752 STEPHEN R. CAPPS 



and a little sandstone, interrupted by sheets and lenses of glacial till 

 in varying stages of induration, and by lava flows. Measured 

 perpendicular to the dip, more than 3,000 feet of beds were 

 examined, and the thickness of the upward continuation of the 

 series is not known, but is considerable. The gravels, which com- 

 prise much the greater part of the entire thickness, are well rounded 

 but only fairly well assorted, and are apparently stream-laid. 

 The pebbles are composed of the Carboniferous lavas and limestones 

 which form the mountains immediately adjoining to the southwest. 

 In one place a considerable thickness of arenaceous shales and 

 sandstones occurs. Only one lava bed is shown in Fig. i, but in 

 other near-by localities similar lenticular lava flows were seen much 

 higher in the section, and farther east, on North Fork of White 

 River, the glacial series here described is overlain by lavas of con- 

 siderable thickness. 



The tillite beds, while forming only a small proportion of the 

 whole series, are nevertheless the most conspicuous members of it, 

 for their outcrops are left in high relief by the removal of the softer 

 surrounding materials. The uppermost bed shown in the figure 

 in places forms the crest of the ridge and stands up in high ragged 

 pinnacles (Fig. 3). The tillite exactly duplicates, except for its 

 induration, the ordinary glacial till which is of such widespread 

 distribution throughout this general region. It has a clayey matrix 

 full of small, angular particles of rock and incloses abundant pebbles, 

 bowlders, and angular fragments of rock, many of which are several 

 feet in diameter. The included bowlders and blocks are of the 

 materials which compose the mountains to the southeast and are 

 mostly of basic extrusive rocks of brown, purple, and reddish color, 

 and the matrix has a slight purple tinge. 



Striae were found abundantly on many bowlders, especially on 

 those of fine texture. Large bowlders in particular showed plenti- 

 ful striations, but typically striated hand specimens were not easily 

 found. The characteristic subangular bowlders, so typical of 

 glacial deposits, are plentiful throughout the tillite, and the whole 

 aspect of these beds leaves no doubt of their glacial origin. A num- 

 ber of striated and subangular pebbles were broken from the hard 

 matrix, and numberless other larger, but equally characteristic, 



