to the Ohio Shale Problem. 163 



as Chattanooga, we have the fuller representation that has 

 induced me to use this term for the whole series. Here the 

 Chattanooga shale begins with a representee of the Huron 

 and includes at its top the Sunbury shale, which, through the 

 pinching out of the normally intervening Bedford and Berea, 

 has come in contact with the Cleveland. That this relatively 

 complete representation of at least the black shales of the 

 series — possibly the Bedford and Berea are everywhere absent 

 to the south of Irviue, Kentucky — occurs beneath the load of 

 younger rocks in the Cumberland plateau, also that only its 

 upper beds have extended far enough by overlap to outcrop in 

 the vicinity of Chattanooga, seems too probable to require 

 proof. If I were to mention any of the evidence on which the 

 latter probability is based it would be a dilation on the fact 

 that fossil shells collected in the typical Chattanooga when 

 compared with specimens of Lingula melie and. Orbiculoidea 

 herzeri from the- Sunbury at Berea, Ohio, proved absolutely 

 indistinguishable to several observers. 



Chattanooyan series a hitherto unrecognized division of the 

 time scale. — The chief result of these studies is not so much 

 a matter of correlation whereby certain formations are removed 

 from one system to another as that a distinct and almost wholly 

 new division of the time scale, of the rank of a series, is inter- 

 calated between the top of the Devonian and the base of the 

 Kinderhookian with which the Mississippian system of prevail- 

 ing classifications begins. The top of the Devonian remains as 

 before, being drawn at the close of the Chemung. If the 

 Catskill contains younger beds than the Chemung it is believed 

 that they are chiefly intersystemic land deposits whose age is 

 in part if not wholly pre-Chattanoogan ; and if any of them 

 are really younger than the beginning of the Chattanoogan 

 then it is likely that they will finally be shown to corre- 

 spond to such of the Waverlyan formations as the Bedford, 

 the Berea, and certain still younger deposits that now fall 

 within the rather broad interval covered by the Cuyahoga 

 formation. Only very detailed stratigraphic studies can settle 

 these questions. However they may turn out they can not 

 materially affect a classification based primarily on marine 

 deposits. The fact then remains that the Chattanoogan is an 

 essentially new series that had not heretofore been recognized 

 in our geological time scales. It is new in that it comprises 

 six formations of which the oldest is placed above the Che- 

 mung and the youngest beneath the Louisiana limestone. The 

 last, as is well known, is the oldest of the formations in the 

 Mississippi Valley now referred to the Kinderhookian. Hith- 

 erto the Chattanoogan formations were divided between the 

 Devonian and the Mississippian, the lower three being indefi- 



