132 BULLETIN OF THE ESSEX INSTITUTE. 



plain transverse fault, the Red Beds on the east side being 

 jogged to the south or up the gulch fully one thousand 

 feet and terminating just north of two mining tunnels. 

 On meeting the transverse fault the sandstone dike appears 

 to turn and border it on the west side, a very plain indi- 

 cation that these transverse faults are contemporaneous 

 with the Ute fault. 



The mesa east of this gulch is probably underlain by 

 Red Beds right up to the steep granite slope, with only 

 sljorht indications of dike sandstone alons^ the fault line. 

 In fact, the slide of disintegrated granite hides all contact 

 phenomena for the next half mile, or to where the main 

 or quarry ridge of red sandstone meets the granite slope 

 (20) with a nearly vertical dip (E. 85°). The next and 

 last red ridge, about six hundred feet farther east, is 

 swerved to the east as it nears the granite, approaching 

 the granite at the last very obliquely. Between Red Rock 

 Gallon and Bear Creek no satisfactory evidence of sand- 

 stone dikes has been observed ; but the Ute fault appears 

 to cross Bear Creek without deflection or offset, and the 

 Jurassic and Cretaceous beds meet it in the same manner 

 as the last of the Red Beds, each formation in turn expe- 

 riencing a sharp flexure parallel with the fault and conse- 

 quent eastward deflection of its outcrop. East of the 

 Cretaceous (Dakota) hogback, forming the gateway ot 

 Bear Creek, the Cretaceous beds form first a sharp and 

 unsymmetrical syncline followed by a gentle anticline. 



SANDSTONE DIKES IN THE VICINITY OF CHEYENNE CREEK. 



From Bear Creek southeast for one and a half miles 

 I was unable, for lack of time, to follow the fault line ; 

 but my observations were resumed at South Cheyenne 

 Creek, working first northwest and then southeast. 



