234 Tertiary. 



There seems to be no unconformabilit}- of the beds included in this 

 Group, and the diiferent beds pass from one to the other graduall}- ; 

 but to the leaden-gray, somber, indurated, . arenaceous clays, which 

 cover a large area east of Fort Bridger, and weather into such unique 

 architectural forms, and contain a large variety of vertebrate remains, 

 Dr. Hayden gave the provisional name of the "Bridger Group." The 

 calcareous layers which underlie the Bridger Group, and are so well 

 displayed lower down on Henry's Fork, he referred to the " Green river 

 Group." Intercalated with the clays of the Bridger Group are beds of 

 rust^'-brown and gray sandstones, all tending to a concretionary struc- 

 ture, and disintegrating b^^ exfoliation in thin concentric laj'ers. 

 Sometimes there are beds of sandstone which form an aggregate of 

 concretions. In the whole mass, arenaceous materials predominate. 

 As we descend, the calcareous sediments prevail, until chalk}- lime- 

 stones and marl are greatlj^ in excess. 



The Green River Group is seen to the best advantage along the 

 valley of Green river, where the sides of the bluff blanks rise to a per- 

 pendicular height of 500 feet or more. Ten miles east of Green river 

 Station, the Green River Group disappears abruptly on the south side 

 of Bitter creek, and the coal formations come up to view. On the north 

 side, the eastern limit of the Green River Group is most sharply marked 

 b}^ a long, high, white bluff, that extends off, far to the northeast 

 toward the South Pass. 



The clip varies from 3° to 5°, and the laminated calcareous shales 

 graduallj- pass down intoj-ellow, gra}-, and brown indurated arenaceous 

 cla^-s, sands, and sandstones, until the well-defined coal strata are ex- 

 posed, without the least appearance of discordanc}'. 



In traveling from Bear river to Great Salt Lake valley, soon after 

 leaving Carter station," toward the west, pinkish Tertiary beds are ob- 

 served. They seem to rise from beneath the Bridger Group. Their 

 dip is about northeast 3° to 5°, and the}- have evidently been disturbed 

 slightly by the later movements which elevated the Uinta range. They 

 are composed of red, indurated, arenaceous claj's, with beds of grayish 

 and reddish-gra}- sandstones alternating;, and for this series of strata 

 Dr. Hayden proposed the name of the "Wasatch Group." Pinkish and 

 purplish claj^s are the dominant features, and give the lithological 

 character of the group as far west as Echo canon, when the conglom- 

 erates prevail. The latter is full of beds of sandstone, largelj' concretion- 

 ar}-, but the sandstones or harder laj'ers are seldom of a reddish color. 



