the
"Basalt and Andesite" unit of Trenblay (1972) .
The base of the unit consi sts of conglarerate
with rounded boulders of baserrent rock up to
40 an across set in a matrix of cobbl es and
sandstone. The sandstone matrix is fr iable,
yellowish grey and feldspathic, and sane lenses
up to 0.5 m thick of simil ar sand are present.
The rest of the fornation is made up of poorly
sorted sandstone , pel::bly sandstone and conglonerate, which display many kinds of textures
and structures juxtaposed. Variation in
oolour is conspicuous. M:IBt rocks are various
shades of yello,,r-orange with red zones scat tered throughout, and rrany bedding planes are
marked by hemati tic stains . Serre cross-bedded
uni ts have foresets outlined by red hernati te
and sare of the massive beds are hematitic
with yello,,r blotches and spots .
Pebbly sandstones, both massive and crossbedded, are cnrmon, with pebbles ranging downward frau 1 cm in s i ze . Conglonerate beds,
rrostly l ess than 1 m thick, occur throughout .
Cross-bedding is ccmron, with uni ts 20 to 40
cm thick and foresets 0. 5 to 1 cm thick. The
central part of the unit contains six major
ma.fie f lows and sills (Trenblay , 1972) , but
these do not seem to have had any effect upon
sedirrentation.
Seaelane_Ba.se Formation:
Seaplane Base Formation nore or l ess
corresponds to the upper three-quarters of
the upper arkose of Trenblay (1972, Fig . 4).
The formation is easily recognized where it
occurs along the Eldorado road by the bright
pink col our and good sorting of the conglonerate and sandstone units . The west ern part
is rrore conglareratic than the eastern, and a
thick conglooarate unit extends northeastward
The
~st of the Beaverlodge Formation i s a hard,
reddish b:ram, and Iredium to dark greenish
grey , fine-grained sandstone and sil tstone .
It is ver:y arkosic with pink streaks and thin
lenses dominantl y corrp:,sed of feldspar grains .
The rock i s uniform over considerable thicknesses, and bedding is conspicuous only where
one-pebble thick layers of conglOI1Brate or
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from Martin Lake past the hill at the hospital.
The basal o::mtact extends from Cinch Bay to
the southern part of Martin Lake. Eastwards
it lies beneath Martin Lake, but on the east
side it is close to the uppemost flo.v.
LEGEND
MELV ILL E L AKE
F ORM ATI ON
S E APL ANE BA SE
FO RMATI ON
Besides the colour, the rrost striking feature
that separates this unit and the succeeding
one from the Gillies Channel Formation is the
good sorting of the sandstone, siltstone and
conglonerates. Although these rocks may be
interbedded on a scale of a few centinetres,
each type is distinct and has a restricted
grain size within its unit. Except for graded
beds, the sandstones are usually of unifonn
grain size. The conglarrerates have a limited
range of rounded pebbles in a matrix of clean
sand. Pebbles are rrostly of basement gneisses
with a predominance of quartz and quartz-rich
gneisses. Cross-bedding occurs everywhere.
The thicknesses of rrost cross-bedded units are
5 to 10 an and foresets l to 4 nm. It is
difficult to find e:xposures that show the
direction of transportation.
GILL IES CHANN EL
F OR MATI ON
BEAV ERL 00G E
FOR MATI ON
CO NGL OMERAT IC
R O CK S
~!ville Lake Fonnation:
-----------------~-~-
The ~lville Lake Formation is distinguished
by the abundance 'o f dark red to maroon, hard,
roodium- to fine-grained, arkosic siltstone
and argilli te, and corresponds to Trernblay's
siltstone rrerrber (1972, Fig. 4). In places,
the siltstone may have buff-yellow bleached
spots and zones. Bright pink sandstone and
a few thin conglonerate beds like those of
the Seaplane Base Formation are intercalated
with the argillites, particularly towards the
base. Typical rocks of this formation are
exposed in the large road cut south of
~lville Lake. Cross-beds are present, but
rrost of these sedinents seem to have been
deposited in ephemeral lakes, for layers
grading from fine sand or silt to argilli te
with abundant ripple marks and nrud cracks on
top are =mon. The lower contact of the
formation can be seen west of the road to
Fredette Lake. The change from the conglorrerates to argillite is abrupt, but thin
layers of pebbly conglorrerate occur scattered
in the argillite. The upper contact has been
rerroved by erosion.
