REPORT OF A. C. PEALE, M. D., GEOLOGIST OF THE GREEN 



RIVER DIVISION. 



LETTER OF TRANSMITTAL. 



Washington, D. C, December 31, 1878. 



Sir : I have the honor herewith to hand you my report on the geol- 

 ogy of the district examined by the Green River Division during the 

 field season of 1877. The party consisted of Mr. Henry Gannett, topog- 

 rapher, directing; J. E. Mushbach, assistant topographer; F. M. East- 

 man, and myself, with two packers and a cook. 



The district examined comprises 13,000 square miles. We began 

 work on June 1, at Green River City, and left the field at Ogden, Octo- 

 ber 1, being in the field four months. Some portions of the districts 

 were, therefore, necessarily more closely studied than others. It was 

 my object to obtain a correct general idea of the region, knowing that 

 the detailed investigation would have to be left for future study on 

 account of the limited time at our disposal. 



I have colored a provisional geological map. Before the final map is 

 colored, several localities, in which the relations of the strata are some- 

 what obscure, must be visited, and a careful paleontological study must 

 be made of several interesting fossil localities. 



The district is divisible into three drainage areas, and to facilitate 

 ^he comprehension of the description, the Descriptive Geology is given 

 in three chapters corresponding to this division of the district. These 

 chapters are necessarily mainly a transcript of the field notes. Preced- 

 ing these chapters, in two others, I have given the general features and 

 an itinerary. In the concludiug chapter I have given a resume of the 

 geological features, presenting also such generalizations as are most 

 obvious. The time allotted to the preparation of the report has been too 

 short to enter into an extended discussion of the orographic problems 

 that present themselves, and they will have to be deferred for the present. 



For the illustrations accompanying the report I am largely indebted 

 to Mr. W. H. Holmes and Mr. F. D. Owen, and the photographs of Mr. 

 W. H. Jackson. The maps are due to the work of Mr. Henry Gannett. 

 The topographical report of the latter supplements this, and wiU give 

 all the topographical details, elevations, &c. 



To my colleagues, both in the field and in the office, I am under obliga- 

 tions for their cordial co-operation in my work. I am especially indebted 

 to Mr. J. E. Mushbach, to whose zeal and industry in the collection of 

 fossils and other data, while in the field, is due the elucidation of a 

 number of obscure points in the geological structure of the district. 



To Captain Bainbridge, in command at Fort Hall, and to his colleague, 

 Lieutenant Hall, we desire to express our thanks for the kindness shown. 

 MS while we were refitting at their beautiful little post. 

 • Hoping this report may meet all requirements, I have the honor to 

 remain, verv respectfully, your obedient servant, 



A. C. PEALE. 



Dr. F. V. Hayden, 



United States Geologist-in-charge. 



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