Stratigraphy Principles of Stratigraphy Types of Stratigraphy Contacts

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: 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 Lithostratigraphic Unit Lithology 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 Lithostratigraphic Unit Lithology 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 *Formation Member / Tongue / Lentil Bed / Flow *Formation: distinct, mappable rock body with definable boundaries

Types of Stratigraphy Lithostratigraphic Units lens / lentil (E. Mc. Bride)

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. Mc. Bride)

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 Muav Limestone 150 million years

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. Mc. Bride)

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