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Geol 22: Fossils and Fossilization
Paleontology
Get Fossil Types, Drill, Gastroliths
• Study of Fossils
• Fossils: (Latin: fodere)
– Any physical evidence of ancient life
– 1.5 million named extant species
– 250,000 named fossil species
Modes of Fossilization
Permineralization:
filling in of pore
spaces with minerals
1. Body fossils
1. Permineralization
2. Replacement
Wood, bone
3. Recrystallization
4. Casts and Molds
5. Amber
6. Carbonization
7. Unaltered Remains
2. Gastroliths
3. Coprolites
Fern, Permian, AZ
4. Trace Fossils
Replacement: substitution of original material by mineral,
molecule by molecule
Recrystallization: change
from unstable mineral to
a stable one
Pyritization, silicification…
Aragonite to calcite
Triarthus, Ordovician
Permian, Glass Mountains, Texas
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Casts and Molds
1. Mold: Impression left behind when original fossil
is dissolved
a. External mold
b. Internal mold: stinekern
2. Cast: Sediment infill into a mold
Amber: Solidified tree sap
Eocene,
Germany
Carbonization: Volatiles removed,
leaving carbon film
Jurassic, Germany
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Unaltered Remains:
Frozen or mummified
Mammoth, Siberia, 1977
Predynastic Egyptian Mummy
Unaltered hard parts (very rare)
Gastroliths
• “Stomach Stones”
Gasparinisaura cincosaltensis
Coprolite
• Fossilized excrement
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Casts
Trace Fossils
(Ichnofossils):
Evidence of past
behaviors, like
Tracks, Burrows,
Borings, Feeding
Traces…
Hhip = Lpes*6
Hhip = Lfoot*5
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Allosaurus Velocity
• Hhip = Lfoot*5
• v = 0.25g0.5 * λ1.67 * Hhip-1.17
g = 32.2 feet/second2
λ = stride
t id llength
th
Hhip = (above)
FIN
• v=?
• Mass? (pg. 187)
Alexander, R. McN. 1976. Nature. 261, 129-130.
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