Ulrich — The Chattanoogan Series. 157 



Art. XVI. — The Chattanoogan Series with Special Refer- 

 ence to the Ohio Shale Problem ; by E. O. Ulrich,* Wash- 

 ington, D. C. 



Introductory matter. — It is many years since I began to 

 doubt tbe validity of the classification of the Devono-Waver- 

 lyan shales in Ohio which was introduced in its essential 

 features by Newberry in 1870, and with occasional modifica- 

 tions has prevailed to the present day. But it is only in the 

 past two years that I have sufficiently investigated the mass of 

 available evidence to permit me to take a decisive stand on the 

 several intricate questions which are involved in the general 

 problem. 



Even in the past year, when I published correlation tables 

 covering the formations in southeastern North America between 

 the base of the Cambrian and the base of the Pennsylvanian 

 in my Revisioa of the Paleozoic Systems,! I was n °t . ve t P re ~ 

 pared to give a definite opinion respecting the relations of the 

 greater part — commonly the lower half to three-fourths — of 

 the typical Ohio and New Albany shales. On plate 28 (op. 

 cit.) it is to be noted that the Chagrin formation is placed at 

 the top of the Devonian. Beneath this, in the same column, 

 as also in the two columns to the left, are found indefinitely 

 limited spaces designated " lower part of Ohio shale " and 

 " lower New Albany shale." In both cases I referred to cer- 

 tain shales which are locally found at the base of the Ohio and 

 New Albany shales and which contain fossils strongly suggest- 

 ive of Genesee and Portage ages. On plate 29 the "Waverlyan 

 is begun with the Cleveland shale in Ohio,:]: the upper part of 



* Published by permission of the Director of the U. S. Geological Survey, 

 who, in view of the fact that this paper uses a new classification, at variance 

 with adopted usage, disclaims responsibility for the classification, corre- 

 lations, names, and re-definitions. 



f Bull. Geol. Soc. of America, vol. xxii, pi. 27-29, 1911. 



% A note of explanation seems desirable here. When these charts were 

 drawn it was my intention to extend the limits of the Cleveland shale down- 

 ward to the first diastrophic break. At Cleveland this meant to the base of 

 the black shale to which the name was originally applied and which there is 

 in contact with the Chagrin ; 8 to 15 miles west of Cleveland it meant the 

 same black shale plus 1-100 feet of softer shale (now called Olmsted shale) 

 which is added without break to its bottom by underlap; and in Erie County 

 it meant both of these shales plus the rest of the " Huron" down to the base 

 of the Dinichthys herzeri beds, which in going westward are similarly added 

 to the bottom without notable evidence of break. In other words, it was my 

 purpose to apply the term Cleveland to the whole series of shales beginning 

 with the concretionary Dinichthys herzeri beds and ending with the top of 

 the black shale, which alone has hitherto been referred to under that name. 

 This intention was based on the conviction that all of these beds are only 

 parts of a single, though lithologically tripartite, formation which loses more 

 and more of its members by overlap eastwardly from Erie County until the 

 last finally disappears in northeastern Ohio. Chiefly for the reason that this 

 tripartite formation is strictly equivalent to the Ohio shale of Andrews, my 

 former purpose is now abandoned. 



