

ROCKY MOUNTAINS—GENERAL CONCLUSIONS. 75 
doubt, that the great limestone series D, represents that attributed to the 
Carboniferous by Dr. Hector, to the north, and by Dr. Hayden and others 
to the south. Above it, we have the reddish and fawn-coloured beds of F., 
G. and H. Of the former, the lower part probably belongs to the Carbon- 
iferous limestone beneath, being only separated from it by the trap H. 
The two latter may represent in part what has elsewhere been called 
Triassic, but, in all probability, are for the most part of Jurassic age. 
169. Below the Carboniferous limestone, a break in the continuity of 
the series obtains in the Boundary sections, and Series C. and B. resemble 
most closely the rocks which to the south have been called Silurian. The 
limestone B., in its rough, metamorphic, and cherty character, closely 
resembles some of the Silurian rocks of the southern region, but does not 
lie so near the base of the carboniferous limestone as is often the case 
there. 
170. The rocks of Series A., as already mentioned, may represent 
those which Dr. Hayden has compared with the Huronian. This, com- 
parison, however, appears to rest on but slender evidence, and to be 
merely of the nature of a suggestion. The similarity of the impure 
dolomites of Series A. with those largely developed in the Upper Copper- 
bearing rocks of Lake Superior, however, is so remarkable as to deserve 
mention, though it be hardly safe to use lithological character as a criterion 
of age at so great a distance. 
171. With regard to the question of the age of elevation of the 
mountains, I have been able to obtain but little information in the region 
examined, and that chiefly of a negative kind. Cretaceous and Lignite 
Tertiary rocks have, however, shared in the resulting disturbance. Mr. 
Clarence King has deduced from his observations on the fortieth parallel, 
three great periods of uplift. The first, he refers to the Jurassic period ; 
the second to the close of the Lignite Tertiary, and the third is supposed 
to have been simultaneous with the great volcanic outbursts of the post- 
tertiary. Evidence of elevation at the first of these periods, does not 
appear to have been very generally found ; and that it cannot have been 
very great, or such as to form a complete barrier between the eastern and 
western regions, the similarity of the marine mollusca of the lowest lig- 
nite beds of the mountains, with those of the rocks of the west coast, 
appears to show.* 
172. Other evidence, however, goes to prove that some movement took 
ee 

* Mining Industry of the Fortieth Parallel, p. 461. 

