THE MISSISSIPPIAN PERIOD 597 



The following subdivisions of the Mississippian system are 

 recognized in the regions indicated: 



Mississippi River States Pennsylvania 



4. Chester (or Kaskaskia) series (including the 



Cypress sandstone below, and the Chester 



beds above). 2. Mauch Chunk 



3. St. Louis series (including Salem limestone 



below and the St. Louis and Ste. Gene vie ve 



limestones above). 

 2. Osage or Augusta (including the Burlington 



limestone, Keokuk limestone, and Warsaw 1. Pocono 



shale) 

 1. Kinder-hook (or Chouteau) 



East of the Great Plains 



The Kinderhook stage. In the early part of the Mississippian 

 period, coarse sediments (sands and gravels, now a part of the 

 Pocono formation) were gathering along the western border of 

 Appalachia. At the same time, the area of Southern Michigan 

 was a sort of bay or enclosed sea into which sediment was washed 

 Vom the surrounding lands. In the central part of the Mississippi 

 basin, the sediments of this stage (Kinderhook) were partly clastic 

 and partly calcareous, and the variations were not only from place 

 to place at the same time, but from time to time in the same place. 

 Of these formations most are marine, but the Pocono has yielded 

 many fossils of land and plants. 



The Osage stage. In the second (Osage or Augusta) stage of the 

 period, the sea of the interior became clearer, and the deposition 

 of purer limestone was in progress. Submergence extended west- 

 ward, probably to New Mexico on the one hand and to Montana 

 on the other. The similarity between the fossils of the Mississippi 

 basin at this stage, and those of the corresponding strata of Europe, 

 is thought to indicate some available route of travel for marine 

 species (especially crinoids) between these widely separated 

 regions. Shallow water, and the absence of great variations of 

 temperature are probably the only conditions necessary for such 

 migration as the faunas of these widely separated regions imply. 



The rich deposits of zinc ore (with some lead) in southwestern 

 Missouri and eastern Kansas are chiefly in the Osage beds, though 

 the metallic compounds were concentrated into ores at a much 

 later time. 



