Fossils That Are Most Useful for Correlation

Trilobites are used as index fossils.
••• Trilobite of Morocco - Period Devonian image by santosilva from

Correlation of the geological layers is the process of matching up rocks of the same age from place to place. Some fossils are much more useful than others during this practice. To study correlation, geologists prefer common fossils with a wide geographic range, distinctive features and habitats and a short geological duration, which translates to a few million years at most, according to the University of Waikato.


Coccoliths are marine microorganisms able to convert carbon dioxide dissolved in the water in calcium carbonate. They have evolved through time and still exist today, but were very common during the early Mezosoic and Cenozoic eras, 251 million years ago and 65.5 million years ago respectively, according to Thomas Taylor in "Paleobotany: The Biology and Evolution of Fossil Plants." The White cliffs of Dover, in England, are mostly composed of coccoliths.

Pectea and Neptunea

The Cenozic is the most recent geologic era. It started 65 million years ago with the extinction of the dinosaurs. Mollusks with shells from this era, including the genera Pectea and Neptunea, are the most used index fossils. The presence of a calcareous shell facilitated the fossilization of these animals on ancient ocean beds. According to Maine Geological Survey, Neptunea fossils are found in some areas of New England.


Trilobites are marine arthropods recognized as the traditional fossils of the Cambrian period, according to Tom McCann in "The Geology of Central Europe: Precambrian and Paleozoic." These creatures were extinguished by the end of the Paleozoic era, about 250 millions years ago. They had a body divided in three lobes and protected by an exoskeleton. The most common trilobite was Paradoxides pinus, which today is used widely in correlation studies.

Related Articles

How Are Fossils Used in Science?
Ancestors of the Hedgehog
Fossil Hunting in Oklahoma
What Is a Body Fossil?
What Information Can Scientists Get From Fossils?
The Three Main Types of Fossils
Plants & Animals of the Quaternary Era
Fossil Hunting in Tennessee
The Climate in the Jurassic Era
Facts About Dinosaurs for Kids
Large Fossilized Sea Shell Identification
Fossil Hunting in Idaho
Facts About Trace Fossils
The Four Types of Fossils
What Do Fossils Have to Do with Wegener's Theory?
What Is Fossil Correlation?
What Are Indian Money Fossils?
About the People of the Coastal Plains
Definition of a Preserved Fossil
What Are the Types of Rocks Found in the Appalachians?

Dont Go!

We Have More Great Sciencing Articles!