LIMESTONES OE WESTERN TENNESSEE 557 



as a shaly clay horizon much farther southward than the Osgood 

 bed. It is typically developed along the Harpeth River near 

 Newsom. At this locality it contains a large part of the fauna 

 characteristic of this horizon at Waldron, Ind. In central and 

 southern Tennessee a thin bed of limestone, 6 to lo inches 

 thick, replaces the clay along the middle of the bed. 



2. Centreville, Riverside, and Iron City, Te?i?i. — At Centreville 

 the Devonian is represented, in descending order, by the phos- 

 phatic nodule layer, 4 inches thick ; the Chattanooga black 

 shale 45^ feet thick; and the Hardin sandstone, 8 inches thick. 

 It rests unconformably upon soft shaly clay, the equivalent of 

 the Waldron bed. The original thickness of the Waldron bed 

 at this locality is unknown ; at present the thickest section pre- 

 served beneath the Hardin sandstone is 2)4, feet thick. Twenty- 

 five feet are assigned to the Laurel bed. It is underlaid by 

 limestone, 4 feet thick, which weathers badly and forms a 

 transition between the more solid limestone' above and the softer, 

 more clayey limestone, 6 feet thick, beneath, which, stratigraph- 

 ically, appears to belong to the Osgood horizon. The upper 

 beds of the Clinton limestone are more solid and more or less 

 cherty. They contain Triplesia Ortoni. Along the railroad only 

 the upper part of the Clinton, 12^ feet thick, is exposed. 

 Ordovician limestone, probably the Leipers Creek bed, occurs 

 about 25 feet lower down. Since a part of the unexposed inter- 

 val is probably occupied by the Mannie clay,' the total thickness 

 of the Clinton at this locality cannot be determined. Across 



'In western Tennessee, west of the Central Basin, the following Ordovician beds 



named in descending order, have been recognized : 



f \ Mannie shale. 



I Richmond It- <- 1 i- ^ 



{ Leipers Creek limestone. 



Cincinnati 



nciuuau , , Warren limestone. 



Oroup 1 Lorraine \ ., r- ^ ^■ 



( bwan Creek limesi 



Swan Creek limestone. 

 Utica Absent in western Tennessee, 



f Trenton Saltillo limestone, belonging to lower part of Trenton. 



j Black River Absent in the Tennessee River valley. 



Trenton , , ^g^g limestone, belonging to the upper part of the 



I Stones River -| Stones River; exposed in central part of Wells Creek 

 (^ / basin ; identified by Safford as the Knox dolomite. 



The Cincinnati Group in Western Tennessee, between the Tennessee River and 

 the Central Basin. JoUR. Geol., January-February, 1903. 



