Devonian Shales of N orthern Ohio. 205 



lies in the fact that there exists between the Cleveland and 

 Chagrin shales just this kind of evidence of unconformity. If 

 it is valid in Tennessee it must be in Oli^o. A good illustration 

 of this occurs in the Rocky River section one-half mile north- 

 west of Kainms. Here the Cleveland shale type of sediment 

 first appears as occasional one-inch bands interbedded with 

 gray sandy Chagrin shale 20 feet or more below the base of the 

 Cleveland or below where gray shales cease to appear. We 

 find the same interbedding or intergrading at the base of the 

 Huron which Ulrich has assumed to rest unconformably on the 

 Olentangy. In the Deep Run section west of Lewis Centre 

 three or four thin bands of fissile black shale appear interbed- 

 ded with the upper part of the bluish gray Olentangy shale 

 before it passes finally into the black fissile shale of the Huron. 

 The lithology of the black shale bears every evidence of 

 being a deposit which formed at a considerable distance from 

 a shore line. Not a trace of coarse sand, pebbles, or any kind 

 of large rock fragments has been found in or at the base of 

 these extremely fine-textured shales. This fact is entirely incom- 

 patible with the overlap hypothesis of the origin of these 

 shales. The Chagrin shale, across which this hypothesis 

 assumes the Cleveland shale sea to have advanced, comprises 

 in its upper portion 100 feet or more of shales interbedded 

 with thin bands of hard sandstone generally ranging from 6 

 inches to 2 feet in thickness. These sandstone bands comprise 

 in many sections not less than one-fifth of the total mass of 

 the Chagrin beds, and many of them are extremely hard and 

 resisting. Wave action along the coast of a sea advancing 

 across a wide tract of interbedded hard sandstones and unresist- 

 ing shales such as these could not have failed to produce 

 immense quantities of coarse shingle which would have been 

 built into the beds of the overlapping sea and have left no 

 question Avhatever of the actuality of the invading coast line. 

 It is not on inference alone that this statement rests. The 

 products of wave action now in progress upon a retreating 

 coast line composed of Chagrin shale may be seen along the 

 Lake Erie shore west of Rocky Rive]-, where immense quan- 

 tities of pebbles, both large and small, have been made from 

 the sandstone bands of the Chagrin shale. With this demon- 

 stration of what wave action actually produces in the shape of 

 coarse materials when working on the Chagrin shale, the case 

 of the overlap theorist falls to the ground unless he can show 

 a basal conglomerate such as must have resulted from the 

 advance of the sea across these beds. The work of various 

 geologists on the northern Ohio section makes it very certain 

 that there are no such beds. We can, therefore, only conclude 

 that the assumed overlap never occurred. 



