420 A. F. FOERSTE — LIMESTONES OF TENNESSEE AND KENTUCKY 



The only Silurian formation which varies considerabl}^, litholo2;ically, 

 is the Osgood bed. This changes from an impure limestone to a clay 

 shale on approaching the northeastern part of the area under investiga- 

 tion. In central Kentucky it appears as a clay bed both west and east 

 of the anticline, the thickest exposures being east of the same. If this 

 is due to the presence of the anticline in Osgood times, the evidence is 

 not clear. Studies of the Osgood bed in central Kentuck}^ (not yet pub- 

 lished) indicate that the Osgood formation once extended entirely across 

 the fold in that area. 



Professor Sufford's observations. — Since the area under investigation 

 in Tennessee was studied by Professor Safford during man}^ years and 

 he never seems to have changed his opinions from those first expressed 

 in his Geology of Tennessee (1869), the few references in his book to 

 the problem of the Cincinnati anticline are here quoted : * 



"By far the most important elevation of the strata in middle Tennessee was the 

 wide dome, the decapitation and denudation of which have given us the Central 

 basin. 



"This dome-like elevation of middle Tennessee is sometimes associated with a 

 similar elevation of strata further north, within an area divided among the states 

 of Kentucky, Ohio, and Indiana. The city of Cincinnati is about the center of 

 this area. The elevation in Tennessee and that in the Cincinnati area doubtless 

 occurred at the same time, and are perhaps parts of a single line or axis of eleva- 

 tion extendinj^ from Tennessee to Ohio. The elevation, however, was greater in 

 the Cincinnati and Tennessee parts than in the intermediate portion. This line of 

 elevation is sometimes called the Cincinnati axis. 



"Along the eastern escarpment of the Central basin, from the Kentucky nearly 

 to the Alabama line, the Black shale rests on the Nashville formation, without 

 any intervening rock. 



" On the vi'estern escarpment this is also the case at a few points, but generally 

 a Niagara bed has appeared to separate the two, bearing above it here and there 

 a trace of the Lower Helderberg. The Niagara and Helderberg strata are uncon- 

 formable to the Nashville, and never covered the dome of the basin." 



Professor Safford was of the opinion that the Clinton did not occur 

 on the western side of the anticline. All of the Silurian formations 

 discussed in this paper were referred by him to the Niagara. His type 

 sections are found along the valley of the Tennessee river, in western 

 Tennessee, and since in that region the sponge Astrxospongia meniscus 

 occurs in considerable abundance in the equivalent of the I^ouisville 

 formation, he applied the name " Meniscus limestone '' to the entire 

 series. This will explain why the most eastern outcrops of Silurian 

 rocks west of the ai)ticline are referred by him to the Meniscus lime- 

 stone rather than to the " Dyestone group," Safford's name for the 



♦Pages 148 and 291. 



