STRUCTURAL GEOLOGY 



403 



undulations on the flanks of the larger, they are called geanticlines, 

 or aniidinoria (Figs. 286 and 313), and geosyndines or syndinoria 

 (Fig. 314). Folding is often accompanied by the development of 

 slaty cleavage (p. 53). 



Fig. 314. Synclinorium, Mt. Greylock, Mass. (Dale, U. S. Geol. Surv.) 



As found in the field, folds are usually much eroded, and often 

 completely truncated (Fig. 313). The structure is then determined 

 by a careful record of dips and strikes. On the field map, the record 



h H 



I- H 



I- H 



Fig. 315. Fig. 316. 



Fig. 315. Map record of dip and strike, showing synclinal structure. 

 Fig. 316 Diagram showing the structure corresponding with Fig. 315, as 

 seen in cross-section. 



may be made as shown in Figs. 315 and 317, where the free ends of 

 the lines with but one free end, point in the direction of dip, while 

 the other lines represent the directions of strike. Applying this 



Fig. 317. Fig. 318. 



Fig. 317. Map record of dip and strike showing anticlinal structure. 

 Fig. 318. The structure of the area shown in Fig. 317, in cross-section. 



method, the structure shown in Fig. 315 represents a syncline, 

 and that in Fig. 317 an anticline. In cross-section, the structure 

 presented by Fig. 315 would appear as in Fig. 316. Fig. 319 shows 



