SILURIC FORMATIONS IN MISSOURI 
131 
SERIAL AFFINITIES OF SILURIC FORMATIONS IN 
NORTHEASTERN MISSOURI 
By Charlds Keyes and R. R. Rowley 
In several respects the Siluric succession in northeastern Mis¬ 
souri is one of the most instructive geological sections within the 
limits of that state. Owing to unusual diastrophic conditions this 
section occurs in a part of the Mississippi valley where it is 
wholly unexpected. Although so meagerly displayed as to be all 
comprised within the space of scarcely a score of feet it represents 
by deposition and by interval more than two-thirds of the entire 
Siluric period. ^ It is divided medially by two marked planes 
of unconformity. There is, as we know, an overlapping of a 
southern, earlier Siluric deposition by northern, later Siluric for¬ 
mations. In their bearing upon the general stratigraphy of the 
state some of these facts have a far-reacing significance. 
In the limited section appear to be represented three great rock- 
series, here so attenuated' that they have not only been long neg¬ 
lected, but their essential features have been wholly misinterpreted. 
The relationships of the several beds recently disclosed by the 
sections furnish for the first time clue to the solution of a number 
of important stratigraphical problems. The testimony of the 
fossils is in strict accordance with facts established by a critical 
consideration of the stratigraphy. 
Furthermore, no more illuminating example exists emphasizing 
the urgent need of directly applying the broader paleogeographical 
principles to the solution of local problems in stratigraphy than 
that presented by the recent attempt to delimit sundry taxonomic 
groups of terranes in this part of the continental interior. 
In northeastern Missouri the older Paleozoic rocks are brought 
to the surface through means of profound displacement to the 
south of the chief Siluric outcrops. Stratigraphically the cities 
of St. Louis and Keokuk are on the same level. At both points 
the uppermost parts of the Paleozoic section are the surface 
