168 ft 'rich — Chattanoogan Series with Special Reference 



sion in Kentucky,* in all of which places the Ohio shale is 

 thinner than in Huron County and the Huron member espe- 

 cially inferior in volume. 



Along Huron lliver the presumed Olmsted seems not to 

 be sharply delimited from either the underlying Huron or 

 from the overlying Cleveland shale. Neither boundary has 

 been consistently drawn by geologists who have studied the 

 rock in this area. Newberry, in his report on Erie County, f 

 speaks of the top of the Huron as being interstratified with 

 the lower beds of the " Erie " which he thought he recognized 

 in the section of that county. Evidently the supposed Erie is 

 what dishing is calling the Olmsted. That he had trouble 

 also in recognizing the boundary between the Cleveland and 

 the Olmsted is evident enough from the fact that the fish 

 beds near Avon Point, which according to dishing and my 

 own views c.rtainly belong in the Olmsted, were first referred 

 to the Huron on the erroneous assumption of continuous east- 

 erly dip, and later to the Cleveland.:}: In fact neither Newberry 

 nor Orton recognized a formation boundary between the Cleve- 

 land and the Olmsted, and so far as I know there is no break 

 between them. Nevertheless the two zones are widely dis- 

 tinguishable and should be recognized in refined stratigraphic 

 work. 



Cleveland shale. — The chief features by which the Cleve- 

 land shale is distinguished from the Olmsted are its relative 

 hardness and slaty structure. Irregular concretionary masses 

 occur in places, but they are less calcareous and seldom or never 

 of the spherical form that characterizes the concretions in the 

 Huron. The typical Cleveland, though varying in thickness and 

 probably not exceeding 50 or at the most 60 feet, seems to 



*In his paper on the Chattanooga shale in the February number of this 

 Journal, Dr. E. M. Kindle refers to similar statements of authors, mentioning 

 Professor Edward Orton, Jr. as "one of the first to claim that the black 

 shale in central Kentucky is the upper or Cleveland Division." Concerning 

 this it may be pointed out that the son was preceded by the father in this 

 opinion, Prof. Edward Orton Sr. having published in 1888 (Ohio Geol. 

 Survey, vol. vi, p. 26) an even more definite statement to the same effect. 

 Further, the senior Orton, who was certainly not "unfamiliar with the 

 subject," leaves the impression that his opinion was based not only on 

 physical criteria but also faunal evidence, when, in his closing remark, he 

 says " the shale that covers the Lower Silurian limestone in central Ken- 

 tucky is the upper or Cleveland division, if the fossils can be relied on 

 to settle the question." To make Orton's position on this matter clear with 

 respect to Professor Cushing's and my own it should be said that he 

 evidently regarded the Cleveland as a formation overlapping from the south 

 and in consequence simply added these underlying Olmsted beds — in which 

 he could recognize neither the Chagrin nor the typical Huron — to the base 

 of the Cleveland. That I intended to follow him in this is evident from the 

 note on page 157. 



t Ohio Geol. Survey, vol. ii, p. 188, 1874. 



X Newberry, J. S., Mon. U. S. Geol. Survey, xvi, p. 129, 1889. 



