to the Ohio Shale Problem. 165 



shale which underlies the Louisiana in Lincoln County, Mis- 

 souri, represents the final, rather than any older, stage of the 

 Chattanoogan transgression in the Mississippi Valley. The 

 merits of the Waverlyan as a distinct system cannot be dis- 

 cussed here. Pending the full discussion that I hope to give 

 at some future time, the reasons presented more or less inci- 

 dentally in various parts of my Revision of Paleozoic Systems 

 must suffice for the present. 



In order that the intercalations and proposed changes in the 

 classification and correlation of the various black shale forma- 

 tions involved in this discussion may be clearly understood, 

 the accompanying table is presented. As will be observed, 

 only the Chattanoogan part of the scale is fully developed, the 

 Neodevonian, Kinderhookian, and Osagian parts being more 

 or less condensed. 



The Chattanoogan sequence in Ohio. 



General statement. — No one as yet is sufficiently informed 

 concerning the surficial and underground behavior of the 

 Chattanoogan formations in Ohio to write them up in a com- 

 prehensive and thoroughly reliable manner. Yet so much has 

 been published about the great shale series in the Ohio state 

 reports that detailed descriptions seem unnecessary here. Only 

 a very generalized account will be attempted. Here and there 

 we may have to enter into some details which are thought to 

 have a more than usually direct bearing on the problems at 

 issue. 



Huron shale. — Beginning at the north, the basal part of the 

 series is formed by the Huron shale. This consists of 200 or 

 300 feet of mostly black shale which is distinguished from 

 other shales of the series by the large calcareous concretions 

 which it contains, especially in its lower half. These concre- 

 tions are often a very conspicuous feature and in many cases 

 they are formed about a fish bone or some other organic 

 nucleus. The formation outcrops in a belt of varying width 

 that extends entirely aci'oss the state from the lake shore in 

 Erie County to and across the Ohio into Kentucky. The 

 Huron evidently overlapped westwardly on the flanks of the 

 Cincinnati axis so that in places only its upper beds are present. 

 It seems also to have suffered diminution by overlap in an 

 eastward direction, but how far from the line of outcrop such 

 overlap thinning begins cannot be decided with the evidence 

 in hand. Nevertheless we have indirect evidence in deep wells 

 and surface relations suggesting that the Huron did not extend 

 far beyond the Carter axis, an old line of uplift that passes 

 through Carter County, Kentucky, and is indicated at intervals 



Am. Jour. Sci.— Fourth Series, Vol. XXXIV, No. 200.— August, 1912. 

 12 



