2 GEORGE V. 



SESSIONAL PAPER No. 25a 



A. 1912 



CHAPTER V. 



STRATIGRAPHY AND STRUCTURE OF THE MACDONALD AND 



GALTON RANGES. 



GALTON SERIES. 



Erom the Flathead river to the Kootenay river at Gateway the mountains 

 are principally composed of the Galton series, the westward extension of the 

 same stratified series that form the peaks and massifs of the Clarke and Lewis 

 ranges. Two of the formations described as constituting the Lewis series — 

 the Altyn and Siyeh — are very clearly represented on the west side of the Flat- 

 head and, in the following account of the Galton series, will bear the original 

 names given by Willis. The other stratified members of the Galton series are 

 related to the corresponding members of the Lewis series but are stamped with 

 distinctly individual characters, and merit special names which will be employ- 

 ed in order to emphasize the contrasts between the two series. The columnar 

 section for the strata actually visible in the Galton range has been supple- 

 mented at its base by the addition of formational units which crop out only 

 in the ACacDonald range. 



The two groups of strata are so similar lithologically that the description 

 of the Galton series scarcely needs great detail. Many features are simply 

 repetitions of those already described for the Lewis series. 



The Galton series includes the formations noted in the following table. 

 Formation. Thickness in feet- Dominant rocks. 



Top, erosion surface. 



Roosville 600+ Metargillite. 



Phillips 550 Metargillite. 



Gateway 2,025 Metargillite and quartzite. 



Purcell Lava 310 Altered basalt. 



Siyeh 4,000 Magnesian limestone and metargillite. 



Wigwam 1,200 Sandstone and metargillite. 



MacDonald 2,350 Metargillite. 



Hefty 775 Sandstone and quartzite. 



Altyn 650+ Silicious dolomite. 



12,460 

 Base concealed. 



At the summit of the McGillivray range heavy blocks of Mississippian 

 limestone have been faulted into contact with the older members of the Galton 

 series. Neither top nor bottom of the limestone is exposed in the Boundary 

 belt. It is certainly younger than the uppermost bed of the Galton series, but 

 it is not known whether the relation was that of original conformity. The 

 maximum thickness of the exposed limestone seems to be about 2,800 feet. 



25a — vol. ii — 7 



