Program, Abstracts, and Guidebooks - University of Minnesota Duluth

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APHEB IAN
The Gunflint Formation (Figs. 1*, 3, 4, 5) has been studied
in
detail by Goodwin (1956) and Moorhouse (1960), the Rove Formation
by Morey (1967). Much of the descriptive detail is taken from these
authors.
Gunf lint Formation (adapted from Goodwin, 1956)
Deposition of the Gunflint Formation was in part cyclical. A
basal conglomerate member is overlain by two members each composed
of chert, tuffaceous shale, and carbonate—taconite submembers. These
members are in turn overlain by a discontinuous limestone member,
(Fig. 2 and Table 2). The Gunf lint Formation was deposited 1635±24
million years ago (Faure and ICovach, 1969).
-TABLE 2-
Stratigraphy of the Gunf lint Formation
(modified from Goodwin 1956)
Limestone—dolomite member
Upper Member
Taconite—chert carbonate submember; taconite (west) fades
chert carbonate (east) facies
Tuffaceous shale submember
Algal chert submember
Lower Member
Taconite—chert carbonate submember;
Tuffaceous shale submember
Algal chert submember
ICakabeka conglomerate member
west taconite facies
chert carbonate facies
east taconite facies
(a)
Basal ICakabeka Conglomerate Member
This member ranges to five feet in thickness and is composed of
polymictic conglomerate. Clasts of Archean volcanic rocks and granite
are cemented in a matrix of chlorite and quartz. The unit is discontinuous
but persistent.
(b)
Lower Member
The lower algal chert submember (Fig. 2) consists of reef—like
mounds of finely banded black, red, and white oolite chert. These
mounds are intergrown or cemented in dolomite. This submember forms
the western margin of Gunf lint outcrop (Fig. 1), but is continuous
only to the west of ICakabeka Falls. It contains abundant microflora
remains (Baarghorn and Tyler, 1965) (Plate la).
The lower tuffaceous shale submember ranges to 20 feet thick
and overlies the lower algal chert in the area west of ICakabeka Falls
is composed of fissile black shale containing much volcanic ash.
* see back cover