Microstructures from the 3.5-billion-year-old Apex Chert have been interpreted as the remains of ancient cyanobacteria. Geochemical analyses suggest similar structures at the same location are instead haematite-filled fractures, although carbonaceous material in the surrounding matrix is consistent with the presence of microbes at this time.
- Craig P. Marshall
- Julienne R. Emry
- Alison Olcott Marshall
