REPORT OX THE GEOLOGY OF THE SWEETWATER DISTRICT. 



By F. M. Endlich, S. N. D. 



ITINERARY. 



During the summer season of 1877, a district was assigned to us lying 

 between north latitude 41° 45' and 43°, and west longitude 107° and 

 109° 30', within the Territory of Wyoming. A portion of the ground had 

 been covered by Fremont's expedition in 1842-'43, and by Dr. Hayden's 

 explorations during 1870. For the purpose of continuing the regularly 

 mapped survey of the Territories, it was necessary that connected explo- 

 rations of this region should be made. The area assigned to us covered 

 11,300 square miles, but a portion thereof remained unsurveyed, owing 

 to the advanced season. Much that heretofore was unknown within 

 the district has been discovered, and points remaining in doubt have 

 been cleared up. As no map can accompany the subj oined geological report, 

 this itinerary may facilitate the determination and recognition of localities 

 referred to therein. A certain amount of repetition will occur ; but as 

 the one description is prepared from the standpoint of a traveller, and 

 the other from that of a geologist, it may be hoped that each will present 

 features which the other does not contain. 



FROM SALT WELLS TO CAMP STAMBAUGH. 



Having left Cheyenne by rail May 31, we reached Salt Wells Station 

 early on June 1. The day was fully occupied in arranging and classify- 

 ing the provisions, instruments, ammunition, and personal property of the 

 party. As might be expected, the mules, which had for seven months 

 been perfectly idle, exhibited a degree of friskiness that promised char- 

 acteristic developments upon their first packing. Proceeding in a 

 direction a little west of north, we left the Union Pacific Eailroad and 

 reached our first camp on Packer's Creek. It was found to be dry, but 

 water was obtained from some small alkaline pools in the vicinity. 

 Early on the day following we started, alter having collected our stray- 

 ing animals, and travelled in a direction north of east. In the distance 

 some prominent black hills appeared, indicating to us the probability of 

 finding water, and furnishing good points for the purposes of topographi- 

 cal work. During the entire day we saw no water, excepting that which 

 Ave received most plentifully in the shape of a drenching rain. A stiff 

 wind blowing it directly into our faces, rather disconcerted the mules, 

 and it required constant "argument" to keep them in line. Some very 

 characteristic scenery was found on the way, indicating that we had 

 left the Cretaceous area and entered that of the Tertiary formation. 

 Fhiviatile erosion has carved deep, narrow canons into the readily yield- 

 ing sandstones and marls. Depositing the detritus in conveniently 

 located valleys, these have been filled with loose soil, often to the depth 

 of 30 feet and more. The first thing that attracted our attention was 



5 



