Article: Micro-organisms from the late Precambrian Narssârssuk Formation, north-western Greenland

Carbonaceous cherts of the late Proterozoic (c. 700 Ma) Narssarssuk Formation, north-western Greenland, contain about twenty microfossil entities distributed in four discrete microbial associations and one allochthonous association. The associations are the preserved remnants of cyanobacterial communities that inhabited different environments within the intertidal and supratidal zones of a hypersaline embayment bordering an arid sabkha-like coast. The palaeoecological distributions of Narssarssuk microbes are comparable to those of other fossil and modern microbial mats from similar environmental settings, suggesting that the Proterozoic evolution of the cyanobacteria has been characterized by physiological as well as morphological conservatism. Environmental explanations for observed differences in Proterozoic fossil assemblages provide the proper null hypothesis against which hypotheses of evolutionary change in stromatolitic cyanobacteria must be tested. Five new taxa are described: Avictuspirulina minuta gen. et sp. nov., Coleogleba auctifica gen. et sp. nov., Gyalosphaera fluitans gen. et sp. nov., Eosynechococcus thuleensis sp. nov., and Oscillatoriopsis variabilis sp. nov.