tain in black silicified carbonate. It contains 10 to 20%
white elongate objects suggested by J.E. Klovan and F.
Stoakes (personal communication, 1978) to be possibly
Amphipora which range from Late Silurian through
the Devonian. The second locality is 850 m north of
the mouth of Limestone Creek (52°59’6.3’’N,
121°11’3.7’°W; GSC Locality C-82851) where conodonts
were extracted from a thin black micritic limestone bed
in black slate. The rocks are exposed near the base of
the cliff along the Cariboo River bank. The conodonts
were identified by T.T. Uyeno as fragments of the Poly-
gnathus varcus Stauffer group of Klapper et al. (1970).
He assigned them to the range Lower Polygnathus varcus
subzone to Lowermost Polygnathus asymmetricus zone,
that is Late Middle Devonian.

In summary the informal units of the Black Stuart
Group range from Late Ordovician to Late Devonian and
possibly younger. Upper Ordovician graptolitic pelite may
be separated from the Lower Devonian chert-carbonate
unit by a Silurian unconformity. The Middle and Late
Silurian brachiopods described by Lenz (1977) may be
from a limestone unit locally preserved beneath the Lower
Devonian chert-carbonate unit. The black pelite overlying
the chert-carbonate unit could span the interval from
Early to Late Devonian. The sandstone unit is Upper
Devonian or younger, because it overlies the black
pelite unit.

The oldest rocks of the Black Stuart Group, the grap-
tolitic slates of the black pelite unit, correlate with Ordo-
vician graptolitic pelites of the Road River Formation
from northern British Columbia. Gabrielse (1975, p. 11)
reported southernmost Road River facies equivalents in
the Fort Grahame map area. Northward from Fort
Grahame map area Road River Formation equivalents
can be traced into the Selwyn Basin of Yukon Territory
(Gabrielse, 1975). Detailed stratigraphy of Road River
Formation has recently been described by Cecile and
Norford (1979) for a part of northern British Columbia
and by Gordey (1978, 1979) for the Summit Lake area
in Northwest Territories and Yukon. In southern British
Columbia correlations are less certain.

The Lower Devonian chert-carbonate unit could cor-
relate with Lower Devonian carbonates of northern
British Columbia. The Muncho-McConnel Formation
(Taylor and Stott, 1973; Taylor et al., 1979) and related
calcareous sandstone and limestone debris flows (Taylor
et al., 1979) in the Ware map area and the ‘‘tapioca’”’
sandstone sequence in McDame and surrounding area
(Gabrielse, 1963) are examples of possible correlative
quartz-sand-rich carbonate of the Lower Devonian. In
contrast to them the chert-carbonate unit has only local
examples of calcareous quartz sand and sandy limestone
from Limestone Creek and one locality on Anderson
Ridge. Besides quartz the Limestone Creek outcrop also
has chert breccia, dolostone breccia, cherty pelite and
rounded sandstone clasts which is not characteristic of
the Lower Devonian occurrences noted in northern
British Columbia.

26

The younger black pelite unit may range into the Mis-
sissippian and is in part correlative with the Earn Group
(equivalents of which are informally called the ‘‘black
clastic’’) of basinal facies throughout northern British
Columbia and Yukon. The Amphipora — bearing Middle
Devonian black fetid carbonates of the McDame Group
(see Gabrielse, 1963) may be in part correlative with a
silicified amphiporal carbonate found 2.8 km southeast
of Black Stuart Mountain.

The age of the sandstone unit is not directly known,
but is probably Upper Devonian or younger because it
overlies one of the conglomerate facies of the Guyet
Formation. Its correlation outside the area is unknown.

Waverly Formation

The name Waverly was first used geologically by
Johnston and Uglow (1926) and was subsequently aban-
doned by Sutherland Brown (1957). The name is repro-
posed for a formation of volcanic rocks found underlying
the conglomerate of the Guyet Formation and which are
well developed on the southwest slopes of Waverly Moun-
tain. Sutherland Brown (1957,1963) included these vol-
canic rocks in the Guyet Formation but did not give them
any status.

The Waverly Formation consists of schistose calcare-
ous basaltic agglomerate and flows, pyroclastics, pillow
basalt and minor breccia, and chlorite-rich quartz siltite.
It is the only volcanic unit recognized from the Cariboo
Terrane of the map area. The calcareous agglomerate,
flows and pyroclastics distinguish the Waverly Forma-
tion from volcanic rocks of the Antler Formation of the
Slide Mountain Terrane.

The Waverly Formation underlies a narrow belt
extending from Summit Creek southeastward to near
Black Stuart Mountain. The reference area of the
Waverly Formation is in the area of Waverly Mountain
where the unit is the most diverse and has a large areal
extent. It was mapped by Johnston and Uglow (1926) as
part of the Waverly Formation, which included rocks now
mapped as Antler Formation. Sutherland Brown (1957)
mapped it as part of the Guyet Formation, and later in
the Black Stuart Mountain area as part of the Midas For-
mation (Sutherland Brown, 1963). Campbell et al. (1973)
included the Waverly Formation as part of the Black
Stuart or Guyet Formation. The thickness of the Waverly
Formation, where present, varies from approximately 2 to
40 m. The lower contact is sharp and suspected to be
conformable above the black pelite unit of the Black
Stuart Group.

The basalt of the Waverly Formation is characteris-
tically pyroclastic and carbonate-rich. In most areas the
basalt is a schistose calcareous greenstone with little indi-
cation of original texture or mineralogy. It consists of
a foliated matrix of chlorite, semi-opaques, sericite and
epidote supporting 0.5 to 4 mm augen-shaped knots of
dark grey to black calcite or dolomite (Table 8). Agglo-
merate with basalt clasts (pebble to boulder size) occurs