A large theropod dinosaur track preserved in rock from the Morrison Formation
NPS Photo / A Shaffer
Discovering Ancient Life
Many people visit Colorado National Monument to see the animals and plants that call the park home, from desert bighorn sheep to prickly pear cactus. But how often do you think about the wildlife that used to call the monument home millions of years ago?
What Is A Fossil?
The geology of Colorado National Monument is something to behold in and of itself, but locked away within the stone lie remnants of Earth’s past, fossils. The term “fossil” refers to any evidence of once living organisms. Remains of living things are generally considered fossils when over 10,000 years old, however the oldest known fossils are billions of years old! Fossils can include petrified wood, snail shells, footprints, and dinosaur bones.All of these types of fossils have been found at the monument. A recent study was done highlighting the paleontological resources at Colorado National Monument.
What Do I Do If I Find A Fossil?
If you find a fossil, congratulations! You've found something that is truly unique.
The most important thing to do is to leave it in place! The context in which a fossil is found provides useful information about the specimen, data that may be lost if the fossil is removed. Instead, take a picture, note the location of the fossil, and let a park ranger know. You may be asked to provide directions or coordinates for the find, if possible. Remember that many of the most scientifically important fossils have been discovered by amateurs.
A large number of National Park Service units have produced fossils. See the webpage on Fossils and Paleontology in the National Park Service for more information.
Fossils are protected under the Paleontological Resources Preservation Act of 2009 and are not allowed to be collected within national parks. Learn more about the Laws, Regulations, and Policies regarding fossils in the National Park Service.
The Morrison Formation — A Jurassic Wild West
Fossils have been found in many of the rock layers of Colorado National Monument. One of the most fossiliferous (meaning “sedimentary rocks containing fossils”) of these layers is the Late Jurassic Morrison Formation. The Morrison Formation is world-renowned for its fossils, particularly those of dinosaurs. This same layer hosts the dinosaur fossils found elsewhere in the Grand Valley, such as at Dinosaur Hill, Riggs Hill, the Fruita Paleo Area, and Rabbit Valley, as well as many of the fossils found at Dinosaur National Monument.
A massive river system (similar to the modern Mississippi or Amazon rivers), broad vegetated floodplains/wetlands, and various localized streams and lakes deposited the Morrison Formation roughly 157 to 149 million years ago during the Jurassic Period. This formation can be found across twelve US states, with outcrops being exposed by the uplift and erosion of the Rocky Mountains.
The ancient ecosystem captured within the Morrison Formation has produced a vast number of fossils from many different organisms. The fossil organisms that have been found from this formation include:
Fungi, Algae, Mosses, Horsetails, Ferns, Cycads, and Conifer Trees
Snails, Worms, Clams, Crayfish, and Insects
Fish, Frogs, Salamanders, Turtles, Lizards, Crocodile-relatives, Mammals, and Pterosaurs
Theropod, Sauropod, Stegosaur, Ankylosaur, and Ornithopod dinosaurs
The extremely diverse ecosystem of the Morrison Formation has provided countless insights into this world, 150 million years past. This includes a handful of significant specimens found at Colorado National Monument, like turtle tracks that can be seen at Dinosaur Journey in Fruita (one of only three examples known from the Morrison Formation).
How are Fossils Formed?
The scientific study of fossils and the history of life on Earth is called paleontology, which quite literally means “the study of ancient creatures.” The scientists that research fossils are called paleontologists.
By studying ancient life, paleontologists can learn important things about the story of life on this planet, a story still being written. Did you know that future fossils are being made today? The same processes that produced fossils of dinosaurs millions of years ago are at work in the modern world. However, these processes rely on a number of specific conditions taking place in order for a fossil to be seen by paleontologists.
Fossils can be divided into two main categories: body fossils (preserved remains of an organism’s body, such as bones, teeth, or hair) and trace fossils (traces left by an organism while it was alive, like footprints, burrows, or feces). The standard process for something becoming a fossil, a process known as fossilization, involves a handful of steps:
An organism’s body or trace is buried by sediment. In the case of an organism’s body, this must happen shortly after death so that the remains aren’t destroyed by decomposition or scavenging. Anything that occurs to an organism after death and before burial is described by the science of taphonomy.
Once buried, the remains of the organism are sometimes dissolved, surrounded by, or replaced by minerals from surrounding groundwater. The exact way this happens helps determine what type of fossil is produced.
Over time, the organism’s remains and the surrounding sediment are compressed, becoming rock.
After even more time, the organism (now a fossil) experiences various geologic processes, such as uplift and erosion, exposing it to the surface.
Every fossil that paleontologists study today has gone through a number of different challenges, including:
Rapid burial without being destroyed by decomposition/scavenging
Transformation into a fossil through geologic forces without being destroyed by too much heat/pressure
Exposure to the surface without being destroyed by erosion or tectonic forces
Discovery without being destroyed by people, accidently or intentionally
The chances are slim that an organism becomes a fossil, survives fossilization, and is eventually found by people without being destroyed in the process. This is why fossils are so important, as each one provides valuable insight into a world long gone that we might not know about otherwise.
