Moose River Basin: geology and mineral potential - Geology Ontario

Moose River Basin
sediments of the lower part of the Mattagami Formation were probably derived
from the Long Rapids Formation.
Palynological analysis of samples from drillhole 77-03 (Verma, Telford and
Norris 1978) suggested a more restricted interval for the Mattagami Forma
tion. Only Devonian palynomorphs were found below 39.6 m and the highest
Cretaceous palynomorphs occurred at 32.9 m.
Age and Correlation
Bell (1928) published a description of macroplant remains from the Matta
gami Formation that suggested a Cretaceous or possibly Late Jurassic age for
the unit. Recent palynological studies reported by Telford et al. (1975), Norris
et al. (1976), and Verma et al. (1978) have provided considerable refinement of
the early age determination. A detailed synthesis of the palynological work is
provided by Norris (this report). The Mattagami Formation ranges from Mid
dle to Upper Albian (Lower Cretaceous) in age and is correlative, in particular,
with the Loon River, Peace River, and lower Shaftesbury Formations of north
west Alberta and the Swan River and Ashville (in part) Groups of Manitoba
and Saskatchewan.
STRATIGRAPHIC RELATIONSHIPS
Identification of precise stratigraphic or geographic boundaries for the Me
sozoic units of the Moose River Basin is difficult, as the sediments mainly occur
in discontinuous lenses of small areal extent. However, some general observa
tions on stratigraphic relationships can be attempted in the light of recent
studies. These have shown that essentially three Mesozoic stratigraphic or dep
ositional units are involved, viz Middle Jurassic Mistuskwia Beds and early
and late phases of the Lower Cretaceous Mattagami Formation.
The configuration of the Precambrian and/or Paleozoic "basement" has ex
erted considerable influence on the development of the Mesozoic units. The
southern margin of the Moose River Basin is marked by a prominent, fault con
trolled, Precambrian escarpment. This feature has had a two-fold effect, in lim
iting the southern extent of Paleozoic and Mesozoic deposition, as well as pro
viding an upland source of terrigenous detritus. As postulated by Price (1978),
a ridge of Precambrian rocks may also be present in the central part of the ba
sin, extending east-west through the Grand Rapids area. Seismic results from
the Ontario Geological Survey winter 1975 programme (Utard 1975) confirmed
the existence of this ridge (probably equivalent to Grand Rapids Arch) but
showed it to be a broad shallow structure with only about 80 m of relief. How
ever, the 1975 seismic work also suggested the presence of two Paleozoic ridges,
in the vicinity of drillholes 75-01 and 75-02, corresponding approximately to
the Precambrian structure (Figure 2.9). The occurrence of two narrow Paleo
zoic ridges rather than a single broad ridge could be the result of the deep post-
Paleozoic erosion that has produced a trough-like structure in the
46