Index Fossils, Evolution, Biostratigraphy and the Geologic Time Scale

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Index Fossils, Evolution, Biostratigraphy and the
Geologic Time Scale
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Bio-Events

• First appearances of new species
• First appearances of new higher taxa
• Extinctions of species
• Mass extinctions of multiple taxa
• Bio-events are unique points in geologic time

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Index Fossils

• Some fossils are more useful than others for
  relative age determinations
• Fossils that are most useful are called INDEX
  FOSSILS
• What factors would maximize a fossils
  usefulness?

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Index Fossils

• Limited Stratigraphic Range
• Widespread Geographic Distribution
• Commonly Pelagic
• Or, tolerant of a wide variety of environments
  (found in many facies)

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Geologic Time Scale

• Standard subdivisions of Earths history
• A common language by international agreement
• Bio-Events are used to subdivide Geologic Time
• Stratotypes or type examples are designated so
  comparisons can be standardized

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Geologic Time Scale

• A hierarchy of time units
• Eon
• Era
• Period
• Epoch
• Age
• Boundaries are defined by bio-events

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Eons

• Phanerozoic obvious life 530 Ma to present
• Proterozoic prototypical life 2.5 Ga to 530
  Ma
• Archean ancient circa 4.6 Ga to 2.5 Ga
• Archean and Proterozoic comprise nearly 90 of
  Earths history!

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Phanerozoic Eon

• Cenozoic Era modern life 65 Ma to present
• Mesozoic Era middle life 248 Ma to 65 Ma
• Paleozoic Era ancient life 543 Ma to 248 Ma

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Learn the following (in order from oldest to
youngest)

• 3 Eons
• 3 Eras of the Phanerozoic
• All of the Periods of the Phanerozoic and the
  Eras to which they belong
• Picks numerical ages of the boundaries
  between Eons and between Eras

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Index Fossils andInternational Stratotypes

• Biostratigraphy and Global Politics

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Systems, Series, Stages

• Devonian System
• Upper Devonian Series
• Famennian
• Frasnian
• Middle Devonian Series
• Givetian
• Eifelian
• Lower Devonian
• Emsian
• Pragian
• Lochkovian
• Silurian System
• Upper Silurian Series
• Prídolí Stage

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Index Fossilsand the S-D Boundary

• Graptolites
• Conodonts
• Chitinozoans
• Trilobites
• Brachiopods
• Cephalopods

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Definition ofthe S-D Boundary

• Stratotype Klonk, near Suchomasty, Czech
  Republic

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S-D GSSP

• GSSP Global Stratotype, Sequence and Point
• First appearance of Monograptus uniformis
  uniformis
• Bed 20
• Klonk, Czechia