Stratigraphy The study of the origin, relationship and extent of rock layers (Strata).
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Transcript of Stratigraphy The study of the origin, relationship and extent of rock layers (Strata).
StratigraphyThe study of the origin, relationship and extent of rock layers (Strata).
LithostratigraphyEach layer is a different rock type.
ChronostratigraphyEach layer is a different age.
BiostratigraphyEach layer contains a different fossil
assemblage.
Lithostratigraphic Units
Supergroup
Group A
Formation A
Member A
Member B
Member C
Formation B
Member D
Member E
Member F
Formation CMember G
Member H
Group B
Formation D
Member I
Member J
Member K
Member L
Member M
Formation E
Member N
Member O
Member P
Member Q
Formation F
Member R
Member S
Member T
Supergroup|
Group|
Formation|
Member|
Bed
Lithostratigraphic Example:
Grand Canyon
How do we Illustrate Stratigraphy?
•Stratigraphic Columns•Cross Sections•Geologic Maps
Stratigraphic Column:John Day
Fossil Beds NM
Geologic MapsSnoqualmie Pass
Chronostratigraphic Map of Washington
Cross Sections
Principles (Laws) of Stratigraphy
Principle of…• Original Horizontality
• Superposition• Lateral Continuity
• Cross Cutting Relationships
• Inclusions• Faunal Succession
Walther’s Law
Nicholas Steno
1. Principle of Original Horizontality
2. Principle of Superposition
Youngest Strata
Oldest Strata
3. Principle of Lateral Continuity
Lateral Continuity
Charles Lyell
4. Principle of Cross Cutting Relationships
5. Principle of Inclusions
6. Principle of Faunal Succession
Sketch by Baron Cuvier (1769-1832)
William “Strata” Smith
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."
Biostratigraphy
Defined by first and last appearance of index fossils and/or fossil assemblages
Superzone - Biozones - Subzones
Diatoms
Boundaries:Conformable Bed Contacts
Gradational Sharp
Boundaries:Unconformities
Gaps in Rock = Gaps in Time
Types of Unconformities: Nonconformity
Nonconformity - Grand Canyon
Using Inclusions to Recognize a Nonconformity
Types of Unconformities: Angular Unconformity
Formation of an Angular Unconformity
Angular Unconformity in the Grand Canyon
The Angular Unconformity
at Siccar Point, Scotland
Source: Edward A. Hay, De Anza College, Cupertino, CA
Types of Unconformities: Disconformity
Formation of a Disconformity
Walther’s Law
Johannes Walther(1860-1937)
Concept ofSedimentary 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.
Facies
Depositional Environments
Facies Example
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
A = Sandstone facies (beach environment)B = Shale facies (offshore marine environment)
C = Limestone facies (far from sources of terrigenous input)
Facies Change
Marine Transgression = Sea Level Rise
Marine Regression = Sea Level Fall
Walther’s LawSedimentary environments that started out side-by-side
will end up overlapping one another over time due to transgressions and regressions.
Limestone Shale Siltstone Sandstone
Reef Lagoon Near Shore Beach
Environment
Facies
Marine Trangression
Walther’s Law
Marine Regression
“The sea goes in, the sea goes out.”
Blue = No deposition
Vail Curve of Sea Level
History
Transgression Regression
Correlation
A B C
Regression
Transgression
Example of Correlation
Colorado Plateau Correlation
Colorado Plateau Correlation
Chronostratigraphic Units
Chronostratigraphic (Time-Rock) Unit • Eonothem• Erathem• System• Series• Stage
Chronostratigraphy and the
Development of the Geologic Time Scale
Chronostratigraphic& Time Units
Time Unit• Eon• Era• Period• Epoch• Age
Time-Rock Unit • Eonothem• Erathem• System• Series• Stage
GeologicTimeScale
Era Age (Myrs) Epoch
0.01Holocene
1.8Pleistocene
5.3Pliocene
23.8Miocene
33.6Oligocene
54.8Eocene
65Paleocene
144
206
248
290
323
354
417
443
490
543
2500
3800
Precambrian
Phanerozoic
Eon
Proterozoic
Archean
Hadean
Period
Quaternary
Tertiary
Neogene
Paleocene
Mississippian
Cenozoic
Mesozoic
Paleozoic
Cretaceous
Jurassic
Age of the Earth 4600 Myrs (4.6 Byrs)Source: Geological Society of America (1999)
Geologic Time Scale
Devonian
Silurian
Ordivician
Cambrian
Triassic
Permian
Pennsylvanian
Relative Dating of Rocks Using Stratigraphic Principles
Example 2 of Relative Time