Stratigraphy
The study of the origin, relationship and
extent of rock layers (Strata).
Lithostratigraphy
Each layer is a different rock type.
Chronostratigraphy
Each layer is a different age.
Biostratigraphy
Each layer contains a different fossil
assemblage.
Lithostratigraphic Units
Member A
Formation A
Member B
Member C
Group A
Member D
Formation B
Member E
Member F
Formation C
Member G
Member H
Member I
Member J
Supergroup
Formation D
Member K
Member L
Member M
Member N
Group B
Formation E
Member O
Member P
Member Q
Member R
Formation F
Member S
Member T
Supergroup
|
Group
|
Formation
|
Member
|
Bed
Principles (Laws) of Stratigraphy
Principle of…
• Original Horizontality
• Superposition
• Lateral Continuity
• Cross Cutting
Relationships
• Inclusions
• Faunal Succession
Walther’s Law
Nicholas Steno Danish physician
Principles of Stratigraphy
1. Original Horizontality
sediments are deposited at the
earth’s surface in flat layers
1. Principle of Original Horizontality
Principles of Stratigraphy
2. Superposition
The oldest rocks are found on the bottom
and the youngest rocks on the top.
youngest
oldest
2. Principle of Superposition
Youngest Strata
Oldest Strata
Principles of Stratigraphy
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.
3. Principle of Lateral Continuity
Lateral Continuity
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
Charles Lyell
4. Principle of Cross Cutting
Relationships
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
5. Principle of Inclusions
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/