68

is exposed along the Athabaska from Boiler rapid to below Calumet river and
along the valleys of tributary streams. It has a thickness of 110 to 180 feet.
The top of the formation is placed at the base of a bed of green sandstone
immediately above which the marine fauna of the Clearwater formation appears.
It contains lignite seams and fragments of fossil wood and carries a small inverte-
brate freshwater fauna.

The Clearwater formation consists of soft grey and black shales and grey
and green sandstones and contains some hard concretionary layers. It has a
thickness of 275 feet, first appears 5 miles below Grand island, and extends down
stream above the Mi¢Murray sandstone. It carries a marine fauna.

‘The Grand Rapids formation is a sandstone 280 feet thick. It is first exposed

- 3 miles above Joli Fou rapid, and below Grand rapids forms almost continuous

cliffs for miles. The upper part carries thin coal seams and is of subaerial origin;
the lower part is highly concretionary, and the large concretions carry a marine
fauna.

The Pelican shale, which has a thickness of 90 to 100 feet, is a black shale
that first appears near Stony rapids and is a conspicuous feature for many miles
down the Athabaska. It thins out toward the northwest, being only a few feet
thick on Moose river and not recognized on the north end of Birch mountain.
It carries poorly preserved species of Inoceramus.

The Pelican sandstone appears from beneath the La Biche shales at the mouth
of Pelican river and forms a low cliff in all the exposures between Stony rapids
and Grand rapids. It is 35 feet thick and is in general conspicuously white. A
species of Inoceramus is found at the top.

The La Biche shales overlie the Pelican sandstone and extend up the Atha-
baska a few miles beyond the mouth of Pembina river, and up Lesser Slave river
into the country surrounding Lesser Slave lake. The shales are also exposed in
Birch mountain, an erosion plateau lying to the west of the lower part of Atha-
baska river. A section at Athabaska, as exposed in the bank and revealed by
boring, consists of 15 feet of yellowish sandstone at the top, 165 feet not well
exposed, and 1,090 feet of grey and blackish shales. These are succeeded down- —
ward by Pelican sandstone.”

The Edmonton formation consists of yellowish and greyish, flaggy and
massive sandstones, often holding large concretions, and alternating with greyish
and dark clays and shales. These sandstones, clays, and shales carry seams of
lignite. and are practically horizontal. The formation extends in a broad belt
eastward from: the foothills nearly to the junction of the Pembina and the Atha-
baska. Sediments that may belong to this formation are well exposed in the
plateaus south of Lesser Slave Lake.®

There are at least 650 feet of strata in these hills that may be placed in the
Edmonton formation, and a section of over 500 feet has been measured along
Driftpile river. The top of the Edmonton is placed where there are two seams
of coal, 20 inches and 21 inches thick, separated by 8 feet of shale, at an elevation
of 3,300 feet. The base is not exposed but the character of the beds and the
presence of a coal seam at an elevation of 2,650 feet are indicative of the Edmon-
ton. This formation is overlain by the Paskapoo formation of Tertiary age.

1 McLearn, F. H., Geol. Surv., Can., Sum. Rept., 1916.

.2 Dawson, G. M., Geol. Surv., Can., Ann. Rept., vol. XII, p. 14 A.
3 McConnell, R. G., Geol. Surv., Can., Ann. Rept., vol. V, p. 53 D.