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Paleoecological analysis of two Early Pennsylvanian mineral-substrate wetlands

Janelle S. Pryor and Robert A. Gastaldo
Paleoecological analysis of two Early Pennsylvanian mineral-substrate wetlands
Palaios (February 2000) 15 (1): 3-13

Abstract

The biomass within two Early Pennsylvanian (Langsettian [Westphalian A] equivalent) penecontemporaneous swamp communities was sampled quantitatively to obtain an estimate of the taxonomic contribution to each assemblage. Blocks of organic-rich shale were removed from a clastic parting within the Black Creek Coal, and approximately 0.5-m (super 2) siltstone quadrats were chain-sawed from a clastic swamp community directly above the Bear Creek Coal. Bedding planes were exposed, and the surface areas for each taxon per bedding surface were measured and used as proxies for biomass contribution in each locality. Biomass over a combined area of 5.47 m (super 2) was assessed for the Black Creek Coal parting; biomass covering an area of 9.70 m (super 2) was evaluated for the assemblage preserved above the Bear Creek coal. In addition to calculating standard diversity indices, this data set was analyzed using cluster analyses and non-metric multidimensional scaling (NMDS) to differentiate variations within the general flora. Low species diversity characterizes both floras. Diversity indices for both assemblages are very similar, indicating essentially no difference in assemblage composition, despite the difference in edaphic conditions. The Bear Creek Coal wetlands show greater variation in species content, while the mineral-enhanced peat of the Black Creek Coal overlaps this species diversity within a slightly more restricted range of variation. Cluster analysis produced 5 stable clusters, whereas three dimensions of the NMDS analysis provided the best fit to explain the variation among the samples. The dimensions are interpreted as representing abundance of (1) arborescent lycopsids, (2) arborescent and climbing sphenopsids, and (3) pteridosperms. The plant community preserved within the clastic parting of the Black Creek Coal is comparable to that of the community found above the Bear Creek Coal. Hence, vegetation that colonized mineral-substrate soils in Early Pennsylvanian coastal lowlands, whether in peat or non-peat accumulating settings, are very similar. The dominance of pteridosperms in these depositional regimes appears to remain stable throughout the Early and Middle Pennsylvanian and portends community replacements in the Late Westphalian D some 8-10 million years later.


ISSN: 0883-1351
Serial Title: Palaios
Serial Volume: 15
Serial Issue: 1
Title: Paleoecological analysis of two Early Pennsylvanian mineral-substrate wetlands
Affiliation: Mississippi College, Department of Biological Sciences, Clinton, MS, United States
Pages: 3-13
Published: 200002
Text Language: English
Publisher: Society of Economic Paleontologists and Mineralogists, Tulsa, OK, United States
References: 62
Accession Number: 2000-051372
Categories: PaleobotanyStratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. col., 5 tables, sketch map
N34°16'60" - N34°34'00", W88°13'00" - W87°32'60"
Secondary Affiliation: Colby College, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200017
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