Studying the PastStudying the Past

Fossils, Relative Time and Fossils, Relative Time and Absolute TimeAbsolute Time

PaleontologyPaleontology

The study of the forms of life The study of the forms of life existing in prehistoric or existing in prehistoric or geologic times, as represented geologic times, as represented by the fossils of plants, animals, by the fossils of plants, animals, and other organisms. and other organisms.

What do you know about What do you know about fossils?fossils?

FossilsFossils

FossilisFossilis is Latin for “ is Latin for “dug updug up”” Fossils are the Fossils are the remains, molds remains, molds

or tracesor traces of organisms that died of organisms that died a long time agoa long time ago

Fossils are usually found in Fossils are usually found in sedimentary rocksedimentary rock like like sandstone, limestone or shalesandstone, limestone or shale

FossilsFossils

Fossils provide Fossils provide evidenceevidence that that different organisms lived long different organisms lived long agoago

Fossil organisms many times Fossil organisms many times do do not existnot exist on Earth anymore on Earth anymore They have gone They have gone extinctextinct or they or they

have have evolvedevolved

FossilsFossils

As we go through the different As we go through the different types of fossils look for what types of fossils look for what each type of fossil needs to each type of fossil needs to form.form.

5 Main Types of Fossils5 Main Types of Fossils

Original RemainsOriginal Remains Replaced RemainsReplaced Remains Molds and CastsMolds and Casts Trace FossilsTrace Fossils Carbonaceous FilmsCarbonaceous Films

Original RemainsOriginal Remains

Very rareVery rare Most animals Most animals

decay or decay or decomposedecompose

ExamplesExamples FrozenFrozen woolly woolly

mammothsmammoths Insects incased Insects incased

in resin (in resin (amberamber))

Replaced RemainsReplaced Remains

Actual remains Actual remains are replaced are replaced with with mineralsminerals

Many Many hard partshard parts fossilize this fossilize this wayway TeethTeeth BonesBones ShellsShells

Molds and CastsMolds and Casts

A replaced A replaced remain fossil remain fossil may may dissolvedissolve leaving behind a leaving behind a moldmold

Later minerals Later minerals may may fill in the fill in the moldmold creating a creating a cast of the cast of the original original organismorganism

Click picture to see cast and Click picture to see cast and mold formationmold formation

Trace FossilsTrace Fossils

No actual part of No actual part of the organism is leftthe organism is left

Give information Give information about the about the locationlocation of different of different organismsorganisms

Traces like Traces like ImpressionsImpressions Bite MarksBite Marks BurrowsBurrows FecesFeces

TracksTracks

CoprolitesCoprolites

Carbonaceous FilmsCarbonaceous Films

An An imprintimprint or or thin film is left thin film is left behindbehind

NotNot the actual the actual organismorganism

Tissue undergo Tissue undergo chemicalchemical changeschanges

What do fossils need to form?What do fossils need to form?

SedimentSediment CompactionCompaction Water Water MineralsMinerals OrganismOrganism TIME!!! Lots of TIME!!!TIME!!! Lots of TIME!!!

Fossil Concept MapFossil Concept Map1. Write in the 5 fossil types1. Write in the 5 fossil types2. Write in a few details about each fossil type2. Write in a few details about each fossil type

FossilFossil

TypeType

FossilFossil

TypeType

FossilFossil

TypeType

FossilFossil

TypeType

FossilFossil

TypeType

FossilsFossils

Dating Past Geologic EventsDating Past Geologic Events

Relative DatingRelative Dating Example:Example:

On the way On the way home I stopped home I stopped for gasfor gas

First, I ate First, I ate dinnerdinner

I drove home I drove home Then I went to Then I went to

the storethe store

Absolute DatingAbsolute Dating ExampleExample

I drove home at I drove home at 5:355:35

I stopped for I stopped for gas at 5:25gas at 5:25

I ate dinner at I ate dinner at 5:005:00

I went to the I went to the store at 5:15store at 5:15

Dating Past Geologic EventsDating Past Geologic Events

What is the difference between What is the difference between these two dating methods?these two dating methods? Relative Time Relative Time has no actual times has no actual times

but can be put in orderbut can be put in order

Absolute Time Absolute Time gives actual timesgives actual times

Relative TimeRelative Time

Puts events in a Puts events in a sequencesequence without telling without telling whenwhen they they actually happenedactually happened

