374 REPORT UNITED STATES GEOLOGICAL SURVEY. 



about one mile northeast of Station XXI. The southwest face in places 

 shows a low mural exposure, in which the surfaces slope southward at 

 an angle of 85° $ hut this appearance is probably due to the cleavage 

 planes. 



One and a half miles to the north and east the surface rises into still 

 more elevated heights which form the culminating crest of this portion 

 of the range — 800 feet higher than Station XXI or 8,000 feet above sea- 

 level. The deposits observed in this slope are as follows : 



51. Light drab calcareous deposits, apparently a heavy bed consisting 

 of limestones and indurated argillo-calcareous shales. 



55. Brown ferruginous sandstone, much broken up and dipping north- 

 eastward, forms a heavy ledge in crest of low ridge opposite side of 

 deep gulch, perhaps a quarter of a mile distant from the limestone ridge 

 at bed 53. 



56. A heavy series of reddish deposits, perhaps half a mile across. 



57. Light-drab indurated calcareous deposits overlaid higher in the 

 slope by still heavier deposits of — 



58. Reddish beds terminating in ridge half a mile below summit of the 

 high barrier ridge. 



The occurrence and apparent relative position of the latter series of 

 deposits are indicated in the diagram of the foregoing section. The age 

 of the limestone beds north of the station was not determined from pa- 

 leontological data; but that the southern exposures of gray sandstones 

 and red shales are clearly identical with the plant-beds in the mountain 

 basin of Fall Creek would seem to warrant the reference of the lime- 

 stones to the Jurassic. The sudden change in the inclination of these 

 strata, from a northerly dip in the southwest slope to southwesterly in- 

 clination in the crest of the ridge at the station, seems to mark the posi- 

 tion of the axis of the inverted strata involved in the overthrow of the 

 fold ; indeed this is quite clearly shown to be the fact in the exposures 

 to the southeast, where the strata are seen to curve over in reversed po- 

 sition. At all events, the identity of the phenomena observed here with 

 what obtains in connection with the same set of strata in the vicinity of 

 Station XX and in the upper basin of Fall Creek is quite apparent. 



Looking northwest, in the direction of Station XXII, the crest and 

 northeast-lying ledges of Station XXI pass along the broken slopes in 

 the order in which they are represented in the above section, the strike 

 wavering slightly from a direct course and trending round more into an 

 east- west and south-of-west direction as they approach the former sta- 

 tion. This is indicated in the position there assumed by the crest 

 sandstone of Station XXI, which is seen to curve over in a low-arched 

 fold, with gentle inclination west of north. This feature is further and 

 better explained by reference to an accompanying sketch, and will be 

 more particularly alluded to presently. About one and a half miles 

 north of Station XXI and the same distance little south of east of Sta- 

 tion XXII, the watershed runs up into a high, isolated dome, 7,600 feet 

 above sea-level, which is crowned by a heavy cap of trachyte similar to 

 that in the high plateau southwest of XXI, but here associated with the 

 rusty, vesicular, obsidian-bearing lava mentioned as occurring in the 

 crest near Station XX. These deposits incline at a moderate angle 

 southwesterly, but do not reach the elevated volcanic plain as at the 

 former locality, erosion having formed a wide gap, separating this 

 remnant from a similar sloping plateau which descends into the plain 

 west of XXII. The debris from the volcanic rocks conceals the sedi- 

 mentaries in the slopes, but in the steep declivity on the northeast side 



