the central basin of tennessee. 77 



Devonian. 



Black Shale. — -This shale which lies immediately undei- the lower 

 division of the siliceous corresponds to the Genesee slates, 

 or Hamilton group of the New York section and the 

 Hamilton formation of western Canada. The charateristic 

 mass of this formation is a nearly black bituminous, rather 

 tough slate or shale. It contains very generally grains and 

 nodules of Pyrite scattered through its mass. West of the 

 Cumberland Table Land the Black Shale has at its top a thin 

 layer of argillaceous very fetid concretionary bodies of round 

 oval, kidney shaped and usually more or less flattened. They 

 vary in size from that of a peachstone to masses two feet 

 across, and occur packed with bluish shale in a layer from two 

 to twelve inches thick. Below the shale there is generally a 

 dark gray bituminous fetid sandstone which sometimes 

 replaces the shale. 



Estimated thickness in Middle Tennessee from 50 to 70 feet. 



Nashville Group — (^Hudson River Group). — -The Nashville forma- 

 tion consists of bluish siliceous calcai'eous shales with beds of 

 dark blue, highly fossil iferous, roughly bedded, impure lime- 

 stones. The Orthis or lowest member of the group consists of 

 blue siliceous and sandy limestones weathering into fine, thin 

 earthy yellowish sandstones and shales. The upper beds 

 weather into thin flaggy beds, the surfaces of which are often 

 crowded with fossils. 



JEstimated thickness in Middle Tennessee about 500 feet. 



Trenton. — The Trenton formation in Middle Tennessee is inti- 

 mately connected with the Nashville series of the Basin and 

 consists mostly of limestones of a light blue or dove colour, 

 sometimes grey, arranged in groups of alternately thick and 

 thin bedding — the thick bedding mostly cherty ; the lower or 

 "Central Limestone" being much more so than the upper 

 beds. 



Estimated thickness in Middle Tennessee about 500 feet. 



The Trenton formation I'eaches the bottom of the Basin — the 

 Central ^Limestone being the lowest bed exposed anywhere 

 throusfhout the Basin. 



