Appalachian Faulting. 



259 



the conformable contact between the newer and older strata 

 and it follows that the older strata dip more or less steeply 

 from the shoreward side to the thickest part of the lense and 

 thence rise more gradually seaward. The condition then exist- 

 ing is represented in fig. 1, and the broad shallow trough 

 formed by the deeper strata may be called an original syncline. 



Fig. 1 . — Syncline of Deposition. 



Fig. 2.— Step fold. 



-7>- 



Fig. 3.— Thrust fault. 



Wills Val. 



Fig. 4. — Section in Northern Alabama. 



That such original synclines of deposition existed in the 

 paleozoic strata of the Appalachians previous to compression 

 is clearly shown from a consideration of the variations in thick- 



