Part III. Stratigraphy: Introduction
The fourfold subdivision of the Mississippian system—Kinderhook, Osage, Meramec, Chester—has come to be generally regarded as the standard since the early usage of Ulrich (1904, p. 90–113). Although various amendments and arguments have been proposed in the past, this classification is adhered to in this writing. The importance of certain questions bearing upon the classification of the rocks of the system into “series” or “groups” is recognized, but until convincing evidence bearing upon controversial points is procured no amendment seems justified.
“Lower Mississippian” rocks as here conceived are those which were deposited during the first part of the Mississippian period up to the beginning of the Meramec epoch. As such they are the formations laid down within the span of Kinderhook and Osage divisions of the standard Mississippian time scale. The controversial Warsaw unit is regarded as the uppermost subdivision of the Osage, supporting the classification of Keyes (1892), Chamberlin and Salisbury (1906), Weller (1914), Cumings (1922), Moore (1928 Moore (1935), Wanless (1929), Stockdale (1931a), Giles (1935), and others. All the rocks thus conceived, except the Warsaw, fall within Ulrich’s “Waverlyan” (Ulrich, 1911, p. 582, pl. 29) and the lower half of Weller’s “Iowan series” (Weller, 1920, p. 282). The immediately overlying rocks regarded as of Meramec age include the Salem, St. Louis, and the controversial Ste. Genevieve formations. In this report the expression “lower Mississippian rocks” is used merely for convenience without intention of arguing for a standard two-fold major subdivision of the Mississippian system or . . .