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Stratigraphy
• Principles of Stratigraphy
• Types of Stratigraphy
• Contacts
• Unconformities
Text: Manual p. 29-35
Stratigraphy
“Stratigraphy can be defined as the complete triumph
of terminology over facts and common sense.”
Attributed to P.D. Krynine by J. Ferm in Burton et al., 1987.
Stratigraphy
Stratigraphy: the study of the 3-D spatial and temporal
relationships among rocks
Stratigraphy
• Principles of Stratigraphy
• Types of Stratigraphy
• Contacts
• Unconformities
Text: Manual p. 29-35
Principles of Stratigraphy
1. Superposition
The oldest rocks are found on the bottom and
the youngest rocks on the top.
youngest
oldest
Principles of Stratigraphy
youngest?
oldest?
Principles of Stratigraphy
younger
older
Principles of Stratigraphy
2. Original Horizontality
sediments are deposited at the earth’s surface
in flat layers
Principles of Stratigraphy
Principles of Stratigraphy
cross-bedding
Principles of Stratigraphy
3. Lateral Continuity
a bed will extend laterally until:
1. Pinches out.
2. Abuts against older rock.
3. Truncated by erosion.
4. Cut by fault.
Principles of Stratigraphy
Principles of Stratigraphy
4. Cross-Cutting Relationships
Rock that are cut by another geologic feature are older
than the feature that cuts them.
Igneous
Intrusion
Fault
Erosion
Principles of Stratigraphy
5. Rule of Inclusions
If pieces of rock A are included in rock B,
rock A formed before rock B.
B
A
Principles of Stratigraphy
6. Faunal Succession
Systematic sequence of fossils with time.
Extinct fossils do not reappear in younger rocks.
http://www.geo.utexas.edu/courses/401/
Stratigraphy
• Principles of Stratigraphy
• Types of Stratigraphy
• Contacts
• Unconformities
Text: Manual p. 29-35
Types of Stratigraphy
Type
Subdivisions
Property
Lithostratigraphy
Lithostratigraphic Unit
Lithology
Pedostratigraphy
Pedostratigraphic Unit
Buried Soils
Biostratigraphy
Bio Zones
Fossil Content
Chronostratigraphy
Chronostratigraphic Units
(Period, Epoch, Age)
Time Relationships
Geochronostratigraphy
Geochronostratigraphic Unit
(System, Series, Stage)
Time Relationships
Magnetostratigraphy
Magnetic Reversals, Chrons
Magnetic Polarity
Chemostratigraphy
Isotope Zones
Chemical
Characteristics
Sequence Stratigraphy
Allostratigraphic Units
unconformity-bounded
packages
Types of Stratigraphy - Allostratigraphy
Types of Stratigraphy
Type
Subdivisions
Property
Lithostratigraphy
Lithostratigraphic Unit
Lithology
Pedostratigraphy
Pedostratigraphic Unit
Buried Soils
Biostratigraphy
Bio Zones
Fossil Content
Chronostratigraphy
Chronostratigraphic Units
(Period, Epoch, Age)
Time Relationships
Geochronostratigraphy
Geochronostratigraphic Unit
(System, Series, Stage)
Time Relationships
Magnetostratigraphy
Magnetic Reversals, Chrons
Magnetic Polarity
Chemostratigraphy
Isotope Zones
Chemical
Characteristics
Sequence Stratigraphy
Allostratigraphic Units
unconformity-bounded
packages
Types of Stratigraphy - Lithostratigraphy
Super Group
Group
*Formation
Member / Tongue / Lentil
Bed / Flow
*Formation: distinct, mappable rock body
with definable boundaries
Types of Stratigraphy
Lithostratigraphic Units
lens / lentil
(E. McBride)
Stratigraphy
• Principles of Stratigraphy
• Types of Stratigraphy
• Contacts
• Unconformities
Text: Manual p. 29-35
Types of Contacts
• Intrusive
• Fault
• Depositional
- Conformable Contact
- Unconformity
Types of Contacts (Depositional)
intercalated
gradual
gradation
abrupt
Vertical Contacts
Lateral Contacts
intertonguing
pinchout
(Boggs, p. 453)
Types of Contacts (Depositional)
Lateral Contacts
(E. McBride)
Stratigraphy
• Principles of Stratigraphy
• Types of Stratigraphy
• Contacts
• Unconformities
Text: Manual p. 29-35
Unconformities
Unconformity: buried surface of erosion; missing rock / time
vs
Hiatus: amount of missing time
vs
Diastem: small amount of missing rock / time
Unconformities
Erosion – Mechanical, Chemical, Biological
Drop in Sea Level
Uplift of Land
Unconformities
Calvert Bluff / Alluvium Contact (Field Trip 1)
Unconformities
Types:
1.
Disconformity
2.
Paraconformity
3.
Nonconformity
4.
Angular Unconformity
Unconformities
1. Disconformity – sediments on sediments (same orientation) with
obvious erosion
Unconformities
Disconformity
Supai Group
20 million years
Redwall Limestone
150 million years
Muav Limestone
Unconformities
2. Paraconformity – sediments on sediments (same orientation)
no obvious erosion surface
(Boggs, p. 456)
Unconformities
3. Angular unconformity – sediments on sediments
(different orientations)
Unconformities
Angular Unconformity
250 million years
Unconformities
Angular Unconformity
Wyoming
Unconformities
Angular Unconformity
(E. McBride)
Unconformities
4. Nonconformity – sediments on crystalline igneous or
metamorphic rocks
Uplift, Erosion, Deposition
Erosional Surface
Unconformities
Nonconformity
550 million years
1800 million years
Unconformities
Enchanted Rock
Nonconformity in
Progress
Canadian Shield