6o8 NORTH AMERICAN INDEX FOSSILS. 



Harpers formation 2,750 ft. 



Weverton sandstone 1,250 ft. 



SUBFORMATION. 



x^lgonkian. 



The series from the base of the Tomstown limestone to the top 

 of the '' Lower Trenton " is included in the general term Shenan- 

 doah group of limestones. The basal series is known as the Chil- 

 howee series. 



In eastern Tennessee the Cambric section comprises :^ 



SUPERFORMATION. 



Chickamauga limestone (Ordovicic). 



Upper Cambric. 



Knox dolomite (partly Lower 



Ordovicic) 3, 500 ft. 



Middle Cambric. 



Nolichucky shale 450- 550 ft. 



Maryville limestone 350- 500 ft. 



Rogersville shale 180- 220 ft. 



Rutledge limestone 350- 450 ft. 



Lower Cambric. 



Rome formation 750- 950 ft. 



Beaver limestone 300 ft. 



Apison shale 1,100 ft. 



(a break in the series) 



Hesse sandstone 500 ft. 



Murray shale 300 ft. 



Nebo sandstone 500 ft. 



Nichols shale 550- 800 ft. 



Cochran formation 1,100-1,700 ft. 



Sandsuck shale 1,000 ft. 



(Base not exposed.) 

 Elsewhere in eastern Tennessee and in North Carolina, the Coch- 

 ran formation is conglomeritic and varies in thickness up to 



^ Keith, Knoxville Folio. 



