NATURE OF THE STRUCTURE 479 



anticlines produced by Appalachian folding, but in the Big Sandy Valley 

 along the border line of West Virginia and Kentucky it swings westward 

 along the Ohio Valley, crossing near the crest of the Cincinnati arch and 

 continuing across Kentucky and Illinois to the Ozark uplift. Surely, it 

 shows some sort of structural relationship between Appalachian structure 

 and these other large uplifts to the west. 



Kature of the Structure in the Disturbance Zone 



The structure varies in its nature from point to point along this zone, 

 depending on whether or not faulting occurs in connection with the fold- 

 ing. In Pennsylvania, West Virginia, and for some distance into Ken- 

 tucky it has been mapped as a low anticline, accompanied locally by dis- 

 placements of slight magnitude. But through central Kentucky and 

 westward to and through Illinois faulting is the predominant feature, 

 though at places it is a fairly regular anticline. In Ohio County, Ken- 

 tucky, it consists of a fault zone with parallel anticlinal folding on the 

 south side. Where faulted, the upthrow side is the south side or south- 

 east side, depending on the direction of strike and showing a thrust from 

 the south or southeast. It bears out consistently the fact that the thrust 

 was away from the direction of the seashore, just as is true of all Appa- 

 lachian structure. Where folded without faulting, the steeper side of the 

 anticline is on the north or northwest, depending on the curve of the 

 strike line. 



'J'ho writer regrets that he is not in a position to make a more complete 

 study of this most interesting subject. What is given here, along with 

 tlie accompanying map, is to serve as a basis for more detailed investiga- 

 1 ions by others. Facts as now known warrant a closer study of the rela- 

 tions of the Ozark Mountains and Cincinnati geanticline to Appalachian 

 folding. The writer does not have the data before him nor the time at 

 Ills conmiand to go into a detailed description of this long line of dis- 

 turbance that appears to tie the three regions together. He does not at- 

 tempt to say just what it means. OIThand it suggests that Appalachian 

 folding was accompanicil l)y strong folding at the same time on the Cin- 

 cinnati arcli and in lln' O/^ark Mountains, this line being a relief of the 

 stresses tliat were set up across the intermediate areas. 



Mappixo of the Line of Weakness 



Very little nee(] he \ouched for by the writer in connection with the 

 authenticity of the map presented here which shows the position of this 

 lin<' 1)1" weakness. Knowledge regarding it in Kentucky has not horoto- 

 XXXVII— Ben.. Geoi-. Soc. Am., Vol. 26. 1014 



