Moose River Basin: geology and mineral potential - Geology Ontario

ABSTRACT
Mesozoic Stratigraphy
Unconsolidated Mesozoic sediments are present in the southeastern part of the Moose River
Basin, James Bay Lowland. Geological studies have been carried out intermittently in this area for
nearly a century, but between 1975 and 1977 the Ontario Geological Survey implemented a major
new programme of drilling, geophysical, and field mapping activities with a view to assessing the
lignite and industrial mineral resource potential of the Mesozoic sediments. Two lithostratigraphic
units have been distinguished. The Mistuskwia Beds (Middle Jurassic) occur toward the central
part of the basin and consist of varicoloured calcareous clays and thin horizons of grey to white, fine
to medium grained, calcareous, quartz sands. The maximum known thickness of the unit is 19.4 m.
Disconformably overlying the Mistuskwia Beds is the Lower Cretaceous Mattagami Formation
which has a maximum known thickness of 121.4 m, and consists of a variable sequence of varicol
oured clays, quartz sands, and both detrital and in situ lignite. This unit is restricted to the mar
ginal areas of the Moose River Basin and deposition took place in two phases. The earlier phase in
cluded the accumulation of the important lignite deposits at Onakawana, while sediments of the
later phase include pure quartz sands and kaolinitic clays.
INTRODUCTION
LOCATION AND ACCESS
The Moose River Basin is a Phanerozoic sedimentary basin covering about
100 000 km2 of the James Bay Lowland (Figure 2.1). It is bounded approxi
mately by Latitudes 50 005' and 52 030' North and Longitudes 78 050' and 84 045'
West. The basin lies mainly within the District of Cochrane, northeastern On
tario, with small easterly extensions into the Province of Quebec and to Akimiski
Island in James Bay.
Of particular interest to this study is the southeastern portion of the basin
where the Paleozoic bedrock is overlain by Mesozoic sediments. This area,
bounded approximately by Latitudes 500 and 51 0 North and Longitudes 80 015'
and 83 045' West, is centred about 150 km southwest of Moosonee and lies
within the Smoky Falls (42-J) and Moose River(42-I) 1:250 000 NTS map areas.
It is crossed by several major north-flowing watercourses, including the Missi
naibi, Mattagami, and Abitibi Rivers, which are tributaries of the large Moose
River. The southern extent of the Mesozoic sediments coincides with the south
ern margin of the Moose River Basin and is demarcated by an abrupt physio
graphic change from flat swampy lowlands to more rugged uplands of the Pre
cambrian Shield (Photo 2.1). Except for the Spruce Falls Pulp and Paper
Company community at Smoky Falls and some Ontario Hydro installations,
there are no settlements within the area. The closest important population cen
tre is Moosonee near the mouth of the Moose River on James Bay. Highway 11,
the closest major road, is some 80 km to the south. Access to the eastern part of
the area is by way of the Ontario Northland Railway line that runs from Co
chrane to Moosonee. The well known site of Onakawana is a mere railway sid
ing about 90 km south of Moosonee.
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