602 



THE AZOIC SYSTEM AND ITS SUBDIVISIONS. 



Mr. King says is eruptive through the granites (T., p. 27), while Mr. 

 Hague makes the same Btatement (IL, p. 13). If this gabbro is 

 E^orian, and Mr. King is correct in stating it to be eruptive through the 

 Laurcntian granites, it follows that the Norian formation is older than 

 the Laurentian ; or else that the supposed Lailrentian granites are not 

 of that age, — that is, if we are to accept the theories of Dr. Hunt and 

 some of his followers : he, however, holds that the granite (gneiss) of 

 the Colorado Range is Laui'cntian. (I. c, p. 276.) 



The Medicine Bow Eangc is referred by Mr. Hague, " with consider- 

 able hesitation," to the Huronian, and this reference is said to be " based 

 entirely upon lithological evidences," Part of the rocks are sedimen- 

 tary ; but a large portion regarded by Messrs. King and Hague as sedi 

 mentary has not been proved by them to be so. The question still 

 remains, therefore, How much of the supposed Huronian characters is 



T 



due to eruptive agencies and their concomitants, and how much to geo- 

 logical age 1 The evidence advanced by Mr. Hague shows that the 

 upheaval of the range was not completed until at least as late as the 

 Cretaceous epoch, while, in fact, no proof is given that it is older than 

 Tertiary. It was seen in contact with no rocks known to bo older than 

 the Triassic, although beds supposed to be of Carboniferous age were 

 observed iu one locality. The kind of contact formed by these Huronian 

 rocks with the supposed later ones was not noted ; neither do wc have 

 any information given that dShris from the Huronian were found in the 

 other formations, until high up in the Tertiary. ' Had such debris been 

 observed it unquestionably would have been mentioned, since not only 

 here, but in the Colorado Range, the occurrence of su(;h material is no- 

 ticed in the Tertiary. 



The supposed Huronian formation has not then been proved to be older 

 than the beginning of the Tertiary, and in the present state of geologi- 

 cal science it is impossible, if the age of the other formations has been 

 correctly determined, to prove it older than the Carboniferous. Wo do 

 not find any evidence given that the uplift of the Park Range took place 

 prior to the Cretaceous-; there being here the same absence of proof as 

 was indicated in the case of the two preceding ranges. , In this case, 

 however, no rocks older than the Triassic were found in contact with 

 the supposed Archaean, and yet the range — on lithoh)gical grounds, 

 purely — is assigned to the Laurentian. The evidence in regard to 

 Rawling's Butte seems to be the same as that rclathig to the Park 

 Range, through the Archrean schists of which Mr. Emmons remarks 

 that basalt is seen to have been erupted. 



