THE CENOZOIC GROUPS. 167 



UPPER GREEN RIVER GROUP. 



^JVI4 



The beds of this group are well exposed in high escarpments on either 

 side of the Green River from the northern boundary of the district embraced 

 on the map nearly to the hogback six miles above Flaming Gorge, and they 

 stretch in a continuous but irregular belt on the west side of that stream for 

 the same distance, and are exposed on Henry's Fork for many miles. 



On the east side of the Green River they are found in outlying discon- 

 nected patches. The most important of the latter are colored on the map. 

 They are also seen in the district east of Po Canon with their edges upturned 

 around the basin of displacement previously mentioned. It is probable 

 that these beds are also found east of Pine Bluffs, but when that country 

 was studied in 1868, I had not separated the Upper from the Lower Green 

 River beds, and not having visited the country since, I am not prepared to 

 give any facts concerning the matter. 



In a former chapter I stated that the Upper Green River beds were 

 interpolated between Bridger and Lower Green River only through a por- 

 tion of the great Tertiary basin north of the Uinta Mountains. These beds 

 have their greatest development in the region about Green River Station, 

 extending for 20 or 30 miles to the north and south, and it is probable that 

 the material of which they are composed was derived in part, at least, from 

 other than the Uinta region, though doubtless this region yielded a share 

 of the detrital matter. Carbonaceous shales and lignitic coal are found at 

 this horizon on Henry's Fork. Two of the coal beds have been explored 

 and when tested are said to have yielded fair coals. 



I have already in a former chapter described the Tower Sandstone at 

 the base of this group, and explained the nature of the unconformity between 

 the Upper and Lower Green River Groups. 



BRIDGER GROUP. 



The Bridger beds are found outcropping on the western border of the 

 district under discussion north of Henry's Fork, and again to the east of the 

 Po Canon district in the sag of displacement north of the Dry Mountains. 



No unconformity has been discovered between the Bridger and Upper 



