CLASSIFICATION OF THE MISSISSIPPIAN SERIES 305 



A name applied to a historical epoch of a geologic province, 

 is applicable as a stratigraphic name to all the strata deposited 

 during that epoch. It may not alwa}^ be possible to draw a 

 sharp and fixed line in the stratigraphic series between two suc- 

 ceeding epochs, so that everywhere, throughout the geologic 

 province the exact limits of the historical epochs may be pointed 

 out. It is not necessary, for the establishment of an epoch 

 name, to select, as the type, a section in which every strati- 

 graphic and faunal phase of the epoch is illustrated. As a mat- 

 ter of fact it would be almost impossible to find a type section 

 for most geologic epochs in which all its varied phases were 

 exhibited. It is only necessary, in the selection of a geographic 

 name for a geologic epoch, that some one or more phases of 

 strata and fauna be well illustrated there. 



In recent years, two classifications of the Mississippian series 

 have been proposed. The first by Williams 1 is a natural faunal 

 classification, while the second by Keyes 2 is a stratigraphic clas- 

 sification which is nothing more than a further elaboration of 

 Hall's earlier one, uniting some of his divisions and dividing 

 others. 



Williams was the first to recognize in the strata and fossil 

 faunas of the Mississippian series, the evidence of three distinct 

 chapters in the history of the continental interior during lower 

 Carboniferous time, and for these chapters or epochs he used the 

 names (1) Chouteau, (2) Osage, and (3) Ste. Genevieve. The 

 commonly recognized local geologic formations were placed, as 

 accurately as was possible at that time, in their respective epochs, 

 and further investigation seems to necessitate no different dis- 

 position of them. Of the three epoch names proposed, Osage 

 and Ste. Genevieve were used for the first time. Chouteau, on 

 the other hand, had long been used as a formation name for one 

 of the local limestone strata in Missouri. The Chouteau group 

 was made by Williams to include, beside the Chouteau limestone, 



^ull. U. S. G. S., No. 80, p. 169. 



2 Bull. Geol. Surv. A., Vol. Ill, p. 283; Iowa Geol. Surv., I, p. 50; and Mis- 

 souri Geol. Surv., IV, p. 76. 



