REPORT OF ORESTES ST. JOHN, GEOLOGIST OF THE TETON 



DIVISION. 



LETTEE OF tea:s^s:mtttal. 



Office United States Geological and 

 Geographical Survey of the Territories, 



Washington, D. C, June, 1878. 



Sir : I have the honor herewith to submit my report on the geology 

 of the country visited by the northern or Teton division of the United 

 States Geological and Geographical Survey of the Territories during 

 the field-season of 1877. 



The party, on the completion of its organization at Cheyenne, pro- 

 ceeded by rail to Ogden, Utah, whence a march of IGO miles to the 

 northward brought us to the southwest corner of the district assigned 

 for the season's operations. The route from Ogden followed the main 

 Avagon-road to Montana, skirting the western base of the Wsaatch 

 Kange to Malade City, thence crossing over into Marsh Yalley and 

 down the Portneuf to where it opens out into the Snake Eiver Basin in 

 the vicinity of Eoss Fork Agency, where active work was begun in the 

 Mount Putnam Group on the 12th June. 



This part of the journey passed through a section which has already 

 been examined and reported upon by yourself and other members of 

 the survey ; besides it lies in the district to which Dr. Peale was as- 

 signed as geologist during the past season, to whose report such desul- 

 tory observations as I was able to make in the course of a rapid march 

 will add nothing. 



The region occupied by this division embraces much of the ground 

 explored by the Snake Eiver Expedition under the direction of Mr. 

 James Stevenson in 1872, to which Prof. Frank H. Bradley was attached 

 as geologist, and to whose elaborate report on the geology of the region 

 traversed by that exi)editioii, within the hmits of the present district, 

 my own observations are merely supplementary. In many instances 

 Professor Bradley has reported on localities which, for lack of time, it 

 would have been inconvenient to revisit, and in such instances, as also 

 where our routes were the same, on which he has fully reported, I have, 

 for the sake of brevity, subordina ted the results of my own examina- 

 tions to his, only noting such facts as may add to the comi)leteness of 

 l^revious exammations, with such reference to these latter as is neces- 

 sary for the unity of the present report. 



The district is so situated that its various sections are somewhat 

 isolated, in some cases necessitating long detours in order to pass from 

 one section to another, in which much valuable time was consumed, 

 though not always without some compensating profit to the observer. 

 Partly from this fact, I have been led to divide the district into several 

 sub-districts or sections, which, indeed, possess some natural value on 

 account of their topographic featiu-es and hydrographic boundaries, and 

 which are separately treated of in the subjoined report. 



21 G s " 321 



