MISSISSIPPIAN-PENNSYLVANIAN UNCONFORMITY 105 



This manner of occurrence calls attention to the surface upon 

 which the Pennsylvanian rests. Whatever may be the case else- 

 where, the writer believes that greater erosion of the upper Missis- 

 sippian occurred in northern Ohio than is generally known. Instead 

 of the Sharon resting upon a nearly uniform plane, it is found that 

 the surface of the Cuyahoga has a relief of nearly 200 feet, and it 

 is significant that where the depressions are greatest, the Sharon 

 is also thickest. The regional or belt-like occurrence of the con- 

 glomerate, and its apparent relationship to depressions in the 

 Cuyahoga, along with the structure and variability of the stratum, 

 have led the writer to the conclusion that these depressions are 

 creek and river valleys, and that the conglomerate is a deposit 

 of stream gravels, and that the overlying sandstones of the Potts- 

 ville are, to a greater or less extent, river and delta deposits. 



Some of the data on which this view is based are added. Val- 

 leys in the Cuyahoga formation are of general occurrence. The 

 most conspicuous and deepest one so far found may be noted in 

 some detail. This valley lies in the eastern edge of Portage and 

 Geauga counties, about half-way between Akron and the state 

 line, and its course is roughly north and south. At Akron, the 

 top of the Cuyahoga formation lies about 940 above sea; due east, 

 at Mineral Ridge, west of Youngstown, at 962; at Newton Falls, 

 between these two points, and 5 miles north of the Akron-Mineral 

 Ridge line, it lies below 850, or about 100 feet lower than to the 

 east or west. If such a line be drawn from east to west half-way 

 between Akron and Cleveland, the same depression in the Cuya- 

 hoga is again found. At Brandywine Falls, 15 miles north of Akron, 

 the top of the Cuyahoga formation lies at 1,040; near Howland 

 Springs, due east of Brandywine, at 1,044; and at Nelson Ledges 

 between these two points at 956, or again nearly 100 feet lower. 



Another east and west comparison may be cited. At Burton, 

 due east of Cleveland, the top of the Cuyahoga lies at 1,090 and 

 due east on the state line at 1,190, or 100 feet higher. These three 

 middle points — Newton Falls, Nelson Ledges, and Burton — are in 

 line, roughly, north and south, and are clearly in a depression of 

 the Cuyahoga formation, since rock of this formation lies higher 

 both to the east and west. Further, this depression cannot be 



