Florissant Formation

Florissant Formation is a geological and palaeontological unit in central Colorado, United States, famous for late Eocene (about 34 million years old) fossil deposits. The formation is best known for finely laminated shales that preserve detailed plant and insect compression fossils.

The site yields large numbers of fossil insects, leaves, and other terrestrial organisms that inform reconstructions of Eocene terrestrial ecosystems and climate. Fossils from the formation have been studied since the 19th century and continue to be important for palaeobotany and paleoentomology.

Work that exposed and described the Florissant fossils occurred in the 19th and 20th centuries; important collections are held by museums and a nearby national monument protects significant outcrops and provides public interpretation. The formation occurs near the modern town of Florissant in the foothills of central Colorado, set among forested terrain and volcanic-capped ridges.

• Age: The deposits are late Eocene in age, roughly 34 million years old, and preserve exceptionally detailed plant and insect fossils.
• Preservation: Fine-grained shales in the formation are the reason for the high-quality preservation of wings, leaves, and other delicate structures.

What to See #

• Fossil beds: A fossil-bearing sequence of fine-grained shales and mudstones that preserve delicate compression fossils of plants and insects dating to the late Eocene.
• Visitor displays: A visitor area and interpretive displays at the protected national monument that explain the palaeoenvironment and show representative specimens found in the formation.