Miospore biostratigraphy of the Lower Mississippian clastics of the Michigan Basin, USA

Two moderately diverse, moderately abundant miospore assemblages are recorded from the Lower Mississippian Coldwater Shale and Marshall Sandstone of the Michigan Basin. The microfloral assemblage from the older Coldwater Shale is similar to assemblages of the Spelaeotriletes balteatus-Rugospora polyptycha Biozone of western Europe. This biozone is generally absent from North America. The overlying Marshall Sandstone has a miospore assemblage representative of the oldest Osagean Spelaeotriletes pretiosus-Raistrickia clavata Biozone of western Europe. Identification of these assemblages indicates the presence of the Kinderhookian-Osagean boundary within or between the two clastic units. The identification of this boundary has important stratigraphical and sedimentological implications for age relations with Lower Mississippian rocks in adjacent basins and also provides information on regional sedimentology and depositional patterns.