22 GEOLOGY OF OHIO. 



But aside from these grounds of objection to the particular names 

 employed, the classification referred to is itself inconsistent with our 

 present knowledge of the shale formations. We have records by the 

 score of wells drilled through the shale at many points in northern Ohio 

 during the last few years, and we have also the results of continued study 

 of the formation in its outcrops. The facts gathered from both these 

 lines of investigation, not only fail to confirm the three-fold division 

 above announced, but they demonstrate the impossibility of applying to 

 the shale formation any system of classification based upon the color 

 of the shales ; and as for the fossils, they are so sparingly distributed that 

 they cannot well be used to mark horizons in the formation, aside from 

 the few that will be mentioned later. 



10a. The Lower Beds — Huron Shale. 



The Huron shale was defined by Newberry as a homogeneous mass 

 of black, bituminous shale, two hundred to three hundred and fifty feet 

 in thickness, directly overlying the limestone series already described. 

 The objection to this definition is that there is no such mass of shale in 

 Ohio The formation on which the main statements pertaining to the 

 Huron rests, and which furnishes nearly all the examples instanced, is 

 the shale stratum of central and southern Ohio, but this is not merely 

 the bottom portion of the shale series of northern Ohio. It comprises all 

 of the elements of the northern section. In other words, the so-called 

 Huron shale of central Ohio is the full equivalent of the Cleveland, Erie, 

 Huron shale of northern Ohio. It is not a homogeneous mass of black 

 shale, as it has been commonly counted, but beds of blue or greenish-blue 

 shale are frequently interstratified with the prevailing black beds, 

 especially in the middle portion of the series. The top and bottom of 

 the column are generally black shale, and the same thing is true in north- 

 ern Ohio. These facts show the grounds on which the classification now 

 referred to is based, but the objection to it is that no line of division can 

 be drawn between the Huron and Erie, or the Erie and Cleveland shales. 

 The records of many drilled wells in northern Ohio show that alternations 

 of black and blue shale occur not once only, but scores of times, in the 

 formation. 



10c. The Upper Beds — Cleveland Shale. 



The Cleveland shale has a somewhat better chance for survival as a 

 distinct division than the Erie or Huron. The upper boundary of it is 

 tolerably distinct, inasmuch as a belt of black shale generally underlies 

 by fifty to one hundred feet the Berea grit, which is by far the best land- 

 mark in this part of the scale, the interval being occupied by the Bedford 

 shale, itself a well characterized formation. In some sections, however, 

 there is no black shale at the point where the Cleveland shale belongs, 



