1 82 Ulrich—Chattanoogan Series with Special Reference 



and the Cleveland. The absence of a break at tbe base of the 

 Cleveland in the Huron County section is, therefore, regarded 

 as strongly corroborative of my claim that there is no "Erie" 

 or Chagrin in the middle part of this section; and that the 

 whole of the black shale series here, beginning with the 

 Dinichthys herzeri zone and ending with the top of the 

 ( ileveland, is in fact a wholly distinct, single, though litho- 

 logically tripartite, formation, thickening westwardly from 

 Cleveland and pinching out entirely in the opposite direction 

 near the Pennsylvania state line. 



The full significance of Newberry's admission that the Cha- 

 grin thins rapidly westward from Cleveland and that all the 

 black shale outcrops in Lorain County are of Cleveland (includ- 

 ing Olmsted) shale has not been appreciated. This admission, 

 if it does not fully establish, at least renders it highly probable 

 that the Chagrin is wholly unrepresented in the outcrops of 

 the black shale series (including the " Huron ? ') to the west of 

 Lorain County. The general unity of the Huron-Olmsted- 

 Cleveland zones, or rather the unbroken stratigraphic record 

 presented by them, is further strongly indicated by the general 

 similarity of their fossil contents. This similarity in types 

 is growing more obvious year by year. The Conodonts show 

 very little differentiation from the Huron on to the Sunbury 

 and some of the true fishes even are being found common to 

 the Huron and Cleveland. Take whatever line of evidence 

 we may, there is no positive and little negative evidence 

 indicating that the Huron is not merely the basal member of 

 an unbroken depositional record in north central Ohio, of 

 which the Cleveland shale constitutes the upper member. 



(3) With the disproval of the probably mistaken belief that 

 the Chagrin belongs above the Huron, the main reason that 

 caused Orton to view the black shale series in central Ohio as 

 representing all three shales — the Huron, the Erie, and the 

 Cleveland — and those other reasons which influenced Prosser 

 and many others in reaching the conclusion that only the 

 Huron is represented in the Franklin County section — all 

 these diversely interpreted reasons disappear. We have, then, 

 in Franklin as in Huron County, also in the southern part of 

 the state, an Ohio formation comprising a Cleveland shale 

 member above and a "Huron " (or whatever it may be called) 

 member beneath, with an unnamed middle member locally dis- 

 tinguishable between them. 



(4) This new conception does not introduce an extraordi- 

 nary condition. Much of the same kind of distribution of 

 stratigraphic units occurred in northern Ohio during the 

 Silurian. This is seen from comparison of wells at Cleveland 

 and Sandusky. At the latter point we find 970 feet of Silurian 



