Fossil Type

Impression Fossils

Impression fossils are flat, two-dimensional imprints left by organisms in soft sediment — typically leaves, feathers, jellyfish, or other thin or soft-bodied organisms. Unlike molds, impressions are shallow and do not capture three-dimensional form, but they can preserve extraordinary detail of delicate structures that rarely fossilize by other means.

Formation

How Impression Fossils Form

A flat or thin organism (leaf, feather, jellyfish) settles on fine-grained sediment such as mud or silt. Before it decays, another layer of sediment buries it. The compressed organism leaves a detailed imprint as the sediment lithifies. Some impressions preserve carbonaceous films — thin layers of carbon from the original organic material — enhancing detail visibility.

Field Guide