of the Devonian of Western Tennessee. 735 



The total thickness of the Devonian strata in Tenn- 

 essee is not over 500 feet and the longest single exposed 

 sequence is less than 200 feet thick. Nevertheless the 

 strata may be divided into nine formations, each sepa- 

 rated by longer or shorter intervals of erosion when 



Generalized Devonian Section of Keetern Tennessee 



Series 



Group 



Formation 



Thick- 

 ness 



Character 



a 

 m 



c 

 o 



Chautau- 



guan 



Chattanooga shale 



Hardin sandstone member 



20'i 



Black fissile carbonaceous shale 

 Thin basal sandstone 



B 



Break 







S 



*> 



Senecan 





a 



Erian 







Ulster- 

 Ian 





o 



> 

 o 





Petfram limestone 



10 •♦ 



Heavy-bedded white limestone 



■ 

 as 



Camden chert 



- 

 200': 



Thin-bedded buff colored 

 novaculite 





Oriekan- 

 ian 





Barrinan chert 



30 - 



55' 



Heavier bedded white and buff 

 novaculite 





Quail limestone 



10 •♦ 



Heavy-bedded cherty gray 

 limestone 





Break 









Helder- 

 berg- 

 ian 

 or 



Linden 









e 



~ 



Decaturville chert 



6'* 



Porous gray chert 



t> 

 ■o 

 o 

 *> 



« 



Pa 



Birdeong shale 



35 - 

 65' 



Bluish sbaly limestone and 

 shale 





i 



o 



> 



o 



Flat Gap 



Bear Branch-Pyburn 



Ross 



0-53' 

 0-45* 

 0-60 'i 



Massive pure limestone 

 Massive limestone and oolitic 

 hematite in north - impure 

 cherty limestone in south 

 Impure thin-bedded cherty 

 limestone 







Rockhouse shale 



0-26* 



Bluish green calcareous 

 sh ale 



some of them were reduced to remnants before the 

 deposition of the suceeding formation. In consequence, 

 the thicknesses of the several formations, and even the 

 sequence, vary from section to section. In spite of this 

 fact, the Devonian strata, like those of the Silurian 

 beneath, are so generally horizontal in western Ten- 



