13 Guo. 5 Pracn River Drsrricr. JI 7

=a

River in three branches and Lynx Creek in two are the principal streams. They have cut
channels in places as much as 100 feet below prairie-level. There are no waterfalls in their
courses, but the gradient is steep, in places amounting to 40 or 50 feet in a mile.

GEOLOGY.
S

In the Peace River District of British Columbia there are three principal formations. In
descending order they are as follows :—

Formation. Character. * General Origin.
WIN WR, oadSennoonc00 So SQopNO su SURDOSDOCUSNGSESOO SandStonesemacieacer eee iee nately seiecia teres Land deposits.
Sis ALY Sass Gans Se 35 z ..|Shale and sandstone ; conglomerate....... Marine deposits.
Bullhead

[Sandstone and shalewenccueisternreiresteetstie Land deposits.

All are of Cretaceous age. The Dunyegan and St. John are referred by Dr. F. H. McLearn,
who has made the latest report of the region for the Geological Survey (Summary Repert,
Geological Survey of Canada, Ottawa, 1917) to the upper or Colorado divisions of the Cretaceons,
and the Bullhead to the Lower Cretaceous, probably equivalent to the Kootenay formation of
Southern Alberta. It is probably from the upper part of this formation that oil is obtained in
the Black Diamond field near Calgary.

The Dunvegan is a land formation. It consists principally of a friable sandstone and
contains an occasional small seam of coal. It occupies only a small area in this district and is
not important to the present investigation beyond marking the upper limit of the St. John.

The St. John formation consists mainly of soft shale with beds of clayey sandstone near the
middle and in the lower part of the formation. It is nearly 2,000 feet thick in one drill-hole
and this apparently is considerably less than the total thickness. It is of marine origin and so
potentially oil-bearing. Since it occurs over a large part of British Columbia east of the Rocky
Mountains and occupies a large area in Alberta its thorough investigation is important. In
structure the rocks lie nearly flat, varied only by low local folds.

The Bullhead is essentially a land formation in its upper part at least. As such it would
not be an original source of oil, but its upper sand measures are better suited for collecting and
retaining oil which may have migrated from other formations than the rather clayey sandstones
of the St. John. A few hundred feet from the top, however, the Bullhead becomes dense and
compact and there offers less prospect of being either easily permeable or of forming a good
reservoir.

The formation is provisionally estimated by Mr. MeLearn (op. cit.) to be upwards of 4.000
feet thick along the Peace River and many contain marine measures near the base. Outside of
the canyon of the Peace it is not exposed in the district until the eastward slope of the foot-hills
is reached and where the strata become more greatly disturbed. The top has been reached in
drilling at varying depths from 800 to 2,000 feet. The Bullhead has been provisionally correlated
(McLearn, op. cit.) with the Peace River sandstone which appears 200 miles to the eastward,
and so it probably underlies the entire district beneath the St. John formation. It rests on rocks
of the Triassic system at the west, while on the east its probable equivalent, the Peace River
formation, rests on the Devonian.

It is notably a coal-bearing formation, especially on the west of the first important fold of
the foot-hills, where coal of excellent quality is found in the canyon of the Peace and westward.

Tue Locariry DRILLED.
Horizons.

In the search for oil and gas in the district three horizons naturally present themselves as
probable or possible sources. There are the sandstones within the St. John formation; the
upper Bullhead, in which oil might accumulate from the St. John shales; and the base of the
Bullhead. where oil might be accumulated from the underlying Triassic shales and impure lime-
stones or from some possible marine member of the lower Bullhead itself. In the area examined
no favourable place could be found outside of the Peace River Block (which being Federal
territory is excluded from the investigation) for testing the middle sandstones of the St. John
formation. Wherever they are found there is lack of either cover or favourable structure, or
of both.