siARVixE.J GEOLOGY SOUTHERN END OF WILLIAMS RIVER RANGE. 189 



there the sedimentary beds have not (by many a thousand feet) been 

 stripped by erosion from off the underlying rocks. It is a form of mount- 

 ain-building, which I think is not uncommon in the West. 



The caiions issuing from the high Park range, or Blue Eiver Mount- 

 ains, are glacier-scored, and cut deeply into the metamorphic rocks 

 between the supposed Cretaceous covered areas, which lie between their 

 mouths. From the edges and ends of these areas commence the moraines, 

 which extend valley ward and end in broad indefinite morainal masses, 

 reaching nearly to the river. The metamorphic rocks exposed in 

 the caiions probably extend some distance down them, and finally be- 

 come covered by the moraines, encroaching on it from either side before 

 the edges of the Cretaceous sandstones which underlie the main valley 

 appear crossing the stream-bed ; these edges apparently being covered 

 by the moraines, as indicated by section C. In this section the plateau 

 area c d is not shown quite high enough to be in its proper relation to 

 the moraine. 



From the lower surfaces of the moraines the terraces sweep off to 

 the river, the upper terraced beds evidently lying directly on the mo- 

 rainal mass ; the two formations being i)robably to a certain extent 

 contemi:)oraueous. 



THE SOUTHERN END OF THE WILLIAMS EIVER RANGE. 



Opposite the portion of the Blue Eiver range last considered, lies 

 the southern end of the more symmetrical portion of the Williams 

 Eiver range, which terminates at a saddle at Pass Creek, its highest 

 point being nearly midway between that stream and the northern end 

 of the range. The Blue Eiver bends near this jjoint, the valley turning 

 from a southeast to a south course, in going up stream. Looking 

 down the valley from a point above the bend, the eye sees, then, the 

 southern end of the Williams Mountains, (see section 6, east end,) 

 with the edges {x, (v) of the prominent upper bed of the range running 

 across it. As shown in the section, it seems to be folded or faulted 

 somewhat. On the south side of Pass Creek is TJte Peak, rising 

 some 3,800 feet above the Blue. This mass shows as somewhat offset 

 to the east with respect to the Williams Mountains. Its western 

 face is terraced like the west face of the latter, the uppermost 

 bed appearing running prominently across it, with the lower promi- 

 nent bed showing on a portion of the face, and both dipping slightly 

 eastward into the mountain, but all the mountain summit is of the 

 metamorphic rocks. There are here mica, schist, and gneiss, rather 

 finely banded, but somewhat distorted or irregular, with some felds- 

 pathic seams, the strike being about north 10° east, with a dip vertical 

 or high to the south. Its eastward slopes carry one at once into a 

 country characteristic of the archgean rocks and different from the 

 valley just left, the first ea.stward descent being directly to the deep 

 caiions of the Upper Williams Eiver, and then on and up on to the 

 massive, deep-cut spurs leading to the Mount Byers and Gray's Peak 

 groups of mountains. 



To the south all seems likewise a mountainous region carved from 

 the hard metamorphics. The western face of the hard archrean rocks, 

 which form the summit of the mountain, is abrupt for about a thousand 

 feet down to the uppermost layer of the sedimentary rocks. Close to 

 the base of this steep upper slope some of the sediments dip slightly 

 away from it, but their inclination just abreast of the peak is mostly 

 toward the latter, at an angle of 8° or 10'^. There passes through 



