ABSTRACT

Megaspores and unidentified plant fragments have been recovered from two thin (0.5 m - 1.5 m) zones within carbonates of the Frobisher-Alida interval of the Mississippian Mission Canyon Formation. This flora was found during a study of the Wiley Field, southwestern Bottineau County, North Dakota. At least five new forms of megaspores were found, and are believed to represent previously undescribed genera and species of arborescent lycopods. Arborescent lycopods are typically associated with fresh-water environments. The remarkable preservation, low diversity, and apparent areally restricted concentration of megaspores indicate growth at or near the place of deposition. This may provide evidence for local subaerial exposure and fresh-water lens development. Preserved organic fragments were deposited in nearby topographic lows. Organic plant and scolecodont material was preserved in an anoxic shallow water setting probably caused by saline brines. These brines dolomitized the sediments in which the organic material was preserved before significant compaction had occurred.