THE CROWSNEST VOLCANICS. 
9 
lenticular nature. Ellipsoidal lavas (pillow lavas) or amyg- 
daloids have not been recognized. Indeed, lava flows or injected 
volcanic rocks are of very exceptional occurrence. The late 
W, W. Leach in a personal communication stated that he had 
seen evidences of small flows a short distance north of the town 
of Coleman, and also on Ma butte, northeast of Crowsnest 
mountain. 
Thickness and Volume. 
The maximum thickness of the volcanics seen by the 
writer is about 1000 feet. Leach 1 gives the thickness west of 
Coleman as 1150 feet, and states that “It appears that the 
volcanics reach their greatest thickness about two miles east 
of Crowsnest mountain, thinning out rapidly to the eastward,” 
This maximum observed thickness occurs in the westernmost 
band of tuffs that are exposed. West of this band, the rocks 
are of the overlying Benton and Allison formations until the 
great overthrust bringing up the Palaeozoic measures on top of 
the Cretaceous is reached. There is no good reason for sup- 
posing that the former areal extent of the volcanics was not 
greater in a westerly direction, and that they are not now con- 
cealed on account of the overthrusting. It is possible that the 
greatest observed thickness of 1150 feet is not the true maximum 
for the tuffs, and they may have been thicker to the westward. 
The horizon of these rocks is not exposed in the Crowsnest 
basin to the west, so definite data is lacking as to their extension 
in that direction. However, it is the writer's opinion, and with 
this statement Mr. Leach agreed, that the former extension 
was not over ten miles west of Crowsnest mountain, and that 
their maximum thickness is not far from that observed. In 
any event, they show a constant decrease in thickness from the 
vicinity of Crowsnest mountain towards the north, south, and 
more rapidly, towards the east. 
The total present areal extent of the volcanics as represented 
on Dawson's map of the Rocky mountains, 2 and on Leach’s 
ff-each, W. W Summ. Rept. Geol. Survey, Canada, 1911, p. 197. 
•Accompanying Part B, Ann. Rept. Geol. Survey, Canada, 1885. 
