What is a fossil?

A fossil is the remains, trace, or imprint of an organism (animal, plant, etc.) that has been preserved in the earth's crust (usually in rock) since some past geologic time. Many people think of fossils as bones, but they are much more, including microscopic remnants and even tracks and trails of past life.

  • Are evidence of ancient forms of life (including extinct forms)
  • Are evidence for changes in life through time (evolution and extinction)
  • Can be useful for interpreting the relative age of rock layers (index fossils)
  • Provide data for correlating rock units across great distances
  • Are useful for interpreting ancient environments, climates, and sea level
  • Are part of the science of paleontology

Some Interesting Kentucky Fossil Facts

  • Big Bone Lick in northern Kentucky is world famous for its ice-age fossils
  • The Falls of the Ohio at Louisville is world famous for its Devonian marine fossils
  • Fossils from Kentucky were part of the original evidence for the concept of extinction
  • More than 4,000 fossil species have been reported from Kentucky
  • Most of the fossils found in Kentucky are much older than dinosaurs!

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The Study of Fossils

The study of fossils is called paleontology; it is not to be confused with archaeology, which is the study of human artifacts. Paleontology is closely associated with geology, which is the study of the physical nature and history of the earth.

Fossil Bearing Rocks

Fossils are most commonly found in sedimentary rocks. Sedimentary rocks result from the consolidation of loose sediment that has accumulated in layers. Almost all of Kentucky's rocks at the surface (but below the soil) are of sedimentary origin, and almost all bear fossils. Consequently, Kentucky is an excellent place to collect fossils.

The common sedimentary rocks in Kentucky are limestone, shale, and sandstone. Limestones began as limey muds and sands that were deposited under shallow tropical seas in a setting similar to the modern Bahamas platform. During burial, the sediment grains became cemented together and they became limestone. Shales and sandstones began as deposits of non-limey mud and sand, respectively. Deposits of mud and sand formed in seas and on land. Again, cementation of the muds and sands transformed the sediment into rocks; this process is called consolidation or cementation. Plant and animal remains trapped in the original deposit became fossils.

Age of Kentucky Fossils

Most of Kentucky's fossils are very ancient, and most are much older than the dinosaurs. Fossils are the same age as the sedimentary rocks that contain them, and the sedimentary rocks at Kentucky's surface are 505 to 438 million years old (putting them in the Ordovician Period), 438 to 408 million years old (Silurian Period), 408 to 360 million years old (Devonian Period), 360 to 320 million years ago (Mississippian Period), 320 to 285 million years old (Pennsylvanian Period), 144 to 65 million years old (Cretaceous Period), 65 to 1.6 million years old (Tertiary Period), and less than 1.6 million years old (Quaternary Period). A geologic map of Kentucky shows the distribution of these different age rocks. Not all ages are found in Kentucky.

Last Modified on 2019-11-06
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