st. JoHN.] TERMINUS JOHN DAY RIDGE BELOW HOBACK’S RIVER. 199 
horizon. The light reddish siliceous beds of the Carboniferous appear 
in castellated masses high up on the mountain side, and above these, in 
the erest of the ridge, occurs a series of light grayish deposits of doubtful 
age. A short distance below, where the valley changes to a north-south 
course, the Triassic quartzitic sandstones appear in force, forming a 
rocky point jutting into the river. These strata hold the same south- 
westerly inclination as do the older formations in the mountain ridge, 
the strike carrying them along the foot of the hills bordering the oppo- 
site side of the river for some distance above this point. They here 
probably attain a thickness of above 2,000 feet, with the same deep-red 
shaly arenaceous layers below. ‘These deposits continue to a point where 
the valley course again trends northeasterly. The hills.on the east side 
are well wooded and roughly scored by short drainage gulches, but those 
on the opposite side are comparatively bare, presenting gentler slopes, 
in which appears a heavy series of chocolate-red and drab-colored sand- 
stones and clays, which resemble and apparently hold the position of the 
Jura. The latter deposits continue in the bordering hills a couple of 
mniles or more, extending inland,. northwards, as far as could be seen. 
Passing round the north end of the John Day ridge, in the neighbor- 
hood of the bend in the valley, about 3 miles below the mouth of Ho- 
back’s River, extraordinary exhibitions of disturbance are introduced 
into the geologic section of this part of the valley. As yet, no clew is 
obtained of the character of the extreme northern portion of this mount- 
ain range, except that the western flank is heavily mailed by the steep- 
ly upraised Carboniferous beds. The trend’of the main crest, however, 
veers round east of north, and, from the manner of weatherin &, it is evi- 
dent that this portion of the ridge is composed of different materials 
from those making up the Carboniferous crest farther south, and which 
probably represent Post-Cretaceous formations. But in the neighbor- 
hood of the tule marsh (which is caused by the overflow of lime-charged 
warm springs that issue in the south side of the Snake) the slopes are 
strewn with drab, spar-seamed limestone débris, also fragments of hard, 
reddish sandstone, recalling the Carboniferous, although no fossils were 
found by which to establish their identity beyond doubt. In the oppo- 
site side of the river, however, the gener ral structural features are well 
display ed, and beyond the necessary explanatory notes on the accom- 
panying section diagram of this locality, I shall not repeat the observa- 
tions here made by Professor Bradley in 1872. 
_ Section in right bank of the Snake, below the mouth of Hoback’s River. 
a. b. Dark reddish sandstones (Trias) and chocolate-red and drab 
sandstones and shales (Jura ?). 
¢. Brownish-red ledge; dip southwestward. 
d. Black shales, interbedded with light colored indurated bed; dip 
northeasterly. 
' € Dirty yellow siliceous beds. In the ridge above apparently hori- 
zontal, light colored, unconsolidated deposits appear, possibly Quater- 
nary or lake beds. 
J. Kked-colored beds, dipping off flank of spur ridge, southwesterly. 
g. Rusty weathered. beds, prebably gray sandstones ; dip southwest- 
ward at a steep angle. 
h. Apparently soft drab or ash-colored beds, obscurely exposed. 
4. Rusty weathered, greenish-gray sandstones. 
j. Chocolate-red beds, apparently indurated clays, curving over and 
dipping steeply northeastward. 
k. Indurated drab beds, dip very steep to the southeastward and 
