Distribution and significance of microfossils in cherts of the middle Proterozoic Dismal Lakes Group, District of Mackenzie, Northwest Territories, Canada

The assemblages consist of coccoid, colonial coccoid, and filamentous forms, which appear to be largely or entirely of cyanophycean affinity. Sedimentologic evidence indicates that the fossiliferous cherts and interbedded dolostones originated in intertidal settings. The occurrence of pseudomorphs after an evaporite mineral, probably gypsum, and the occurrence of displacement structures believed to have originated by precipitation of an evaporite mineral, suggest that these microbiotas originated in hypersaline settings. This study illustrates several problems that confront paleontologists investigating and interpreting microfossils preserved in Proterozoic cherts which must be carefully considered when speculating on the nature and evolution of life during the Proterozoic Eon.--Modified journal abstract.