Ediacaran biota on Bonavista Peninsula, Newfoundland, Canada

摘要

Newly found fossils in the Conception and St. John's groups of the Bonavista Peninsula considerably extend the known geographic distribution of the Ediacaran fossils in Newfoundland. They occur in deepwater sediments and are preserved as epireliefs, forming census populations underneath volcanic ash layers throughout a more than 1 km thick turbiditic sequence. The exposed fossiliferous units comprise the Mistaken Point, Trepassey, Fermeuse, and Renews Head formations. The remains are tectonically deformed, with long axes of elliptical discs aligned parallel to cleavage strike; shortening of originally circular bedding surface features is on the order of 30-50% (averaging similar to 35%). The assemblage includes Aspidella, Blackbrookia, Bradgatia, Charnia, Charniodiscus, Fractofusus, Hiemalora, and Ivesheadia. These occur throughout the succession, with Aspidella being the most common genus, followed by Charnia and Charniodiscus. Four new taxa are described, with candelabra-like fossils with a Hiemalora-like base referred to Primocandelabruin hiemaloranum n. gen. and sp., bush-like fossils to Parviscopa bonavistensis n. gen. and sp., ladder-like fossils to Hadryniscala avalonica n. gen. and sp., and string-like fossils with basal disc to Hadrynichorde catalinensis n. gen. and sp. The remains also include dubiofossils. The stratigraphic ranges of some taxa on the Bonavista Peninsula are longer than previously reported from the Avalon Peninsula, with Fractofusus spindles present in the Trepassey Formation, Bradgatia, Chamia, Charniodiscus, and Ivesheadia reaching as high as the Fermeuse Formation, and Aspidella extending into the middle of, the Renews Head Formation. The spindles in the Trepassey Formation are comparable to those found mainly in the stratigraphically older Briscal Formation on the Avalon Peninsula.