outlying Oc=ences
Rocks correlated with the Martin Group occur
at several locations within 50 km of Martin
Lake (Fig. 2) • These rocks have been called
Martin principally because they are corrq::osed
of urutEtarrorphosed red sandstone, and lie
unconforrnably over a gneissic Precarrbrian
baserrent. No correlation based upon specific
sedinentacy features had been undertaken
previously. The present study involved visits
0
'
Fi g. 2 - Geol ogical ma p of the Martin and
Thluicho Groups in the greater
Bea verl odge Area
to all areas; sorre were limited to a few days,
and sorre for a f ew weeks. The correlations
proposed are shown in Table 2.
Gruchy_Ba:L_Area:
The Jug Bay Fm:rnation * occurs along the -west
side of the Crackingstone Peninsula and, for
the rrost part, lies in a graben between the
Jug Bay and Black Bay Faults (Fraser, 1954;
Bell, 1959). The northern end ma.y be limited
by an unconfonni ty, but it has not been well
mapped. The south end lies beneath Lake
Athabasca. The fonnation consists of hard,
silicified, reddish brown and dark greenish
grey, fine-grained sandstone. Although well
~sed, unifonn induration produced srrooth
rounded outcrop during glaciation, and this,
canbined with a thin tenacious cover of lichen,
has produced featureless outcrops. Along the
wave-washed shore of Gruchy Bay, outcrops show
a great many delicate sedirrentary structures,
especially cross-bedding and scour channels,
that are ccrcpatible with deposition by
currents from the north.
In fresh hand specinens, the rock ai:pears
unifonn except where bedding planes are marked
by a difference in grain size. M::>st of the
grains are 0.1 to 0.5 ITin across, and sporadic
*Tenninology
proposed in this paper
'
__ _______________,,
,_,
__ _ ________
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Table 2.
Correlation Chart of the Martin Group, Greater Beaverlod.ge Area, Saskatchewan
Tazin Lake
Martin Lake
Gruchy
Bay
Gravel
Islands
Cam.sell
Portage &
Slate Island
Fair Point
Formation
Athabasca
Group
Melville
Island
Formation
Seaplane
Base
Formation
Gillies
Channel
Formation
Martin
Group
Thluicho
Group
erosion
erosion
erosion
Taz Bay
Fonnation
Beaver lodge
Formation
Jug Bay
Formation
Gravel
I slands
Formation
Thluicho
Group
Thluicho
Group
pink feldspar grains up to 1 rrm are cormon,
along with isolated granite and quartz pebbles
1 to 2 cm across. Grain size contrast is
greatest in thick beds. This rock has a very
close resemblance to the fine-grained sandstone of the Bea'\lerlodge Fornation and is
considered correlati'ile with it (Table 2).
Gra'\lel Islands Area:
------~-------~--
The Gravel Islands Formation* occurs as a westward dipping and facing honocline exposed on
the Gravel Islands. The rocks differ from the
Jug Bay Formation in the Gruchy Bay area close
by, and are separated from them by the Black
Bay Fault.
