PHYTODETRITUS AND PLANT REMAINS WITHIN THE EARLY MISSISSIPPIAN NORTHVIEW FORMATION, SOUTHWEST MISSOURI

Mississippian plant fossils in the Midwest are rare, although a few petrified logs have been found within the Osagean Reeds Spring Formation in Missouri. Early Mississippian plants, however, have not been reported for Missouri. Geologists at Missouri State University recently proposed that the Early Mississippian Northview Formation in southwest Missouri includes a deltaic lobe trending east-west within a structural depression called the “Northview Basin.” Basinal Northview is a thick shale at the base, coarsening upward into a sequence of coarse siltstone with thin shales cut by numerous channel fills.

Plant fragments (phytodetritus) are recognizable within thin sections from areas well south of the basin, and their concentration increases toward the basin center, their presumptive source area. The size and concentration of phytodetritus both increase upward within the lower shale, indicating progradation of proximal environments over more distal. The upper shales contain branching fragments of plant debris up to 3 cm long and small leafy fragments in some thin sections. The upper shales also include beds with concentrations of vertical carbonized rootlets and fragments of horizontal compression-impression plant axes and/or roots. Several larger pieces of possible sphenopsid and lycopsid remains have been found, but the preservation is too poor for definite identification.