Abstract

A meandering fluvial channel body at Coal Mine Point in the Joggins Fossil Cliffs, Nova Scotia contains an unusual fossil assemblage. During an early stage of channel abandonment, a wrinkled surface attributed to microbial mats was traversed by large arthropleurids (Diplichnites cuithensis trackways). Closely associated are smaller Diplichnites gouldi trackways, probably made by myriapods, as well as tetrapod tracks (Pseudobradypus?, Dromillopus, Hylopus) and invertebrate traces (Cochlichnus, Gordia), collectively representing the Scoyenia ichnofacies. The mats stabilized the sediment surface, allowing excellent trackway preservation, and may have formed a food source, although no feeding traces were identified. Overlying strata yield Protichnites followed by a succession containing paired mud drapes and an impoverished Skolithos ichnofacies encompassing Skolithos, Arenicolites, Cochlichnus, and possible Rhizocorallium, collectively suggesting brackish influence. The channel deposits contain some logs and large plant axes, and were colonized in late stages by lycopsid and calamitalean trees. The assemblage indicates that Early Pennsylvanian channels on a vegetated coastal plain near the tidal limit had a diverse and interconnected aquatic and riparian ecosystem, with tetrapods and terrestrial arthropods entering the channel. Microbial mats may have been common components of Pennsylvanian channels, much as they are in modern fluvial and tidal channels.

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