A New Plant Macrofossil Assemblage from the Rhaetian–Hettangian Fosheim Member of the Heiberg Formation on Ellesmere Island, Arctic Canada

Abstract

Premise of research. During two recent field seasons in the Arctic Archipelago of Canada (Nunavut), assemblages of well-preserved plant macrofossils have been collected at five different sites from the Fosheim Member of the Heiberg Formation, which are here reported. Methodology. The plant fossils are analyzed, described, illustrated, and identified. The assemblage is compared with the other two reports of plant macrofossils from that area, and the overall vegetation of the Fosheim Member of the Heiberg Formation is put in relation to well-known Rhaetian–Hettangian macrofossil assemblages of Greenland, north-central Europe, and central and eastern Asia. Pivotal results. Among the sphenophytes and ferns, Neocalamites lehmannianus, Todites roessertii, Cladophlebis cf. ingens, and Dictyophyllum exile have been encountered; ginkgophytes are represented by three species (Ginkgoites taeniatus, Baiera minuta, and Sphenobaiera spectabilis) and conifers by two Podozamites species (Podozamites schenkii and Podozamites punctatus). For the bennettites, only one species could be identified, but this species (Otozamites micrauritus) was so far unknown from Arctic Canada and described only from the Rhaetian of South Korea. Cycads are absent. Taeniopteris sp. and Desmiophyllum sp. represent two species of so far unknown affinity. Conclusions. An evaluation of the composition of the flora, together with the fossiliferous sedimentary succession, indicates that the plants grew in a variety of exposed and disturbed habitats of wide floodplains within lowland, deltaic, or coastal plain settings or brackish to tidal mudflat areas, in a relatively warm climate with abundant rainfall and well-developed seasons. The age of the fossil-bearing strata is briefly discussed based on the stratigraphic information retrieved from the elsewhere occurrence of the identified taxa.