408 



INDEX TO THE STRATIGEAPHY OF NORTH AMERICA. 



:e age. 



In originally defining the Mississippian Williams "^^ discussed previous attempts at 

 correlation and proposed the following classification : 



Recent studies of the fossils, their original grouping into local faunas, and their association 

 in other parts of the province have led me to recognize three fairly well differentiated faunas 

 in the Mississippian series, the subdivisions of which are believed to be local and therefore very 

 unsatisfactory for purposes of correlation. 



The following table sets forth the proposed classification and nomenclature : 



structure scale. Time scale. 



Chester stage 1 



St. Louis stage [ Genevieve age. 



Warsaw stage. ... J 

 Keokuk stage. . . .\ 

 Burlington stage. .1 



Kinderhook staee f Chouteau limestone 



in 1 idinc '< Vermicular shale and sandstone. A Chouteau age. 



[Lithographic limestone J 



The Chouteau age is the age of the Chouteau group of Broadhead. The Osage age is the 

 age of the faima of the Burlington and Keokuk formations, which are locally distinguishable 

 but in the sections on the northwestern, western, and southwestern flanks of the Ozark uplift 

 are so blended that it seems impracticable in most cases to differentiate them. The name is 

 suggested by the fact that the Osage River drains the region in which this confusion of the two 

 faimas is clearly exhibited. The Genevieve age is the age of the faima of the Archimedes group 

 of Shumard. 



The name is suggested by the fact that Shiunard first called attention to the union of the 

 several formations in which the common fauna prevails in his description of the geology of 

 Ste. Genevieve County, Mo. The name he applied was Archimedes group, but this is not a 

 satisfactory name, and in the county of Ste. Genevieve and on the eastern and northeastern 

 margins of the Ozark uplift, above and below this county, are found the typical outcrops of the 

 individual formations included in the group. 



The term Mississippian is now generally used for the lower Carboniferous in 

 North American stratigraphy, but the definition of its limits and the classification 

 of its subdivisions have been subjects of continued research and discussion. Cham- 

 berlin and Salisbury ^^^ give the following list of divisions in the Mississippian 

 province, together with those of other sections of the eastern interior: 



Subdivisions of Mississippian series. 



a Williams, Bull. U. S. Geol. Survey, No. 80, p. 169. St. Genevieve was the term applied by Williams to the 

 upper part of the Mississippi system. 



b Prosser, Jour. Geology, vol. 9, p. 215; vol. 11, p. 520. See also Am. Geologist, vol. 34, p. 335. 



" Pennsylvania Repts. and folios of U. S. Geol. Survey. 



<* O'Harra, Maryland Geol. Survey, Allegany County, pp. 109-113. 



« The Greenbrier is absent in eastern Pennsylvania. It comes in as a lentil of limestone farther west, and thickens 

 southward, becoming an important formation in Virginia, largely replacing the Mauch Chunk shale. See Brownsville- 

 Connellsville folio, U. S. Geol. Survey (Campbell). 



