48 



Pre-Cam- 

 brian. 



Kitchener formation. . .Thin-bedded dark grey argill- 

 aceous quartzites and lime- 

 stones. Thickness 4,500 ft. 

 (1,372 m.). 



fCreston formation. . . .Light grey argillaceous quartzite. 

 and purer quartzites. Thickness 

 5,000 ft. (1,525 m.). 



Aldridge formation. . . . Rusty weathering heavy and thin- 

 bedded argillaceous quartzites 

 and slates. Numerous sills of 

 gabbro at various horizons. 

 Thickness 6, 000+ft. (1,830+m.) 



DESCRIPTION OF FORMATIONS. 



ALDRIDGE FORJMATION. 



The Aldridge formation is the oldest known sedimentary 

 member of the Purcell series in the Purcell range. It 

 consists of argillaceous quartzites, purer quartzites, and 

 a subsidiary amount of argillite. The beds have an average 

 thickness of 6 inches (15-2 cm.) but vary from a few inches 

 in the argillitic members to eight feet (2-4 m.) in the 

 purer quartzites. The argillaceous quartzites are grey to 

 almost black in colour on fresh fracture. They weather to 

 a rusty brown, and since the argillaceous quartzites are 

 in greater abundance, they give the characteristic reddish- 

 brown colour to the formation as a whole. The thick 

 bedded purer quartzites weather to a light grey colour. 

 Shallow water features, except some conglomerates on 

 Goat river, are not noticed in the Aldridge formation. In 

 places, cubes of pyrite are abundant. A fact, worthy of 

 emphasis, is that in this region the Aldridge formation is 

 characterized by the presence of a relatively large number 

 of thick gabbro sills, called the Purcell sills. The succeeding 

 younger formations contain only a few gabbro sills, and 

 these are relatively thin and unimportant. The Aldridge 

 formation contains the greatest number of economic 

 ore-deposits, and in it are situated the St. Eugene, Society 

 Girl, Aurora, North Star, and Sullivan ore-deposits. 

 Also, the majority of the copper-bearing veins occur in 

 the gabbro sills which are intruded into the Aldridge 

 formation. 



