204 GEOLOGICAL SURVEY OF TflE TERRITORIES. 



Glen Eyrie it is north and south. This turns slightly to the eastward, 

 until we reach the "Fontaine qui boule," when there is rather an abrupt 

 turn to the w^est. Between the " Fontaine" and Bear Creek the strike is 

 N. ^Q° east to S. 40° west. Where the strata cross the creek is still 

 another turn to the eastward, and the strike here is north 25° east. 

 On the south side of the creek is a more abrupt turn, and the strike is 

 south 15° east. From this point southward the beds are entirely con- 

 cealed, and do uot appear again until we get south of Cheyenne Mount- 

 ain, where they are in Dr. Endlich's district, and will be considered in 

 his report. 



In section No. 3, we have seen that the lower beds (Silurian) dip at 

 an angle of only 10°, while the red-beds (Triassic'?) just above are 

 tipped 5° degrees past the vertical, and that the inclination of the 

 succeeding layers becomes less and less as we go eastward, until on 

 Monument Creek it is only 5°. This variation, especially the abrupt 

 change from the Silurian to the Triassic, can, I think, be best explained 

 as follows: After the deposition of the Silurian, and possibly the Car- 

 boniferous beds, there was an elevation of the range north of Pike's 

 Peak, the peak itself being the center of elevation. Succeeding this, 

 we have the period during which the red sandstones were deposited. 

 These beds near the Silurian shore had a slight inclination, perhaps only 

 a fraction of a degree. Then, after the deposition of the red sandstones 

 and the succeeding layers, there was a second elevation of comparatively 

 modern date, which tipped up the sedimentary formations as we now 

 find them along the entire range. This force at the foot of Pike's Peak 

 caused the slightly-inclined red-beds to be tipped past the vertical. 

 The following explanation also is possible : It may be that the difference 

 in the angle of inclination is due simply to a fold, and that the red sand- 

 stones that we ought to find resting on No. 14 of section Ko. 3 have from 

 their softness been entirely removed, leaving only the vertical portions. 

 If this be so, we should expect to discover beneath the surface that the 

 lower limestones conform to the Triassic beds, (No. 16, section 3.) The 

 case then would be analagous to that near Golden, which is described 

 in Mr. Marviue's report. 



At the foot of Pike's Peak, around the northeast side, during the 

 Silurian age, a bay probably extended in to the westward. That it ever 

 extended across to the west side is exceedingly improbable. The beds 

 extend farther up on the hills here than at any other point north of 

 the peak. At the South Platte Eiver, in section ]^o. 1, the Triassic (?) 

 sandstones rest immediately upon the granite, and it is not until we 

 get some distance south that we have any older beds exposed. At Pleas- 

 ant Park we have. Carboniferous beds beneath the Triassic layers, but 

 it is uot until we get to Glen Eyrie that undoubted Silurian shows itself. 

 That both the Silurian and Carboniferous layers are beneath the red- 

 beds (Triassic?) along the entire range is scarcely to be doubted. Their 

 non-appearance to the northward can be readily explained. The force 

 that elevated the range radiating from the center at Pike's Peak, and 

 very likely also from Mount Evans to the northeast from the first point 

 and eastward from the second, caused a general elevation of the plains 

 to the northeast and east. This elevation would enlarge the ancient 

 sea-border, and cause the succeeding deposits to overlap the older ones, 

 and therefore rest immediately on the granite. 



The same effect might of course have been produced by a general de- 

 pression of the country. In this case, however, I think it is improbable 

 that depression, has been the cause. All the facts seem to point toward 

 an elevation. The overlapping diminishes as we go southward. The 



