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GY 112L: Earth History Lab
Week 5: Fossil Preservation
Instructor: Dr. Douglas W. Haywick
UNIVERSITY OF SOUTH ALABAMA
Today’s Agenda
1) Types of fossils 2) Types of fossil preservation
Types of Fossils
Body Fossils: Actually physical remains of a beastie (shell, skeleton, tests, bones, eggs, feathers, scales, wood etc.)
175 million year old “bird” Archiopteryx sp.
Types of Fossils
Body Fossils: Actually physical remains of a beastie (shell, skeleton, tests, bones, eggs, feathers, scales, wood etc.) Trace Fossils: Evidence that a beasties once lived in a particular environment.
Source: www.humboldt.edu/.../MakingFossils.html
50 million year old bird footprints
Trace Fossils (Ichnofossils)
Ichnology: The study of trace fossils
• Burrows: mostly vertical passages made in soft sediment.
• Feeding Traces: mostly horizontal paths made on top of sediment
• Borings: mostly vertical passages made in solid material (wood, rock)
• Encrustation: attachment of fossils on top of hard materials (e.g. worm tubes)
• Coprilite: fossil turds
Trace Fossils (Ichnofossils)
Ichnology: The study of trace fossils
• Burrows: mostly vertical passages made in soft sediment.
• Feeding Traces: mostly horizontal paths made on top of sediment
• Borings: mostly vertical passages made in solid material (wood, rock)
• Encrustation: attachment of fossils on top of hard materials (e.g. worm tubes)
• Coprilite: fossil turds
Trace Fossils (Ichnofossils)
Ichnology: The study of trace fossils
• Burrows: mostly vertical passages made in soft sediment.
• Feeding Traces: mostly horizontal paths made on top of sediment
• Borings: mostly vertical passages made in solid material (wood, rock)
• Encrustation: attachment of fossils on top of hard materials (e.g. worm tubes)
• Coprilite: fossil turds
Trace Fossils (Ichnofossils)
Ichnology: The study of trace fossils
• Burrows: mostly vertical passages made in soft sediment.
• Feeding Traces: mostly horizontal paths made on top of sediment
• Borings: mostly vertical passages made in solid material (wood, rock)
• Encrustation: attachment of fossils on top of hard materials (e.g. worm tubes)
• Coprilite: fossil turds
Trace Fossils (Ichnofossils)
Ichnology: The study of trace fossils
• Burrows: mostly vertical passages made in soft sediment.
• Feeding Traces: mostly horizontal paths made on top of sediment
• Borings: mostly vertical passages made in solid material (wood, rock)
• Encrustation: attachment of fossils on top of hard materials (e.g. worm tubes)
• Coprilite: fossil turds
Body Fossils
How does something get fossilized?
•Possess hard body parts •Die “peacefully” •Get buried quickly •Stay buried •Avoid oxygen (anaerobic environment) •Get “fossilized”
Modes of Fossil Preservation
Most fossils in the rock record were deposited in marine environments. Most are composed of CaCO3
Modes of Fossil Preservation
Most fossils in the rock record were deposited in marine environments. Most are composed of CaCO3 Two major mineral forms: Calcite and Aragonite
Modes of Fossil Preservation
Aragonite Calcite More soluble Less Soluble
Modes of Fossil Preservation
Unaltered (Pristine) Aragonite
Modes of Fossil Preservation
Unaltered (Pristine) Aragonite Chalky Aragonite
Partially dissolved
Modes of Fossil Preservation
Unaltered (Pristine) Aragonite a “hole” or mold
Completely dissolved
Modes of Fossil Preservation
Molds and Casts External Mold: Impression of the outside of a shell.
Source: www.humboldt.edu/.../MakingFossils.html
Modes of Fossil Preservation
Molds and Casts External Mold: Impression of the outside of a shell. Internal Mold: Impression of the inside of a shell.
Source: www.humboldt.edu/.../MakingFossils.html
Modes of Fossil Preservation
Molds and Casts External and Internal Molds: Impression of the inside and outside of a shell.
Modes of Fossil Preservation
Molds and Casts Cast: an filled-in external mold
Modes of Fossil Preservation
Molds and Casts Cast: a filled-in external mold
source: http://paleo.cc/casts/yuep3.jpg
Modes of Fossil Preservation
Mineral Replacement
Original shell/skeleton material (calcite/aragonite) replaced by other minerals: Dolomite, chert, pyrite, phosphate, hematite, calcite etc.
Source: http://gpc.edu/~pgore/myphotos/fossils/cast&mold.jpg
Modes of Fossil Preservation
Mineral Replacement
Original shell/skeleton material (calcite/aragonite) replaced by other minerals: Dolomite, chert, pyrite, phosphate, hematite, calcite etc.
Source: http://gpc.edu/~pgore/myphotos/fossils/cast&mold.jpg
Modes of Fossil Preservation
Petrifaction
Originally porous materials (wood or bone) are replaced by silica, and the original pore space is filled by silica (perimineralization)
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Petrified Bone Petrified Wood
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Modes of Fossil Preservation
Concretions
Fossils are encased in nodules that protect them from compaction (leaves, shells). When split open, you get an impression of both sides of the beastie
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Modes of Fossil Preservation
Carbonization
Soft organic materials (leaves, graptolites, worms) are preserved as a thin (black to brown) carbon film in sedimentary rocks. Requires anaerobic conditions
Source: www.humboldt.edu/.../MakingFossils.html
Modes of Fossil Preservation
“Entombment”
Soft organic remains (insects) are preserved in amber (fossil tree sap)
Today’s Lab 1) Lot’s of fossils, lots of short questions
Next Time Lab 7 Paleozoic Rocks and Fossils
Lab 6 is a bonus opportunity
GY 112/112L: Earth History
Week 5: Fossil Preservation
Instructor: Dr. Doug Haywick [email protected]
This is a free open access lecture, but not for commercial purposes. For personal use only.