Program, Abstracts, and Guidebooks - University of Minnesota Duluth

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the Quetico belt by Stockwell (1964). The relationship between
these two belts has been considered in recent papers by Goodwin
(1968), Kalliokoski (1968) and Ayres (1969, 1970). Goodwin and
Kalliokoski postulate that the Keewatin belt is older than the
Quetico belt while Ayres suggested that Quetico rocks are over—
lain by those of the Keewatin belt.
Early Precambrian Metavolcanic and Metasedimentar"T Rocks
1. Lithologies:
A — Metasediments
Metasedimentary rocks form two distinct lithologic groups:
a thick sequence of relatively uniform greywacke, siltstone, and
argillite that is predominantly within the Quetico belt; and a
thinner sequence more variable and coarser—grained of conglomerate,
greywacke, argillite and iron formation that isinterlayered with
metavolcanic formations of the Keewatin belt. The finer—grained
metasediments within the Quetico belt and the southern part of the
Keewatin belt have been tentatively correlated with the Couchiching
formation by many authors (liorwood and Pye, 1955; Macdonald, 1942;
Pye, 1952). The coarser grained metasediments within the Keewatin
belt form part of the Windigokan series of Tanton (1921).
B —
Metavolcanics
The metavolcanic rocks in the southern part of the area are
predominantly maf Ic to intermediate, massive, pillowed and amygdaloidal
flows. In the northwestern part of the belt, however, intermediate to
felsic volcanic breccias and flows are abundant.
2. Stratigraphic Relationships:
Reconstruction of the stratigraphy is difficult because of
paucity of good exposure along contacts, deformation by folding and
faulting, and interfingering of the various units.
In the southern part of the area the finer—grained relatively
un:iform metasediments (Couchiching) are overlain in most cases by
the coarser—grained lithologically heterogeneous
m?tasediments (Windigokan). Both of these units thin northward
and interfinger the metavolcanic sequence.
The finer—grained metasedimentary unit contains a thin but
laterally extensive mafic metavolcanic unit that defines the boundary
between the Quetico and Keewatin belts. Metasediments above
and below this metavolcanic unit are lithologically similar (Peach,
1951; Mackasey, 1970). Metasedimepts above the metavolcanic unit
are part of PyeTs (1952) group B defined in the eastern part of the