330 A. KEITH OrXLIXES OF APPALACHIAX STRUCTURE 



RELATION OF CROSS-FOLDS TO SALIEXTS 



The general plan of the axes of eastern Xorth America clearly exhibits 

 two systems — one due to folding in the major Appalachian direction 

 with trends from southwest to northeast, and the other substantially at 

 right angles to this trend. The plan of the axes further exhibits a major 

 relation to the deforming force of the Appalachians, in that the principal 

 cross-anticlines extend northwest from the principal salients in Vermont 

 and Xorth Carolina, where the horizontal pressure and motion have been 

 the greatest. Thus, from the Vermont salient the cross-anticline extends 

 northwestward through the Adirondack uplift, cuts off the Ontario 

 trouoii from the Saint Lawrence trouo-h, and o'oes to and throuo-h the 

 uplift between the basins of Lake Superior and Hudson Bay. From the 

 Xorth Carolina salient (the greatest of all) there extend the Xashville- 

 Ozark cross-anticline and the Cincinnati-Wisconsin cross-anticline. Be- 

 tween these major cross-anticlines lies the great synclinorium of the Illi- 

 nois coal basin, which passes southeastward into a minor recess in the 

 Xorth Carolina salient. Similarly, the Arkansas synclinorium and the 

 central Alabama coal basin line up with the recess of central Alabama. 

 Also, the cross-syncline through the Lake Superior basin, the Michigan 

 basin, and the deep AVest Virginia coal basin passes directly into the Vir- 

 ginia recess. A considerable syncline extends northwestward from the 

 Xew York recess through Penns3d\ania, but dies out in western Xew 

 York. The great recess of the Gulf of Saint Lawrence is occupied, so 

 far as can be determined, largely by Carboniferous beds in a great syn- 

 cline. It is thus seen that the major salients and recesses of the folded 

 Appalachians, which are the expression of greater or less horizontal ad- 

 vance, are directly connected with the major cross-folds of the plateaus 

 and the Mississippi Valley. Their community of nature is shown by the 

 fact that the salients of maximum thrust are continued in the cross- 

 anticlines, where uplift is most, while the recesses of minimum advance 

 are continued in the cross-synclines, where uplift is least. From such 

 relations the conclusion can hardly be avoided that one cause is to be 

 assigned to them all. These relations are shown on the map, plate 4. 



AGE OF AXES SHOWN 



In tracing the numerous axes shown on the map the endeavor has been 

 made to show only those which were formed at the close of the Carbon- 

 iferous. Axes of other ages have been determined, but this has usually 

 been possible only where they diverge considerably from the axes of 

 Carboniferous age. The Adirondack axis, for instance, existed to some 



