KCKUL.l IOWA. 161 
of Its close association with clay and a very good coal bed is probably 
of value. Analyses show that it is practically free from magnesia and 
runs from 74 to 93 per cent in calcium carbonate. The following 
analysis, by Lundteigen, is representative. 
Analysis of Fifty-foot rock, Rathbun. 
Silica (Si0 2 ) 9. 90 
Alumina (A1 2 3 ) | .. ... 
Iron oxide ( Fe 2 3 ) / 
Magnesia ( MgO) , Trace. 
Lime carbonate (CaC0 3 ) 83. 37 
MISSO I RJAN FORMA TION. 
DISTRIBUTION. 
The southwestern portion of Iowa is underlain by the rocks of the 
Missourian formation or upper Coal Measures. In contrast with the 
lower Coal Measures or Des Moines formation, the Missourian includes 
considerably less sandstone and very little coal. The beds are mainly 
shales and limestones. The latter are almost entirely free from mag- 
nesia, are occasionally somewhat earthy, are usually free from chert, 
and are easily ground. They are accordingly well adapted to cement 
manufacture, and, indeed, the equivalent beds are now in use at lola. 
Kans. The individual members of the Missourian formation have not 
been mapped in Iowa, though they are discussed in the county reports. 
The most important limestone lies at the base of the formation, and 
its outcrop is accordingly indicated on the accompanying map by the 
eastern edge of the formation. This limestone, which is variously 
known as the Winterset, Earlham, and Bethany, is discussed in some 
idetail in the Madison County report. 
The Bethany limestone in Madison County includes four separate 
ledges occurring in the following order and thickness: Fusulina, 25 
feet; Winterset, 20 feet; Earlham, 21 feet; Fragmental, 10 feet. 
These ledges are separated by shale beds, usually 10 to 20 feet in thick- 
ness and in part calcareous. The rocks are quarried at various points, 
particular^ Earlham, Winterset, and Peru, and the same ledges have 
been recognized as far south as Decatur County, on the Missouri 
jboundary. 
COMPOSITION. 
Analyses of individual ledges at Peru, made by Lundteigen, show 
a lime content ranging from 60.50 to 83 per cent. A cement mixture 
made from them gave 75.50 per cent CaC0 3 . At Earlham the follow- 
ing section was measured by Mr. T. E. Savage, and an analysis of an 
average mixed sample of the stone was made in the laboratory of the 
Bull. 243—05 11 
