Palynological Correlation of Mississippian (Carboniferous) Stage Boundaries In the Midwest USA and Europe

The global recognition of the Mississippian and Pennsylvanian as subsystems of the Carboniferous has drawn attention to difficulties in correlation at a finer scale, especially at stage level. A miospore zonal scheme for the Carboniferous of Western Europe is well established but no comparable zonation exists in the USA. Latest Devonian / early Carboniferous miospore assemblages from Kentucky, West Virginia and Ohio can be tentatively assigned to the LN, VI, BP and PC miospore biozones of Western Europe. However, Kinderhookian, Osagean and Meramecian miospore assemblages from Illinois, Indiana, Missouri and Iowa in the Mississippi Valley region differ considerably in composition from assemblages of similar age in the Eastern USA and Europe. Many stratigraphically significant European miospore taxa are absent or occur later in the Mississippi Valley. For example, Lycospora pusilla first occurs slightly below the Tournaisian / Viséan boundary in Europe but is notably absent from Osagean / Meramecian assemblages in the Mississippi Valley, finally appearing in the Chesterian (late Viséan) at Coles Mill, Illinois. Miospore assemblages from the Chesterian more closely resemble European assemblages from a similar age. The Coles Mill assemblage contains Namurian taxa such as Tripartites vetustus and Crassispora maculosa and can be tentatatively assigned to the VF Miospore Biozone of Western Europe. Possible causes of the relatively low diversity of the Mississippi Valley assemblages include locally adverse palaeoecological conditions and limited palaegeographical distribution of many of the European parent plants. An alternative miospore zonation for the Carboniferous of the Mississippi Valley is presented and its correlation with the European scheme is discussed.