46 W. A. Yerwiebe — Correlation of the 



in Ohio. It shows 203 feet of black (Huron) shale underlain 

 by 10 feet of limestone (Prout) and 120 feet of shale (Olentangy). 

 The base of the Berea is calculated from other wells in the 

 vicinity. Section B from Wellington show^s 96 feet of red shale 

 (Bedford) beneath which are 145 feet of black shale (Cleveland). 

 The remainder, 658 feet, is given as alternating blue and black 

 shale. In section C from Akron there are three zones of black 

 shale, tbe thickest being 150 feet. The rest consists of alter- 

 nating dark and light blue and grey shales. This section was 

 discussed above (p. 37). The next section (D) constitutes the 

 record of a well drilled in the early part of 1916 three miles 

 southwest of Niles in Trumbull County. It shows ten feet of 

 red shale (top of Bedford) and below that 2589 feet of "blue, 

 white^ and cinnamon" shale. An interesting detail is the 35 

 feet of sandy shale and sandstone occurring 612 feet above the 

 base. This showed a trace of oil and may represent one of the 

 lower sands found in western Pennsylvania. Section E takes 

 us into Crawford County, Pennsylvania. Unfortunately the 

 record was not well kept and the sands indicated must there- 

 fore be considered as generalized. The Chemnng is about 

 1200 feet thick, the Portage, Hamilton and Marcellus about 

 1500 feet, making a total of 2700 feet for the Devonian shales 

 in Crawford County. The last section (Erie, Pa.) was intro- 

 duced partly to show that the thickness of the shales increases 

 toward the south and partly because this record has been kept 

 with such perfect detail that the formations may be delimited 

 with considerable confidence. At the base are shown 25 feet 

 of black shale (Marcellus), above this 170 feet of Hamilton and 

 finally 1105 feet of Portage and Genesee. The top of the sec- 

 tion has been extended by the writer, from calculations based 

 on a study of outcrops in the vicinity, to include the top of the 

 Devonian. An addition of 170 feet of Portage is indicated. 

 Above that 550 feet of Chemung (lower 225 feet-G-irard) and 

 450 feet Bradfordian (Piceville and Yenango group). In all 

 the sections the top of the Devonian limestone is used as the 

 lower datum plane and the base of the Berea sandstone as the 

 upper. 



Summary. 



The correlation of the Devonian shales of Ohio and Penn- 

 sylvania with those of New York is a difficult problem because 

 the ordinary criteria, lithology, and paleontology are unsatis- 

 factory guides. A careful consideration of all the available 

 data at hand seem to justify the following conclusions : 



1. The 750 feet of shales in central Ohio expand into and 

 are stratigraphically equivalent to the 2700 feet of shale in 

 western Pennsylvania. 



