362 REPORT UNITED STATES GEOLOGICAL SURVEY. 



taries are generally determined by tlie same causes. In the present in- 

 stance, the side affluents of the streams which rise in this block have 

 molded it into a series of parallel spurs united by a median ridge to 

 the watershed, and this in turn by devious and exceedingly variable 

 ridges hitching on to the main heights which lie to the east of the drain- 

 age divide. From any of the high points in the range, the above-de- 

 scribed features stand out in bold relief. 



Passing from the basin-plain to Station XVIII, which occupies the 

 crest of a highish ridge some four miles to the northeast, the first rock 

 exposures encountered are low in the foot of the outer ridge, where an 

 obscure ledge of (1) reddish gray sandstone forms a low bench peering 

 above the gravelly second-bottom which here borders the East Fork of 

 Gray's Creek. Higher in the slope the surface is covered with the debris 

 of (2) fine drab indurated argillo-calcareous deposits and drab-gray lime- 

 stone, above which appears (3) laminated grayish buff sandstone asso- 

 ciated with red arenaceous shales and sandstone layers, dipping south- 

 erly or southwesterly. A little higher in the slope, and in the crest of a 

 low ridge west of the debouchure of the East Fork, similar (4) sand- 

 stones interbedded with deep and pale-red sandy shales, making up a 

 heavy deposit, show moderate inclination to the northeastward, indicat- 

 ing a low anticlinal fold. The foregoing exposures are, however, very 

 obscure, as is the case with many yet to be mentioned in the easterly 

 portion of the section here referred to ; so that it is only now and then a 

 ledge affords satisfactory observation on their position as determined by 

 the direction of strike and inclination of the strata. Crossing up through 

 the narrow gap, the way lies over a series of dexjosits, which to the west- 

 ward are seen outcropping in successive bands, one above the other, in 

 the steeper and higher portion of the ridge, and also appear, though ap- 

 parently less distinctly marked, in the more rounded ridge east of the 

 gap. These deposits were found to consist of (5) sandstone and red 

 sandy shales, dipping steeply northward, at one point at an angle of 70°, 

 standing up in the surface like narrow dikes or combs, the harder ledges 

 breaking into rhombic blocks. In the opposite southeast side of the 

 narrows, the shales are seen in steep banks of a bright red color, while 

 everywhere they give to the soil its peculiar tint. Entering here the 

 little mountain basin, its floor is over deposits similar to those last men- 

 tioned, or (0) dull chocolate-red shaly sandstone and reddish shales, which, 

 however, dip southerly at a much less steep angle of inclination. The 

 little basin is hemmed in by broken hills covered with shrubs, and 

 patches of conifers in the shaded deeper ravines and northern slopes. 

 The little streams are obstructed with beaver-dams and their narrow 

 flats, a jungle of willow and low growth. It is headed off by the water- 

 shed, here an extremely broken ridge 1,600 to 2,000 feet in height, with 

 quite considerable tracts of pine and fir. Just to the southwest lies the 

 parallel ridge of Station XVIII, in ascending which the following ob- 

 servations were made : In the foot of the southwest slope, a heavy de- 

 posit consisting of (7) ledges of reddish-gray sandstone interbedded with 

 red shales with flakes of selenite and calcite, occurs, dipping southerly 

 or west of south, at an angle of 35°. The much-encumbered slope shows 

 only imperfect exposures of (8) bluish limestone debris, (9) red gritty 

 shales, and (10) drab argillo-calcareous deposits, which latter at one 

 point appear in the crest of the ridge, where their decomposition has 

 produced a soil peculiar to these shaly beds. The crest of the ridge, 

 w r hich lies a little to the north and south of the hue of strike of the 

 strata, shows in its southeast portion heavy ledges of (11) rusty gray 

 and deep red shaly sandstone, showing slickenside surfaces and false 



