Program, Abstracts, and Guidebooks - University of Minnesota Duluth

STOP 10
ROVE FORMATION
Rove shale is black, carbonaceous, and forms part of
the lower argillite unit (Morey, 1967); it contains several
large, irregular "mushroom" shaped concretions. The concre—
tions are composed of calcite with pyrite—marcasite bands and
anthraxolite, and appear to have formed diagenetically.
Remnant shale bedding planes are evident in some concretions.
Shale beds are warped around the top and bottom of some
concretions. Concretions are found throughout the lower
argillite, and more commonly, have a distinct ablate spheroid
shape.
Proceed southeast on Highway 587.
4.1 A large area of outcrop extends along the north side of the
C.N.R. railway tracks and Highway 587 where they parallel
Pass Lake.
STOP lla SIBLEY GROUP - +ROVE
FORMATION
At the western end of this outcrop, a sandstone quarry
provides an excellent exposure of Sibley sandstone. In the
railway cut at the western edge of the quarry, Rove shale
is altered to a reddish colour. This alteration affected
the Rove for several feet below its contact with the Sibley
Group. Basal conglomerate is absent at this point but is
exposed to the east behind the small railroad house along
the siding opposite the Pass Lake station.
Clasts in the basal po1ymictic conglomerate are composed
of 93 per cent Gun! lint iron formation, 6 per cent quartz
and 1 per cent granite. Boulders are of variable size and
angularity, and are cemented in a sandy matrix. The contact
with overlying sandstone is sharp; only a few pebbles are
found in the base of the overlying unit. The sandstone is
moderately to poorly indurated, thick bedded at the bottom
of the section, and composed of quartz, with minor chert and
feldspar, in a calcite matrix.
STOP llb
At the west end of Pass Lake, a quarry, which may be
reached by a short road leading from Highway 587 just east
of the entrance to Sibley Provincial Park, has an excellent
exposure of the contact between Rove shale and Sibley sandstone.
The contact is occupied by a thin porphyritic dia—
base sheet. Sandstone beds have a few poorly developed
cross laminations and ripple marks. Very little basal
conglomerate is present in this outcrop.
Return to Highway 587 and follow it back to Highwar
11—17.