Stratigraphy

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Stratigraphy

• The study of the origin, relationship and extent
  of rock layers (Strata).

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LithostratigraphyEach layer is a different rock
type.
ChronostratigraphyEach layer is a different age.
BiostratigraphyEach layer contains a different
fossil assemblage.
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Lithostratigraphic Units
Supergroup Group A Formation A Member A
Supergroup Group A Formation A Member B
Supergroup Group A Formation A Member C
Supergroup Group A Formation B Member D
Supergroup Group A Formation B Member E
Supergroup Group A Formation B Member F
Supergroup Group A Formation C Member G
Supergroup Group A Formation C Member H
Supergroup Group B Formation D Member I
Supergroup Group B Formation D Member J
Supergroup Group B Formation D Member K
Supergroup Group B Formation D Member L
Supergroup Group B Formation D Member M
Supergroup Group B Formation E Member N
Supergroup Group B Formation E Member O
Supergroup Group B Formation E Member P
Supergroup Group B Formation E Member Q
Supergroup Group B Formation F Member R
Supergroup Group B Formation F Member S
Supergroup Group B Formation F Member T
Supergroup Group Formation Member Bed
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Lithostratigraphic ExampleGrand Canyon
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How do we Illustrate Stratigraphy?

• Stratigraphic Columns
• Cross Sections
• Geologic Maps

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Stratigraphic ColumnJohn Day Fossil Beds NM
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Geologic MapsSnoqualmie Pass
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Chronostratigraphic Map of Washington
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Cross Sections
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Principles (Laws) of Stratigraphy

• Principle of
• Original Horizontality
• Superposition
• Lateral Continuity
• Cross Cutting Relationships
• Inclusions
• Faunal Succession
• Walthers Law

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Nicholas Steno
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1. Principle of Original Horizontality
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2. Principle of Superposition
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3. Principle of Lateral Continuity
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Lateral Continuity
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Charles Lyell
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4. Principle of Cross Cutting Relationships
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5. Principle of Inclusions
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6. Principle of Faunal Succession
Sketch by Baron Cuvier (1769-1832)
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William Strata Smith
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6. Principle of Faunal Succession
" . . . each stratum contained organized fossils
peculiar to itself, and might, in cases otherwise
doubtful, be recognized and discriminated from
others like it, but in a different part of the
series, by examination of them."
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Biostratigraphy
Superzone - Biozones - Subzones
Defined by first and last appearance of index
fossils and/or fossil assemblages
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Diatoms
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BoundariesConformable Bed Contacts
Gradational
Sharp
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BoundariesUnconformitiesGaps in Rock Gaps in
Time
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Types of Unconformities Nonconformity
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Nonconformity - Grand Canyon
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Using Inclusions to Recognize a Nonconformity
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Types of Unconformities Angular Unconformity
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Formation of an Angular Unconformity
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Angular Unconformity in the Grand Canyon
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The Angular Unconformity at Siccar Point,
Scotland
Source Edward A. Hay, De Anza College,
Cupertino, CA
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Types of Unconformities Disconformity
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Formation of a Disconformity
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Walthers Law
Johannes Walther(1860-1937)
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Concept ofSedimentary Facies
Depositional Environments
Facies
Sedimentary Facies refers to all of the
characteristics of a particular rock unit. The
characteristics of the rock unit come from the
depositional environment.
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Facies Example
Facies Change
A Sandstone facies (beach environment) B
Shale facies (offshore marine environment) C
Limestone facies (far from sources of terrigenous
input)
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Marine Transgression Sea Level RiseMarine
Regression Sea Level Fall
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Walthers Law
Sedimentary environments that started out
side-by-side will end up overlapping one another
over time due to transgressions and regressions.
Facies
Limestone
Shale
Siltstone
Sandstone
Lagoon
Beach
Reef
Near Shore
Environment
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Marine Trangression
Walthers Law
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Marine Regression
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The sea goes in, the sea goes out.
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Blue No deposition
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Vail Curve of Sea Level History
Transgression Regression
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Correlation
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A
B
C
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Example of Correlation
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Colorado Plateau Correlation
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Colorado Plateau Correlation
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Chronostratigraphic Units

• Chronostratigraphic (Time-Rock) Unit
• Eonothem
• Erathem
• System
• Series
• Stage

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Chronostratigraphy and the Development of the
Geologic Time Scale
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Chronostratigraphic Time Units

• Time Unit
• Eon
• Era
• Period
• Epoch
• Age

• Time-Rock Unit
• Eonothem
• Erathem
• System
• Series
• Stage

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GeologicTimeScale
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(No Transcript)
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Relative Dating of Rocks Using Stratigraphic
Principles
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Example 2 of Relative Time