624 GEOLOGY OF OHIO. 



c. Nodules of oxide or sulphuret of iron quite frequently occur, which 

 are decomposed by exposure to the air, and which by their decay not 

 only weaken the stone, but disfigure it by rusty stains that spread widely 

 from these points. 



The deposits that belong to this horizon constitute by far the most 

 valuable of the geological products of the county. They are exposed in 

 almost every square mile of the western half of the county. The Sun- 

 fish valley is walled with it throughout its whole length, as are also all 

 of its tributaries, small and great, and a bold escarpment of the quarry 

 courses, broken only by the streams that seek the river, constitutes a con- 

 siderable portion of the western margin of the Scioto valley. 



3. Immediately above the Waverly quarries comes in a very interest- 

 ing formation, to which attention has been repeatedly called in the pre- 

 vious reports of the Survey. The formation in question has been desig- 

 nated by the Chief Geologist the " Cleveland Shale," and by Professor 

 Andrews the " Waverly Black Slate." It consists of a black shale more 

 highly charged with bituminous matter than the great black slate below 

 it, the proportion sometimes rising as high as twenty-four per cent. 

 Unlike the slate below it, viz., the Huron, it is often highly fossiliferous. 

 Two species of brachiopods are especially abundant in it, viz., Discina 

 capax and Lingula sub-spatulata. The remains of fishes are also of frequent 

 occurrence. Its thickness, as measured in the Scioto valley, varies from 

 seventeen and a half feet to twenty-seven feet. The former measure- 

 ment was taken from an exposure on the land of John Gregg, Esq., op- 

 posite the village of Waverly ; the latter was obtained from the best sec- 

 tion of it to be found in all the Scioto valley, viz., on the banks of Stony 

 Creek, just north of the line of Pike county. 



The highly bituminous character of the stratum makes it frequently 

 give rise to oil springs, the fair promise of which has led to many un- 

 profitable borings in various portions of the county. The most notable 

 display of petroleum in this region is to be found at the "Tar Spring," in 

 Sunfish township, on Chenowith's Fork, about five miles above its mouth. 

 The locality may be more accurately defined as belonging to Chestnut's 

 Mountain. The horizon of the spring is in the Buena Vista stone, a fine 

 ledge of building rock that directly overlies the slate. The volume of 

 water is weak, and the petroleum, which rises with the water in part, 

 and in part oozes out of seams in the rock, is so abundant that the 

 surface of the water in the spring is constantly covered with a dark, tar- 

 like product, the result of the inspissation of the oil. A considerable 

 amount of money was expended here — several thousand dollars — as is 

 stated, in the days of the oil excitement ; but, as will be recognized from 



