94

The Gastroplites zone has not been identified in the Cretaceous section
on either Sikanni Chief or Buckinghorse Rivers. If, however, no hiatus
occurs, some upper part of the Buckinghorse formation may include beds
of Gastroplites age, and so be of the same age as the upper part of the
Commotion formation on Pine River plus the lower part of the Hasler in
Peace River Valley. On the basis of lithological and stratigraphic evidence,
the uppermost part of the Buckinghorse can be correlated with the upper-
most part of the Hasler formation in Pine and Peace River Valleys. The
Gastroplites fauna has not been found in the Cretaceous section on Tetsa
River, but some upper part of the ‘lower shale’ may include beds of
Gastroplites time. On Petitot River, Hage (1945) suggests that the unfossili-
ferous sandstone, the lower lithological unit of the section described by
him, is of the same age as the Scatter formation on the upper Liard and so
of Gastroplites time.

Some uncertainty exists as to the age of the lower part of the ‘lower
shale’ of Tetsa River Valley and the basal shales of the Garbutt formation
on Liard River. Northward the sandstones of the Bullhead group dis-
appear from the geological column; are absent in Tetsa and Liard Valleys;
and no longer set a downward limit to the overlying shales as they do to
the south in the Pine, Peace, and other valleys. The basal shales may be
of the same age as the Bullhead group and represent a replacement of
sandstone by shale in the north; they may be a northward continuation of
the shales of the Jurassic Fernie group; or they may be of post-Bullhead age.

The Neogastroplites fauna has not been found on Liard River in the
area studied by Kindle (1944). Some beds high in the Lépine formation
may, however, be of Neogastroplites time. The uppermost strata of the
Fort St. John group, above the zone of Neogastroplites, in northeastern
British Columbia are everywhere lacking in diagnostic fossils. Because of
similar stratigraphic position, however, a tentative correlation can be made
of the Cruiser formation on Pine and Peace Rivers with the upper shale
member of the Sikanni formation on Sikanni Chief and neighbouring
rivers; with the ‘upper shale’ on Tetsa River; with the top of the Lépine
on Liard River; with the upper part of the ‘fissile shale’ on Petitot River;
and with the top of the ‘Shaftesbury’ shale on Peace River, east of Cache
Creek.

External Correlation

Correlations have been attempted of the Fort St. John group in north-
eastern British Columbia with Lower Cretaceous formations in other parts
of the western interior of Canada (McLearn, 1932, 1944B, 1945). Some
difficulties, however, have been encountered. Faunal studies to date have
been confined mostly to the macrofaunas, which unfortunately have a
limited distribution: the Neogastroplites fauna is little known outside of
northeastern British Columbia; the Gastroplites fauna is known as far east
as the lower part of Peace River, but has not been found on the lower
Athabasca River, on the Manitoba escarpment, or in the southern Foot-
hills and Plains; the Beudanticeras or Lemuroceras fauna has a wider distri-
bution in the north than either the Gastroplites or Neogastroplites fauna and
is known as far east as the lower part of Athabasca River, but it has not
been obtained from the Manitoba escarpment or from the southern Foot-
hills and Plains. Evidence from the study of microfaunas is needed ; and
indeed is now becoming available, but not yet in sufficient amount to settle