196 GEOLOGY OF THE BLACK HILLS. 



gated as to render the ascent of the peak a toilsome task. Where they 

 cover the side of the peak the entire slope is marked with zigzag paths a 

 few inches wide that ascend at angles of from 20° to 30°, crossing and 

 recrossing each other in a perfect net-work. These are supposed to have 

 been made by mountain sheep, but none were seen in the vicinity. On 

 the summit and here and there on the sides of the peak are a few stunted 

 pines, but its general appearance is barren and has led to the suspicion that 

 its name was originally and more properly Bare Peak. 



The rock is a gray trachyte, with weathering surfaces much darker 

 than the fresh fracture, giving to the peak a somber appearance. It is hard, 

 compact, and tough, and has a ring somewhat like phonolite. 



The butte stands in the gray shales and clays of the lower Cretaceous, 

 and around its immediate base are the -uplifted strata of the Dakota sand- 

 stone, with partial exposures of the Jura and Red Beds. The base of the 

 peak, however, is so much concealed by fragments of the igneous rock and 

 by grassy slopes that there is little opportunity to examine the lower of the 

 disturbed strata. A dense quartzite is visible in numerous places at the base 

 of the peak standing vertical in a prominent ridge, but its continuity is not 

 perfect around the peak. West from the summit ridge there are a series 

 of imperfect outcrops, in curves concentric with the peak, which are thought 

 to belong to the Red Bed series. On the same side of the peak, close to 

 the base and underlying the metamorphosed Dakota sandstone, the follow- 

 ing strata were observed in a deep wash-out. They rise toward the peak 

 with increasinjr angles. 



Feet. 



13. Yellow saudstono — 



12, Gray shale or marl, black at top L'O 



11. Sandstone, full of rounded grains 1 



10. Shale, biowu or yellowish 15 



1). Calcareous marl 3-4 



8. Shale or marl 15-20 



7. Calcareous marl 20 



G. Yellow sandstone .... 10 



5. Yellow, red, and green clays, becoming sandy at base 30-35 



o 



1. Soft white shaly sandstone 20-2 



3. Greenish shaly sandstone ; top somewhat argillaceous 75 



2. Sandstone, yellow and shaly 3-5 



1 . Deei) red elays exposed . . 8 



