Notes SPI 0807.5.5 Fossils

What Are Fossils? Fossils are the preserved physical remains of deceased organisms that are at least 10,000 years old NOTE: Most organisms DO NOT become fossils after death NOTE: The formation of fossils is a RARE event

How Are Fossils Formed?Watch this amusing video: Link: Video: How Fossils Are Made

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Primate Fossil:47 million years old

Whale Fossil:25 million years old

A) Fossils In RocksB) Fossils In AmberC) Petrified FossilsD) Fossils In Asphalt

E) Frozen FossilsF) Trace FossilsG) Mold/Cast Fossils H) Index Fossils

8 Types of Fossils

Notes SPI 0807.5.5 Fossils

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A) Fossils In Rocks Found in sedimentary rock An organism died –was covered with mud, dirt, sand, ash, etc. Later the mud, dirt, sand, or ash became sedimentary rock

Notes SPI 0807.5.5 Fossils

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B) Fossils In Amber Tree sap fell on a small organism, enclosed it, killed it Over time the sap hardened into amber The amber became covered with mud, dirt, sand, ash, etc.

Example:Insects In Amber

Notes SPI 0807.5.5 Fossils

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C) Petrified Fossils Organism died- then was covered with mud, dirt, sand, ash, etc. The structure of the organism was replaced with minerals

(Also known as petrifaction)

Example:Petrified Wood

Example:Petrified Wood

Sometimes when wood is buried, groundwater will flow through the sediment and deposit minerals in the cells of the wood.

The wood rots away & the minerals remain in the shape of the tree.

Notes SPI 0807.5.5 Fossils

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D) Fossils In Asphalt Animals fell into tar pits, were trapped, and died The asphalt hardened preserving skeletons, shells, teeth, etc.

Saber Tooth Tiger Fossil(From La Brea Tar Pits, California)

Notes SPI 0807.5.5 Fossils

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E) Frozen Fossils Animals died in a cold climate region and were frozen The cold temperatures preserved both soft and hard parts Many mammoths became frozen during the last ice age

Frozen Baby Mammoth(From Siberia, Russia)

Approx: 40, 000 yrs old

Frozen Baby Mammoth(From Siberia, Russia)Approx. 42,000 yrs old

Notes SPI 0807.5.5 Fossils

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F) Trace Fossils

Are impressions or “traces” left by plants and animals Can be simple tunnels or burrows in the mud Can be footprints or imprints in the mud etc.

Trace FossilImprint Of A Fish

(Also called ichnofossils)

Trace Fossil Dinosaur footprints

Notes SPI 0807.5.5 Fossils

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G) Mold/Cast Fossils In sediment, ground water may dissolve shells, leaving a

shape called a mold Sometimes the shell dissolves and is replaced by minerals,

leaving behind a mineral cast of the fossil

Mold Fossil Cast Fossil

Notes SPI 0807.5.5 Fossils

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H) Index Fossils A way to relatively date rocks Some fossils are commonly found at certain strata levels

across large geographic areas

(A.K.A. relative dating)

…we call these index fossils

Example: Ammonite fossils

Example: Trilobite fossils

Notes SPI 0807.5.5 Fossils

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