18 



FLUORSPAR DEPOSITS OF SOUTHERN ILLINOIS, [bull. 255. 



division and classification of the Carboniferous, the scheme nsed 

 by Mr. Ulrich in his discussion of the adjacent Kentucky district 

 has been adopted in its entirety, with the exception that, as a matter 

 of practical convenience in preliminary mapping, the dividing line 

 between the St. Louis and the Tullahoma is drawn at a slightly 

 higlier horizon than the one recognized by him, and the Spergen 

 HHl discriminated by him between the St. Louis and the Ste. Gen- 

 evieve was not recognized in the course of this work. Mr. Ulrich con- 

 siders the Birdsvnie and Tribune formations the equivalent of 

 Kaskaskia as originally defined, and these with the Cypress and 

 the Ste. Genevieve as riiaking up the Chester. In the earlier work 

 of Engelmann and Worthen « the lines were somewhat differently 

 drawnrbut for reasons which Mr. Ulrich has elsewhere discussed it is 

 impracticable to follow them exactly. A general tabular arrange- 

 ment of the formations is presented below. 



Table of formations, southern Illinois. 



System. 



Quaternary 



Tertiary 



Carboniferous 



Formation. 



Lafayette (?) 



Character. 



Loess loam. 



Gravels. 



Mansfield Sandstone and conglomerate. 



Birdsville Sandstone, shale, and thin limestones. 



Tribune ' Limestones. 



Cypress Heavy-bedded sandstone. 



Ste. Genevieve 



St. Louis 



Tullahoma 



Devonian Ohio 



Oolitic limestones. 

 Limestones and chert. 

 Chert and limestone. 



Black shale. 



DESCRIPTION OF SEDIMENTARY FORMATIONS. 

 DEVONIAN ROCKS. 



OHIO SHALE. 



Character.— T\\Q Ohio shale as developed in this area is a black, 

 fissile shale or slate. It splits in very thin sheets parallel to the 

 original bedding and is very uniform in character. The only excep- 

 tion to this statement is that at the top a thin bed was observed which 

 Mr. Ulrich considers the equivalent of a similar bed forming the top 

 of the formation in middle Tennessee.'' In it there are small, rounded 



<•■ Geo). IlUnois. vol. 1, pp. 76-83, 348-^95. 

 " Geologic Atlas U. S., folio 95, IT. S. Geol. Survey, 1903, p. 2. 



