Program, Abstracts, and Guidebooks - University of Minnesota Duluth

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42.1 Bridge over Current River, cross bridge, turn right into
Boulevard Lake Park and proceed 0.3 miles; park on right
side of road. Traverse begins on creek bed.
STOP 6 LOWER CäERT-CAR.BONATE FACIES (FIG. 2)
The lower chert-carbonate facies is overlain by the upper
tuffaceous shale subñiember. An upstream traverse encounters
ferrugineous carbonate, interrupted by thin layers and lenses
of granular and algal chert, and dark, fissile shale. At
the beginning of the traverse, note the rounded chert lenses
showing concretionary structures, attributed to action of
algae. Please refrain from sampling some of the better preserved
structures.
Features to observe include stylolite surfaces lined
with anthraxolite, pyrite veinlets, imbrication of thin chert
layers and the striking, weathered appearance of the rock.
Under the bridge, a bed of gray, massive limestone,
enclosing pancake—like lenses of serpentine material, and
interrupted by a thin band of pyrite—bearing chert, is over—
lain by upper tuffaceous shale. Note the humrnocky upper surface
of the limestone at the shale-limestone interface.
Several hundred feet north of the bridge, at the lookout,
a diabase sheet caps the shale. East of the bridge, in the
picnic area, several well developed river terraces are preserved.
Prom bridge, proceed east along Arundel Street.
43.1 Intersection, Arundel St. and Hodder Ave. Turn left on Hodder
Ave. at Hodder Avenue Hotel.
44.1 Highway 17—11, Turn right.
44.7 Scenic lookout. View of Thunder Bay harbour. Park car and
walk 500 feet east to roadcut, on north side of road. Exercise
extreme caution.
STOP 7
UPPER LiMESTONE MEMBER OVEELAIN BY DIABASE
Sill of Logan diabase overlies argillite and fragmental
limestone of the upper limestone member. The contact is gently
undulating and visible effects of contact metamorphism are
little evident. In thin section, however, a microporphyroblastic
texture is developed in the argillite. Pyrite is altered to
pyrrhotite.