UNIVERSITY OF SOUTH ALABAMA
GY 112L: Earth History Lab
Week 5: Fossil Preservation
Instructor: Dr. Douglas W. Haywick
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.
50 million year old bird footprints
Source: www.humboldt.edu/.../MakingFossils.html
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
Source: http://www.lapidaryjournal.com
http://www.panoramio.com/photo/13153670
Originally porous materials (wood or bone) are replaced by silica, and
the original pore space is filled by silica (perimineralization)
Petrified Bone
Petrified Wood
Modes of Fossil Preservation
Concretions
Source: www.humboldt.edu/.../MakingFossils.html
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
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 Test 1 (labs 2, 3, 4)
Bring calculator, ruler, eraser, pencils,
GY 112/112L: Earth History
Week 5: Fossil Preservation
Instructor: Dr. Doug Haywick
dhaywick@southalabama.edu
This is a free open access lecture, but not for commercial purposes.
For personal use only.