344 



CHARLES S. PKOSSKR 



compiled from the separate sections described above, which shows 

 the formations from the upper part of the Richmond in the Ordo- 

 vician system to the lower part of the Springfield dolomite in the 

 Silurian system. Some of the zones or formations vary in thick- 

 ness in different outcrops, in which case the variation in thickness 

 has been given. This necessarily causes a variation in the entries 

 in the column oi total thickness. 



GKXKRAL SECTION ALONG LUDLOW, CREEK 



fota] I'hickness 



rhickness oi Zone 

 or Formation 



Names of Series and Formations 



S7f to or 



49 \ to 5;,y 



4-1 to 45l y 



*oi' to 4 :J' 

 »ol' to 3iJ' 



si' 



ttt't0 3*' 



a6j'to .•>!• 



Niagarao Scries 

 Springfield dolomite (only lower part shown) 



Mottled zone 



Laurel limestone 

 Top oi Osgood beds 

 Shale zone 



Dayton limestone 

 Base of Osgood beds 



0<\\c±.\n Scries 



Brassfieid limestone 



Cincinnatian Series 

 Belfast bed at top of Richmond formation 



A mere outline of the classification of the formations of the 

 Niagaran series along the Ohio-Indiana state line was published 

 by the writer on April jo. 1015. l and the Brassfieid limestone was 

 given in the Oswegan series. - 



Correlation of the Brassfieid limestone. — The limestone in the 

 foregoing sections, which is called the Brassfieid, is the one which in 

 Ohio has generally been called the Clinton and correlated with the 

 well-known Xew York formation of that name, which forms the 



of Field Fi ( Ohio, The College Book Store. 



Columbus. Ohio. p. iS. 



