KeoJiiiJc (rr(n(p^ Mhi<:imppiYalh'y . — Beachler. <S9 
James Hall, 1858, Geological Survey Iowa, volume i, in arranging the 
sub-Carboniferous rocks of Iowa, places the Cherty and Archimedes 
limestone as two distinct beds under the division Keolnklimestone, which 
term he uses instead of Owen's name Archimedes limestone, dropping 
the term Shell beds; the Geode bed is made a transition bed, and the 
Magnesian limestone is termed the W((rsaw limes.tone and placed imder 
that division. 
Warsaw limestone. 
Geode B^d. 
(Keokuk) 
1858. Keokuk limestone. 
Hall. Cherty limestone. 
A. H. Wortheu, 1866, Geological Survey of Illinois, volume r, unites the 
whole section of Owen and Hall under the name Keokuk Group, with 
the exception of the Magnesian or Warsaw limestone, which he seems to 
consider as a division of the Saint Louis, as seen by his referring the 
equivalents of the Iowa Magnesian limestone, in Indiana at Blooming- 
ton and Spurgeou Hill to the St. Louis group. 
Warsaw Limestone. 
Keokuk Group. [ Geode bed. 
Worthen. ■{ Keokuk limestone proper. 
1866. 1 Cherty limestone. 
Charles A. White, 1870, Geological Report of Iowa, volume i, uses 
Hall's names and divisions. 
Synonym — Silicic >us Group. 
James M. Safford, 1869, Geology of Tennessee, proposes the name 
Silicioiis Group for rocks of the age of the "Highlands" of Middle Ten- 
nessee, and refers the 
Upper Silicious to the W((rs(iw <iiid St. Lou in. 
Lower Silicious to the Keokuk. 
Geology. 
The rocks of the Keokuk group occur in broad belts on both 
the eastern and western borders of the great Illinois coal field; in 
Indiana and Kentucky on the eastern border, extending into 
Tennessee and Alabama, and in Illinois and Iowa on the western 
border extending into Missouri. 
On the western border in Illinois and Iowa, where typical lo- 
calities are found, the rocks are exclusively of a calcareous char- 
acter attaining a maximum thickness of at least two hundred 
feet; in Missouri the uppermost member of the group, the Mag- 
nesian limestone, forms the principal representative and has un- 
dergone great local disturbances in the central part of the state. 
On the eastern border in Indiana and Kentucky the rocks occur 
as alternating beds of argillaceous sandstone, limestone and shale, 
thinning out toward the east and pass downwards into the Knol)- 
