Delicate Impressions
As outcrops of shale weather, they separate into paper-thin sheets, exposing fossils on their surfaces. Within these delicate pages, a chapter of Earth's history unfolds.
Size played a key role in determining what was preserved at Florissant. The first volcanic mudflows destroyed everything in their path but the big trees. Later mudflows dammed a stream, creating a lake in the valley. Further eruptions repeatedly covered the ground with powder-fine volcanic ash. Over time the ash washed into the lake, where it weathered to thin layers of clay on the bottom. Microscopic lake algae called diatoms periodically died off, and their silica shells also settled to the bottom. These alternating layers of sediment eventually compacted into shales, preserving in exquisite detail the tiny parts of insects and plants.
When splitting the delicate paper shales, a razor blade, not a chisel, is used to leverage small cracks apart. If split correctly the part and counterpart of a fossil will reveal themselves.
Fossil Types
Part/Counterpart
Once split, the shale usually displays two halves of the fossil organism-the part and
this page online
Impression/Compression
Many of the Florissant shale fossils are compressed carbon remains-a thin film of dark residue from the original living thing. Others may be a shallow impression of the organism in the rock.
Microscopic Fossils
Some of the most spectacular fossils found in the Florissant valley are revealed only under the lens of a microscope. The distinctly shaped pollen grains reveal the presence of plants that were not preserved in the fossil leaf record.
Erected by National Park Service.
Topics. This historical marker is listed in these topic lists: Animals • Environment • Paleontology • Parks & Recreational Areas.
Location. 38° 54.808′ N, 105° 17.189′ W. Marker is near Florissant, Colorado, in Teller County. Marker is under the large Florissant Fossil Beds National Monument pavilion covering exposed petrified Redwood stumps, west of the Visitor Center. Touch for map. Marker is at or near this postal address: 15807 County Road 1, Florissant CO 80816, United States of America. Touch for directions.
Other nearby markers. At least 8 other markers are within walking distance of this marker. Florissant Valley Today (here, next to this marker); Dawn of the Recent Past (a few steps from this marker); Reading the Rings
Also see . . . Florissant Fossil Beds National Monument. (Submitted on October 22, 2020, by William Fischer, Jr. of Scranton, Pennsylvania.)
Credits. This page was last revised on October 22, 2020. It was originally submitted on October 22, 2020, by William Fischer, Jr. of Scranton, Pennsylvania. This page has been viewed 115 times since then and 12 times this year. Photos: 1, 2. submitted on October 22, 2020, by William Fischer, Jr. of Scranton, Pennsylvania.
