﻿314 G. M. Dawson — Mocks of British Columhia and Chile. 



mate more or less to the type in Yoredale. Considering the peculiar 

 character of the Yoredale beds, so different from the Millstone Grit, 

 I think it would be a mistake to throw tliem into the same class as 

 the latter group ; nor would Prof. Hull find it everywhere so easy, 

 as it is in Derbyshire and Lancashire, to separate the Upper Lime- 

 stone Shales from the Carboniferous Limestone, the fact being that 

 the thick limestone splits up north-eastward into a number of sub- 

 divisions of limestone, sandstone, and shale. I do not mj'self 

 believe, pace Prof. Hull, in the possibility of finding any classifica- 

 tion of the Carboniferous rocks applicable to the whole of England, 

 other than the philosophical one recommended by Prof. Eamsay, of 

 treating the whole as one indivisible formation and mapping 

 separately each important bed, or group of beds, of grit, limestone, 

 chert, ironstone, plate, or shale. 



VIL — Mesozoic Volcanic Eocks of British Colubibia and Chile. 



Relation of Volcanic and Metamokphic Eocks. 



By Geoege M. Dawson, F.G.S., 



of the Geological Survey of Canada. 



IN Chile and adjacent regions of South America, Mr. Darwin, in his 

 " G-eological Observations," has described a great series of Meso- 

 zoic rocks, which he calls the " porphyritic formation," and which 

 shows an interesting resemblance to certain rocks in British Columbia. 

 These I had provisionally designated in my report in connexion with 

 the Geological Survey of Canada for 1875, as the Porphyrite series, 

 without at the time remembering Mr. Darwin's name for the Chilian 

 rocks. Many of Mr. Darwin's descriptions of the rocks of Chile 

 would apply word for word to those of British Columbia, where the 

 formation would also appear to bear a somewhat similar relation to 

 the Cascade or Coast Eange, which that of Chile does to the Cordillera. 

 By its fossils, the porphyritic formation of Chile is proved to occupy a 

 position intermediate between the Jurassic and Cretaceous, which is 

 much that which the Porphyrites of British Columbia must hold. 

 Beds overlying the Porphyrites onTattayoco Lake by some thousands 

 of feet — probably conformably — hold fossils characteristic of the 

 Shasta Group or lowest of the Cretaceous in California, which is 

 believed to represent the English Series from the Gault downwards. 

 Fossils collected last summer in the porphyrite and felsite — altered 

 ash rocks — of the Iltasyonco, a branch of the Salmon River in latitude 

 52^ 50', present a more distinctly Jurassic fades, though their 

 paleeontological value will be more certainly known when Mr. 

 Whiteaves shall have finished his examination of them. 



Of the South American Series Mr. Darwin writes:^ — "The 

 alternating strata of porphj'ries and porphyritic conglomerates, and 

 with the occasionally included beds of felspathic slate, together make 

 a grand formation ; in several places within the Cordillera I esti- 

 mated its thickness at from 6000 to 7000 feet. It extends for many 

 hundred miles, forming the western flank of the Chilian Cordillera ; 



^ Loc. cit. p. 476. 



