834 J. A. BOWNOCKER 



The Dunkard or 300-foot sand is quite generally regarded as 

 the equivalent of the Mahoning. That this cannot be correct is 

 shown by the following partial section of the Hocking Valley 

 coal field. 1 



Thickness. 



Cambridge limestone ... - 2-10 feet 



Mahoning sandstone, upper division, - 50 



Brush Creek coal (No. 7a) - 



Brush Creek limestone ... 4 



Mahoning sandstone, lower division - 1 5 — 25 



Upper Freeport coal - - - -0-3 



2K 



( Clay 



Upper Freeport < Shales - - \ 35 



( Limestone and sandstone ) 

 Middle Kittaning coal (No. 6) - - 5-13 



This shows the Mahoning sandstone lying immediately below 

 the Cambridge lime, but experience in the field demonstrates that 

 the two are not ordinarily in contact. Measuring from the base 

 of the lime rock to that of the Mahoning, an interval of 76 feet 

 is found, while, according to the records in the Dunn well, the 

 interval is 210 feet. A divergence of this sort cannot be 

 explained by assuming that the section expands eastward, for a 

 study of the relative positions of the Pittsburgh coal, the Ames 

 and Cambridge limestones farther west with the same formations 

 near Macksburg, shows no material change, and it is certainly 

 unreasonable to assume that the formations just below the Cam- 

 bridge limestone expand at anything like the rate that would be 

 necessary to make the interval which this nomenclature requires. 

 Further, naming the sand in question the Mahoning makes impos- 

 sible a rational classification of the lower formations. The position 

 of the sand with reference to the Cambridge lime is that of the 

 Upper Freeport. 



1 Geological Survey of Ohio, Vol. V, p. 918. 



