Upload
dyllis
View
37
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Lecture 004. Fossils and the Discovery of Earth History. FOSSIL Evidence of the existence of past life. Problems with using fossils: only organisms with hard parts will be fossilized and leave a record - PowerPoint PPT Presentation
Citation preview
Fossils and the Discovery of Earth History
Fossils and the Discovery of Earth History
Lecture 004
FOSSIL
Evidence of the existence of past life
Problems with using fossils:1. only organisms with hard parts will be
fossilized and leave a record2. if you find a fossil in a certain place, it
doesn’t mean it lived there; example-continent moved after extinction
3. record is uneven in time and area4. many fossils that get preserved are a
dead end5. most of record is lost or unexplored;
missing link- look at homonids
Benefits of using fossils:
1. provides evidence that it once existed
2. provides minimum ages
3. documents extinction’s
4. use them to put together scenarios in paleoclimatology or extinction/immigration scenarios-----complete record with Hyracotherium
Horse Evolution
Horse Evolution Timeline
Hyracotherium
55 myaEOCENE ERA
Mesohippus
40 myaOLIGOCENE ERA
Miohippus
30 myaOLIGOCENE ERA
Merychippus
20 myaOLIGOCENE ERA
Pliohippus
10 myaOLIGOCENE ERA
Equus
4 myaMODERN ERA
Hyracotherium55 mya
Miohippus35 mya
Merychippus17 mya
Equusmodern
Note: diagram is scaled so organisms appear to be the same size
TYPES OF FOSSILS
Body Fossils Remains of the organism itself
Trace FossilsEvidence of the movement or activity of
the organism
Body Fossils
stingray
fish
TRACE FOSSILS
Tracks and TrailsBurrows and Borings
Coprolites
Trace FossilsTracks Trails
Trace FossilsBurrows & Borings
This section of fossil conifer wood is Cretaceous of the Antarctic Peninsula.The round holes, filled with brown mudstone or white crystals, were formed by wood-boring bivalves that bored into the log while it was floating on the Cretaceous seas as driftwood.
CoproliteCoprolite
Trace Fossils
Modes of Body Part Preservation
1. Unaltered fossils• Soft parts (rare) & Hard parts
A. peat bogsB. amber C. tar pits D. mummification or desiccation E. refrigeration
Jellyfish fossil- Precambrian Edicarian Fauna
Modes of Body Part Preservation
2. Altered fossils• petrifaction
permineralizationreplacementrecrystalization
• carbonization
Modes of Body Part Preservation
3. Imprints• molds• impressions
1. Unaltered FossilA. Peat bog
A variety of fossils preserved by rapid burial in this anaerobic environment.
Amber is the pitch from conifer trees
1. Unaltered Fossil B. Amber With Insects
Mosquito in AmberMosquito in Amber
1. Unaltered FossilC. Tar Pits
La Brea Tar PitGround Sloth
1. Unaltered Fossil D. Mummification
LeonardoDuck-billed dinosaur
77 myo. Montana
Wooly Mammoth frozen in Siberia(found 1987)- 20,000 years old
1. Unaltered FossilE. Refrigeration
2. Altered FossilPetrifactionPermineralized- original pore space is filled in with minerals
Shark’s Tooth
2. Altered FossilPetrified wood
coal
2. Altered FossilCarbonization
3. Imprints
Glossopteris impression
Gastropod mold
Other Kinds of Evidence For Past Life
GastrolithsFossil Fuels
• Fossils exhibit great diversity in forms, some resembling living forms, some appearing very different from modern forms.
• Physical consistency is usually that of stone rather than of the materials exhibited by comparable living species.
• Many fossils are found high in the mountains resembled forms that normally occur in the ocean.
• Fossils are often found encased in hard stone.
Characteristics of Fossils Known to the Ancients
• 80,000 year old Neanderthal site with fossil snail and coral skeletons.
• 35,000 year old Cro-Magnon burial site with fossil-shell necklaces.
• Early Egyptian site (perhaps 3200 B.C.E.) with fossil mounted in metal.
• It is possible, but not certain, that these prehistoric peoples regarded fossils as magical.
Evidence for Early Human Interest in Fossils
Mythical Ideas About FossilsMythical Ideas About Fossils
Fossils grew in the rocksNo distinction between fossils and crystals and oresMagical and curative powers Artifacts of the Devil
155 - 222 C.E.Tertuillian
The view that great floods were a major contributor to earth evolutionExample of catastrophism
Leonardo da VinciLeonardo da Vinci
1452 - 1519
• Observed fossils on mountains• Rejected flood theory• Argued that the earth is old• Grasp concept of superposition
Petrified Wood
Studied fossils and compared them to living organisms
Robert Hooke (1635-1703)
Nicholaus StenoNicholaus Steno
1638 - 1686Compared sharks teeth to “tongue stones”Argued that fossils could be altered in chemical composition without changing their formSteno’s Law of Superposition
SuperpositionSuperposition
SuperpositionSuperposition
Stratigraphic setting of the Cambrian Burgess Shale
540 MYA
505 MYA
Georges-Louis Leclerc de BuffonGeorges-Louis Leclerc de Buffon
1707 - 1788
Origin of the Earth- collision of a comet with the sunAge of Earth ~75K
Histoire Naturelle
Baron Georges CuvierBaron Georges Cuvier
1769 - 1832
CatastrophistSpecies don’t change over timeTheory of extinction
• Fossil record provided evidence for catastrophes
• Earth is young• E.g. Noah’s flood• Recent: meteor impact &
volcanism
William SmithWilliam Smith
Development of the Geologic Time ScalePrinciple of faunal succession
1769 - 1839
Correlating Rock Layers
James Hutton
• The Rock Cycle
• Deep Time
• Uniformitarianism
1726 - 1797
The Rock CycleThe Rock Cycle
Deep TimeDeep Time
"we find no vestige of a beginning and no
prospect of an end"
UniformitarianismUniformitarianism
• The present-day earth has been shaped slowly by everyday forces of erosion and deposition
• Earth is old
• E.g., erosion & uplifting = mountains
Charles LyellCharles Lyell
1797 - 18751797 - 18751797 - 18751797 - 1875
Percentages of TertiarySpecies Still Living
Recent Pliocene
Older Pliocene
Miocene
Eocene
96
42
17
3
CATASTROPHISM
VERSUS
UNIFORMITARIANISM
• The earth's surface has been shaped by the cumulative effects of episodic events over long periods of time.
• Some may have been catastrophic, resulting in mass extinctions.
• The geologic evidence was not consistent with the theory of catastrophic global floods
• The earth is ancient, far longer than the 6,000 years provided by a literal reading of the Bible.
Catastrophism vs. UniformitarianismResolution
Questions:
• Jellyfish are not often seen in the fossil record because:
• The shark’s tooth is an example of an altered fossil that underwent _________.
• Stenos Law of Superposition stated that:• Evidence to support catastrophism included:• Leonardo da Vinci theorized that shells found
on a mountain top got there because _____________.