Hijpley Island Area of Southern Indiana. 323 



Ohio, Cayugan formations extend from the western Put in Bay 

 islands in the western part of Lake Erie into Lewis county in 

 northern Kentucky, crossing the Ohio river at Vanceburg, Ky. 

 In Indiana, Cayugan strata are known only from Kokomo, 

 although their occurrence in northeastern Indiana has been con- 

 sidered probable. 



In Indiana, the Niagaran has been divided into the following 

 subdivisions, named in descending order : Louisville, lime- 

 stone ; TValdron, clay; Laurel, limestone; Osgood, clay and 

 limestone ; Clinton, limestone. 



Pre-Meso-Devonic origin of the Cincinnati Geanticline. 



Along the western flank of the geanticline, in Kentucky and 

 Tennessee, the edges of these subdivisions of the Niagaran, 

 where not covered by overlying subdivisions of the same Nia- 

 garan series, thin out eastward toward the Ordovician axis,* 

 and are overlaid un conform ably by Middle Devonian limestones 

 or by Devonian black shale. Along the eastern flank of the 

 geanticline, in Kentucky, the uncovered edges of Silurian for- 

 mations equivalent to the Clinton and Osgood beds thin out in 

 a similar manner westward toward the same Ordovician axis 

 and are also overlaid uncomformably by Middle Devonian 

 limestones or by Devonian black shale. No Silurian rocks 

 are exposed along the eastern margin of the Ordovician area in 

 Tennessee. However, their presence in the Sequatchie valley 

 indicates that Silurian strata exist also along the eastern flank 

 of the geanticline in Tennessee, but are concealed by the cover 

 formed by later strata. The character of the unconformity 

 between the Niagaran and Devonian formations places the origin 

 of the Cincinnati geanticline in times preceding the Middle 

 Devonian. 



Pre-Niagaran origin of Geanticline. 



Inconclusive nature of certain arguments advanced. — In 

 western Tennessee, Professor Safford and others thought they 

 could trace the upper Niagaran formations up the western flank 

 of the geanticline, farther eastward than the lower Niagaran for- 

 mations, the former overlapping the latter. From this they 

 concluded that the origin of the Cincinnati geanticline took 

 place in times preceding the deposition of the Kiagaran. 

 More recent investigations have not confirmed this overlapping 

 of the upper Xiagaran formations, so that this argument 

 becomes ineffective. Other writers have regarded the thinning 

 of the Silurian formations from the flanks toward the crest 

 of the geanticline as sufficient evidence of pre-Niagaran origin. 



* Silurian and Devonian limestones of Tennessee and Kentucky, Bull. Geol. 

 Soc. Am., xii, pp. 398, 422. The Cincinnati anticline in southern Kentucky, 

 Am. Geol. 1902, pi. 26 ; Am. Geol., 1903, pi. 20. . 



