LIMESTONES OF WESTERN TENNESSEE 555 



H. The Age of the Cincinnati Geanticline. 



15. As determined by observations in Tennessee. 



16. As determined by observations in Ohio, Indiana, and Kentucky. 



I, Localities Mentioned in this Paper. 

 J. Lists of Fossils. 



Clinton fossils. 



Waldron fossils. 



Brownsport fossils. 



Linden (Helderbergian) fossils. 



A. SILURIAN strata ALONG THE WESTERN FLANK OF THE 

 CINCINNATI GEANTICLINE. 



I. In southern hidiana, Kentucky, and northerti Tefmessee. — In 

 southern Indiana' the Silurian strata are divided into the follow- 

 ing beds, named in descending order : 



Louisville limestone. 

 Waldron shaly clay. 

 Laurel limestone, 

 Osgood shaly clay. 

 Clinton limestone. 



Southward, along the western flank of the Cincinnati geanti- 

 cline, the equivalents of these beds may be traced with varying 

 success even as far as northern Alabama. 



The ease with which any beds may be traced for long dis- 

 tances depends greatly, of course, upon the constancy of their 

 lithologic features. In this respect the subdivisionsof the Silurian 

 along the western flank of the Cincinnati geanticline are remark- 

 able. Very little change is shown in the lithological character- 

 istics of any of these subdivisions between southern Indiana and 

 northern Tennessee. North and south of this area, however, the 

 Osgood bed rapidly becomes more calcareous and is changed 

 from a shaly clay to a soft limestone, weathering more readily 

 than the Clinton limestone below or the Laurel limestone above. 

 The Waldron bed also becomes calcareous northward, and is 

 replaced by limestone in central Indiana. Southward it may be 

 traced as far as northern Alabama, but in central and southern 

 Tennessee it is only 3 to 4 feet thick, and along the middle part 



"^ Twenty -first ■iXiA Twenty-seco7id Annual Reports of the I^tdiana Survey, iov the 

 years 1896, 1897. 



