74 C. L. DAKE 



implies that the Hermosa beds of Moab are present beneath the section 

 examined by Powell and Newberry. Such a break must occur at the base of 

 the Paleozoic "Red Beds," and no suggestion of such a hiatus has come from 

 observations in Colorado; but it is to be remembered in this connection that 

 in southern Utah and northern Arizona, PoweU, Gilbert, Button, Walcott, 

 and others have noted a persistent unconformity by erosion between the Aubrey 

 and the succeeding strata now commonly referred to the Permian through 

 Walcott's discovery of fossils in the Kanab Valley. All of the above-named 

 geologists have observed a conglomerate more or less widely distributed at 

 the base of the Permian series, composed in large part of pebbles derived from 

 the Aubrey rocks, as shown by fossUs contained in them. It is, of course, 

 possible that the denudation at this horizon may have been much more exten- 

 sive than the observations thus far reported would suggest. 



The direction even of this change corresponds to the facts 

 observed by the writer. According to the statement by Cross, 

 the beds on which the Moenkopi rests are younger to the west, 

 older to the east. Similarly the writer finds that in the San Juan 

 Oil Field, about in the longitude of Moab, the Moenkopi rests on 

 beds which are possibly as old as Redwall, while farther west, at 

 Tolchico and at Mule Twist Canyon, the Moenkopi seems to be 

 resting on younger beds, probably the Kaibab. 



That the beds below the Moenkopi near Mule Twist Canyon 

 were equivalent to the Kaibab and Coconino, and were not equiva- 

 lent to the Goodridge, was the independent conclusion reached by 

 the writer, even before he was aware of the foregoing statements 

 by Girty and by Cross. In view of the uncertain condition of 

 this correlation, it was felt that these few notes might add to the 

 general knowledge regarding the extent and magnitude of this 

 break. 



