6T.J0IIX.] SECTION ACROSS CARIBOU RANGE. 393 



Salt Eiver from tlie far less important western drainage. A similar but 

 lower ridge projects in the opposite direction, forming the before-men- 

 tioned divide between McCoy Creek and John Gray's Lake. The monn- 

 tain flanks are well wooded with coniferons forests, and lovely little mead- 

 ows are encountered in unexpected places between the lower and more 

 rounded outljing ridges on the west side. The summit commands nearly 

 the whole of the southwestern section of the district, besides the exten- 

 sive basin region to the southward. The country lying westward ap- 

 pears surprisingly flat, notwithstanding we found it diversified by suffi- 

 ciently rugged low mountain ridges, broad basin i^lains, and cauoned 

 water-courses. The Snake Eiver is hidden in the deep trough of its 

 lower valley, but to the southeast, overlooking the comparatively low 

 intervening mountain belt, its southerly continuation opens out in the 

 broad basin of Salt Eiver, which like all these basm areas is covered by 

 extensive tracts of marsh, whose willow copses give the not uncommon 

 effect of cloud-shadows resting on the extensive levels. 



In the valley course of McCoy Creek a magnificent section, reaching 

 three-fomths the way across the range, is displayed, the study of which, 

 notwithstanding the limited time at our disposal, resulted in the secur- 

 ing of data from which it is possible to gain an approximately acciu'ate 

 knowledge of the structure of this portion of the range. As the exami- 

 nations were continued comi)letely across the range, via Iowa Gulch 

 and Mount Bainbridge, to the plain of John Gray's Lake on the south- 

 west border, in collating all these data the section has been located along 

 a direct line bearing about E. 35° X. and W. 35° S., intersecting Mount 

 Caribou the western portion of the valley of McCoy Creek, along 

 which the observations were made, lying a little north of the line of the 

 section, the lower or northeast portion of which closely corresponds with 

 the direction of that part of the valley — the profile making no pretence 

 at showing the actual surface contour, being merely a partially ideal 

 adaptation to facilitate the illustration of stratigraphic and structural 

 features. The section in which are incorporated such details as were 

 noted in a hasty examination, is shown in an accompanying plate, and 

 exhibits the following stratigraphic elements, commencing at the debou- 

 chure of McCoy Creek into the lower valley of the Snake, and i)roceeding 

 thence south westward across the range : 



Section across the Caribou Eange^ via McCoy CreeTc. 



1. Variegated soft arenaceous clays of Tertiary age, resting on the up- 

 turned edges of the older strata, and dipi)ing northeastward at angles 

 of 25° to 40°. These deposits occur in the valley of the Snake and Salt 

 Eivers, and will be further noticed in the section devoted to the lower 

 valley of the Snake. 



2. Deep-red sandstone, dipping south westward at a moderate angle of 

 inclination. 



3. Obscure exposure of light-drab deposits. 



4. Eed sandstone ledge forms a low faU in the bed of the creek at its 

 debouchure. 



o. Eed shales and indurated arenaceous layers, forming a heavy bed. 



6. Light-red sandstone, 30 feet exposed. 



7. Eed shales, pale red above, 100 to 200 feet. 



8. Eed sandstone. 



9. Chocolate-colored shales. 



10. Eed sandstone, deep red thin-bedded below, 50 feet exposed. 



11. Eed shales. 



