536 GEOLOGICAL SURVEY OF THE TERRITORIES. 



range of hills to the westward. At the base of these hills we leave the 

 series entirely, it passing underneath the Tertiary beds of which the range 

 is composed. We did not examine the junction of the two series, but 

 there seems, from a passing view, to be an unconformability here, the 

 upper beds having a very slight dip to the west of not over 2° or 

 3° altogether. These Tertiary beds, where they are cut through by the 

 gorge of Bitter Creek, which the railroad follows, appear as thinly lami- 

 nated, whitish, or light-grayish arenaceous shales, showing in recent 

 railroad-cuts a slightly bluish tinge. In places there appear bauds of 

 darker shale, and capping the hills as the road nears Green Eiver is seen 

 a heavier brownish or reddish sandstone bed, which forms the perpen- 

 dicular mural escarpments and isolated castle-like knobs which form so 

 prominent a feature near Green River Station. In some layers the 

 shales are dark-colored on freshly fractured surfaces and seem impreg- 

 nated with petroleum, but they all appear to weather uniformly light 

 yellow or whitish. 



Green Eiver. — A hill about two miles east of the station, at Green 

 River crossing, on the southern side of Bitter Creek, gave the following 

 section 'from a rough measurement with a pocket-level: , 



Section near Green River 8tatio7i. 



1. Heavy reddish-brown sandstone 100 feet or more. 



2. Whitish arenaceous clays br shales 500 feet. 



3. Reddish or brownish arenaceous shales 50 feet. 



4. Whitish arenaceous clays 130 feet. 



The dip was very slight, but one or two degrees to the westward, and 

 is indeed scarcely perceptible. It is best seen on the bluffs, on the im- 

 mediate bank of the river, above the station, where the beds are seen to 

 dip, with some slight local undulations, to the westward ; and the well- 

 known petrifled-lish bed which, at its exposure on the railroad about two 

 miles or a little more from the station, is only 40 or 50 feet above the 

 river, at Green River City, is said to be found near the summit of the 

 bluffs some hundreds of feet higher in actual level. The reddish sand- 

 stone which caps the hills at the station to the eastward does not appear 

 very prominently to the westward, and perhaps passes into arenaceous 

 shale in that direction. It appears probable that there are some local 

 variations in this formation, but as a whole it presents in this respect a 

 striking contrast to the series below. 



Bri.:an. — West of Green River City the beds seen at the river disap- 

 pear, and still higher ones of the same group come in view. These we 

 examined in the vicinity of Bryan, where we visited one or two conical 

 buttes lying to the south of Black's Fork and three or four miles from 

 the station. We found these to consist of thinly laminated grayish 

 sandstone or sandy shale, with, near the summit, some bluish, more 

 argillaceous layers, and on the extreme summit a stratum of harder 

 grayish sandstone filled with rough casts of Melanians, Unio, &c., and 

 on one a great abundance of bivalve crustaccous remains, {Gypris,) all 

 more or less silicified. The height of the buttes was not over 150 to 200 

 feet, the strata perfectly horizontal. Beside these buttes the country in 

 the vicinity afforded no good exposures, the surface being rather level 

 and uniformly covered with a gravell}^ superficies completely hiding the 

 underlying rocks. 



Brid&er Station. — West of Bryan we made no stop till we reached 

 Bridger Station, where we examined to some extent the underlying 

 greenish-gray sandstones and reddish clays, &c., of the Wasatch group. 



