THE CROWSNEST VOLCANICS. 
5 
C Disconformity?) 
Turtle Mountain Group Devonian and Car- 
boniferous 
This section is conformable throughout, with perhaps a 
slight disconformity at the base of the Dakota, indicated by a 
very persistent twenty-five foot bed of cherty conglomerate. 
The beds of the Turtle Mountain group are light to dark 
grey, massive cherty limestones; the Fernie and the lower Koot- 
enay are dark grey to black carbonaceous shales, and the upper 
Kootenay is composed of more arenaceous beds with several 
coal seams, which are extensively mined in the Crowsnest pass. 
The Dakota beds are mostly fine to medium quartzose sand- 
stones of a striking green colour, alternating with more shaly 
beds. Near the top are several bands of soft, bright red fer- 
ruginous clay shales. The Benton measures are almost wholly 
fine-grained, dark grey fissile clay shales, and the Allison beds 
are typically soft, light grey, cross-bedded sandstones. 
For further information in regard to the stratigraphy and 
structure of this region see the reports already referred to and 
also the Summary Report of the Geological Survey of Canada 
for 1912. 1 
Relations to the Underlying Dakota. 
The contact between the upper Dakota measures and 
the volcanic rocks is a gradational one. On approaching the 
horizon of the volcanics the Dakota beds as a rule become coarser, 
and distinctly tufaceous material becomes noticeable. The 
beds often pass gradually from greenish sandstones and shales 
into well stratified tufaceous rocks, and the exact contact can 
often not be placed at any given horizon. 
The character of the sediments at the top of the Dakota 
indicates shallow fresh-water or terrestrial conditions. Layers 
of bright claret coloured ferruginous shales are common, and 
mudcracks and rather indistinct ripple-marks have been ob- 
served. 
I MacKenzie, J. D., Summary Rept. Geol. Survey, Canada, 1912, pp. 235- 
246. 
