| dc.description.abstract | Detailed mapping was carried out in the Shebandowan
Lakes area and eastward to the Kaministiquia River to study
the structural and stratigraphic relationships between the
Keewatin and Timiskaming rocks (herein referred to as
Keewatin-type and Shebandowan-type, respectively, to avoid
connotations of time-stratigraphic equivalence with type
areas) of the region.
It is believed that the Shebandowan-type rocks are
younger than the Keewatin-type rocks. Although no actual
contact between the two has been seen in outcrop in the
study area, the trend of their contact is discordant with the trend of cleavage in the Shebandowan-type rocks. This,
along with the less recrystallized appearance of the
Shebandowan-type rocks, and the presence of clasts of
jasper in conglomerates of the Shebandowan-type sequence
similar in appearance to the jaspilitic iron formation
interbedded with the Keewatin-type mafic volcanics, leads
to the conclusion that an unconformity separates the two
groups of rocks. Recent geochronological work on some of
the rocks in the region, carried out by the Ontario
Geological Survey, supports this theory.
The macroscopic, microscopic and sub-microscopic
structure of both groups of rocks was examined in detail.
The minor structures seen in outcrop, the examination of
thin sections, scanning electron microscope work, and the
determination of the magnetic fabric of the rocks all show
that the rocks in the present study area contain a single,
penetrative, primary cleavage, which has a consistent trend
across the whole area. The regional structural picture
which emerges from the data is characterized by
close-spaced, isoclinal folding with sub-vertical fold
axial traces trending roughly east-west. Local variations
exist in the eastern portion of the study area where more
widely-spaced and open folding is more common. No evidence
of a second, significant period of deformation in the
present study area has been found. | |