The lower unit occurs on the southeastern
islet and consists of massive conglorrerate
containing cobbles and pebbles of baserrent
rocks. The easte:rnrrost 60 m of the main
island consists of purplish grey, well-bedded,
coarse-grained arkosic sandstone. Bedding
is conspicous and the sandstone is interbedded with layers of coarse pebble conglorrerate. The central part of the main island
is occupied by conglorrerate much like the
lower unit on the southeast islet, but it
*Terminology proposed in this paper
Charlot
Point
Formation
contains layers of arkosic sandstone and about
10 per cent of the cobbles are conposed of
reddish brown sandstone like the Jug Bay
Formation. Arkosic, purplish grey sandstone
is dcroinant on the west side of the main
island. The islet to the northwest is a
mixture of sandstone and conglOTIErate and the
peroentage of reddish brown, fine-grained sandstone pebbles and cobbles is greater here.
Cross-bedding is very COITTIDn in the sandstone
beds, and indicates that the tops face west
and the depositing currents cane from the north.
The presenoe of substantial nurrbers of pebbles
and cobbles of reddish bro,,m, fine-grained
sandstone identical to that of the Jug Bay and
Beaverlodge Formations suggests that part of
the Gravel Islands Formation was derived from
their erosion. For these pre-existing sedirrents to have survived as clasts rreans they
were probably well indurated shortly after
deposition.
Carnsell Porta~e Area:
The Charlot Point Formation occurs in a small
basin at Carnsell Portage. These rocks were
first designated as the Martin Formation by
Scott (1978) who also established an underlying Thluicho Group. The Charlot Point
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Fo:rnation oonsists of a boulder oonglorrerate
facies that intertongues with a sandstone
facies. Red boulder conglorrerate, like that
at Charlot Point, also unconformablv overlies
the Thluicho Group on Slate Island. The
Charlot Point Fonnation is unconformably
overlain by the Fair Point Formation of the
Athabasca Group.
The sandstone is pale pinkish grey, in part
purplish, medium- to coarse-grained, =ossbedded and arkosic. Beds are 5 to 40 an
thick and there are rrany thin conglorrerate
beds with a variety of clasts. Near the
conglorrerate facies, coarse trough crossbedding, with sets up to 0.5 rn thick and
foresets 1 to 2 an thick. dominates the unit.
The cross-bedding indicates =ents frcm
the northwest.
The dark red boulder conglorrerates form a
thick unit lying east and north-northeast of
the sandstone. The cx.mglorrerates form very
cx.mspicuous outcrops along the Charlot Peninsula and the lakeshore south of the Charlot
River. The conglorrerates conprise clasts
ranging from pebble to boulder in size, and
all are corrp::>sed of hard, reddish bro..m and
greenish grey, fine-grained sandstone like
that forming the Jug Bay and Beaverlodge
Formations. Except at the base, where sorre
of the underlying basement gneiss and
Thluicho rocks are incorporated, clasts of
baserrent rock oc= only as small isolated
pebbles widely scattered here and there. The
boulders and cobbles are rrostly subrounded.
The interstitial sand, and the sand in the
pebbly sand lenses in the boulder conglorrerate, is dark red, arkosic, JXX)rly sorted
and quite unlike that of the sandstone facies.
It is envisaged that the Charlot Point Formation was deposited in a southeasterly trending valley. The axis of the valley was
occupied by a substantial stream, flowing
from the ll.€st-northwest, which deposited the
sands and thin gravels of the sandstone
facies. The boulder conglarerates famed a
series of alluvial fans along the north and
east sides of the valley, which received their
sedirrents from the erosion of the exposed
Beaverlodge Formaticm further north and east.
The presence of boulder conglorrerate at Slate
Island may indicate that the stream channel
curved toward the southwest.
It has been suggested in discussion that the
clasts in the Charlot Point conglorrerate were
derived from the Thluicho Formation. Although
these clasts appear to reserrble fine sandstone
of the underlying Thluicho Group, the majority
of rock types in the Thluicho Group, including
felsic volcanics, argillite and sandstone, are
not represented in these clasts, suggesting
therefore that the 'Ihluicho Group was not
their source. The absence of ma.fie volcanic
fragrrents, which might be ~ t e d to derive
from basaltic horizons in the Gillies Channel
Fonnation, supports the idea that the Charlot
Point clasts were derived from the Beaverlodge
Formation before the Gillies Channel rocks
were deposited. Thus the Charlot Point rocks
are equated with an erosional period after
deposition of the Beaverlodge Formation, and
are possibly equivalent to the conglarerate
at the base of the Gillies Channel Formation.
