I feel like we're talking past each other here. The very first sentence of your link says "The cyanobacteria have an extensive fossil record." In the next parag

I feel like we're talking past each other here. The very first sentence of your link says "The cyanobacteria have an extensive fossil record." In the next paragraph it says "Cyanobacteria are among the easiest microfossils to recognize. Morphologies in the group have remained much the same for billions of years..." So not a truly short-lived event in ancient sediments then.