those of the directly underlying conglomerate in the island
at the north end of Spectacle Lakes implying a continuity
of stratigraphy not seen to the west.

The crinoidal limestone is light grey weathering light
grey to grey and contains debris of corals, brachiopods,
echinoderms, bryozoans and gastropods. Microscopically
it has minor amounts of finely crystalline quartz, heavy
minerals, secondary pyrite, conodonts and fish teeth. The
size and percentage of crinoid and other bioclastic debris
is highly variable, with the rock ranging from crinoid
wackestone to crinoid rudstone. The rudstone has the
greater diversity of secondary fauna. Transitions from
rudstone to wackestone are gradational in some locali-
ties (Fig. 21), but elsewhere are represented by abrupt
irregular boundaries. All the biological material is frag-
mentary and shows no evidence of being in or near
growth position. In most places the limestone is massive
and devoid of sedimentary structures, however, in the
outcrop south of Mount Tinsdale 15 to 40 cm beds are
internally graded with respect to crinoid fragment size.
The bedding and generally massive accumulation of
broken fossils suggests that the unit was deposited as a
debris flow rather than in situ.

Figure 21. Greenberry Formation limestone near Mount
Tinsdale. A) normally graded. (GSC 191019) B) inversely
graded. (GSC 191020)

34

The Greenberry Formation has undergone various
amounts of tectonism and neomorphism. Tectonic effects
include pressure solution features, crushing-shearing
phenomena and later profuse fracturing and calcite and
quartz veining. Many outcrops display well developed
shear foliation with rotated, granulated, and disrupted
bioclasts. The light grey bioclastic limestone on lower
Stewart Creek has two tectonic planes at 30° to each
other. The first phase is characterized by surfaces of
remobilization and pressure solution with carbonate-filled
pressure shadows adjacent to crinoid fragments. The tails
of the pressure shadows lie in the plane of flow. This sur-
face of flow is cut by 1 to 2 mm spaced surfaces along
which clasts have been granulated and disrupted.

Neomorphism was never sufficient to obliterate all
bioclastic features, but coarsely crystalline carbonate was
developed locally. Silicification, dolomitization and
replacement by pyrite are local effects. Where the lime-
stone has been partly silicified, such as, southwest of
Mount Tinsdale, the silicification is in discrete layers 4
to 20 cm thick. The layers are continuous across outcrop
widths of 10 to 30 m and appear to mimic original bed-
ding. Chert and dolomite replace limestone both com-
pletely and preferentially. The chert is white or more com-
monly light grey and dark grey as in outcrops north of
Nine Mile Lake and south of Mount Tinsdale. Dolomite
is predominantly cream and is invariably associated with
chert. In places pyrite selectively replaced crinoid stem
fragments on a fine scale and is a common but minor
secondary mineral.

Age and correlation. The Greenberry Formation is Lower
Mississippian as determined from conodonts collected
from many exposures. More precisely, the conodonts
recovered are confined to the Upper Tournasian and
Lower Visean (Orchard and Struik, 1985). The cono-
donts, identified by M.J. Orchard, are listed in Appen-
dix A along with his comments. The age suggested by the
conodonts agrees with earlier assessments from poorly
preserved corals and brachiopods (Johnston and Uglow,
1926). Although the Greenberry Formation is the same
age as many other crinoidal limestones in the Canadian
Cordillera and elsewhere it does not appear to be a lateral
continuation of any of them. Rather the Greenberry may
be a local carbonate buildup on a hardground provided
by the Guyet Formation. The conodont Mestognathus
has not been found in the Rocky Mountains (North
American Terrane) to the east and may represent a pro-
vinciality which distinguishes the Cariboo from the North
American Terrane.

Alex Allan Formation

The Alex Allan Formation is here introduced to include
Pennsylvanian black micritic limestone, and shale. It is
similar to the interbedded shale and limestone of the
underlying Black Stuart Group except for its thicker beds
and more abundant limestone.

The formation underlies the area from Summit Creek
northwest to the edge of the map area (Fig. 1). It is