SANDSTONE DIKES OF UTE PASS. 119 



and about three hundred feet west of the trail, a dike of 

 sandstone, which may be ten or fifteen feet wide, out- 

 crops quite plainly for a few rods. Beyond this is the 

 front of the great moraine which stretches quite across 

 the valley — an immense accumulation of granite bowl- 

 ders and debris, and beyond this, as far as Cascade, no 

 farther traces of the sandstone dikes were observed. 

 Between Cascade and Green Mountain Falls I have not 

 searched for dikes, assuming that Cross had covered this 

 ground. Although it appears probable that thorough 

 search would reveal traces of the sandstone dikes along 

 the entire distance from Manitou to Green Mountain 

 Falls, it is a very significant fact that they are practically 

 coterminous with the sedimentary rocks, alike of the 

 Manitou and the Manitou Park basins. 



SANDSTONE DIKES SOUTHEAST OF MANITOU, BETWEEN 

 RUXTON CREEK AND BEAR CREEK. 



Having demonstrated that northwest of Manitou the 

 great fault is bordered by sandstone dikes on the south- 

 west as far as it is by the sedimentary rocks on the north- 

 east, and somewhat farther, I naturally anticipated that 

 the same relation would l^e found to hold southeast of 

 Manitou ; but I was not prepared for the great develop- 

 ment of sandstone dikes in that direction which my 

 observations disclose. 



Immediately south of Ruxton Creek the structure is 

 rather complicated ; and it appears to me that the best 

 explanation of this complexity is found in a transverse 

 fault in the valley of Ruxton Creek, as shown on the 

 map (9) and more in detail in Fig. 1. This transverse 

 displacement, which may be called the Ruxton fault, 

 evidently breaks the great Ute fault ; and it affords the 

 simplest and most natural explanation of the fact that the 



