2S8 C. R. KEYE5 — THE PRINCIPAL MISSISSIPPIAN SECTION. 



Among the earliest references to the rocks of this group in the conti- 

 nental interior is made in connection with Owen's explorations in south- 

 eastern Iowa.* This author called some sixty feet of ash-colored shales, 

 exposed above the level of the water in the Mississippi river to the base 

 of the encrinital limestone at Burlington, the " argillo-calcareous group," 

 and regarded them as belonging to the lower part of the Subcarboniferous. 

 These shales were actually a portion of the median member of what 

 Swallow,! in Missouri, termed the "Chemung" group. This group was 

 divided into (1) the Chouteau limestone, (2) the Vermicular sandstone 

 and shales, and (3) the Lithographic limestone. Within the limits of the 

 region under consideration these three divisions are quite persistent and 

 easily recognizable over a wide area. For present convenience the last 

 two members may be termed more appropriately the Hannibal shales 

 and the Louisiana limestone respectively, since at these places in eastern 

 Missouri they are exposed in their full development. 



Throughout Iowa, Illinois and Missouri, at least, and perhaps in other 

 states also, wherever the Kinderhook rocks are exposed, its members, as 

 here designated, will always be recognized to a greater or less extent, 

 particularly in faunal studies. Over all the three states named these 

 subdivisions are sharply defined lithologically, except possibly toward 

 the northern known limits, though there these rocks have received very 

 little or no attention. At the present time it seems very probable that 

 the third or lowest member — the Louisiana or Lithographic limestone — 

 will find a closer relationship with the Devonian than with the Carbon- 

 iferous, and that eventually it will he regarded as the capping stratum 

 of the former over all the territory contiguous to the Mississippi. 



In 1858 Hall still continued to regard the Burlington, Iowa, section 

 below the oolite layer as Chemung. But he also included in the group 

 some yellow sandstones occurring fifty miles to the northward, which 

 Calvin J has recently proved conclusively to be of Devonian age. 



Although Owen had referred the shales lying immediately below the 

 limestone at Burlington. Iowa, to the Subcarboniferous more than a 

 decade previously, Meek and Worthen,§ in 1861, were the first to prove 

 beyond a doubt that the faunas of the rocks along the Mississippi river 

 between Burlington and St. Louis and lying between the "black shale" 

 and the Burlington limestone have much closer affinities with those of 

 the overlying strata than with those below, and therefore that the rocks 

 in question properly belong to the lower Carboniferous series. The name 

 " Kinderhook " was then proposed for the formation. 



*Geol. Sur. Wisconsin, Iowa and Minnesota, 1852, p. 92. 



t A ii ii. Rep. Geol. sur. Missouri, 1855, p. 103. 



;.\m. Geo4., vol. iii, 1889, p. 25. 



f.Vni. .lour. Sri.. 2d series, vol. xxxii, p. 228. 



