314 A.. KEITH OUTLINES OF APPALACHIAN STRUCTURE 



Georgia; (2) in southeastern Pennsylvania; (3) northern Vermont and 

 near-by Canada; and (4) the extreme eastern part of Quebec near Gaspe. 

 A fifth salient is probably submerged in the Atlantic Ocean not far north 

 of Newfoundland, and a sixth may be buried by the Cretaceous sediments 

 of southern Alabama and Mississippi. Between the salients are corre- 

 sponding recesses around which the folds curve in the opposite direction 

 to the curves on the salients. The southernmost recess is partly shown 

 in central Alabama, where the Appalachian rocks pass under the Cre- 

 taceous cover; a second recess shows about midway in the course of the 

 Appalachians through Virginia; and the third appears in northern New 

 Jersey and southern New York, these two being the best defined recesses 

 on the mainland. The fourth and weakest recess lies in northern Maine 

 and Canada about midway between Lake Champlain and Gaspe. The 

 fifth recess is located under the Gulf of Saint Lawrence, probably about 

 midway between Gaspe and the west end of Newfoundland ; this is the 

 deepest recess of all and also, of course, the least known. There appears 

 to be a rhythm in these salients and recesses in that they are somewhat 

 evenly spaced. They have a very important bearing on the question of 

 the direction and application of the thrust which deformed the Appa- 

 lachians. 



SOUTHEASTWARD INTENSITY 



The Appalachian folds appear at the northwest in low, symmetrical 

 anticlines and synclines. Toward the southeast the folds become higher, 

 their beds dip more steeply, and their axial planes are more and more 

 overturned toward the northwest. Many of the anticlines are broken by 

 faults which dip to the southeast, and the upthrust portions are shoved 

 from the southeast over on the synclines at the northwest. Locally this 

 process was carried to excess, as, for instance, in northern New York and 

 Vermont and adjacent Canada, and also at the opposite end of the sys- 

 tem in Tennessee, Georgia, and Alabama. In both of these regions few, 

 if any, of the anticlines have escaped being heavily faulted. Many of 

 these faults exhibit great horizontal motion and low, eastward dips. 

 These are especially numerous along the junction of the Appalachian 

 Valley and the Appalachian Mountains which extend southeast of the 

 valley. Viewed in a very broad way, the folds and faults have so raised 

 the Appalachian rocks that, beginning with the nearly flat strata of the 

 Appalachian plateaus, successively lower and older rocks appear toward 

 the southeast until the very roots of the range are laid bare in the Green 

 Mountains of the north and the Blue Ridge of the south and in the adja- 

 cent plateaus lying east of those mountains. 



