102 Ulrioh — Cltattanoogan Series with Special Reference 



Desirability of 'method in drawing stratigraphic hounda- 

 ries. — The location of systemic boundaries in stratigraphy, 

 indeed of all f ovulational boundaries that are not based purely 

 on lithologic changes, is a matter of method. But the same 

 method should be used in all cases. If this is granted, namely, 

 if consistency is admitted to be an essential feature of method, 

 and if the basic principle of our method is the introduction of 

 new faunal elements, of new seas and of other new physical 

 conditions, then I would say that we can not avoid closing the 

 Devonian at the hiatus marking the top of the Chagrin ; for if 

 the Helderbergian is Devonian and the Morrow group of 

 Arkansas Pennsylvanian, both of which represent the first 

 invasions of the sea following a long state of emergence, then 

 for the same reasons the whole of the Chattanoogan is Waver- 

 lyan. That the general aspect of the faunas in these introduc- 

 tory deposits often retains much that recalls faunas of the next 

 preceding period is to be expected. This is more especially 

 true of faunas which invaded from the same oceanic basin. 

 Organisms modified slowly in these and in no case known to 

 me was the change from one period to the next complete. 

 There are always some forms which survived for a time into 

 the succeeding stage. 



In further explanation of my attitude respecting the age of 

 the Chattanoogan it should be added that until it is actually 

 proved that the Chagrin belongs between the Cleveland and 

 the Huron and not, as I believe, beneath both, I must insist 

 that the Waverlyan begins in Ohio with the Dinichthys her- 

 zeri zone of the Huron. True Devonian black shales— even 

 younger then the Olentangy, which also at times was included 

 in the Huron — may occur locally beneath the Dinichthys zone, 

 but these are not to be considered at this time. 



The Term Chattanooga. — As regards the standing and sig- 

 nificance of the term Chattanooga, its wide and varied use by 

 the geologists of the Federal Survey makes it clear that it was 

 intended to cover all the black shale zones between the middle 

 Devonian and the first limy or sandy beds of the Mississippian. 

 This evident intention gives the term a somewhat broader 

 significance than is warranted in practical taxonomy. There are 

 two sets of black shales in this wide interval, a lower of which 

 the Genesee is the chief element and an upper of which the 

 more important members are comprised in the Ohio shale. 

 Now as it is the later of the two that is represented at Chatta- 

 nooga it seems to me proper to confine the name derived from 

 this locality to this upper series. As developed at Chattanooga 

 and in middle Tennessee, the Chattanooga includes only the 

 upper member or members of the series. In central Kentucky 

 however, where Campbell* mapped the black shale series 



* Campbell, M. R.: Folios Nos. 46, 47, U. S. Geol. Survey Atlas, 1898. 



