Moose River Basin: geology and mineral potential - Geology Ontario

Moose River Basin
garni and Abitibi Rivers in the extreme southeast portion of the basin (Figure
l, Price 1978). One line of these inliers, trending east-west and passing through
Grand Rapids on the Mattagami River, may represent a Precambrian base
ment ridge or younger tectonic structure, and has considerable bearing on the
interpretation of Mesozoic depositional patterns. Price (1978) also used physio
graphic features such as the prominent deflection of the Missinaibi River im
mediately downstream from its confluence with the Soweska River, the clast li
thology of Pleistocene sediments which blanket the entire lowlands region, and
schistosity trends in Precambrian rocks east of the Moose River Basin, to sup
port the existence of a major arch structure extending through Grand Rapids.
DISTRIBUTION AND THICKNESS OF MESOZOIC SEDIMENTS
The distribution of Mesozoic sediments in the Moose River Basin is incom
pletely known. Maps in Martison (1953), Sanford and Norris (1975), and Price
(1978) show various interpretations but, as indicated by Price (Figure l, 1978),
large areas of supposed Mesozoic deposits are based on very poor data. Much of
the geological work undertaken in the Moose River Basin has tended to be con
centrated in only a few specific areas or consist only of isolated drillholes from
which reliable extrapolations are difficult. The recent activities of the Ontario
Geological Survey have added a considerable amount of important and useful
information to the data base. Nevertheless, much more information is required
before a clear understanding of the distribution of the Mesozoic sediments can
be reached.
The concentration of past geological activities in particular areas, such as
Onakawana, is understandable. The work was prompted by the economic po
tential of lignite, silica sand, and fireclay in the Mesozoic sediments and such
interests were focussed logically on areas where these valuable deposits are
close to surface. The Mesozoic sediments are close to surface and/or outcrop ex
tensively in only three parts of the basin, viz Onakawana, Kipling Township,
and in the vicinity of Missinaibi and Coal Rivers in McBrien and Burstall
Townships. Elsewhere, the Mesozoic sediments are covered by thick sequences
(up to 150 m) of Pleistocene glacial and glaciolacustrine sediments and, in the
north, by marine clays of the postglacial Tyrrell Sea. As illustrated by Price
(Figure l, 1978) all known surface exposures of the Mesozoic sediments lie
within 35 km of the Precambrian rocks bounding the southern and eastern
margins of the Moose River Basin.
In the Onakawana area, outcrops of Mesozoic sediments (the Cretaceous
Mattagami Formation) are confined to the banks of the Abitibi River. Exten
sive drilling operations west of the Abitibi River, that have been documented in
numerous reports (e.g. Trusler et al. 1974), indicate a maximum thickness of
about 51 m for the Mattagami Formation. Two lignite fields, known as the
Main and East Fields, have been defined in this area.
The fall 1977 drilling by the Ontario Geological Survey (Verma, Telford
and Norris 1978) revealed a 17 m thickness of the Mattagami Formation east of
the Abitibi River (Figure 2.2), though the distribution of Mesozoic sediments is
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