Does not reveal Does not reveal actual ageactual age but but age in comparisonage in comparison to other to other eventsevents

Relative DatingRelative Dating

The evidence is The evidence is in the in the rocksrocks

Each Each layerlayer represents a represents a different place different place in timein time

Every Every layer of layer of rockrock is another is another part of the part of the timelinetimeline

UniformitarianismUniformitarianism

““the present is the key to the pastthe present is the key to the past””

We can watch We can watch how things happen how things happen nownow to understand how to understand how they they happened before.happened before.

UniformitarianismUniformitarianism

James HuttonJames Hutton realized these realized these processes did processes did not happen not happen quicklyquickly therefore the therefore the Earth Earth must be must be very old.very old.

UniformitarianismUniformitarianism

Siccar pointSiccar point in in Scotland is Scotland is where he made where he made the the observationsobservations

Came up with Came up with the idea of the idea of DEEP TIMEDEEP TIME

Principles of Relative DatingPrinciples of Relative Dating

The Principle of SuperpositionThe Principle of Superposition The Principle of Cross-Cutting The Principle of Cross-Cutting

RelationshipsRelationships Embedded FragmentsEmbedded Fragments

The Principle of SuperpositionThe Principle of Superposition Draw This…Draw This…

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WaterWater

The Principle of SuperpositionThe Principle of Superposition

The The OLDESTOLDEST rock is on the rock is on the bottom and thebottom and the YOUNGEST YOUNGEST is is on the topon the top

Rocks are deposited Rocks are deposited horizontallyhorizontally

The Principle of Cross-Cutting The Principle of Cross-Cutting RelationshipsRelationships

Draw This…Draw This…

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WaterWater44

The Principle of Cross-Cutting The Principle of Cross-Cutting RelationshipsRelationships

An igneous intrusion isAn igneous intrusion is YOUNGERYOUNGER than the rock it than the rock it intrudesintrudes

A fault is A fault is YOUNGERYOUNGER than the than the rock it breaksrock it breaks

The Principle of Embedded The Principle of Embedded FragmentsFragments

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2233

WaterWater44

The Principle of Embedded The Principle of Embedded FragmentsFragments

Rocks that are embedded in Rocks that are embedded in other rocks are other rocks are OLDEROLDER than the than the rock they are found.rock they are found.

UnconformityUnconformity

GapsGaps in time in time Surfaces have been Surfaces have been erodederoded

awayaway New rock has been New rock has been laid on toplaid on top

UnconformityUnconformity

Putting in all togetherPutting in all together

Rock layer correlationRock layer correlation Matching rock in one area to rocks Matching rock in one area to rocks

in anotherin another Match characteristicsMatch characteristics Match index fossilsMatch index fossils Using fossils to tell what type of Using fossils to tell what type of

environment existedenvironment existed

Index FossilsIndex Fossils

Fossils that can be used to Fossils that can be used to identify a identify a certain rock layercertain rock layer

Fossils that lived within a Fossils that lived within a certain certain timetime can give the rock a relative can give the rock a relative age. See page 653age. See page 653

FossilsFossils

Fossils can also give clues to Fossils can also give clues to the type of environment existed.the type of environment existed. Is there a lot of Is there a lot of coralcoral?? Are there a lot of Are there a lot of amphibiansamphibians?? Are there a lot of Are there a lot of deep sea deep sea

animalsanimals??

Relative TimeRelative Time

Use the present to determine Use the present to determine past processespast processes

No No actual timeactual time is given is given Fossils can be used to indicate Fossils can be used to indicate

a a general timegeneral time 3 Principles3 Principles