Moose River Basin: geology and mineral potential - Geology Ontario

Mesozoic Stratigraphy
Detailed descriptions of the occurrences of the unit in the two drillholes are
provided below, and in the following chapter by A.P. Hamblin. Briefly, the Mis
tuskwia Beds consist of varicoloured (grey, green, brown, pink and red), calca
reous clays and thinner horizons of nonlithified, grey to white, fine to medium
grained, calcareous quartz sands.
Drillhole 75-02
Petrographic studies by Hamblin (1976; this report) have established the
occurrence of the Mistuskwia Beds at a depth of 107.7 m to 125.8 m in this drill
hole (Figure 2.3). This was confirmed by Price (1978) after examination of the
Ontario Geological Survey material.
From 107.7 m to 114.2 m the sequence consists of greenish-grey, greybrown,and
light brown, calcareous clay with occasional thin laminae of white
kaolinitic clay. Between 114.2 m and 121.2 m the dominant lithology is a
white, medium to fine grained, calcareous, quartz sand with minor green clay
laminae. From 121.2m to 123.7m the sands are much coarser grained, and the
basal 2.0 m of the Mistuskwia Beds is a conglomerate with abundant limestone
fragments, small pyrite concretions, reddish sandstone fragments, and quartz,
chert, and volcanic pebbles in a sandy silt matrix.
Overlying the Mistuskwia Beds in this drillhole is an 8.4 m interval of
grey, medium to coarse grained, quartz sand interbedded with grey and brown
clay and sandy clay. Lower Cretaceous palynomorphs were extracted from clay
samples in the upper part of the interval (Telford et al. 1975). The boundary be
tween these probable Lower Cretaceous sediments and the Mistuskwia Beds is
quite sharp. The lower boundary of the unit is also sharp with the nonlithified
Middle Jurassic sediments underlain by brown and buff, argillaceous lime
stone that is probably referable to the Middle Devonian Williams Island For
mation.
Drillhole 75-03
This northernmost drillhole (Figure 1.3) displays an incomplete section of
the Mistuskwia Beds extending from 116.3 m to the bottom of the hole at
135.7 m depth (Figure 2.4). Middle Jurassic palynomorphs were identified by
Norris (1977) from samples between 119.1 m and 128.6 m. Using parameters
such as sorting, roundness, and sphericity, Hamblin (1976; this report) confi
rmed that grey quartz sands occurring between 116.3 m and 119.1 m were dis
tinctly different from sands of the Mattagami Formation.
The lithologies of the Middle Jurassic sediments in this drillhole are very
similar to those of drillhole 75-02. Clays, which make up most of the section are
varicoloured and calcareous. Quartz sands, which are interbedded with the
clays in the upper 8.0 m of the section, are grey or light brown, medium to fine
grained, well sorted and rounded, and calcareous. The upper boundary of the
Mistuskwia Beds with overlying Pleistocene gravel is sharp although, as noted
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