The Pennsylvanian tropical biome reconstructed from the Joggins Formation of Nova Scotia, Canada

摘要

The Pennsylvanian (Langsettian) Joggins Formation contains a diverse fossil assemblage, first made famous by Lyell and Dawson in the mid-19th century. Collector curves based on c. 150 years of observation suggest that the Joggins fossil record is relatively complete. A key feature of the site is that fossils occur in (par)autochthonous assemblages within a narrow time interval (<1 Ma). Analysis of co-occurring taxa within a precise facies context permits ecosystem reconstruction, and three main communities are recognized in this study. Brackish seas, the distal extension of European marine bands, were populated by Foraminifera, molluscs, annelids, arthropods, fishes, and aquatic tetrapods. Poorly drained coastal plains were covered by rainforests of lycopsids, calamiteans, ferns, pteridosperms, and cordaitaleans, inhabited by a terrestrial fauna of molluscs, annelids, arthropods, and tetrapods, including the earliest known reptiles. Well-drained alluvial plains were covered by fire-prone cordaitalean scrub containing a low-diversity fauna of molluscs, arthropods, and tetrapods, locally preserved in waterholes. These three environments repeatedly interchanged with one another in response to base-level fluctuations forced by tectonism and glacioeustasy. Located further inland than other well-studied Pennsylvanian tropical sites, the Joggins Formation is significant because it contains a record of intra-continental terrestrial ecosystems.