Late Precambrian microfossils from Brioverian cherts and limestones of Brittany and Normandy, France

Abstract

THE discovery of assemblages of unicellular, colonial and multiunit (endosporangium-like) algal microfossils in thin sections and in macerations of carbonaceous cherts and dolomitic limestones from the late Precambrian Brioverian ‘Series’ of northwestern France is reported here. These assemblages represent new links in the now rapidly expanding known record of Precambrian life. They are of interest because of (1) their similarity to microbiotas of comparable age reported from Canada and Alaska, a similarity suggesting that such assemblages could prove useful for global biostratigraphic correlation of late Precambrian strata; (2) their presence in partially metamorphosed sediments, an occurrence indicating that Precambrian organic-walled microfossils may not be as susceptible to metamorphic alteration as has widely been assumed; (3) one of the assemblages is preserved in carbonates, a facies previously little studied by Precambrian micropalaeontologists.