388 REPORT UNITED STATES GEOLOGICAL SURVEY. 



Station XXVI, which attains an altitude of about 8,400 feet, com- 

 mands the whole of the upper basin of the lower valley of the Snake, 

 the rugged barrier of the Snake Elver Mountains, and a wide belt of 

 the Caribou Eange, embracing the summits between Fall Creek on the 

 northwest and Tin-Cup Creek to the southeast, with the loftier portions 

 of the range in view. Four miles to the west the view is shut out by 

 a still higher mountain crest, only second in elevation to Mount Cari- 

 bou, or 9,600 feet above the sea, and which occupies the axis of an 

 anticlinal fold. The side toward the east shows great plates of red depos- 

 its, which contrasted beautifully with the snow cornice stretched along 

 the brow, and the deep green of the fir-clad lower intermediate ridges. 

 The mountains are sharply and cleanly sculptured ; there are few rounded 

 or indistinct hues in then contour, and none of those jagged outlines such 

 as archsean and sometimes volcanic rocks often impart to mountain 

 topography. The ravines and northeast slopes of the mountain ridges 

 are generally clothed in coniferous forests and undergrowth, giving to 

 the whole aspect of the abrupt mountain front, as seen from the valley, 

 a densely wooded appearance. The depression between Station XXVI 

 and the culminating crest of this block of the range to the west marks 

 the position of a sharp synclinal fold, from which the strata more gradu- 

 ally rise up into the crest of the ridge at the station, and where they 

 have the appearance of flattening out in a broad-topped arch. This may 

 indeed prove to be the roof of the fold, before described, in the lower 

 part of Pyramid Creek Canon. Even from the necessarily meagre data 

 obtained in so hasty a visit, it seems almost certain that, while the axes 

 of elevation hold a general and uniform course throughout the range, 

 but which erosion has thrown into a relative position more or less oblique 

 to the general direction of the range, the folds exhibit in their minor or 

 local manifestations great diversity both in course and magnitude, so 

 that their characteristics are subject to greater or less change within 

 short distances, and tending greatly to increase the labor requisite for 

 the thorough elucidation of the geologic features of the whole range. 



Ascending the valley in a south-southeast direction, the mountain 

 presents an exceedingly steep front, cut by numerous little streams 

 which debouch from picturesque caiions, whose mouths are usually filled 

 with accumulations of debris brought down by torrents. At a place 

 some four miles above Pyramid Creek the steep mountain-side shows 

 heavy deposits of red shales and sandstones dipping southwestward into 

 the mountain. These beds continue several miles, until reaching an ex- 

 tensive tract of beaver-swamps, perhaps midway between Pyramid and 

 McCoy Creeks, just above which in the southeast angle of the debouchure 

 of a little caiion, where the river approaches close to the mountain-side, 

 similar rusty-red deposits appear, steeply inclined northeastwai^l. It 

 is presumed that this locality marks the axis of the pinched synclinal 

 fold already remarked in the lower part of Pyramid Creek Caiion ; at 

 all events, the strike of the strata at the latter locality would cause them 

 to appear in the valley-side at about this point. These deposits thence 

 continue in the steep slope, with frequent interruption in the continuity 

 of their outcrop, to a point two or three miles below McCoy Creek. 

 Here, in a low point in the west angle of a recess in the hills, heavy 

 ledges of dark, dull red, fragmentary, thin-bedded sandstone, banded 

 with lighter shades of color, appear in low mural exposures, dipping 

 southward at an angle of 25°. The same deposits also appear in the 

 low ridges and bed of McCoy Creek where its valley opens into that 

 of the Snake, and where they dip southwestward at the same moderate 

 angle. Above the latter point a high bench of the mountain borders 



