230 A. WINSLOW — GEOLOGY OF WESTERN ARKANSAS. 



A study of these sections leads, therefore, to the conclusion that there was 

 lateral movement and that this movement was from the south. A consider- 

 ation of the horizontal extent of the flexures and of their distribution de- 

 velops also many suggestive facts. The axes of the flexures are located on 

 the topographic map accompanying this paper, and their topographic rela- 

 tions can be well studied there. Perhaps the most striking feature is the great 

 number of distinct flexures represented in so small an area ; but the lack of 

 persistency in the plications, some of which are of great intensity, also de- 

 mands attention. Thus, the anticlinal arch north of the Poteau mountains, 

 termed the Coops anticline, which, opposite the middle point of its axis, is 

 characterized by dips ranging from 10° to 20°, disappears eastward within 

 a distance of about five miles and is immediately followed, in the prolonga- 

 tion of its axis, by the Magazine syncline, the plication being transferred to 

 the Belva anticline on the south, the axis of which runs parallel to that of 

 the Magazine syncline. The Washburn anticline illustrates this feature in 

 a still greater degree. Here, within a distance of five miles from a section of 

 80° dips, the flexure disappears entirely, and in the prolongation of its axis 

 westward there is a plateau in which the rocks are in a nearly horizontal posi- 

 tion. The Backbone anticline, which is also characterized by excessive 

 northerly dips, together with some faulting, terminates similarly toAvard the 

 east at Greenwood, and in the position of its prolonged axis the rocks dip 

 uniformly southward at angles of only a few degrees. The Biswell anti- 

 cline, northeast of Greenwood, dies out westward and eastward within a dis- 

 tance of four miles from its center, and the Potato hill syncline is exactly 

 in the line of the eastward prolongation of its axis. Along the southern 

 foot of the Boston mountains, the synclinal flexure already mentioned and 

 illustrated is seen to be composed of a series of short flexures which, in places, 

 overlap each other. 



Thus, in general terms, an interlocking system of flexures is produced. 

 Invariably, where one of prominence begins to die out another of the same 

 character begins to assert itself, either toward the north or toward the south, 

 and generally a flexure of opposite character is developed in the prolongation 

 of the axis of the expiring one. The plications thus seem to be, to a certain 

 extent, compensatory ; the relief from strain afforded by the flexing along 

 one axis being supplied by the folding along a contiguous axis, while the 

 first disappears. 



From the last consideration it seems probable that developed cross-sections 

 of the same bed across this area would have approximately the same length ; 

 though, even if this were so, such a result depends upon too many indefinite 

 factors to be of much value. But, how^ever exact such cross-sections might 

 be, their mere development would not replace the strata of this flexed area 

 in their original positions and relations. A restoration by stereogram of 



