Abstract

Mississippian palynomorphs have been recovered from two successions of the Hannibal Shale in Missouri, U.S.A., which is the lowermost Carboniferous unit in the Mississippi Valley. The assemblages are dominated by acanthomorph acritarchs, with Micrhystridium stellatum being the principal species. The miospore assemblages are well-preserved and of low taxonomic diversity. They are dominated by long-ranging taxa that survived the latest Devonian mass extinction event. This assemblage closely resembles assemblages assigned to the Vallatisporites verrucosus-Retusotriletes incohatus (VI) Biozone of Western Europe. However the assemblage from the Mississippi Valley is relatively impoverished in comparison with European assemblages, and many key European zonal taxa are absent. Independent biostratigraphic correlation suggests that the Hannibal Shale is equivalent to the VIBiozone, the Cristatisporites hibernicus-Umbonatisporites distinctus (HD) Biozone, and possibly the lowermost part of the Spelaeotriletes balteatus-Rugospora polyptycha (BP) Biozone in Europe. This indicates the relatively condensed nature of the succession. Palynofacies analysis suggests a shelf to basin depositional environment for the Hannibal Shale; this is consistent with the paleogeographic location of this area during the Early Carboniferous.

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