14 THREE GEOLOGICAL PROVINCES. 



upper beds appear ; but where the faulting is on the side of the zone of 

 maximum flexure farthest from the axis, the ridges of the lower beds appear; 

 and where the displacement is chiefly or entirely by faulting, there are no 



monoclinal ridges. 



IV. KAIBAB STRUCTURE. 



In the region under discussion we often find the sedimentary beds 

 broken into great blocks by faults or their homologues, monoclinal flexures, 

 and these blocks have been gently tilted in broad masses. I have dis- 

 cussed this subject somewhat at length in my Report on the Exploration of 

 the Colorado River of the West and its Tributaries, published in 1875 ; and 

 in Figure 3 I reproduce a section and bird's eye view of the plateaus north 

 of the Grand Canon, which was used in that volume. An examination of 

 this will fully reveal the characteristics of what I have called the Kaibab 

 structure. The grand topographic features which result from this structure 

 are plateaus with broken edges where they are bounded by faults, flexed 

 edges where they are bounded by monoclinal flexures, and with escarp- 

 ments where they are bounded by canons or lines of cliffs. 



CONCOMITANT FORMS. 



1. Cliffs of Displacement. When a plateau is bounded on one side by 

 a fault, the edge of the plateau is an escarpment often so abrupt as to 

 present a more or less irregular line of cliffs. 



2. Slopes of Displacement. When the displacement is a flexure rather 

 than a fold, the edge of the plateau is a broken slope. I have discussed 

 these cliffs and slopes of displacement somewhat at length in the volume 

 already quoted several times, page 182 et seq. 



3. Monoclinal Ridges on the Flanks. On the flanks of these monoclinal 

 flexures, under proper conditions which have already been described, 

 monoclinal ridges are formed. 



4. Monoclinal Ridges with Plateau Carried Aivay. As in simple anticlinal 

 upheavals the central mass may be entirely carried away leaving but 

 monoclinal ridges, in like manner in the Kaibab structure the principal 

 plateau mass may be carried away leaving only the monoclinal ridges. 

 This I have also discussed in the volume already quoted. 



