458 EEPOET UNITED STATES GEOLOGICAL SUEVEY. 



A large portion of the superficial Tertiary strata incline from Walisatch 

 and Green Eiver Mountains, showing that these deposits were probably 

 distnibed at the same time by the uplifts of these ranges. * * So far 

 as we have yet seen, at least iifty miles of the dividing crest of the 

 mountains [Wind Eiver Eange] are covered with Tertiary rochs." 

 * The Tertiary deposits above referred to Dr. Hayden describes in the 

 following terms, under date " June 1. — On the west slope of the Wind 

 Eiver Mountains [vicinity of Union Pass] we meet with a thick dei)osit 

 of drift materials, which, as we descended to Gros Ventres Fork, soon 

 exj)anded into a great thickness of recent strata, evidently quite recent 

 Tertiary. * * * i should think that this formation had been depos- 

 ited after the surface of the country had attained, for the most part, its 

 present configuration. The strata consist of loose, fine arenaceous clays, 

 the layers containing more or less arenaceous matter, which does not 

 effervesce, and layers of harder rock, a fine-grained and coarse sandstone, 

 and sometimes an aggregation of grains of quartz with ferruginous 

 matter and particles of mica. The materials are all evidentlj^ derived 

 from the vicinity. Some of the masses of rock present a compact, fine 

 siliceous structure, and effervesce feebly." 



Again, under date "June 4. — To-day the Tertiary strata begin to as- 

 sume a good deal of importance. We have the brick-like materials which 

 result from the burning out of the lignite beds. There were also masses 

 of indurated clay, covered with vegetable remains, and impure lignite 

 beds ; indeed, all the indications which the lignite Tertiary beds present 

 on the east side of the mountains. The beds are also much disturbed, 

 inclining at various angles. The following section of the lignite beds 

 was taken here, which mil serve to show their resemblance to those on 

 the eastern side of the mountains : 



"9. A yellow, fine-grained sandstone and dark-gray limestone with a 

 parting of clay. The limestone is quite brittle, breaking into thin lam- 

 inae, and contains impressions of dicotyledonous leaves and a distinct 

 species of JJnio. 15 feet; inclination, 28°. 



" 8. Light-yellow sandy marl. 15 feet. 



" 7. Impure lignite. 4 feet. 



" 6. A series of marly clays, which, when saturated with water, form 

 a thick paste, variegated in color. IS^ear the summit, just below the 

 lignite, is a thin seam, four to six inches, of hard-shell limestone, with 

 the shells in the most comminuted condition. I recognized Unios, Vivi- 

 2Kiras, &c., sufficient to show that the deposit is fresh-water. 150 feet. 



"5. Alternate dark-gray and brown-yellow gray, fine sandy and clay 

 layers, with some calcareous matter and a few seams of uicoherent sand- 

 stone, sometimes assuming a concretionary character. 200 feet. 



"4. Impure lignite and clay. 8 inches. 



'^3. Yellowish-gray clay. 4 feet. 



"2. Impure lignite. Cinches. 



"1. Yellowish clay with some calcareous matter." 



''The general inclination of these beds is about 20°." 



These deposits were traced westward down the valley of the Gros 

 Yentre, where they evidently pass to the north side of the stream, along 

 which Dr. Hayden encountered successively Cretaceous, Jurassic, and 

 the arenaceous "red beds" of the Triassic, as he descended the valley 

 to Jackson's Basin. The lithologic and paleontological cliaracteristics 

 of the latter formations, as described by Dr. Hayden, show them to 

 bear intimate resemblance to the same horizons as developed on the east 

 side of the Wind, Eiver Mountains. A section, representing a thickness 

 of between 300 and 400 feet, represents the Cretaceous as made up of 



