COMPARISON OF THE BLACK CREEK
COAL-PARTING SWAMP COMMUNITY WITH
THE BEAR CREEK CLASTIC SWAMP
COMMUNITY OF ALABAMA (WESPHALIAN A)
JANELLE S. PRYOR
Tougaloo College, Tougaloo MS 39174
&
Robert A. GASTALDO
Auburn University, Auburn AL 36849-5305
Stratigraphically continuous sections of shale and siltstone were manually excavated from a clastic
inclusion within the Early Pennsylvanian (Westphalian A equivalent) Black Creek Coal (Walker
County, AL) and the stratigraphically equivalent overburden of the Bear Creek coal (Franklin
County, AL). Fossiliferous sections were approximately 0.5 m2 and individual bedding surfaces
from both localities were quantitatively sampled for biomass of contributing plant species.
Biomass was determined for each sequential
bedding surface that could be uncovered (each
surface approximately 0.5 cm apart) using area of plant parts preserved on bedding planes. The
data were analyzed using cluster analysis and non-metric multidimensional scaling (MDS) in order
to differentiate variations within each and between the two plant communities. The flora of both
the coal swamp clastic parting and the clastic swamp community has a low species diversity. The
samples from the Black Creek Coal exhibit limited variation in species content, while the samples
from the Bear Creek shale (clastic swamp community) show the same species with a greater range
of variation in abundance. Cluster analysis
produced 5 stable clusters of samples, with most
samples falling within a single cluster characterized by a dominance of pteridosperm debris. Three
dimensions of the MDS analysis provided the
best fit to the data. The dimensions are interpreted
as representing abundance of (1) arborescent lycopsids, (2) calamitean plants, and (3)
pteridosperms. We conclude that Early
Pennsylvanian vegetation colonizing mineral substrates in
coastal lowlands, whether they are in a peat or non-peat accumulating setting, are virtually
identical. The dominance of pteridosperms in these depositional regimes appears to remain stable
throughout the Early and Middle Pennsylvanian.
Citation: Ecological Society of America, Abstracts, 1997.
