Fossils
Learning Objectives
A fossil is the trace or remains of a once living organism.
Fossilization is more likely if the organism has hard parts (bones, shells) and is buried rapidly. There are different ways that a fossil can be preserved:
A) Direct Fossilization: fossilization of the organism
2) Altered Hard Parts:
Permineralization: mineral material is deposited within the cells of the organism. If the mineral material is dissolved then some of the original organism will remain.
3) Carbonization: Pressure from overlying rock strata squeeze organic compounds out of an organism leaving a carbon film behind. Common method for soft organisms.
4) Mold: the depression left behind by an organism. Retains detail of the external structure.
5) Cast: a mold that has been filled in with mineral material.
6) Other: some rare methods of fossilization: these methods tend to preserve soft tissue and in some cases the skin and hair of an organism.
B) Indirect Fossilization: no part of the organism remains or is represented but there is evidence that the organism existed.
1) Tracks, Trails, Footprints
2) Gastroliths: gizzard stones
3) Coprolite: preserved dung
4) Artifacts: useful for studying human evolution.
Fossils can also help reconstruct past environments:
Paleoecology: The study of ancient ecosystems. Geologists look at modern ecosystems and the hard parts contained within to understand ancient ecosystems.
An understanding of paleoecology can help geologists determine: