DEFORMATION INCREASES SOUTHWARD. 



229 



sents a section across the great Washburn anticline and the interesting series 

 of ridges southeast of Greenwood ; the latter a similar section across Back- 

 bone anticline, an analogous flexure and series of ridges west of Greenwood. 

 The overturn of the fold is well marked in both of these cases ; in fact, the 

 flexure has passed to the extreme condition of a fault with an upthrow on 

 the southern side, which toward the termini of the anticline diminishes to 

 nothing. The character of these flexures and faults is typical of that at- 

 tributed to lateral compression. 



Figure i.— Cross-Section through the Backbone Anticline. 



Scale, horizontal and vertical, 1.25 miles= 1 inch. Looking westward. Showing overturned fold 

 and fault, indicating lateral movement from the south. 



Finally, figures 5 and 6 are sections across the southern base of the Boston 

 mountains, illustrating the general synclinal plunge of the strata before 

 they rise in a monocliual arch to form the Boston uplift. It is probable 

 that along with the production of the monocline some faulting took place, 

 evidence of which is presented by abrupt rock-faces, with smooth surfaces, 

 found alons: the foot of the mountains in the line of the flexure, sometimes 



£.,«.,, Po„</ ^A . 



Figure 5.— Cross-Section into the Boston Mountains. 



Figure 6.— Cross-Section into the Boston Mountains. 



Scale, horizontal and vertical, 1.15 miles = 1 inch. Looking westward. Showing monoclinal 

 flexure along the southern base. 



accompanied by chalybeate springs; but the throw w^as probably 'slight and 

 the horizontal extent short. Thence northward the strata dip gently south- 

 ward or lie flat almost uninterruptedly, as shown in figure 1. 



