to the Ohio Shale Problem. 167 



Explanation of Figs. I-III, p. 166. 



Fig. I. Generalized schematic section due east and west from Sandusky, 

 Ohio, to Pennsylvania state line, showing new conception of the stratigraphic 

 relations of the Chagrin shales to the Huron, Olmsted, and Cleveland 

 divisions of the Ohio shale. Vertical scale greatly exaggerated. 



Fig. II. Similarly generalized section southward from Lake Erie to 

 southeastern Kentucky, showing pinching out of the Bedford and Berea 

 formations in central Kentucky, the inclusion of the Sunbury with the 

 members of the Ohio shale in the Chattanoogan and the southward thinning 

 of the Huron in northern Ohio. 



Fig. III. Section showing supposed overlap thinning of Chattanooga 

 shale in Tennessee whereby the formation may be locally represented only 

 by the Sunbury division. 



southward through this state iuto Tennessee and northward 

 through Ohio to the lake shore west of Cleveland.* The lower 

 heds of the formation at least are thought to be confined to the 

 shallow structural trough between the Carter and Cincinnati 

 axes. At any rate, so far as I can learn, none of the deep wells 

 to the east of the Carter axis have ever been reported passing 

 through the hard calcareous concretions which are character- 

 istic and widely distributed. So far as known, the Huron is 

 always separated from underlying formations by a stratigraphic 

 hiatus. At the top, however, no evidence of break has been 

 observed. 



Olmsted shale. — This name is proposed in a letter to me by 

 Professor H. P. dishing for the body of relatively soft, mainly 

 blackish, though parti)' bluish shale which wedges in at the 

 base of the Cleveland shale in West Cleveland, where it — first 

 the typical Cleveland and then the intercalated bed — rests on 

 and is sharply distinguished from the Chagrin formation. 

 West from Cleveland the Olmsted shale gains with moderate 

 rapidity, attaining a thickness of nearly 100 feet at the western 

 edge of the Berea quadrangle. Though not traced beyond this 

 point, I am confident that this shale expands still more to the 

 west and finally passes into the middle member of the Ohio 

 shale as developed in Erie and Huron counties. I believe 

 further, and I may say that Professor Cushing is of the same 

 opinion, that this Olmsted member constitutes the bulk of the 

 Ohio shale seen in central and southern Ohio and of its exten- 

 sile northern extension of this axis is incorrectly represented in the 

 small map on page 293 of my paper in Bull. Geol. Soc. America, vol. xxii, 

 1911. As drawn there two distinct axes are wrongly connected at the Ohio. 

 The Carter axis passes farther west in Ohio and should run more nearly 

 parallel to the Cincinnati axis. 



