The Dresser stromatolites
Layered mounds built by microbial mats inside a volcanic caldera — among the oldest convincing fossils.
- When
- Known to
- ± 30 million years
- Era
- Paleoarchean, Archean
The Dresser Formation preserves stromatolites, fractionated sulfur and carbon isotopes, and microfossils together in one setting: a shallow volcanic caldera flushed with hydrothermal fluids. Having several independent lines of evidence agree in the same rocks is what makes this case strong, where single-strand claims from older rocks remain contested.