Shale Outcrop

Some of the key layers of the Florissant Formation can be seen here: the Caprock conglomerate unit, which is remnant of the debris flow that came into the lake; the Middle shale unit, which is remnant of the ancient lake containing thousands of insect and plant fossils; the Lower mudstone unit, containing lahar or volcanic mudflow that buried the redwood trees.

 The majority of Florissant's fossils are plants and insects preserved in delicate shales. Some pieces of shale are as thin as a sheet of paper, which makes them very fragile records of the past. A split piece of shale usually displays two halves of the fossil organism. 

Paleontalogists have described 1,800 fossil species from Florissant, making it one of the richest fossil sites in the world.