WESTON'S PASS. 173 



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field from a considerable distance through the whiteness of the quartzite 

 and of the interbedded White Porphyry. The anticlinal fold of the main 

 crest, like that of Sheep Ridge, gradually 'dies out to the south of the map, 

 and at Buffalo Peaks has entirely disappeared, being merged into a single 

 monoclinal continuation of that to be described on South Peak. 



Western's pass. On the steep western face of the crest, towards the 

 valley of the Little Platte below Weston's pass, the Lower Quartzite and 

 White Limestone beds lie at an angle of 45 to 50, resting against the 

 steep slope of the hill like tiles on a roof. The valley of the Little Platte 

 presents a somewhat singular structure. At first glance it is a simple syn- 

 clinal fold. On the east side are the beds of the Lower Quartzite and 

 White Limestone dipping steeply westward, while on the west they rise 

 with the slope of the next ridge, which from South Peak southward forms 

 the main crest of the range. More careful examination, however, shows that 

 the series of beds on either side of the syncline do not exactly correspond, 

 and that the change from eastern to western dip is abrupt and not gradual, 

 as it should be in a normal syncline. The bottom of the valley, where 

 outcrops are visible, shows the Blue Limestone dipping eastward, and above 

 it a thin bed of White Porphyry, succeeded higher up by sandstones and 

 black shales of the Weber Grits formation. Through the latter, near the head 

 of the Little Platte, and just at the boundary of the map, a branch from the 

 northeast has cut a deep, picturesque gorge. Climbing the eastern slopes 

 of the gorge to the main ridge, across easterly dipping Weber Shales, one 

 comes suddenly, at the foot of the steeper slope, upon beds of White Lime- 

 stone dipping steeply to the westward. It is evident, therefore, that the 

 movement of the Weston fault has been continued somewhat beyond the 

 boundary of the map, though it dies out before the Little Platte takes its 

 bend to the eastward, just south of this boundary. 



On the summit of Weston's pass the structure can be more clearly seen, 

 though it is complicated here by a sudden curve in the beds which form 

 the western member of the fold, giving them for a short distance a strike 

 nearly east and west, instead of northwest and southeast. This pass, which 

 has an elevation of only 11,930 feet, was formerly the main approach to 

 Leadville from the east. Its summit is a low saddle, on the east of which 



