14 KENTUCKY GEOLOGICAL SURVEY. 



is more pronounced in the Richmond. Here the Ohio and In- 

 diana regions indicate regions very congenial to animal life, 

 while in Kentucky the faunas are comparatively meagre and 

 considerably different from those of the Ohio-Indiana area, in- 

 dicating differing zoological provinces, due to the different con- 

 ditions produced by the progressive shallowing of the bottom. 



Probably by the opening of Silurian times some parts of the 

 region had come to be a little above sea level. The Silurian for- 

 mations on the east and west of the Ordovician area show by 

 their differing lithological character that decided changes had 

 come. Probably later in Silurian time there came an uplift 

 which exposed the land generally to subaerial agencies of decay. 

 After these had been at work for an unknown period, there was 

 again a subsidence which permitted the laying down of Devon* 

 ian and even later sediments unconformably upon the eroded 

 surface of various Silurian and Ordovician formations. Whether 

 the whole island was submerged and received a new coating, or 

 only part of it, we can not know. All covering of the central 

 part, if such there was, has been removed by erosion. 



What vicissitudes beset the island in Carboniferous times, or 

 whether Carboniferous strata overspread the uplift, we can only 

 surmise. No evidence has yet been discovered from which we 

 can infer the conditions then prevailing. Since Carboniferous 

 times the area has been continuously above sea and subject to 

 aerial decay. That an enormous amount of material must have 

 been removed in the time that has elapsed since thati ancient 

 day is evident. As pointed out by Campbell, the region seems 

 to have been peneplaned in Cretaceous times, re-elevated, again 

 peneplaned in Eocene time, again elevated, and is now once more 

 undergoing the process of peneplanation. 



