He also sampled a jet-black chert layer which, when observed petrographically, revealed some lifelike small spheres, rods and filaments less than 10 micrometres in size.

While older microfossils have since been described, the Gunflint microfauna is a historic geologic discovery and remains one of the most robust and diverse microfaunal fossil assemblages from the Precambrian.

[7] Microfossils can be found in the stromatolitic chert layers, consisting of cyanobacteria, algal filaments, spore-like spheroids, and organic-rich ooids.

A. M. Goodwin later examined the geologic facies of the Gunflint Iron Formation in 1956, resulting in one of the first science publications on the region,[5] but his report is devoid of any mention of microscopic life.

The publication of these two seminal papers opened the floodgates to a vast array of paleontological and geochemical studies to explore Precambrian microfossils from similar Proterozoic environments.

The Gunflint chert microfauna is mid- to late-Paleoproterozoic in age (approximately 1.878 Ga ± 1.3 Ma, as determined by Uranium-Lead dating techniques).

The most abundant organisms in Gunflint are filaments found in stromatolitic fabrics, and typically range from 0.5-6.0 μm in diameter and up to several hundred microns in length.

[2] Since then various new genera and species have been identified, some named after Barghoorn, Tyler, and Cloud in acknowledgement of their early contributions in defining the Gunflint microbial assemblages.

The spheroidal bodies have been hypothesized to be various things, such as unicellular cyanobacteria, endogenously produced endospores of bacterial origin, free-swimming dinoflagellates, and fungus spores.

Hematite preservation is a less common taphonomic mode, but is occasionally found at the interface between black stromatolitic cherts and red jasper.

The discovery of the Gunflint microbiota revealed that photosynthesis (or an ancient autotrophic precursor modality) was occurring 1.8 billion years ago, and that the atmosphere was oxygenated enough to sustain microbial life.

This discovery spurred generations of paleontologists and geomicrobiologists to contemplate ancient atmospheric oxygen conditions and redox states, and to continue searching for older microbial life.