Course Outline 

Fossils 

	Activity 1: The Preservation of Fossils Activity 2: A Fossil Timeline

Background Information
One branch of Geology is Paleontology or the study of ancient life. A paleontologist is a person who studies fossils. Fossils are the remnants of ancient life. They can come in a variety of forms including original remains, casts and molds of original remains, impressions, carbon films, petrified organisms, and trace fossils (burrows, footprints, etc.). Geologists have even found fossilized feces! All of these types of fossils can be found in Oregon.

There are a number of reasons to study fossils beyond pure curiosity about the history of our planet. By reconstructing the history of the Earth we can determine what changes have happened in the past and thus what might happen in the future. Fossils can be used to tell what type of environment existed in a place, what age a rock is, and where to find oil.

The geologic timescale is based on the history of life on our planet. Eras, epochs, and periods all relate to the changes in Earth's biology. Early geologists noticed that certain species, families, or even phyla disappear completely or appear in the rock record. The most famous example of this is the dinosaurs that appeared during the Triassic and disappeared at the end of the Cretaceous. The era that the dinosaurs existed in was the Mesozoic meaning middle life. After the dinosaurs went extinct, mammals expanded and became the predominant group of land animals. The time of the mammals is called the Cenozoic, or new life.

Until recently, there was no way to determine how old the rock units actually were. Thus determining the age of rocks was done relatively. For instance dinosaurs came and went before large mammals. This can be determined by studying the relationships between rock units. Worldwide, rock units that bear dinosaur bones are underneath those that bear mammal bones. According to the principle of superposition, they must be older. Thus, a geologist finding two widely separated rock units, one containing mammal bones, and one containing dinosaur bones knows that the unit with dinosaurs is older than the one with the mammals. This is called relative dating. It wasn't until the discovery of radioactivity in rocks that geologists were able to give rocks absolute ages (for example: dinosaurs went extinct 66 million years ago). Relative dating is cheaper and easier and so is regularly used by geologists for most purposes.

Resources:
For more information about fossils in Oregon, try some of the following resources:

Books:
Oregon Fossils by Elizabeth Orr and William Orr. 1999. Kendall Hunt Publishing Company, Dubuque

Websites:
Department of Geology and Mineral Industries
http://sarvis.dogami.state.or.us/learnmore/fossils.HTM

Natures Wonders
http://www.geocities.com/SouthBeach/Coast/8385/

Other resources:
National Park Service: John Day National Monument
32651 Highway 19Kimberly, OR 97848-9701phone: 541-987-2333
Nature of the Northwest Bookstore
800 NE Oregon St., Suite 177, Portland,
OR 97232 | (503) 872 - 2750 TDD (503) 872 - 2752

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