268 DESCRIPTIVE GEOLOGY. 



of this valley is formed of beds of Weber Quartzite, having a gentle soiitheni 

 dip, varying from 5° to 10°, along its northern face. 



To the north of the river, at Ashley Park, and at the eastern end of 

 the plateau region above mentioned, is a high table-topped mountain-mass, 

 of crystalline schists and quartzites of Archaean age, which forms the western 

 end of the Red Creek Archaean body. This body, which, as will be seen 

 by reference to the map, is exposed over a comparatively small area, is 

 composed of steeply- dipping beds of crystalline schists and white quartzites, 

 which bear evidence of having suffered intense compression and distortion, 

 and which are distinctly unconformable to, and of an older system than 

 the conformable series involved in the Uinta uplift. The relations of these 

 older rocks with the beds of the Weber Quartzite are clearly seen, as the 

 latter are found along the southern base of this mountain, preserving their 

 regular inclination of 10° to 15° north, in direct contact with the steeply- 

 inclined beds of the crystalline rocks; and in one instance, near the mouth 

 of Red Creek, on the face of the Archaean cliifs, overlooking the western 

 end of Brown's Park, a detached fragment of the red quartzites remains, 

 still dipping 15° north, while the main mass of the cliffs is formed of beds 

 dipping from 45° to 70° north. 



It is thus evident that these and the succeeding conformable beds were 

 originally deposited around the shores of an Archaean island, the highest 

 peak of a submerged Archaean ridge, which was itself involved in the move- 

 ment that raised the Uinta Range. 



On the northern edge of the Archaed,n body, however, at the ridge 

 forming the divide or water-shed between Henry's Fork Basin and the val- 

 ley of Red Creek, the sandstones of the Fox Hill Cretaceous, the eastern 

 continuation of the Big Horn Ridge, are found in contact with the Archaean 

 rocks, standing at angles of 70° and over, and showing signs of local dis- 

 placement and faulting. The entire western limits of the Archaean body 

 were not traced; but it is not probable that the Triassic or Jurassic forma- 

 tion comes in contact with the Archaean rocks in this region. The fact that 

 beds of the Middle Cretaceous are thus found in contact with this body on 

 the north, opposite the point where the beds of the Weber Quartzite adjoin 

 it on the south, presents a somewhat difficult structural problem. The solu- 



