210 DESCEIPTiVE GECLOGY. 



which, as elsewhere, is wholly structureless, and made up of coai'se pebbles 

 of the quartzites and more compact schists of the Park Range. The upper 

 500 or 600 feet of the peak are composed of brown sandstones and thin, 

 blue, calcareous shales and clays of the Green River series, which are here 

 nearly horizontal. Below these, on the eastern face, are the striped bedtj 

 of the Vermillion Creek series, dipping westward at an angle of 4° to 5°. 

 Eastward from the base of the mountains is a long stretch of the red clayey 

 country, without outcrops, and just at the edge of the valley are other 

 bluffs, of the pinkish striped beds of the Vermillion Creek series. 



From the top of Washakie Mountain, which aifords an extensive view 

 over the country for 50 to 100 miles westward, the outlines of the different 

 groups of Eocene Tertiarj^ may be studied to great advantage. A line 

 drawn through this mountain to Cathedral Bluffs, thence to Pine Bluffs, and 

 southeastward through Cherokee Ridge, represents roughly the outline of a 

 rudely circular basin, marked by lines of Ijluffs, which slope back toward the 

 centre, presenting their escarpments outward. The centre of this circle is 

 probably the lowest point of the Tertiary sea, since the beds all dip toward 

 it, and, except along the line of Cherokee Ridge, have not suffered any pli- 

 cation since their original deposition. Erosion, in general, acts much faster 

 upon the edges of the strata than upon their surfaces, hence we find here 

 that the deepest erosion has taken place around the outer edges of this 

 basin, where the strata, being slightly upturned, are exposed in section, 

 while toward the centre the greatest thickness of the original beds is pre- 

 served. The central portion of the basin is occupied by a remnant of the 

 beds of the Bridger series, which is encircled by ridges formed of the more 

 resisting beds of the Green River group; while in the valleys and more 

 deeply-eroded ravines, which lie beyond these ridges, are exposures of the 

 underlying VermilHon Creek beds. 



At Washakie Mountain, there is a discrepancy of angle of 5° to 4° 

 between the beds of the Green River series and those of the Vermillion 

 Creek group. From this and more definite evidence obtained in other por- 

 tions of the basin, it is evident that there was a slio^ht movement in the beds 

 of the latter group before the deposition of the Green River shales. The 

 question of a want of conformity between the beds of the Green River group 



