280 TRANSACTIONS OF THE [mAR. 15, 



Stratigraphy of the Typical Mississippian Section. 



The typical Mississippian section, as developed in Iowa, 

 Missouri and Illinois, will here be treated after the same manner 

 in which the Batesville section has been discussed, in order that 

 a comparison of the two sections ma^' be made. 



1. At the base of the Mississippian series in Missouri there is 

 often present a stratum of sandstone containing numerous small 

 ferruginous pebbles or concretionary masses, similar to those in 

 the Sylamore Sandstone. This bed is well exhibited on the 

 Mississippi River, near Sulphur Springs, Mo., and also in the 

 southwestern part of the State, near Springfield. The thickness 

 of the stratum has never been observed to be more than one 

 foot and is often altogether absent. 



2. Kinderhook Groiqj. — In its typical outcrops in Illinois, 

 Missouri and Iowa this group is three-fold in its development, 

 a limestone member below and another above, with an inter- 

 mediate series of shales and sandstone. In southern Missouri, 

 near the shore-line of the ancient Ozark Island, this three-fold 

 development is well marked, but southward from this shore- 

 line the intermediate sandy and shaly member thins out and 

 disappears, leaving tlie Kinderhook beds to consist wholly of 

 a limestone, formation. This calcareous development of the 

 Kinderhook is well seen in Christian count}', Missouri. At one 

 locality south of St. Louis the Kinderhook beds have tlie red 

 color of the St. Joe Marble. The Kinderhook group attains an 

 average thickness of about one hundred feet. 



3. Osage Group* — This is one of the most conspicuous mem- 

 bers of the Mississippian series. It consists largely of a very 

 pure, light-colored, crj'stalline limestone almost entirely com- 

 posed of crinoidal fragments. Included in the limestone are 

 interstratified beds and concretionary masses of chert. The en- 

 tire formation attains a thickness of from two hundred to three 

 hundred feet. 



♦Some confusion has been introduced into the nomenclature of the ISIississippian 

 formations in the adoption, by thts Geological Surveys of Iowa and Missouri, of the 

 term Augusta in place of Osage, for this series of strata. The name Osage was first 

 proposed by Williams in 1891 (Bull. U. S. Geol. Surv. No. 80, p. 409) to include the Bur- 

 lington and Keokuk groups of earlier authors. In 1892 Keyes (Bull. Geol. Soc. Am , 

 Vol. 3. p. 298) adopted the same name, giving It the same significance, but in 1893 he 

 proposed the name Augusta (Iowa Geol. Surv., Vol. 1, p. .59) for the same series of 

 strata. At the time of the proposal of the name Augusta it was recognized by its author 

 as synonymous with Williams' term Osage ; the only excuse oflered for the adoption 

 of the new name was that at the localities on the Osage River, from which the name 

 Osage was derived, only a portion of the whole series of strata are present, while at 

 Augusta, la., a more complete section is exposed. This is, of course, an invalid reason 

 for the introduction of such a synonym into geologic nomenclature. Otlier series of 

 geologic strata have been named from localities where only a portion of the whole 

 series is exposed. The Chemung group is a well established division in the New York 

 series, yet at the typical locality. Chemung Narrows, only a small portion ot the whole 

 formation is exposed. Other instances of the same kind could be mentioned, but 

 this is enough to show that such a precedent has been established. 



