176 VI rich — Chatlanoogan Series toith Special Reference 



and Mt. Vernon. In this area thinning of the shale complex 

 is fairly uniform and does not vary much from 20 feet per 

 mile. As will be noted, the rate continues about the same as 

 between Akron and Wellsville. A few miles farther north, 

 however, as between Lodi and New London, it advances to 30 

 feet per mile. 



Taking the published records of wells to the west of a line 

 connecting Cleveland, Lodi, and New Lexington, the average 

 W.N.W. thinning of the shale complex seems not to be less than 

 30 feet to the mile. In places, as stated, it drops to 20 feet, in 

 others it rises to 40 feet and even to more than 50 feet. Accept- 

 ing 30 feet per mile as a fair average for north central Ohio, 

 nearly the whole (over 1000 feet) of the 1116 feet of the shale 

 complex beneath the town of Lodi will have disappeared before 

 reaching the outcrops along Huron River, 34 miles away in 

 Erie and Huron counties. That such thinning actually occurs 

 in the first 19 miles of this distance is established by comparing 

 the Lodi well, in which the shale complex is 1116 feet thick, 

 with the well near New London, in which it is only 650 feet. 

 Now, at the expense of which part, the top or the bottom, of 

 the shale complex of eastern Ohio is this diminution taking 

 place ? In view of the uumistakable trend of modern strati- 

 graphic geology, the possibility of the reduction being due to 

 correspondingly varying rates of deposition seems so improb- 

 able that it need not be considered. 



To begin with, especially since it is certain that we are deal- 

 ing with overlapping formations, is it not quite reasonable to 

 assume that the loss in thickness is by overlap thinning, hence 

 from the bottom and not the top % Next, if we admit that the 

 upper part of the shale complex under Lodi comprises beds 

 referable to at least the Bedford and Cleveland shales, and most 

 likely also beds corresponding to the recently named Olmsted 

 shale, all three of which continue without break along the lake 

 shore from west Cleveland to Huron River, it is clear that the 

 fully demonstrated thinning of the shale complex affects only 

 the beds beneath the Olmsted. More than that, Cushing 

 shows that the Olmsted thickens westwardly along the lake 

 from in east Cleveland to approximately 1O0 feet at the west- 

 ern edge of the Berea triangle ; in other words, this shale 

 thickens westwardly, so far as followed, at the rate of about 6 

 feet to the mile. Should this rate of thickening continue west- 

 ward to Huron River, an added distance of 26 miles, the Olm- 

 sted shale alone would there be something like 250 feet thick. 

 But we know from outcrops studied by Newberry and Read, 

 as described in the Ohio Survey reports on Erie and Huron 

 counties, that both the Cleveland and the Bedford shales are 

 represented in the highland rim of the Huron River valley by 



