FLORAL PROVINCIALISM DURING THE LOWER MISSISSIPPIAN: EVIDENCE FROM THE BORDEN DELTA OF KENTUCKY AND INDIANA, U.S.A

Many authors are convinced the Early Mississippian was too soon after the Frasnian – Famennian event to support true floral provincialism, and the simple flora that did exist was globally cosmopolitan; however, some authors believe there were floral provinces present during this time (Sullivan, 1965, 1967, & Van der Zwan, 1981). Historically, the Lower Carboniferous strata of western Europe has been biostratigraphy zoned using palynomorphs, primarily miospores (Clayton et al., 1977 & Higgs et al., 1988), in which the 14 miospore biozones were assigned. These miospore biozones have been used to correlate many localities from western Europe to Gondwana. Of these biozones, parts of three are present in the Osagean and, in turn, should be present in Kentucky and Indiana. Very little work has been done to try to correlate equivalent Lower Mississippina strata in North America to the zonal sections in western Europe (Coleman and Clayton, 1987; Clayton et al, 1998). The Borden Delta in Kentucky and Indiana represents a clastic wedge that prograded across Kentucky and Indiana during the Early Mississippian (Osagean; Tournaisian). The boundaries between the members of the Borden Delta sediments are time-transgressive, making regional correlations difficult. No biostratigraphic framework exists for the entire Borden succession, due to the absence of a useful biostratigraphic fauna. Miospore occurrences were analyzed throughout the Borden Formation (Kentucky and Indiana) and compared to pre-existing Lower Mississippian palynofloral assemblages from other locations globally. The (pretiosus – clavata) PC Biozone, and the (claviger – macra) CM Biozone, are correlative with the miospore biozones of western Europe (Osagean; Tournaisian); however, the Visean palyno-assemblage in the study is completely different from other areas globally. The fact that this discrepancy exists within the palyno-assemblage provides a basis for floral provincialism during the earliest parts of the Carboniferous.