40 J.J. STEVEKSON — LOWER CARBONIFEROUS, APPALACHIAN BASIN 



It must be clear, however, to the reader who has followed the preceding 

 summary that the loss in thickness is due very largely to disappearance 

 of the lower members of the section, as is the case also southward from 

 central Kentucky and southern Virginia, so that in Alabama and much 

 of Tennessee onl}^ the uppermost beds remain. A new correlation ap- 

 pears to be necessary. 



As already stated, Dr I. C. White's work first made clear the relations 

 of the Pocono divisions in northwest Pennsylvania. His Shenango 

 shales, Shenango sandstone, and Meadville shales, down to and including 

 the upper Meadville limestone, are undoubtedly Lower Carboniferous, 

 while the underlying divisions — the lower part of the Meadville shales, 

 the Sharpsville sandstones, the Orangeville shales, and the Oil Lake 

 group — are evidently later Devonian. Doctor White obtained from the 

 upper Meadville limestone an abundant fauna, vertebrate and inverte- 

 brate, which was submitted to Professors Worthen and St. John. The 

 invertebrate fauna has a Kinderhook facies, though some of the species 

 are allied to Burlington and Keokuk forms. The vertebrate fauna, 

 though in some respects resembling the Chester, is more nearly related 

 to that of a lower horizon, probabl}^ Kinderhook. The fossils from the 

 Shenango sandstone are unlike those from the Shenango shales, which 

 are Chester. 



In the Sharpsville sandstones is the lower Meadville limestone, which 

 has been recognized in Crawford, Mercer, Warren, and Venango counties 

 by Doctor White, and in McKean and Elk by Mr Ashburner; farther 

 east is the impure limestone of Tioga and Lycoming counties, while on 

 the eastern outcrop, at much the same horizon, allowance being made 

 for thickening in that direction, are the somewhat calcareous, fossilif- 

 erous shales described by Doctor White in the report on Huntingdon 

 county. This limestone, hard and flinty at the northwest, is almost 

 non-fossiliferous in Crawford county, but is rich in fossils within Warren 

 and Venango, where the most characteristic fossil is a Spirifer very near 

 to Sp. disjimctus. Devonian forms occur in the lower divisions, and the 

 Oil Lake group rests on the Riceville shales, which are rich in typical 

 Chemung forms and extend downward to the first Venango oil-sand, the 

 Allegrippus of White in eastern Penns3^1vania, the upper Chemung con- 

 glomerate of Stevenson. 



Closel}^ following this work by Doctor White came that by Professor 

 C. L. Herrick upon the Waverly of central Ohio, which was developed 

 gradually in several publications and took final form in the discussion 

 published in volume vii of the Ohio Reports. 



Professor Herrick's investigation was one of the most painstaking ever 

 performed in our countr3^ The " Waverly problem,'' as it was termed 



