160 Ulrich — Chattanoogan Series with Special Reference 



be.* It had. in fact, been established that the Chattanooga shale 

 of the London and Richmond folios of the U. S. Geological 

 Survey Atlas comprised not only the Ohio shale of Andrews 

 but also the southern extension of the Sunbury shale of Ohio. 

 Moreover, the work of Foerste and Morse made it highly prob- 

 able that the Chattanooga, as developed in different parts of 

 Tennessee, may occasionally consist of representatives of only 

 the Cleveland, and in other cases of only the Sunbury shale 

 of the Ohio section. Finally, it had become reasonably prob- 

 able, not to say positively assured, that the outcrops of typ- 

 ical Chattanooga shale in east and middle Tennessee never 

 included beds older than the Cleveland. 



The third point on which my views differ strongly from those 

 now commonly held pertains to the taxonomy of the beds involved 

 in this discussion. Beginning with the publication of New- 

 berry's classification in 1870-73, the base of the Waverlyan 

 has been drawn by many geologists at the base of the Cleve- 

 land. In 1886-8, however, Orton repeatedly expressed 

 his disapproval of Newberry's arrangement and transferred 

 the Devono-Waverlyan boundary to the base of the Bedford 

 shale, a step in which he was followed by the majority of 

 American geologists. The removal of the Cleveland to the 

 Devonian was occasioned by his inability to discriminate suc- 

 cessfully between the three formations — the Huron, the Cha- 

 grin (Erie), and the Cleveland — which in the order named were 

 thought to fill the interval between the Delaware limestone 



* Much to my surprise, I learn that there are yet a few geologists who do not 

 admit a stratigraphic hiatus within the Chattanooga shale at Irvine. Do 

 they hear in mind all the facts in the case when they explain the pinching- 

 out of the Berea and Bedford as mere thinning of deposits without interrup- 

 tion of sedimentation hy emergence ? Apparently no one doubts that the 

 bed of black shale overlying the thinned extremity of the Berea-Bedford 

 wedge at Irvine is Sunbury and that the black shale beneath the wedge is, 

 if not exactly Cleveland, at least pre-Berea in age. And those acquainted 

 with the subject know that the Berea-Bedford wedge expands from practi- 

 cally nothing at Irvine to between 200 and 300 feet locally in northern Ohio. 

 What was going on in southern Kentucky when these thick deposits were 

 being laid down in northern Ohio ? But more than that, do these sceptics 

 remember that the Berea in northern Ohio, even where best developed, is 

 separated by a clearly defined unconformity — hence an hiatus — from the 

 Bedford shale which underlies it ? Most probably also there is an hiatus 

 between the Cleveland and the Bedford, and perhaps another between the 

 Berea and the Sunbury. Now what becomes of these in part definitely estab- 

 lished hiatuses when the formations bounded by them pinch out entirely so 

 as to bring the Sunbury in contact with the Cleveland ? As I see it, merely 

 this— they are merged in a greater hiatus. To deny this is to fly in the face of 

 absolute fact and logic. That the increased hiatus is inconspicuously 

 indicated is not extraordinary. Stratigraphic breaks between shale forma- 

 tions, even when the time is long, are always inconspicuous. But however 

 obscure to the uninstructed, the evidence of a stratigraphic hiatus even in 

 these cases is indubitable and obvious enough to those who have mastered 

 the criteria sufficiently to recognize the break when it is before them. 



