PRINCIPLES OF STRATIGRAPHIC CORRELATIONS 551 



rupted sedimentation. The significance of this fact is apparent when we 

 realize that, in addition to the Holston, three other east Tennessee for- 

 mations — the Athens shale, the Tellico sandstone, and the Ottosee forma- 

 tion — as shown in the table on page 544 and more fully described on page 

 555, are intermediate in age between the Stones Kiver and the Low- 

 ville. The Hancock County occurrence may seem especially significant in 

 this connection, because here the Lowville attains a thickness of over 400 

 feet, which is the maximum for areas in which the upper Stones River 

 is present; also, because the areal distribution of the Lowville and the 

 Holston in Tennessee is widely different, hence indicative of oscillation 

 and sea-shifting between the two formations. Sea withdrawal being 

 established between the oldest known Lowville deposits and the youngest 

 of the upper Chazy or Holston beds in the Appalachian Valley, and no 

 deposits of intermediate age being recognized elsewhere in America west 

 of the Appalachian Valley barrier (see map, page 293), the conclusion 

 seems inevitable that practically the whole continent shared in the inter- 

 vening emergence. 



Similarly extensive emergences are indicated by the same kind of evi- 

 dence at the close of the Black River group, the close of the Helderber- 

 gian, the Ozarkian, and the Saint Louis. The emergence at the close of 

 the Clinton doubtless was no less widely effective, but the evidence in this 

 case is only partly recorded in the Appalachian Valley. Besides these, 

 many other withdrawals are more or less clearly indicated by detailed 

 stratigraphic studies in southeastern^ North America. A considerable 

 number of these may have been quite local or perhaps provincial in scope, 

 but in others again the emergence seems to have been general, not to say 

 continental, in extent. 



The Ozarkian-Canadian emergence. — The relations of the Canadian 

 and Ozarkian formations in central Pennsylvania will serve to illustrate 

 the course pursued in proving complete withdrawal of the sea from the 

 Appalachian Valley basins at the close of a system whose upper beds are 

 known to be wanting in the immediate area of a succeeding full sys- 

 temic sequence — in other words, when the fact of such withdrawal at 

 the close of the older system may be established only by correlation with 

 sections elsewhere in which the missing later deposits of the same are 

 present. The example to be discussed is exceptionally difficult, and the 

 complete solution of its problems as yet impossible, first, because the 

 youngest Ozarkian formation, namely, the Jefferson City dolomite of 

 the Missouri section, is nowhere recognized in the Appalachian Valley, 

 and, second, because of the uncertain relations of the first Canadian de- 



