NO. 12 



SMITHSONIAN EXPLORATIONS, I917 



'■Z 



types of sediment, and the phenomenon of fossil coral reefs for 

 which the exhibit was primarily planned. 



The most valuable resvilt of the summer's work was achieved at 

 Elkins, Kentucky. Here a single limestone slab, six feet long and 

 several feet wide and thick, showing an unconformitv distinct enough 

 to be appreciated by the layman, was quarried out and shipped to the 

 Museum without breakage, where it now forms a most instructive 



Fig. 22. — Unconffirmity lietween Juirly Pjlack River limestone (while) and 

 Early Trenton strata (dark) at I'dkins. Ky. rhoto,L;ra])h by Bassk-r. 



exhibit. .\s shown in figure _'-'. the (itUcrojJping limestone ledge, sev- 

 eral feet in thicl-;nc-ss. i> C()nip(i>ed of a distinctly while lower jiorlion 

 and a dark-colored upper part, tbe bead of the hammer marl^iIlg their 

 line of contact. Tliis bne ;dso marks an tnuisualK' cU'ai^ tiiicon lormil}'. 

 Both of these layers are riib i)) fossil--, ibose of k.arK I'.lac-k River 

 CLowville) age occurring in tbe lower white rock and tlio^e ot |'";irl\- 

 Trenton in the up])er dark material. .'~>ini-e at other places in tbe 

 I idled .Slates live lunidreil or more feet of strata of .Middle ;ind 

 Lale lilack River age intervene belweeii tbese two layers, il is shown 



