6 
MUSEUM BULLETIN NO. 4. 
It is worthy of note that a thin bed of tuff occurs inter- 
stratified in the Dakota, near the middle of the formation on 
Ma butte, northeast of Crowsnest mountain, 1 The following 
section across the lower beds of the volcanics was observed on 
Jackson creek, in the Southfork valley. 
Measures Thickness 
Massive beds of coarsely fragmental agglom- 
erate. 
Coarsely fragmental orthoclase agglomerate. 10 ft. 
Black carbonaceous seam, full of rounded sand 
grains but clearly of a coaly nature. 2 4 in. to 8 in. 
Hard, light purplish tuff. 0 ft. 8 in. 
Soft green, fine-grained tuff. 2 ft. 0 in. 
Hard, coarse to medium, dark green tuff, frag- 
mental orthoclase up to \ inch. 8 ft. 0 in. 
Conformable on fine, dark green (tufaceous) sandstones of 
the upper Dakota. 
Relations of the Volcanics to the overlying Benton. 
Here again is a gradational relationship. Owing to the soft 
character of the Benton shales this contact is usually obscured 
by detritus, and was only actually observed in one locality, where 
a prospect trench had been dug across it ; but as the volcanics are 
usually finer and thinner bedded toward the top, the transitional 
relationship had been inferred before it was actually seen. The 
trench above mentioned is on the south bank of the Southfork 
river, just below the junction of its west and south branches. 
The following section was observed, In descending order: — 
^each, W. W., Sumrn Rept. Geol. Survey, Canada, 1911, p. 196. 
^This is the only occurrence of the kind noted by the writer. Dawson 
speaks of havingseen plant remains in the volcanics elsewhere in the Southfork 
valley. 
Dawson, G. M. Ann. Rept. Geol. Survey, Canada, 1885, Part R, p. 57B. 
