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Roger Weller, geology instructor

by Christian Cruz
Physical Geology
Fall 2011

To Fossilize or Not to Fossilize?

Description:            Fossils are a very important variable in today’s studies of earth’s and everyone living on it history. Many people do not know that fossils are the remains or traces of prehistoric life and are important inclusions in sediment and sedimentary rocks. The word fossil comes from the Latin fossilium, which means “dug up from the ground.” In medieval times, a fossil was a stone, ore, or gem that came from an underground source. Paleontology is the study of fossils which is a blend of geology and biology. These guys have been digging since the early 1900 finds dinasour bones to any remains of the Ice Age. (Textbook).







     Nowadays fossils can be found everywhere like in a simple child’s card game such as Pokémon. (Photo credited to

            When a person hears the term fossil they think of a very old rock with some sort of imprint left in it like a leaf or foot print form and animal. Fossilization includes many different types that can help tell a story to a person. These different fossilizations include petrified wood, molds and cast, carbonization, impressions, amber, coprolite, and among them are tracks, burrows, and gastroliths.


Description: Petrified Wood Fern Brazil

Petrified wood (Credit to

Sometimes a fossil can become petrified which means they turn into stone. This happens when the tiny pores and cavities of an organism get filled with precipitated mineral matter. It is basically a replacement that occurs with the cell walls and other solid materials get swapped out for mineral matter.












Trilobite (Credit to

Sometimes a shell will get buried in sediment and with underground water it would dissolve creating a mold into the sediment. Usually the mold imitates only the shape and surfaces imprint of the organism that was repressed beneath the surface.


Carbonized bee. (Photo credited to

This form of fossilization is carbonization and is a preservation of plants and animals. This happens when adequate sediment encases the remains of an organism and over time added pressure squeezes out the liquid and gaseous components leaving behind thin carbonized residue.


Impressions (photo credited to

These impressions occur in the result of the carbon that has preserved an organism has been lost. Sometimes the environment has a lot of carbonized remains that sediment just cannot hold anymore.  This results in an imprint of an animal and plant to be left behind still showing great detail of the organism.

(Photo credited to

Amber is the fossil of ancient and extinct coniferous trees. It often contains fossils of insects,spiders or small vertebrates which have got trapped in the sticky substance at the time when the amber formed. It can be transparent or transculent and it can be found in sedimentary rocks. Some of the most famousdeposits are found around the Baltic Sea.

Nice colored dung. (Photo by

A coprolite is fossilized animal dung. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behavior corresponding to how they survived based on what they consumed. 

            Other types of fossils are tracks, burrows, and gastroliths. Tracks are a very common form because they can be found almost anywhere. They deal with an animal’s foot print that was made into the sediment and was lithified later on. Burrows, looking in the right spot, can be helpful in determining what kind of organism is around. They usually are tubes created by animals in sediment, rocks, or in wood. You can easily preserve these holes by adding mineral matter and it is believed that the oldest known fossils are the worm’s burrows. There are stomach stones that when polished were used for grinding food by extinct reptiles, they are known as gastroliths.

            Fossils have been around forever but it took quiet sometime before realize the importance of understanding them. Fossils are like a photo, they tell a person a thousand words even more. A very important yet basic principle was made by William Smith, an English engineer and canal builder, and many like him followed: “fossil organisms succeed one another in a definite and determinable order, and therefore any time period can be recognized by its fossil content”. Thus derived the Principle of Fossil Succession. In simple terms it is when fossils are put in order chronological order based on age by applying the law of superposition in which where a rock is found. Maybe people might appreciate their own coprolite one of these days until then let’s leave the dung studying to the professionals.(Textbook)

 Any informations that was not my own will be credited to GEOS textbook.