LIMESTONES OE WESTERN TENNESSEE 565 



accomplished the stratigraphy of the Silurian at this locality 

 must remain more or less in doubt. 



Along the western flank of the Cincinnati anticline, the 

 Osgood bed is reduced to a thickness of 3 or 4 feet. This is 

 shown by the exposures at Riverside and Iron City. With the 

 exception of the exposures in the immediate vicinity of Clifton, 

 the thickness of the Osgood bed is small also along the Ten- 

 nessee River in southern Tennessee. At the base of the Silurian 

 section at Swallow Bluff, Maddox mill, ana W. D. Helton, also 

 at New Era and Kelley Landing, there is a considerable section 

 of limestone, usually whitish in color, massive at the base, and 

 more distinctly bedded near the top. This limestone occurs 

 below the beds referred to the Osgood horizon. It thins out at 

 Glenkirk and Clifton. It apparently thins out also from the W. 

 D. Helton locality toward Riverside and Iron City. The base of 

 the section, at least, is equivalent to the Clinton. The top may 

 belong to the Osgood horizon. The position of the intermediate 

 part is doubtful. It is evident that the plane of division between 

 the Clinton and the Osgood beds is rising southward and that 

 the lithological divisions here do not correspond strictly to 

 those farther north and northeast. For the present the name 

 Maddox limestone may prove convenient for the massive lime- 

 stone in question. 



II. LEGO AND DIXON BEDS. 



4. Nomenclature. — Along the western flank of the Cincinnati 

 geanticline, in southern Indiana, Kentucky, and Tennessee, the 

 name Louisville bed has been given to the Silurian rocks overlying 

 the Waldron bed. In the Tennessee River valley, in western 

 Tennessee, the Silurian section overlying the Waldron bed is so 

 thick that it has been found necessary to subdivide it. 



At the base is a series of limestones, varying from 30 to 45 

 feet in thickness, to which the name Lego li?nesto?ie is here given. 

 Stratigraphically, this bed occupies the same position as the 

 Louisville bed. Its paleontological equivalence, however, has 

 not yet been determined, owing to the small number of fossils 

 so far obtained in the Lego limestone. Overlying the Lego 

 limestone is a series of red clays, 30 to 45 feet thick, to which 



