Carboniferous.. 
Upper Ordovician. 
220 CEMENT MATERIALS AND INDUSTRY. [bull. 243. 
stones are therefore assured of cheap fuel and water and rail trans- 
portation to a number of important cement markets. 
The Missouri limestones which are best adapted for use as Portland- 
cement materials are of Mississippian and of Trenton (Ordovician or 
Lower Silurian) age. The Cambrian limestones, which cover nearly all 
of southeastern Missouri, are almost always too high in magnesia to 
be worth considering in this connection. The nonmagnesian Silurian 
limestones occurring along the Mississippi between Chester, 111., and 
Cape Girardeau, Mo., however, are worth investigation. 
The geologic relations of these limestones, and of the shales and 
clays which will be required for mixture with them, are indicated in 
the following table. This table shows the portion of the geologic 
column of Missouri that is of interest in this connection, the oldest 
rocks being those placed at the bottom. 
Portion of geologic column of Missouri. 
Quaternary Loess and surface clays. 
Upper Coal Measures Shales, sandstones, etc. 
Lower Coal Measures Coal beds, shales, etc. 
Mississippian Limestones, sandstones, and 
shales. 
Devonian Dark-colored shales. 
Silurian Magnesian limestones in part. 
Girardeau limestone Shale and sandstone. 
Thebes formation, or late Ordo- 
vician shale Shale and sandstone. 
Trenton Limestone. 
Lower Ordovician and Cambrian Magnesian limestones, sand- 
stone, etc. 
The formations listed above will now be described in order, from 
the Trenton upward, attention being paid mainly to the Trenton and 
Mississippian, which contain most of the nonmagnesian limestones 
occurring in the State. A detailed map showing the geology of north- 
eastern Missouri is given as PL IX. In the following descriptions 
attention will be paid chiefly to their distribution and composition 
of the formations in the area covered by this detailed map, for it is 
in this portion of Missouri, along or near Mississippi River, that 
the best prospects for a Portland-cement industry exist. Southeastern 
Missouri, as already noted, has practically no limestones lit for use 
as Portland-cement materials, except along the Mississippi River to 
Cape Girardeau. The western half of Missouri contains extensive 
areas of Mississippian limestones, but a cement plant located in that 
portion of the State would be brought into direct competition with the 
existing Kansas plants, which have the advantage of a cheap fuel — 
natural gas. 
