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

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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