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Vegetational patterns in the Springfield Coal (Middle Pennsylvanian, Illinois Basin): Comparison of miospore and coal-ball records

By
Debra A. Willard
Debra A. Willard
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Published:
January 01, 1993

Coal-ball peats and miospore floras were sampled quantitatively in profiles from the upper Middle Pennsylvanian Springfield Coal of the Illinois Basin. Coal profiles for miospore analysis were sampled at 13 sites, forming two transects across the Galatia paleochannel. Miospore assemblages near paleochannels differ from those near the coal margin. Near the Galatia paleochannel, four species of tree-fern spores (Laevigatosporites globosus, L. minimus, Punctatosporites minutus, Thymospora pseudothiessenii) share dominance throughout the profile, and Lycospora is subdominant. In profiles near the coal margin, T. pseudothiessenii dominates the lower three-fourths of the seam, and Laevigatosporites globosus dominates the upper one-fourth of the seam. Lycospora is at its most abundant in the lower one-fourth of the coal, and Anacanthotriletes spinosus is abundant in the middle of the seam.

Three coal-ball profiles were collected in conjunction with miospore profiles to compare species abundance in the two records. Lycopods are the dominant biovolume producers in coal-ball floras, and tree ferns usually rank second. This differs from the miospore floras, in which tree-fern miospores are dominant over those of lycopods. Disparities between the two records were evaluated with R-values, ratios of percent abundance of species in the miospore record to that in the coal-ball record. In the Springfield Coal, tree ferns are 2 to 3 times and lepidodendrid lycopods 0.5 to 0.75 times as abundant in the miospore record as in the peat. Sigillaria and Diaphorodendron, however, are much more poorly represented by spores and have R-values less than 0.2. Although R-values are too variable among zones in profiles to accurately reconstruct the peat, they provide an estimate of how over- or underrepresented species are in the miospore record and should be considered when estimating vegetational biomass from percent miospore abundance.

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GSA Special Papers

Modern and Ancient Coal-Forming Environments

James C. Cobb
James C. Cobb
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C. Blaine Cecil
C. Blaine Cecil
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Geological Society of America
Volume
286
ISBN print:
9780813722863
Publication date:
January 01, 1993

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