The Fossilization Flow Chart

FOSSIL!

Body Fossils Trace Fossils

Unaltered Remains Altered Remains

Encasement•Amber•TarMummificationFreezing

TracksBoringsBurrowsCoprolite

PermineralizationReplacement

Recrystallization

Molds and Casts

Carbonization

Some Original Material

No Original MaterialOriginal Material Changed

PyritizationSilicification

FOSSIL!

Body Fossils Trace Fossils

Unaltered Remains Altered Remains

Encasement•Amber•TarMummificationFreezing

TracksBoringsBurrowsCoprolite

PermineralizationReplacement

Recrystallization

Molds and Casts

Carbonization

Some Original Material

No Original MaterialOriginal Material Changed

PyritizationSilicification

MOST OF THESE ARE NOT MUTUALLY EXCLUSIVE IN A GIVEN SPECIMEN!!

FOSSIL!

Body Fossils Trace Fossils

Unaltered Remains Altered Remains

Encasement•Amber•TarMummificationFreezing

TracksBoringsBurrowsCoprolite

PermineralizationReplacement

Recrystallization

Molds and Casts

Carbonization

Some Original Material

No Original MaterialOriginal Material Changed

PyritizationSilicification

Trace Fossils(AKA “Ichnofossils”)

EVIDENCE OF AN ORGANISMS ACTIVITIES (tracks, borings, burrows, coprolites)

Tracks (locomotion)

Burrows (domocile)

Coprolite (digestion)Borings(domocileor feeding)

FOSSIL!

Body Fossils Trace Fossils

Unaltered Remains Altered Remains

Encasement•Amber•TarMummificationFreezing

TracksBoringsBurrowsCoprolite

PermineralizationReplacement

Recrystallization

Molds and Casts

Carbonization

Some Original Material

No Original MaterialOriginal Material Changed

PyritizationSilicification

Body FossilsThe actual remains of ancient organisms (as opposed to traces of life)

Teeth

Bones

Wood/plants

ShellsExoskeleton

Any part of a body from an animal older than 10,000 years old!

FOSSIL!

Body Fossils Trace Fossils

Unaltered Remains Altered Remains

Encasement•Amber•TarMummificationFreezing

TracksBoringsBurrowsCoprolite

PermineralizationReplacement

Recrystallization

Molds and Casts

Carbonization

Some Original Material

No Original MaterialOriginal Material Changed

PyritizationSilicification

Altered RemainsBody fossils that have been changed in some way

after the organism died. Many fossils are formed this way.

Permineralization

Pyritization

Molds and casts

Carbonization Recrystallization

FOSSIL!

Body Fossils Trace Fossils

Unaltered Remains Altered Remains

Encasement•Amber•TarMummificationFreezing

TracksBoringsBurrowsCoprolite

PermineralizationReplacement

Recrystallization

Molds and Casts

Carbonization

Some Original Material

No Original MaterialOriginal Material Changed

PyritizationSilicification

PermineralizationA common form of fossilization where the pore spaces of a

skeletal element (bones, teeth, shells, etc.) are filled in by minerals that have precipitated from groundwater.

Some original material from the original element remains.

Pore spaces filled in with a mineral (usually quartz or calcite)

Many fossil bones and teeth have been

at least partially permineralized

Petrified wood is another good example, though

replacement and recrystallization can also be factors in fossil wood

FOSSIL!

Body Fossils Trace Fossils

Unaltered Remains Altered Remains

Encasement•Amber•TarMummificationFreezing

TracksBoringsBurrowsCoprolite

PermineralizationReplacement

Recrystallization

Molds and Casts

Carbonization

Some Original Material

No Original MaterialOriginal Material Changed

PyritizationSilicification

ReplacementThe slow, microscopic process of exchanging molecules

from the original bone or skeletal element with molecules that were not associated with the organism before death. This means that no original material is

left in the fossil unlike in permineralization.

A type of replacement called pyritization where all of the original material is replaced by “fool’s gold”

or pyrite

This type of replacement, silicification, has replaced the

original calcium carbonate shell with a mineral called quartz

FOSSIL!

Body Fossils Trace Fossils

Unaltered Remains Altered Remains

Encasement•Amber•TarMummificationFreezing

TracksBoringsBurrowsCoprolite

PermineralizationReplacement

Recrystallization

Molds and Casts

Carbonization

Some Original Material

No Original MaterialOriginal Material Changed

PyritizationSilicification

Molds and CastsIn this type of fossilization, the original fossil creates

an impression on the surrounding rock creating a mold.

A cast would be created if the space where the original shell was then filled in with new sediment.

External Mold------ Shell------ Internal Mold

If sediment was to fill in the external mold on the left, then a cast would be formed. So it would look similar to the half of the actual shell, but be made of sediment.

FOSSIL!

Body Fossils Trace Fossils

Unaltered Remains Altered Remains

Encasement•Amber•TarMummificationFreezing

TracksBoringsBurrowsCoprolite

PermineralizationReplacement

Recrystallization

Molds and Casts

Carbonization

Some Original Material

No Original MaterialOriginal Material Changed

PyritizationSilicification

CarbonizationThis mode of preservation occurs when heat and

pressure chemically transform “volatile compounds” (such as nitrogen, hydrogen, and

oxygen found in protein) and leave a carbon film.

Carbonized beeCarbonized eurypterid

FOSSIL!

Body Fossils Trace Fossils

Unaltered Remains Altered Remains

Encasement•Amber•TarMummificationFreezing

TracksBoringsBurrowsCoprolite

PermineralizationReplacement

Recrystallization

Molds and Casts

Carbonization

Some Original Material

No Original MaterialOriginal Material Changed

PyritizationSilicification

RecrystallizationIn this process, unstable minerals from the original organism are transformed to more stable minerals. This most commonly occurs in animals with shells

made of minerals called aragonite or high-magnesium calcite (like sea urchins!) that is highly unstable and transforms into more stable calcite.

The original shell material from this gastropod has been changed to a more stable form of calcium carbonate

This one is visibly harder to observe but the coral has transformed from aragonite to more stable calcite

FOSSIL!

Body Fossils Trace Fossils

Unaltered Remains Altered Remains

Encasement•Amber•TarMummificationFreezing

TracksBoringsBurrowsCoprolite

PermineralizationReplacement

Recrystallization

Molds and Casts

Carbonization

Some Original Material

No Original MaterialOriginal Material Changed

PyritizationSilicification

Unaltered RemainsBody fossils in which the original material hasn’t been changed or replaced by another substance

Encasement in amber Freezing

Encasement in tarUsually only very young coral and

shells are found unaltered