46

Valley (See Figure 6). Here, they consist of about 75 feet of dark, cal-
careous siltstone and dark shale, separated from the underlying ‘Flagstones’
by a concealed interval equivalent to 30 feet of strata and immediately
overlain by massive, calcareous, fine sandstone of the ‘Grey beds’. At
about 40 feet above the exposed base and near the top they carry the
Nathorstites fauna (McLearn, 1947A).

In Sikanni Chief River Valley, west of Mount Withrow, the geologists
of an oil company have discovered dark siltstones, carrying species of the
Nathorstites fauna.

Prophet River Drainage Basin

Collections of the Nathorstites fauna have been made by geologists of
oil companies in the valley of Prophet River and near Kluachesi Lake.
Details of sections are not available, but some of the collections were obtained
from ‘shale’ and are probably from the ‘Dark siltstones’ lithological unit.
This unit has not been recognized to the north, neither in the northern part
of the basin of Muskwa River nor in Laird River Valley.

Age and Correlation

The ‘Dark siltstones’ carry the Nathorstites fauna, and, therefore, can
be correlated with a part of the Liard formation. Their age and that of
other units carrying this fauna will be dealt with in discussing the sueceed-
ing ‘Grey beds’.

‘GREY BEDS’

Definition

‘Grey beds’ is a provisional name assigned by McLearn (1940) to a
thick lithological unit lying between the ‘Dark siltstones’ and the Pardonet
beds. Like the Liard formation, this unit consists of massive, thick-
bedded, grey, calcareous, fine sandstones and grey limestones, with a small
proportion of calcareous siltstone and shale. Its thickness is about 2,500
feet. The ‘Grey beds’ appear to constitute a good mappable unit, and may
prove to have the status of a formation. The unit is left unnamed at
present, however, pending further experience in the mapping of the Triassic
of northeastern British Columbia.

The ‘Grey beds’ contain three, fairly well-defined faunas: the
Nathorstites fauna in the lower part; the Mahaffy Cliffs or Red Rock Spur
fauna near the middle; andthe Lima? poyana fauna near the top (McLearn,
1940). The fossiliferous zones are separated by barren strata or strata
with only rare or poorly preserved fossils,

Pine River Foothills

The ‘Grey beds’ have as yet been little studied in the Pine River Foot-
hills. The upper part of these beds, however, is exposed near the mouth
of Mountain Creek, for Williams and Bocock (1932) obtained species of
the Lima? poyana fauna there.

Peace River Foothills

The ‘Grey beds’ are well exposed in the Peace River Foothills. A
lower part is represented on ‘Beattie Hill, between Aylard and Adams