REPORT ON THE GEOLOGY OF THE SWEETWATER DISTRICT. 



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



ITINEEAET. 



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

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

 109° 30', Avithin tlie Territory of Wyoming. A i)ortion of the ground had 

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

 explorations diu-ing 1870. For the i)urpose of continuing the regidarly 

 mapped survey of the Tenitories, 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 i)ortion thereof remained imsurveyed, owing 

 to the advanced season. Much that heretofore was imknown within 

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

 been cleared up. As no map can accomi)any the subj oined geological report, 

 this itinerary may facilitate the determination and recognition of localities 

 referred to thereia. A certaiu amount of repetition will occur ; but as 

 the one description is prepared fi^om 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. 



FEOM SAJLT WELLS TO CAIMP STA2IBAUGH. 



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

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

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

 party. As might be expected, the mules, which h?.d for seven months 

 been perfectly idle, exhil3ited a degree of friskiness that promised char- 

 acteristic developments upon their lii-st packing. Proceeding in a 

 direction a little west of north, we left the Union Pacific EaUi-oad and 

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

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

 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 Mils appeared, iudicating to us the probabihty 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 

 we received most plentifully in the shape of a drenching rain. A stilt" 

 wind blowing it directly into oui' faces, rather disconcerted the mules, 

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

 characteristic scenery was foimd on the way, indicating that we hah. 

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

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

 ing sandstones and marls. Depositing tlie detritus in conveniently 

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

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



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