24 ON THE GEOLOGY AND NATURAL HISTORY 
Our course to-day led us over a bed of blue limestone from the head of Beaver creek to 
Inyan Kara Paha or Stone peak. Scattered throughout the valley and over the hills are 
the incoherent materials of the brick-red grit beds, giving to the country a most pictu- 
resque appearance. Stone peak is chiefly composed of basalt, which at this locality 
assumes a columnar form similar to the columnar trap in the Lake Superior region. The 
rock is usually of an ashen-gray, sometimes becoming an iron-rust color, with much the 
texture of granular sandstone. A portion of the rock forming a lower ridge, but more 
recent, is trachytic, retains its stratification, has a much lighter color and a more porous 
structure. 
We remained in our camp three days, surrounded by a wall of blue limestone, which 
has been disturbed in every conceivable way, yet seeming to adapt itself with wonderful 
flexibility to all the inequalities of the surface ; sometimes it paves the valleys or the lower 
plains, again it seems to be wrapped about some conical hill like a garment. As cut 
through by the little stream near our camp, it varies in thickness from twenty-five to 
thirty feet, becoming yellowish on exposure. Many portions of it have a fine silicious or 
cherty structure. ‘The following section will show the different beds seen in this vicinity 
in descending order. 
Yellowish gray argillaceous grit. 
Light-red incoherent sand and clay. 30 feet. 
. Laminated bluish clay shale. 8 feet. 
. Gray and grayish-brown sandstone. 6 feet. 
Bluish ash-colored argillaceous shale, with Avicu/a (Monotis) tenuicostata, Lingula brevirostris. 30 to 40 feet. 
Oo Be oo PD 
Compact blue limestone, not fossiliferous at this locality. 26 to 30 feet. 
Near the head of Beaver creek bed 2 of the above section presents the following layers: 
Gypsum 15 feet, passing down into 25 feet of red argillaceous grit; then 20 feet of gypsum ; 
then incoherent brick-red grit, passing down into a heavy-bedded sandstone. 40) feet. 
On our route to-day the blue limestone bed was very 
Fig. 7. 
conspicuous, attaining a thickness of forty or fifty feet, 
presenting many peculiarities. Portions of it are made 
up of thin lamin, which by pressure, when the mate- 
rials of which the bed is composed were in a yielding 
state, have become very much contorted. ‘These flex- 
ures in the lamine have been quite common throughout 
our day’s march. In some localities this bed contains 
many fine compact silicious nodules from which the 
laminee seem to bend each way, so as to clasp them, 