Tazin Lake Area:
Red sandstones of the Taz Bay Formation were
mapped at Tazin Lake by Koster (1968, 1970) .
He divided the fo:rnation into three lmits.
The lower one consisted of alternating sandstone and shale on Oliver Island, but this,
along with sare similar rocks at the southeast
comer of Tazin Lake, was renapped by Scott
(1978) as Thluicho Group. 'l'he rest of
the Taz Bay Formation, the basal conglorrerate
and overlying sandstone, is similar to the
Beaverlodge Formation.
The sandstone is rrediurn reddish brown with
variable grain size, ccmronly in graded beds.
Trough cross-bedding is cannon and ripple
marks are conspicuous in places. r-bst of the
sandstone is laminated and sorre beds are
separated by shaly partings. Besides the
basal conglarerate, beds of conglorrerate up
to 5 rn thick, with a variety of baserrent rocks
forming cobbles and snall boulders, are interbedded with the lower part of the sandstone.
The Taz B":l.y rocks have nore variation in
texture than typical reddish brown sandstone
of the Beaverlodge Fo:rnation. Ha,,,ever, much
of the sedirrent indicates depositional conditions similar to the Beaverlodge Formation.
Thus, these rocks are considered correlative,
and the Taz Bay Formation could have supplied
many of the clasts found in the Charlot Point
Formation.
Conclusion
The closing stages of the Hudsonian orogeny
were marked by uplift, faulting and formation
of epherreral sedirrentary successor basins.
The roots of b,,,:J of these, the Thluicho and
Martin basins, have been preserved. The
initial Martin sedirrentation of the Beaverlodge Formation was widespread, and was
follCMed by a sharp uplift which caused rruch
of it to be eroded and redeposited in other
basins. Following this, a thick sequence of
elastic sed:inEnts with sorre lava flows was
deposited, but only the part at Martin Lake
has been preserved. '!he record of even ts and
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the types of rocks produced are appropriate
for this tectonic envirorurent.
References
Alcock , F. J. ( 19 36) : The geology of the Lake
Athabasca region, Saskatchewan; Geol.
Surv. Can., ~ - 196 .
Bell, K.C. (1959):
Saskatchewan:
Map 38- 1959.
Milliken Lake, Sheet 1 ,
C?eol. Surv. Can. ,
Chri stie , A.M. (1953) : The Goldfiel ds- Martin
Lake m3p area, Saskatchewan; Geol. Surv.
Can ., t>an. 269 .
Fahrig, W.F . (1961): The geol ogy of the
Athabasca Formation; Ceol . Surv. Can . ,
Bull. 68 .
Fraser, J. A. (1954) : Crackings tone ,
Saskatchewan: Geol. Surv. Can.,
Pap . 54-8 .
Gussow , W.C. (1957): Correlation and age o f
the Athabasca fonration; Alberta Soc.
Pet . Geol. Jour . , v . 5 , p . 2-5.
(1959) : Athabasca formation of
western canada; Geol. Soc. Arrer. Bull.,
v . 70, p . 1- 18.
Koster , F. (1968) : Geology of the Zin Bay
ar ea; Sask . Dept . Mineral Res . ,
Rept. 121.
(1970) : Ceol ogy of the Burchna ll
Lake area, Saskatdlewan ; Sask. Dept.
Mineral Res. , Rept . 131.
Scott , B.P . (1978): Geology of the area east
of Thluicho Lake , Saskatchewan; Sask.
Dept. Mineral Res ., Rept. 167.
Tr errblay, L.P. (1972) : Geology of the
Beaverlooge mining area , Saskatchewan;
Ceol. Surv . Can. , t,en. 367 .