418 A. F. FOERSTE LIMESTONES OF TENNESSEE AND KENTUCKY 



In other words, the facts so far accumulated indicate that the thinning 

 of the various subdivisions of the Silurian is not due to lack of deposi- 

 tion, but to subsequent erosion. They suggest that these subdivisions 

 once extended much farther up the western flank of the anticline. A 

 similar series of observations in central Kentucky indicates that the cor- 

 responding formations once extended also much farther up on the eastern 

 flank of the anticline. In central Tennessee there is no evidence to show 

 whether these subdivisions once extended entirely across the axis of the 

 anticline, but in Kentucky and northern Tennessee there are some rea- 

 sons for believing that at least the lower subdivisions — the Clinton and 

 the Osgood beds — once were continuous across the axis of the fold. 



The Cincinnati anticline was certainly fairly developed at the time of 

 deposition of the so-called Corniferous limestone of Kentucky, and of 

 the Pegram bed in Tennessee. Facts so far accumulated in Tennessee 

 do not demand the existence of this anticline in Silurian times before 

 the close of the deposition of the Louisville limestone. The anticline 

 may have existed during Silurian times, but the proof has not yet been 

 secured. 



Since the elevations of all of the localities are not known, the sections 

 of figure 5 are so drawn that the horizon at the base of the Black shale 

 forms a horizontal line. It is believed that this will give a better idea 

 of the character of the Silurian sections in times immediately preced- 

 ing the deposition of the Black shale than would be given by any other 

 method possible with the data at hand. 



Siliu'ian overlaid by other SUarian beds. — The facts given in the preced- 

 ing pages indicate that the absence of the Clinton limestone in the region 

 immediately west of Lafayette is due to pre-Devonian erosion. The rapid 

 thinning of this limestone on passing from Whites Bend to Lafayette 

 (figure 3), however, suggests that not far east of Lafayette there may 

 have been a region where the Clinton was never deposited. Since an 

 area northeast of Lafayette would lie along the axis of the Cincinnati 

 anticline, this is equivalent to stating that the Clinton may never have 

 been deposited over a part of the Cincinnati anticline. This at once 

 raises the question whether the Cincinnati anticline had begun its devel- 

 opment in early Silurian times, and therefore was already sufficiently 

 developed in the Clinton period to prevent the deposition of the Clinton 

 limestone. Various writers have held this view, their data being derived 

 chietiy from more northern regions. In Tennessee the only instance of 

 thinning of the Clinton limestone toward the anticline is that just men- 

 tioned. Present observations indicate a fair degree of uniformity in the 

 thickness of this limestone in the more southern part of the area so far 

 examined, south of Whites Bend, as far as Maury county. 



