WILLIAMS.] 



Lesley's scheme of formations. 



97 





The scheme of formations published in Report of Progress HH., 1875 

 is repeated, but with change in names, in Report HHH, 1877. In 

 the preface of this report, 1 by J. P. Lesley, the following scheme of for- 

 mations is given : 



I. The Carboniferous system : 



1. Monongahela River coal series : 



Upper Barren Measures. 



(a) Greene County group. 



(&) Washington County group. 

 Upper Productive Coal Measures. 



2. Alleghany River coal series : 



Lower Barren Measures. 



Lower Productive Coal Measures. 



(a) Freeport coal group. 



(6) Kittanning coal group. 



(c) Clarion coal group. 



Pottsville Conglomerate (Serai) 



(d) Sharon and Quinnemont coal group. 



Mauch Chunk red shale ) 



Mountain limestone > 



(e) New River coal group.. ) 

 Pocono sandstone (Vespertine) (mountain sands) , 



II. The Devonian system : 



1. Catskill sandstone (Old Red) (? Oil Sand group) 



2. Chemung sands and shales 



3. Portage shales and sands 



4. Hamilton formation 



Genesee black shales 



.Hamilton sandstoucs , = . 



Juniata River coal group 



Marcellus black shales 



5. Upper Helderberg limestones 



6. Oriskany sandstone 



III. The Silurian system. 

 1. Lower Helderberg limestone 



XII 



XI 



IX 



> XIII 



VII 



VI 



The name u Quinnemont beds" is here substituted for the name 

 u Kanawha River system" of the former reports, because the latter 

 name was found inapplicable. 2 



In the report on Indiana County 3 Mr. Piatt notes the discovery of 

 fossils in an exposure of the Mountain limestone on the bank of the 

 Dunbar Creek, three of which were identified with species of the Ches- 

 ter group. 4 



This correlates the series XI, Mauch Chunk of Lesley, with the upper 

 division of the Lower Carboniferous limestone series of the Mississippi 

 Valley. 



'Geol. Survey of Pennsylvania, Kept, of Progress H 3 . Report on Somerset County, by F. and W. 

 G. Piatt, pp. 348, 1877. 

 * See p. xxii. 



• Geol. Survey of Pennsylvania, Kept, of Progress H 4 : Report on Indiana County, by W. G. Piatt, pp. 



-7 



316. 1878. 

 « Ibid., p. 60. 



Bull. 80 



