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LOWER CRETACEOUS

FORT ST. JOHN GROUP
Definition

The late Lower Cretaceous (Albian) formations of the northern
Foothills and Plains, lying between the Bullhead group below and the
Dunvegan formation above, are incorporated in the Fort St. John group.
Because the lithological succession varies from place to place it is not pos-
sible to use one, uniform classification of the strata for all of northeastern
British Columbia. Local classifications are required. Thus in the Pine
and Peace Kiver Foothills the Fort St. John group embraces five formations:
Cruiser (top), Goodrich, Hasler, Gates or Commotion, and Moosebar;
farther north, in Sikanni Chief and Buckinghorse River Valleys, the group
comprises two formations: Sikanni (top) and Buckinghorse; and in Liard
River Valley, it consists of three formations: Lépine (top), Scatter, and
Garbutt. The Garbutt may extend lower stratigraphically than either the
Moosebar or the Buckinghorse formation; that is, it may possibly include
beds of pre-Albian (pre-latest Lower Cretaceous) age.

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The name Fort St. John has been used in more than one sense. It was
originally given by Dawson (1881) to the ‘Lower dark shales’ of Peace and
Pine Kiver Valleys. The upper limit was clearly defined, at the base of
the ‘Lower sandstones and shales’, that is at the base of the Dunvegan
formation. The lower limit was not so definitely established. It was
stated, however, that the ‘Lower dark shales’ extend from about 6 miles
below Hudson Hope to a little below the mouth of Pine River North, now
called Beatton River. The shales, thus located, do have a fairly well
defined range, namely, from the top of what is now called the Gates forma-
tion up to the base of the Dunvegan; but Dawson was merely describing
the distribution of the shales, was indeed quoting from Selwyn’s field notes,
and, moreover, knew nothing about the Gates formation. It cannot be
said, therefore, that Dawson set any lower limit to the ‘Lower dark shales’
or Fort St. John group.

In 1893, R. G. McConnell used the name Fort St. John for shales on
the lower Peace River, between the Peace River and Dunvegan formations.

In 1918, McLearn placed all strata between the Bullhead group and
the Dunvegan formation in the Fort St. John formation. In 1932, he gave
Fort St. John a shorter range, to embrace all beds between the Gates and
Dunvegan formations. Later, in 1943, Wickenden and Shaw reverted to
McLearn’s usage of 1918, including all strata between Bullhead and
Dunvegan. They also recognized Fort St. John as a group name.

Peace and Pine River Foothills

The Fort St. John group of Pine River Valley has been studied by
Spieker (1921, 1922), M. Y. Williams (1939, 1940), Williams and Bocock
(1932), C. R. Stelek (1941), Wickenden and Shaw (1948), and others.
The same group on Peace River has been studied by McLearn (1918, 1923,
1932, 1945), Williams and Bocock (1930, 1932), and Beach and Spivak
(1944).

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