10 
MUSEUM BULLETIN NO. 4. 
map of the Blairmore-Frank Coal Fields, 1 supplemented by 
data obtained by the writer in the country south of that shown 
on Leach’s map, is about 550 square miles. Shortening of 
the width of the formation due to faulting has been allowed 
for when information in regard to it was available. 
Supposing a former extension westward of ten miles beyond 
their present width, the area originally subjected to the deposi- 
tion of volcanic sediment may be conservatively placed at 700 
square miles, with a maximum length of fifty miles from north 
to south, and a width of about fifteen miles. Assigning a max- 
imumthickness to the formation of 1000 feet (a moderate estimate) 
and supposing them to thin out gradually to nothing towards 
the north, south, and east (neglecting for a moment their prob- 
able former extension westward from the longitude of the 
Crowsnest mountain) we arrive at a volume for the volcanics 
of about thirty-five cubic miles. The inferred westward ex- 
tension of the formation is wholly uncertain as regards quanti- 
tative data, but it seems probable that there should be 
assigned a total volume for the volcanics of about fifty cubic 
miles. 
Conditions of Deposition. 
Summary. 
It is evident from the stratified nature of the deposits, 
and their conformability with and gradation into both the under- 
lying Dakota and the superincumbent Benton that the vol- 
canics are very largely of subaqueous origin. Furthermore, 
the large number of water worn fragments of considerable size 
in many beds, the frequent false bedding, and the occurrence 
of coal in at least one locality indicate that the formation was 
largely deposited in shallow water. The unsorted character 
of numerous individual layers, and their lenticular nature 
supports the same conclusion; and it is possible that some 
beds are subaerial in origin, laid down where transporting and 
classifying currents did not sort the material. 
Accompanying Part A, Ann. Rept. Geol. Survey, Canada, vol. XV, 1903. 
