TYPES OF MOUNTAIN STRUCTURE. 21 



In the foregoing characterization of certain types of structure found in 

 these regions, I have not attempted to adopt a system of exact classifica- 

 tion, which should be both inclusive and exclusive as the types do not 

 admit of such classification. No " hard and fast lines " can be drawn. I 

 have simply attempted to indicate the important types with their primary 

 and concomitant forms. 



It is manifest that the structure of a sedimentary mountain will depend 

 primarily upon two elements the type of the displacement and the char- 

 acter and extent of erosion. The erosion may be antecedent or superim- 

 posed, or it may be consequent, or these methods may be combined, and 

 the erosion may be modified by dip, texture, and other characteristics of 

 the beds producing concomitant forms. 



For convenience, I subjoin the following : 



SYNOPSIS OF THE TYPES OF MOUNTAIN STRUCTURE 

 RECOGNIZED IN THE FOREGOING DISCUSSION. 



MOUNTAINS COMPOSED OF SEDIMENTARY STRATA, AL- 

 TERED OR UNALTERED. 



I. APPALACHIAN STRUCTURE. 



(Not found in the three provinces.) 



II. SIMPLE ANTICLINAL STRUCTURE. 



Primary topographic form. Plateau with rounded vertical outline. 

 Concomitant forms : 1. Monoclinal Ridges on the Flanks. 



.2. Monoclinal Ridges only. 



3. Inclined Plateaus. 



III. UINTA STRUCTURE. 



Primary topographic form. Plateau with rounded summit and abrupt 

 shoulders on the flank. 



