﻿574 Reports and Proceedings — American Association. 



be identical with the last, and probably at Dean 'Bridge, Several of 

 the species which occur low down in this series attain their greatest 

 development in, and are characteristic of, the Carboniferous Lime- 

 stone series. 



II. — Amekican Association foe, the Advancement of Science, 

 Nashville, Tenn., August 31, 1877.— Prof. T. Sterry Hunt read a 

 paper on " The Geology of the Older Eocks of Western America," of 

 which the following is a synopsis : — 



Prof. Sterry Hunt called attention to the great types of crystalline 

 stratified Eozoic rocks which he has recognized in the eastern part 

 of the continent and in Europe, and which he has endeavoured to 

 show constitute distinct groups, well marked, both lithologically and 

 geognostically. He then gave some conclusions drawn from obser- 

 vations made by himself at a few points among the crystalline rocks 

 during a late journey in the West. His examinations of those in 

 the Eocky Mountains were made in the Sangre de Christo Eange, 

 near Garland ; in the Front or Colorado Eange ; at the Ute Pass and 

 Glen Eyrie ; and also along Clear Creek Caiion, and about George- 

 town. In all of these localities he found gneissic rocks, frequently 

 granitoid, often hornblendic, but scarcely micaceous, and apparently 

 identical with the Laurentian series of the East. He referred to the 

 published observations of the late Mr. Marvine, in Hayden's Eeport 

 for 1873, who had carefully studied these rocks in the Colorado 

 Eange, and who compared them to the Laurentian ; and he agreed 

 with Mr. Marvine in regarding as indigenous the red granitoid rocks 

 in the region of the Ute Pass. Similar granitoid rocks at and near 

 Sherman, on the Union Pacific Eailroad, are also, according to 

 Prof. Hunt, probably of the same nature. He referred in this con- 

 nexion to the area of labradorite rocks having the character of the 

 Norian series, found in the Eocky Mountain region, in Wyoming, but 

 known to the speaker only through specimens. 



The rocks of the Wasatch Eange, as seen in the Devil's Gate 

 on the Weber Eiver, are Laurentian, to which are to be referred 

 also the crystalline stratified rocks found in the same range further 

 south, in the upper part of the Little Cottonwood Canon. Here, 

 among loose blocks of the gneiss, are found occasional masses of 

 coarsely crystalline limestone, with mica, and others of a peculiar 

 type of pyroxenic rock, which accompanies similar limestones in the 

 Laurentian series. The crystalline rocks in the lower part of the 

 same Canon are, however, well-marked exotic or eruptive granites. 



Eruptive granites are found in California, where they abound 

 among the foot-hills of the Sierras, in Placer and Nevada counties. 

 The crystalline schists seen by the author in these counties, and in 

 Amador county, are Huronian, and have all the characters of the 

 Huronian series, as seen in the eastern regions of North America, 

 and of the pietri verdi of the Alps. To this horizon are also to be 

 referred the similar crystalline rocks of the Coast Eange of California, 

 as seen near San Francisco and San Jose. The auriferous veins 

 which, in the Eocky Mountains, intersect the Laurentian gneisses, 

 are found in the Sierras alike in the Huronian schists, and in the 

 eruptive granites which probably penetrate the Huronian series. 



