UPPER CRETACEOUS OF TENNESSEE 389 



THE RIPLEY FORMATION 



The Ripley formation has the greatest areal distribution of any 

 of the Upper Cretaceous formations in Tennessee. It is extensively 

 developed both in the northern and southern part of the state. 

 It outcrops in a broad belt in general along the Tennessee- 

 Mississippi divide, a hilly and sandy area with little fertihty 

 or agricultural productiveness. In certain localities this forma- 

 tion is highly fossiliferous and contains an abundance of 

 beautifully preserved animal and plant remains, but these 

 are rather exceptional, for the Ripley of Tennessee is made up 

 largely of non-fossiliferous sands and clays. In the southern 

 part of the state the Ripley formation has been segregated 

 into the following lithologic and faunal members or horizons: 

 Owl Creek horizon or member; McNairy sand member; ferruginous 

 clay horizon or member ; Coon Creek horizon or member. In the 

 central and northern parts of the state the Owl Creek member and 

 the ferruginous clay member lose their identity and become a part 

 of the McNairy sand member which constitutes by far the major 

 portion of the Tennessee Ripley. 



The Coon Creek horizon or member in the northern part of the 

 state consists of ferruginous sands with few or no fossils, but in the 

 southern part of the state it is glauconitic and fossiliferous. In 

 some localities it contains beds of sandy marl which have yielded 

 a very large fauna of beautiful and unusually well-preserved marine 

 fossils. An announcement of the discovery of these fossils and a 

 somewhat detailed description of the Coon Creek locality together 

 with some preliminary observations on the fauna were published 

 in the March, 191 7, number of the Johns Hopkins University 

 Circular. Figures and plates of this fauna of about three hundred 

 and fifty species are now being made for a monograph report by 

 the author to be published by the United States Geological Survey. 



The occurrence of so many well-preserved shells in deposits 

 as old as the Cretaceous is uncommon. No other single locality 

 in the American Cretaceous, that has yet been studied, has produced 

 so large an assemblage of such excellent fossils, which even rival 

 best Cretaceous collections from any of the well-known European 

 or Indian localities. Some of the well-known Cretaceous localities 



