32 
MUSEUM BULLETIN NO. 4. 
petrographic province farther north and form an areal link 
between the rocks of Ice river, B.C., and those of Montana. 
It is suggested that this international area characterized 
by alkalic rocks of widely varying types, from the nalsic blair- 
morite to the mafic analcite basalts, for instance, be termed 
the Rocky Mountain Petrographic Province. 
This large area, characterized on the whole by alkaline 
rocks, and containing subdivisions which form smaller pet- 
rographic provinces, illustrates the idea that the regional progres- 
sion of types, first mentioned by Pirsson 1 by which he means the 
varying relative distribution of types among different localities 
in the same province, may be extended to include the "regional 
progression of petrographic provinces.” Just as any individual 
province is characterized from place to place by varying related 
individual rock types, so the larger petrographic provinces may 
be characterized by varying related individual provinces. Id- 
dings states virtually this same idea in the form of a question 
in volume two of his work on "Igneous Rocks .” 2 
It is perhaps worth reiterating that the Rocky Mountain 
alkaline province is in sharp contrast with the even more ex- 
tensive subalkaline province of the northern Coast ranges of the 
Cordillera. 
The earlier age of the volcanic rocks which are here des- 
cribed is compatible with the generally accepted sequence of 
igneous action; first volcanic, then plutonic, and lastly dyke 
phases. Pirsson , 3 infers that the time of igneous activity in the 
Highwood mountains was coincident with the general geologic 
disturbance at the close of the Cretaceous and in the early 
Tertiary. 
The stratigraphic position of the Crowsnest volcanics may be 
evidence that the first tectonic disturbances of the Laramide 
revolution took place in Alberta in mid-Cretaceous time. After 
these first uneasy stirrings of the earth's crust, a period of sub- 
sidence and quiet ensued, before the final upheaval began, that 
culminated in the folding and uplift of the Rocky Mountain 
i L oc. cit p 48 
2 Iddings, J. P. Igneous Rocks, Vol. 2, John Wiley & Sons inc., N. Y., 1913, 
p. 467. 
®Pirsson, L. V. Bull. U. S. Geol. Survey No. 237, p. 199. 
