Trace Fossils from the Brioverian (Ediacaran–Fortunian) in Brittany (NW France)
Abstract
The Ediacaran–Fortunian ichnofauna from Central Brittany (NW France) is revised for the first timesince the pioneering work by Lebesconte at the end of the 19th century. The study is based onfossils from the type-localities of the historical Brioverian taxa Montfortia (traces from Montfortsur-Meu) and Neantia (wrinkle surfaces from Neant-sur-Yvel), and on two new outcrops fromSaint-Gonlay. The ichnofossil assemblage includes Helminthoidichnites tenuis, Helminthopsis tenuis,Gordia marina, Palaeophycus tubularis, ?Neonereites uniserialis, and ?Spirodesmos archimedeus.Locally, the grazing traces are associated with wrinkle surfaces considered as microbially inducedsedimentary structures (MISS). The sedimentological characteristics of these deposits correspond toa shelf marine environment. Both U-Pb datings on detrital zircon and ichnostratigraphic criteriatend toward an Ediacaran age of the fossiliferous deposits, but we cannot exclude the possibility ofa Fortunian age at the present state of knowledge.