to the Ohio Shale Problem. 171 



I leave the Maury in the position assigned to it by Hayes and 

 Ulrich.* 



As intimated at the head of the preceding paragraph the 

 Sunbury shale is widely distributed. From Berea in northern 

 Ohio it extends eastwardly to some unknown point — possibly 

 beyond the Pennsylvania line — in which case it would seem to 

 form the basal part of the Orangeville shale. Southwardly it 

 has been traced by several observers, notably Prosser, across the 

 state to Vanceburg, Kentucky, and thence by Foerste and 

 Morse to the Kentucky Eiver at Irvine. South of this point 

 the Sunbury shale, through failure of the Bedford and Berea 

 formations which underlie it in Ohio, rests with obscure but 

 unquestionable unconformableness on the Cleveland. In Ten- 

 nessee, finally, it is believed that in certain places the Sunbury 

 alone represents the Chattanoogan. In such places the Chat- 

 tanoogan shale, though very persistent, is usually less than 10 

 feet thick, as in the Columbia quadrangle. Both features are 

 regarded as indicating gradual overlap across a nearly plane 

 surface rather than diminution due to erosion subsequent to 

 more complete deposition. 



The Chagrin formation. 



The Chagrin formation, or, as Newberry and the geologists 

 of his Survey called it, the Erie shale, is not included in the 

 Chattanoogan series. In my opinion it is clearly late Devonian 

 in age and older than the Huron member of the Ohio shale. 

 Furthermore, on the basis of stratigraphic continuity and 

 fossil contents, I can not see how we can avoid correlating the 

 upper part at .least of the Chagrin as Chemung, hence, accord- 

 ing to the now prevailing interpretation of the New York 

 standard, as latest Devonian. This correlation of the Chagrin 

 was indubitably fastened by Newberry in the early seventies, 

 and no one has since succeeded in materially shaking the con- 

 viction of those who accepted his view. It is therefore deemed 



*It seems desirable here to correct a misapprehension that seems to have 

 arisen in certain quarters respecting the reputed '' migration" of the uncon- 

 formity indicated at the top of the Chattanooga by Hayes and Ulrich in the 

 Columbia folio. In the February number of this Journal, Mr. E. M. Kindle 

 refers to this unconformity as " belonging to the evanescent class of uncon- 

 formities." This unconformity is neither evanescent nor has it migrated to 

 any other position than that assigned to it by Hayes and Ulrich. If Mr. 

 Kindle had carefully read the text of the Columbia folio, he must have 

 noted that this unconformity was not regarded by the authors of the folio as 

 of high importance. For instance, at the close of the description of the 

 Chattanooga, he would have found this statement : " Earely as in the upper 

 part of East Fork of South Harpeth Creek, the green, glauconitic shale 

 usually at the top of the formation is absent or not distinguishable, and in 

 these cases the black shale seems to pass very gradually into overlying cal- 

 careous green shale (now known as the Ridgetop shale) which is without 

 glauconite and constitutes the base of the full Tullahoma section." 



