368 REPORT UNITED STATES GEOLOGICAL SURVEY. 



G9. Gray, fine-grained sandstone ; clip G5°, X. 30° E. 



70. De&m-covered space, 12 yards. 



71. Dark drab brittle limestone, 2 feet exposed. 



72. Drab shales and debris, 30 yards. 



73. Gray limestone, 3 feet exposed. 



74. Drab shales, 40 yards. 



75. Drab-gray, brittle limestone, 30 feet exposed. 



76. Abrupt slope into depression, covered with debris, 100 yards. 



77. Sandstone ledge, obscure. 



78. De&m-covered slope, 125 yards. 



79. Drab and gray, fine-grained, fragmentary limestone, a heavy ledge, 

 dipping 70°, X. 30° E. 



80. Reddish shales, 80 to 90 yards. 



81. Gray, brown-stained, laminated sandstone, 10 feet, or more, ex- 

 posed in rugged dike-like ledge ; strike E. 33° S., dip wavering from 

 vertical to the north or south, at an angle of 85°. 



82. Eed shales, 30 yards. 



83. Sandstone, like bed 81, but less well exposed, standing in vertical 

 ledges, or dipping steeply to the north or south, locally. 



84. Slope over red shales, and covered with gray sandstone and lime- 

 stone debris, 80 yards. 



85. Dark gray, brown-weathered, fragmentary limestone, 10 to 15 feet 

 exposed, passing below into greenish, gritty, calcareous layers ; dip 40° 

 to 45°, X. 18° E. The upper layers are charged with the broken re- 

 mains of a small Ostrea, like O. strigulecula, an undetermined Lamelli- 

 branch, and a fragment of a shell doubtfully referred to Rliynchonella. 



The last-described limestone ledge forms the crest of the ridge bound- 

 ing the northeast side of Fall Creek Basin, and as the ridge rises to the 

 southeast, the limestone is carried up to higher elevations, culminating 

 in a rugged mountain cluster 8,400 feet actual altitude, and 1,000 to 

 1,200 feet higher than the crest at the point crossed by the section a 

 couple of miles south of Fall Creek Canon. The ridge breaks down into 

 a deep parallel gulch on the northeast, beyond which a series of similar 

 ridges and ravines occupies the interval extending to the lower valley of 

 the Snake, 8 miles distant. In the latter quarter the broken surface is 

 covered with shrubs and conifers, the latter especially flourishing in the 

 steep northerly slopes and filling the gulch beyond our ridge with a 

 dense forest. The south-facing slope, however, is grassy with a sparce 

 growth of scrubby cedars. To the northwest the highlands are much 

 cut up by deep, narrow ravines, radiating from the watershed north of 

 Station XX, which also forms the culminating crest in the northern part 

 of the range. To the westward hies the depression, opening into the 

 Middle Fork of Willow Creek, a region of low undulating surface con- 

 tours, surmounted by the peculiar inclined benches which mark the 

 presence of the gently upraised volcanics. The latter appear in the 

 north slope of the depression, resting on the divide, and thence sweep 

 round north of west, continuous with the great flows which fill the Wil- 

 low Creek Basin. 



Ascending to Station XX, opportunity was had for carrying our sec- 

 tion still farther into the heart of the range, where a variety of geolog- 

 ical phenomena of unusual interest were noted. The way led up a 

 gulch tributary to Fall Creek, and gaining the end of the spur rising 

 north into the summit on which the station was established, the first 

 ledges encountered cannot Me far north of, and consequently above (?), 

 the uppermost stratum shown in the preceding section. South of this 



