(50 GEOGRAPHIC DISTRIBUTION. 



The outcrop of these Carboniferous groups has been traced from point to 

 point throughout the areas described above. In most places the exposures are 

 complete and the relations of the -beds can be well understood, and nowhere 

 has any unconformity between its members been observed. Nor has any 

 unconformity between the Upper Aubrey and the lower Mesozoic been 

 observed; but as the lowest beds of Mesozoic Age are of very friable ma- 

 terial, the exact junction is rarely seen. 



In the line of the fault between the Flaming Gorge district and the Po 

 Canon district there is a fragment of Red Wall limestone, as seen on the 

 map, on the northwest corner of the (3-wi-yu-kuts Plateau, which was not 

 carried down by the fault ; i. e., the fault is to the north. 



JTJKA TRIAS GROUPS. 



SHINARUMP GROUP. 



These beds are shales and soft sandstones, and hence in this region, 

 which is plicated, they are found in valley spaces. The Lower Aubrey on 

 one side and the Vermilion Cliff on the other stand in ridges. At the foot 

 of the cliff on the south side of Flaming Gorge the Green River runs into 

 the beds of this age and soon passes across them to enter the Upper Aubrey 

 beds. Looking westward a towering cliff is seen on the right and a .broken 

 slope on the left and a narrow valley immediately in front, which may be 

 followed untir the bank of Sheep Creek is reached ; then turning up Sheep 

 Creek that stream is found to run nearly its entire course, as represented 

 on the map, in beds of this age. The steep wall of vermilion sandstone on 

 the north side of this valley is, except at one point, an impassable barrier. 

 Eastward from Flaming Gorge the outcrop of the Shinarump Group is seen 

 in a narrow valley between two ridges, for about six miles, until it is cut off 

 by the great Uinta fault. 



Outcrops are also found in the Po Canon district. Here again the beds 

 are found in the spaces between the ridges. The same is true along the 

 foot of the Yampa Plateau to the- east, south, and west ; and also in a general 

 way in its outcrop from the foot of Whirlpool Canon through the Island 

 Park district. But this topographic peculiarity is not shown on the map in 



