188 /:'. M. Kindle — StrtUigraphic Relations of the 



Quite recently* a new hypothesis concerning the relations of 

 the Lighter and darker colored shales of the Ohio group has 

 been advanced by Mr. E. O. Dlrich which requires consider- 

 ation in the present attempt to present the writer's observations 

 on these terrenes in Ohio. This hypothesis assumes that the 

 hlack shale formations of the Ohio group — Cleveland and Huron 

 — overlap on the light-colored Chagrin shale instead of includ- 

 ing it between them, as heretofore held by all geologists who 

 have studied these heds. (See tig. 3, p. 2o4."i The interpre- 

 tation of northern Ohio stratigraphy presented in Mr. Ulrich's 

 paperf is an entirely novel one, and if it should prove to he also 

 true, a most important one. It merits, therefore, a careful exami- 

 nation. If we are to have a science of stratigraphic paleontol- 

 ogy we must not accept either plausihle explanations or good 

 guesses without critical examination. We can not, of course, 

 accept without scrutiny Mr. Ulrich's preliminary assumption 

 that "since it is certain we are dealing with overlapping forma- 

 tions," X etc. If we should take this as our major premise without 

 first demonstrating its truth, it is possihle that our conclusions 

 would hear much the same relatiou to the facts as did those of the 

 medieval geographers who started with the dictum regarding the 

 surface of the earth, that " it is certain that we are dealing with a 

 flat plain." In the course of presenting some of the results of 

 the writer's observations on the stratigraphy of the Ohio shale 

 group, it is proposed to test Mr. Ulrich's theory by ascertaining 

 whether it will fully ht the facts, both new and old. which are 

 now available concerning the Ohio group. If it will accom- 

 modate all of the data concerned, it will then be in order to 

 consider whether it does so more perfectly and has a greater or 

 less degree of probability than the conception which has hith- 

 erto been held regarding the relations of the terranes known 

 collectively as the Ohio shale before we can decide which is 

 to be discarded. Before taking up this specific problem it 

 will be worth while to get as clearly as possible Mr. Ulrich's 

 general viewpoint on stratigraphic problems. By so doing we 

 shall see that the theories which he has applied to the Ohio shale 

 group are legitimate deductions from some of the general prop- 

 ositions advanced in his work on Be vision of the Baleozoie 

 Systems.§ The one which is most pertinent to the case in hand 

 is the doctrine of the " geographic persistence of lithologic 

 units." The very wide or universal extent of a given kind 

 "i -ediment within the limits of any Baleozoie sea is a rather 

 fundamental part of Mr. Ulrich's system of diastrophic corre- 



* Paper presented before the Geol. Soc. Washington. 

 + Read before the Geol. Soc. Washington. Feb. '24. 1912: see also the 

 paper in this number of the Journal. 



X Idem. 5 Geol. Soc. America, vol. xxiii, 1911. 



. Idem., p. 318. 



