VARIATIONS IN DEPOSITIONAL ENVIRONMENT AND PALEOECOLOGY AMONG LIGNITES IN THE UPPER MISSISSIPPI EMBAYMENT

Lignite deposits in the upper Mississippi embayment range in age from Cretaceous to upper middle Eocene. All are reported in the literature to have been deposited as oxbow lake-fill. Beyond this generalization, variations in depositional environment that resulted in both different plant communities colonizing the mire and surrounding area, as well as differential preservation of the constituent plants. Both gymnosperm and angiosperm-dominated communities occur, each with a unique associated fungal community. The angiosperm-dominated community preserved in the Fancy Farm lignite contains the fewest fungal remains overall, however saprophytic forms are generally associated with telohuminite-rich horizons. The angiosperm-dominated community preserved in the Carlisle lignite contains abundant fungal remains associated with detrohuminite-rich horizons. The Weakly lignite contains the greatest abundance of gymnosperms and ferns. Both the Weakly and Carlisle lignite contain more evidence for standing fresh water than the Fancy Farm lignite. All three lignites are primarily telmatic, with little to no evidence for ombrotrophic mire development. There is evidence for seasonally ponded environments in the Carlisle lignite. Variations in lignite depositional environment appear to be tied to small-scale differences in both the amount of water reaching the mire and also the substrates the mires developed upon.