VERMILLION CEEEK VALLEY. 275 



This bed has been found to be very constant Avherever a good section 

 of the Upper Coal-Measure group in the Uinta Range, and lias been 

 considered as forming the dividing line between this group and the Pernio- 

 Carboniferous. It is noticeable that in the beds exposed in a canon- 

 section like this, the siliceous members seem to predominate over the lime- 

 stones ; whereas, when found forming ridges projecting above the surface, 

 the limestone beds are the more prominent. While it is evident that beds 

 of the same horizon may change in character in very short distances, this 

 may be also explained by the fact that the limestone beds are, in general, 

 more massive, and present fewer bedding-planes than the siliceous beds, 

 and are, therefore, better able to resist the action of erosion, 



Vermillion Creek Valley. — Above the canon of Vermillion Creek, 

 and to the east of the high ridge which borders the Owi-yu-kuts Plateau, 

 is a remarkable valley, in which, b}^ the denudation of the overlying Ter- 

 tiaries, the beds of the entire Mesozoic group, from Carboniferous to Upper 

 Cretaceous, are exposed in a series of ridges running northwest and south- 

 east, parallel to the Owi-yu-kuts Ridge, but curving outward toward the 

 centre of their exposure in the arc of a large circle. This curve, as we have 

 seen before, is partly due to a flexure, which, in the lower and less elastic 

 beds, has resulted in the dislocation of the beds of the Upper Coal-Measure 

 group, but is partly also to be explained by the change of dip noticeable, 

 which is less in the centre of the curve, and also in the outer or uppermost 

 beds. This dip changes from 31°, as we have seen, in the Upper Coal- 

 Measure series, to 25° in the highest Cretaceous beds' exposed. 



Their section, in ascending order from the cherty BelleropJion bed, 

 which forms the upper gate of the caiion, is as follows : A gap of several 

 hundred feet, in which the greenish clays and mud-rocks, whicli represent 

 the Permo-Carboniferous, are too much eroded to afford a definite section ; 

 above these are several sandstone ridges, at the base colored red, and con- 

 taining some conglomerate beds, in which is included a seam of compact, 

 greenish-drab limestone, above which a second series of reddish sandstones, 

 several hundred feet in thickness ; then beds of massive buff sandstone, in 

 thickness from 500 to 1,000 feet, corresponding to the cross-bedded sand- 

 stones of Flaming Gorge Ridge, above which a fine white and red sandstone, 



