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.”
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“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: the study of the 3-D spatial and temporal relationships among rocks
The oldest rocks are found on the bottom and the youngest rocks on the top.
2. Original Horizontality
sediments are deposited at the earth’s surface in flat layers
3. Lateral Continuity
a bed will extend laterally until:
4. Cross-Cutting Relationships
Rock that are cut by another geologic feature are older than the feature that cuts them.
Principles of Stratigraphy
5. Rule of Inclusions
If pieces of rock A are included in rock B, rock A formed before rock B.
6. Faunal Succession
Systematic sequence of fossils with time. Extinct fossils do not reappear in younger rocks.
Member / Tongue / Lentil
Bed / Flow
*Formation: distinct, mappable rock body with definable boundaries
lens / lentil
Types of Contacts (Depositional)
(Boggs, p. 453)
Hiatus: amount of missing time
Diastem: small amount of missing rock / time
Unconformity: buried surface of erosion; missing rock / time
Erosion – Mechanical, Chemical, Biological
Drop in Sea Level
Uplift of Land
Calvert Bluff / Alluvium Contact (Field Trip 1)
150 million years
2. Paraconformity – sediments on sediments (same orientation)
no obvious erosion surface
(Boggs, p. 456)
3. Angular unconformity – sediments on sediments (different orientations)
4. Nonconformity – sediments on crystalline igneous or metamorphic rocks
Uplift, Erosion, Deposition
550 million years
1800 million years
Nonconformity in Progress