Program, Abstracts, and Guidebooks - University of Minnesota Duluth

-84—
Outcrops near the road are of a wide, north striking,
porphyritic diabase dike that closely resembles Matachewan
diabase. The altered green feldspar phenocrysts in the
dike have given rise to the local term "Greenspar porphyry".
Faulted offsets of what is believed to be the same dike,
can be followed for more than ten miles to the north.
A contact between porphyritic diabase and younger
massive diabase is exposed on the first main ridge south
of the road. The younger diabase is believed to be a
part of the same diabase sheet seefl at STOP 11.
Inclusions of foliated mafic lava and rounded to
angular fragments of granitic material and quartz can be
observed further south along the footpath.
Return to Highway 11 and enter Beardmore.
0.0 Leave Beardmore and head south on Highway 11. Mileage
count begin at railway crossing.
8.6 Road cut on east side of Highway 11.
STOP 15
This stop demonstrates the unconformable relationship
existing between the Proterozoic strata of the region and
the underlying Archean rocks.
Pink sandstone of the Sibley Group rests with angular
unconformity on an eroded Quetico metasediment surface.
Fragments of the underlying rock can be found suspended in
what is a possible paleosol or limestone layer along the
unconformity.
the pink colour of the sandstone is caused by the
presence of approximately 0J% hematite. (3. M. Franklin,
personal communication).