18 H. .1. Wrir'wbe — Berea Formation. 



Stratigraphic position was considered most helpful in trac- 

 ing the Berea. It is overlain in Ohio and to a certain extent 

 in Pennsylvania by a black shale, which is, in addition, rather 

 fossiliferous, containing numerous Lingular and Discinse. This 

 is the Sunbury shale of Ohio, and is equivalent to the lower 

 part of the Orangeville shale in Pennsylvania. It gradually 

 loses its black color when traced into Pennsylvania, but it 

 can always be identified by its characteristic fauna. In addi- 

 tion to this the Meadville limestones are excellent horizon 

 markers, being very persistent and of a peculiar lithologic 

 character. Finally, the Shenango sandstone, if it can be found, 

 is of great value in interpreting the section. It is a rather 

 coarse, siliceous sandstone, weathering a deep brown by the 

 alteration of iron, scattered abundantly through its mass in the 

 form of concretions, secretions and veinlets ; it is also ijuite 

 uniform in thickness. 



In this manner the upper part of the Berea or the Corry was 

 traced, it is felt with certainty, as far as the Allegheny Eiver. 

 The determination of the base of the formation was not so 

 easy. Where the Cussewago sandstone is present in typical 

 development the succession and correlation are perfectly clear, 

 but where it is missing it is somewhat difficult to draw the line 

 marking the base. The Cussewago shales are very similar to 

 the underlying Devonian shales ; however, in this region buff 

 sandstones occur in the former but are absent in the latter ; 

 also the Cussewago shales are quite barren, whereas the Devo- 

 nian shales are not, and contain a Spirifer disjunotus fauna 

 (Chemung) practically to the top. The section secured at 

 Miller Farm is a typical one to illustrate this point. It will be 

 seen that the Corry is underlain by 30 feet of buffish sand- 

 stone and bluish-grey shale and sandstone, which in turn rests 

 upon a 6-inch layer of calcareous sandstone containing fossils. 

 This layer is therefore chosen to mark the base of the Berea, 

 partly because it is fossiliferous and partly because below it no 

 prominent buff layers occur. It is more than likely that the 

 Cussewago sandstone is represented in this section by a part of 

 the 30 feet mentioned. In that case it would seem to be but a 

 horizontal variation of the lower buff sandstones of the Berea, 

 in Pennsylvania, exactly as it has proved to be in Ohio. A 

 bit of evidence which may perhaps substantiate this view is 

 the fact that the well drillers in this region call the Berea the 

 " Forty-foot." A typical well drilled (section M in fig. 1) 

 less than three miles east of Miller Farm, where section I was 

 secured, illustrates in excellent fashion the character of the 

 formations underlying the Berea. It appears from this record 

 that the drillers would include a good share of the 30-foot 

 interval in their " Forty -foot," which thus indicates the sandy 



