DOMES AND BASINS 



235 



accordance with the length of the axis and the steepness of the 

 pitch, the uneroded anticlinal is either short and dome-like, or 

 elongate and cigar-shaped. 



FIG. 91. — Anticlinal limb of fold. P, axis pitching to the left; S S, line of strike; 

 D, line of dip. The dotted line is the plane of the axis. (Willis.) 



(2) The Syncline is the complement of the anticline, and in 

 this the beds are bent into a downward fold or trough, dipping 

 from both sides toward the bottom of the trough, which forms the 

 longitudinal synclinal axis. As in the anticline, the axis may be 

 long or short, with gentle or steep pitch, forming long, narrow, 

 "canoe-shaped" valleys, or oval, even round, basins. In section 



FIG. 92. — Synclinal limb of fold. (Willis.) 



the syncline may be shallow and widely open, or with steep sides 

 and angular bottom. 



Domes and Basins are special cases of anticlines and synclines. 

 The dome is an anticlinal fold, in which the axis is reduced 

 to zero, the dip of the beds being downward in all directions from 

 the summit of the dome. As the dip changes, the strike changes, 



