30 GEOLOGY OF OHIO. 



Under cover it retains the same characteristics in composition that 

 it possesses above ground, ranging from fine to middling grain, and very 

 seldom showing pebbles. It has been proved by many hundred borings 

 in southeastern Ohio during the last few years, and its composition at 

 great depths is almost as well known as in its outcrops. 



He — The Bwear Skated- Wayerly Black Shale of Andrews. 



A bed of dark, often black shale, fifteen to fifty feet in thickness 

 makes the constant and immediate cover of the Berea grit throughout its 

 entire extent in Ohio. The shale is highly fpssiliferous. The bottom 

 layer, which is especially rich in fossils, is very hard and stubborn, 

 being composed of sand bound together with pyrites ; consequently this 

 bed when struck in the drilling of wells, is often referred to the sand- 

 stone below, rather than to the shale above, but its fossils and its bitum- 

 ■ inous character favor the reference here given, inasmuch as it marks no 

 new conditions in the history of these beds. 



The stratum was first described by Andrews under the name of the 

 Waverly black shale, the typical outcrop being found at Rockport on 

 the Ohio River, but about the same time Meek, who was studying the 

 fossils of the formation in northern Ohio, introduced the designation 

 Berea shale. The latter name is clearly preferable and ought to obtain 

 currency. 



In southern and central Ohio, and indeed in almost all of its out- 

 crops, the boundaries of the Berea shale are sharp and perfectly distinct. 

 The Berea grit is its base, and the blue beds of the Cuyahoga shale over- 

 lie it. In Cuyahoga county) however, and eastward, the upper limit can- 

 not always be fixed with precision, neither the dark color nor the fossils 

 of the shale disappearing- abruptly, but both gradually diminishing. 

 There are, however twenty to forty feet that always deserve to be 

 counted here. 



When struck by the drill under cover, the formation uniformly 

 yields a line of facts similar to that already reported. Of the records of 

 the many hundred wells that have been carried down to and below this 

 horizon in southern Ohio and in adjacent territory, during the last few 

 years, there has not a single one been found that has failed to give a 

 place to this little band of black shale. Its services in setting in order 

 our Sub-carboniferous geology have been simply invaluable. It is 

 apparently wanting at a few points in northern and central Ohio. At 

 least some of the drillers who have sunk deep wells here declare that 

 they have found no trace of this stratum. 



The Berea shale contains a larger percentage of bituminous matter 

 than the Ohio shale, the amount sometimes reaching twenty-four per cent. 

 It is a source of petroleum on a small scale, as is shown by the fact that in 

 southern Ohio an important ledge of sandstone that belongs just above 

 it is often saturated with mineral tar derived from this source. 



