RemavTtS on the Trenton Limestone of Kentucky. 145 



fertile countiy. The cuts become few and insignificant, but an atten- 

 tive stuc\y of the lower third of the deeper ones, and the entire section 

 of others, seems to prove what has already been so well indicated by 

 the topography, that we are gradually approaching a very different for- 

 mation. Instead of the continued alternation of thin-bedded lime- 

 stones and shales, the latter become insignificant in ratio to the for- 

 mer, and we finally reach the heav3^-bedded limestones of the Trenton 

 Group, which first appear in considerable force at , the Lexington 

 quarries, eighty miles south of Cincinnati. 



The lower strata here exposed begin to exhibit the light color, and 

 more compact texture, which are so characteristic of the Trenton lime- 

 stones further south at High Bridge. Bej'ondNicholasville, and within 

 three or four miles of the Kentuck}^ river, outcrops of these light- 

 colored limestones, somewhat shal}^ and chert}^ at top, begin to appear. 

 These rocks have but little dip, and as the elevation at Section 11, 

 C.S.R.R., three fourths of a mile north ofNicholasville, is 957 feet above 

 tide-water, or 525 feet above low-water of the Ohio, and the top chord 

 of High Bridge, 765.7 feet above tide-water, or 333.7 feet above low- 

 water of the Ohio, we have a vertical section of these rocks 191.3 feet 

 in thickness, between Nicholasville and the top of the Kentuck}^ river 

 gorge, which furnishes an additional section of nearly 300 feet, making 

 in all an exposure of nearly 500 feet of rocks, none of which, I am 

 quite satisfied, is higher than t3^pical Trenton. These rocks present 

 much the same variation that thej^ do at points where I have studied 

 them in Tennessee, though no section that I have seen in the latter 

 State, reaches appoint so low in the series as the bottom of the gorge of 

 Kentuck}' river, or the lower part of Dix river. 



In this connection it seems desirable to consider the section of the 

 Trenton Limestones of Tennessee, as arranged by Prof. Saflbrd in his 

 excellent geology of that State. These divisions have local names, 

 but they represent well-marked sections of the Trenton as there ex- 

 hibited, and may be indicated, in part at least, by their equivalents in 

 the Kentucky section now under consideration. The}^ are, in descend- - 

 ing order, as follows : Carter's Creek Limestone — A heavy-bedded, 

 light-blue or dove-colored limestone, often gray in the upper part. 

 Thickness from 50 to 100 feet. The Glade Limestone — A stratum of 

 thin-bedded, light-blue, flaggy limestones, marked by the '' Cedar 

 Glades." Thickness at maximum 120 feet. The Ridley Limestone— 

 A group of heavy-bedded, light-blue or dove-colored limestones. Maxi- 

 mum thickness 95 feet, as observed by Prof Safi'ord. The Pierce 

 Limestone — A group of thin-bedded, flaggy limestones, with a heavy- 



