PRE-MOENKOPI UNCONFORMITY OF COLORADO PLATEAU 69 



already been described by Gregory/ who says of it: "If strata of 

 Pennsylvanian age once covered the quartzite the pre-Moenkopi 

 erosion interval, elsewhere poorly marked, becomes here a strati- 

 graphic feature of great significance. In my opinion the quartzite 

 is a monadnock of a pre-Cambrian erosion surface — an elevated 

 mass which outlived its contemporaries through Cambrian, Silurian, 



Fig. 6. — Same unconformity as in Fig. 5 



Devonian, and early Carboniferous time^ only to be itself buried 

 by the streams of Permian time." It would appear from this state- 

 ment that Gregory does not incHne to beHeve that the quartzite- 

 Moenkopi unconformity is related to the Pennsylvanian-Permian 

 erosion interval, but represents earlier unconformity with overlap. 

 Here also it is not possible to determine the facts. 



^ H. E. Gregory, loc. r.U. 



