Fossils and Geologic Time Topics

• Introduction
• Fossil Basics
• Methods of Preservation
  1. Petrifaction
  2. Perminera-
     lization
  3. Carboniza-
     tion
  4. Molds and Casts
• Important Animal and Plant Fossils
• Selected Virginia Fossils
• Tips For Fossil Collecting
• Geologic Time

Methods of Fossil Preservation (Part 1)

Fossils can be preserved by several processes. These include: petrifaction, permineralization, carbonization, and molds and casts.

Petrifaction

• When the original material of the organism is replaced with minerals, the fossilization is called petrifaction.

Petrified wood forms when minerals replace the original organic material.  These petrified wood samples are made up of silica.  Calcite is another common mineral in petrifaction. (Photographs by Parvinder Sethi)

Permineralization

• When holes in the original material are filled with minerals, the fossilization is called permineralization.

The pores in this permineralized bone have been filled with mineral material.  This was a rib bone of a marine mammal. (Photograph by Parvinder Sethi)

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