The Stephanian of North America: Early 1900s controversies and problems

Abstract

The recognition of the Stephanian in North America was first made in the early 1900s by D. White and E. H. Sellards on the basis of plant megafossils. In the middle 1930s, their biostratigraphic conclusions were largely confirmed by W. C. Darrah and P. Bertrand (an expert on Stephanian floral biostratigraphy), who together refined the Appalachian correlations with the Westphalian D and Stephanian floras of France. W. J. Jongmans, in collaboration with W. Gothan, considered the Stephanian as a limnic facies that would be absent in the United States, where its time-equivalent in paralic and limno-paralic facies was identified by Jongmans as "Westphalian E." The latter would be characterized by the presence of Neuropteris ovata and Stephanian pecopterids. The range zone of Neuropteris ovata was equated with Westphalian D by H. Bode, who proposed the incorporation of the Stephanian into an expanded Westphalian D that he subdivided on the presence or absence of associated Stephanian megafloral elements. N. ovata ranges into the Dunkard, a unit assigned to lower Permian by D. White, W. C. Darrah, and other workers on the basis of the occurrence of Autunia (Callipteris) conferta and other Rotliegend megafloral taxa. Controversies in the literature (still partly unresolved) related to different species concepts, lack of examination of type specimens on both sides of the Atlantic, the phytogeographic distribution of late Carboniferous megafloral taxa in Europe and North America (Amerosinian Realm), the biostratigraphic significance of endemic species, the stratigraphic ranges of key megafloral elements, the role of biofacies, and the presence or absence of stratigraphic breaks and their relative importance in the Carboniferous successions in Europe as well as in North America. Jongmans's Westphalian E Stage has not been accepted because it is essentially a floral facies concept and not a chronostratigraphic unit.A historical analysis of work on the Carboniferous floras of North America, with particular regard to the Stephanian, is accompanied by a brief review of the problems attached to the type Stephanian of Europe, and a full discussion is presented of the views expressed by the European palaeobotanists who traveled to the United States.Acknowledgments for this chapter are on p. 388.

Cyclic changes in Pennsylvanian paleoclimate and effects on floristic dynamics in tropical Pangaea

“…These rare and unusual floras, rich in conifers and other xeromorphic plants, have been characterized as typical of the early Late Pennsylvanian (e.g., Wagner and Lyons, 1997), which they are not. Also contributing to this missing-time argument are some taxa typical of Late Pennsylvanian (Stephanian late A through C in particular) floras of Europe that are rare or missing in the American sections (Lyons and Wagner, 1995;Wagner and Lyons, 1997). Missing flora may just as likely be related to latitudinal and longitudinal variation in paleoclimate or to biogeographic factors, as it is to a stratigraphic hiatus.…”