LATE DEVONIC SEQUENCE OF THE IOWA REGION. 
(SYNOPSIS.) 
BY CHARLES KEYES. 
The great Devonic limestone succession in Iowa was long treated as 
if it were a single stratigraphic unit. To it the title Cedar Valley 
formation was generally attached. This vaguely defined term was 
suggested by D. D. Owen as early as 1852. Little or no attempt was 
seemingly ever made to differentiate this hundred-odd feet of limestone. 
Singularly enough the only efforts to separate the section into sub- 
ordinate terranes, based upon the lithologic differences and the pale- 
ontologic peculiarities and resemblances, have never been published. 
Twenty-five years ago, when yet a student at the State university, I 
made a very careful and complete determination of the vertical range 
and faunal elements of the various groups of organic remains, and as a 
result distinguished four principal subdivisions. These were easily and 
clearly contrasted by their contained faunas. The lines of demarkation 
wjetfe readily made out over half a dozen counties. Active work in other 
fields prevented giving the solution of the Cedar Valley problem its 
finishing touches. The subdivisions then determined were accepted by 
Professor Calvin and in his report on the geology of Johnson county 
they are distinctly recognized but no specific names appended, probably 
for reason of the fact that he considered the credit as properly belong- 
ing to another worker in the same field. 
For these subdivisions the names Solen, Rapid, Coralville and Lucas, 
from well-known localities in Johnson county, are now proposed. The 
Devonic section as originally made out for the neighborhood of Iowa 
City, and as given by Professor Calvin, is as follows: 
