68 



C. L. DAKE 



on gray massive limestones, of which perhaps fifty to one hundred 

 feet are exposed. No fossils were noted, but it is confidently 

 believed that the gray limestone is Aubrey and the red sandy shales 

 and sandstones Moenkopi. The marked uneven character of the 

 contact leaves no room for doubt as to the unconformable relation 

 between them. 



Above the Moenkopi is a thin conglomeratic sandstone taken 

 to be the Shinarump, since above it rest characteristic ashy gray 

 and purple shales highly suggestive of the typical Chinle (Dolores), 



Fig. 5. — Nearly flat-lying Moenkopi unconformable on folded pre-Cambrian, 

 Quartzite Canyon, near Fort Defiance, Arizona. 



SO widely exposed in the De Chelly (Fort Defiance) Uplift.^ The 

 exceptional thinness of the Moenkopi here (50 to 100 feet) may be 

 due in part to post-Aubrey and pre-Moenkopi erosion, in part to 

 post-Moenkopi and pre-Shinarump erosion, and possibly in part 

 to lack of deposition. No information was secured which would 

 enable one to decide which of these niight be the most important 

 factor. 



Fort Defiance. — In Quartzite Canyon, near Fort Defiance, 

 Arizona, the Moenkopi rests directly on steeply dipping, much 

 jointed, vitreous quartzite (Figs. 5 and 6). This relation has 



'H. E. Gregory, "Geology of the Navajo Country," U.S. Geol. Surv., Prof. 

 Paper 93, 191 7. 



