62 



C. L. DAKE 



Carboniferous," 



' Kaibab limestone 1 

 Coconino sandstone \ Upper Aubrey group, Pennsylvanian 

 Supai formation j 

 Redwall limestone, Pennslvanian and Mississippian 



DETAILED OCCURRENCES OF THE UNCONFORMITY 



Mule Twist Canyon. — The first locality at which the uncon- 

 formity was noted is about four miles northwest of Mule Twist 



Fig. I. — ^The Colorado Plateau 



Canyon, a well-known pass through the La Plata "reef" or "ledge," 

 a prominent escarpment on, the east flank of the Water Pocket 

 Flexure, west of Henry Mountains, Utah (Fig. i). At this point 

 the unconformity is distinctly indicated by basal conglomerates, 

 by the uneven surface on which the Moenkopi rests, and by the 



