128 GEOLOGY OF THE DENVER BASIN. 



Folds in the ridge east of Coal Creek. TllC strata (III till' Western slopes lit' tllO 



ridge between Coal and Dry creeks arc compressed into an irregularly 

 distributed scries ill' flexures, which conform in trend with thai general for 

 tliis portion of the liel<l — that is, they lie approximately north-and-south. 

 The flexures are of considerable length, of moderate bi*eadth, and are com- 

 paratively slight in the vertical displacement of the beds. They appear 

 wholly in the clays of the upper Laramie. 



THE FAULT M STEM. 



The fault system of the Boulder Valley region comprises no fewer 



than nineteen individual fractures, enumerated as follows: 



IM :t i ii or Northern fracture. 

 Soul hern fracture. 



Marshall subsystem, including -[ Middle fracture; 



Bluff fault. 

 Terminal cross-fault. 



I >avidson fault 



Sand Gulch fault. 



North Boulder faults 



f South branch. 

 \ North branch. 



( No. 1, or west fault. 

 | No. 2. 



No. 3. 



No. 1, or easl fault. 

 Lower ( !oal Greek fault. 

 Baker fault. 

 Louisville fault. 

 Rock < !reek fault. 

 Canal fault. 

 Erie fault. 

 Baker cross fault. 

 Jackson Star fault. 

 Valinont dike fissure. 



The lilies of dislocation, with the exception of certain cross-faults, 

 lie in three directions, the southernmost with a trend of N. lit' E., the 

 median having a direction X. 30 lv. and the northernmost a direction 

 north, or a lew degrees west of north. A rude though distinct curvilinear 



arrangement in concentric lines is thus imparted to the system, the distance 



