NPS photo.
Introduction
Fossils (paleontological resources) are evidence of past life preserved in geologic context. Fossils include bones, shells, teeth, leaf impressions, casts of tree roots, footprints, delicate impressions of insect wings, and other physical remains of past organisms or traces of biological activity.
Fossils are frequently beautiful, often intriguing and compelling, and always scientifically important. With fossils being present in at least 286 different units of the National Park System, the paleontological resources of national parks tell much of the story of ancient life of North America over the past billion and a half years.
Fossils are a tangible connection to past life, landscapes, and climates. They show us how environments have changed over time and how living things responded to those changes. These lessons are particularly important as human activity is driving rapid changes to modern climates and environments.
Explore Fossils in Your National Parks
Fossils found in national parks tell many stories about how they formed, the sizes and shapes of past organisms and their life activities, the ancient environments where animals and plants lived, and how life changed over geologic time.
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How Fossils Form
The evidence of past life—whether it is a bone, shell, or petrified wood, or even a trace of an organism like a fossil footprint or burrow –is preserved in geologic strata through a variety of processes. Sometimes minerals fill small pores or cavities in bone or wood, or replace original organic material. Imprints of shells, leaves, and even of soft tissues like skin or delicate flowers can be impressed into sediment. In rare circumstances, an organism’s remains may be preserved practically unaltered through freezing, drying, or entrapment in amber.
Taphonomy is the study of what happens between the time an organism dies and when it becomes a fossil. Only a small percentage of the organisms who have lived in the geologic past became fossilized. Rapid burial and a body plan including hard parts like shells, bones, or wood greatly increase the odds that remains will become part of the fossil record.
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Body and Trace Fossils
Fossils consist of either the altered (or rarely unaltered) bodily remains of ancient organisms, or preserved evidence of biological activity of an organism while it was alive.
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Body fossils: The physical remains of part or all of an ancient organism, whether it was a vertebrate, invertebrate, plant, or other (microorganism). Organisms with hard parts like wood, bones, teeth, or shells are much more likely to be preserved than those without them. Even the fossils of these organisms are most likely to consists only of the hard shells rather than their soft parts like skin, feathers, internal organs, fruit, or flowers.
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Trace fossils (ichnofossils) consist of evidence of a living thing's activities or interaction with its environment but without any part of the actual organism. Footprints and trackways, burrows or dens, casts of tree roots, and even coprolites (fossil dung) are all examples of trace fossils. Trace fossils animate ancient animals or plants by recording a moment of their life.
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Fossils through Geologic Time
Fossils in national parks range in age from Precambrian (Mesoproterozoic) stromatolites (mounds of mounds composed of sediment and cyanobacteria) in Glacier and Grand Canyon national parks to Holocene (less than 11,700 year old) deposits in caves or packrat middens (nests) containing plant debris, animals bones, insects, and pollen.
Some parks contain rocks and deposits that sweep across vast swaths of geologic time, like Death Valley National Park, whose geologic record extends from the Precambrian to the Pleistocene and Holocene. Others contain rocks of a very limited time interval, like the Early Miocene Epoch in Agate Fossil Beds National Monument.
Every park contains some slice of geologic time, whether it is the Precambrian, Paleozoic, Mesozoic, and/or Cenozoic. The fossil records in these parks help to tell the story of ancient life, including evolution and major extinction events.
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Fossils and Ancient Environments
Most fossils are found in sedimentary rocks that formed as sediment accumulated on Earth’s surface. As such, sedimentary rocks are records of ancient environments where organisms lived. The fossil record in sedimentary rocks provides evidence of life in marine environments, marshes, and river deltas. Sedimentary rocks deposited in other environments may contain fossils of organisms that lived in or along rivers, in lakes, or in dune fields. Fossils may also sometimes be found in volcanic rocks when volcanic deposits buried but didn’t destroy all of the evidence of past life.
Fossils and paleontological sites are irreplaceable and nonrenewable. They are invaluable to science as they provide our only evidence of the history of life on Earth. A single fossil may be the only evidence of the existence of an entire species. Like rocks and other natural and cultural objects, collecting fossils for recreational, commercial, or educational use is prohibited in all national parks, and collection for scientific purposes is only permissible with a park approved permit.
Fossil sites are also vulnerable to damage from inappropriate activities. Be sure to practice Leave No Trace principles whenever you are in the outdoors, particularly if you are in an area where fossils may be present. Of particular importance at potential fossil sites is to:
- Travel and camp on durable surfaces, and
- Leave what you find.
If you see signs of vandalism or someone acting inappropriately during your visit in a park, please contact a park ranger or make a report through NPS Investigative Services.
If you discover a fossil in a national park, take a photograph of it, mark its spot on a map or record its position with a GPS or smartphone, leave it where you found it, and tell a ranger.
Last updated: September 16, 2024