——_ as F s
76 ES + a” - ee &

Figure 13. Chert breccia of the chert-carbonate unit of
the Black Stuart Group in the keel of the Black Stuart
Syncline. (GSC 191009)

Figure 14. Limestone breccia, probably tectonic, pos-
sibly of the Lower Cambrian, at the base of the chert-
carbonate unit of the Black Stuart Group in the keel of
the Black Stuart Syncline. (GSC 191010)

by poorly exposed tan weathering cream moderately
crystalline dolostone overlying grey limestone of the
Mural Formation. Chert breccia similar to that found
at the base of Black Stuart Group south of Cariboo
River is poorly exposed (possibly float) in the creek which
drains from the south of Waverly Mountain to Pleasant
Valley Creek.

Black pelite unit

The black pelite unit consists primarily of dark grey to
black shale, slate, cherty argillite, siltstone and phyllite
and lesser amounts of dark grey limestone, dolostone and
sandy dolostone and black chert. The black pelite can be
confused with those of the Isaac and Dome Creek

24

formations of Cariboo Terrane, those of the Harveys
Ridge and Hardscrabble successions of Barkerville
Terrane and those of the Triassic of Quesnel Terrane.

The black pelite unit can be traced from the type area
at Black Stuart Mountain north to Big Valley Creek. It
is involved in several thrust sheets and unconformably
rests on most older formations excluding the Cunning-
ham Formation. The thickness of the black pelite unit
is unknown but is estimated to be less than 500 m.

The pelite is slate where it contains Ordovician grapto-
lites and is mainly siliceous phyllite and argillite where
it overlies the Lower Devonian chert-carbonate unit. Silt-
stone is dark grey and thinly interbedded with the pelite.
Limestone is dark grey and black, finely crystalline (sec-
ondary); occurs in 1 to 5 cm beds in pelite and in one
locality has yielded conodonts. A single locality of light
grey oolitic and intraformational conglomeratic limestone
occurs on the logging road along Loskey Creek. Dolo-
stone has a restricted occurrence, is dark grey, finely
crystalline and in places sandy. Its bedding character is
like that of the limestone. Chert is black to grey, pure
to muddy and thinly laminated. Locally the chert is
secondary where it has replaced amphiporal limestone
(Fig. 15).

Sandstone unit

The sandstone unit of the Black Stuart Group consists
of grey siltite and fine grained quartzite interbedded with
grey and dark grey pelites, light pink to white moderate-
ly fine grained quartzite and what appear to be silicified
carbonates. The quartzite, siltite and pelite are unique in
the Black Stuart Group but resemble those from the
Yankee Belle and particularly the Vic Sandstone of the
Midas Formation.

Figure 15. Amphipora in the black pelite unit of the
Black Stuart Group near Black Stuart Mountain. Canadian
nickel for scale. (GSC 191011)