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Stratigraphic Laws and Geohistory
Time and Stratigraphy Core
Learning Objectives
By the end of this lesson, you will be able to:
Describe the six basic Laws of Stratigraphy (i.e. the study of Strataor Layers of the Earth):
Original Horizontality
Lateral Continuity
Superposition
Cross-cutting Relationships
Law of Inclusions
Law of Faunal Succession
Basic Geology_________________________________________________________________________________________________________Time and Stratigraphy Core
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Stratigraphic Laws
Stratigraphic Laws are basic principles that all geologists use in deciphering the spatial and temporal relationships of rock layers
These laws were developed in the 17th to 19th centuries based upon the work of Nico Steno, James Hutton and William Smith, among others
The six Stratigraphic Laws are:• Original Horizontality
• Lateral Continuity
• Superposition
• Cross-cutting Relationships
• Inclusions
• Faunal Succession
Law of Original Horizontality
• Original Horizontality
• Lateral Continuity
• Superposition
• Cross-cutting Relationships
• Inclusions
• Faunal Succession
• Assumes that the sedimentary rocks are deposited in horizontal layers
• If the rocks are tilted or folded we can infer that they have been subjected to a deformation event
• In general, most sedimentary rocks are deposited horizontal or very close to horizontally
Basic Geology_________________________________________________________________________________________________________Time and Stratigraphy Core
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Law of Lateral Continuity
• Original Horizontality
• Lateral Continuity
• Superposition
• Cross-cutting Relationships
• Inclusions
• Faunal Succession
• Assumes that sedimentary rocks are laterally contiguous over large areas
• “Material forming any stratum were continuous over the surface of the Earth unless some other solid bodies stood in the way.” Steno, 1669
Law of Superposition
• Original Horizontality
• Lateral Continuity
• Superposition
• Cross-cutting Relationships
• Inclusions
• Faunal Succession
• Assumes that most sedimentary rocks were originally deposited in horizontal layers (law of horizontality)
• Therefore, the oldest rocks will be on the bottom of the sequence and the youngest on the top
Basic Geology_________________________________________________________________________________________________________Time and Stratigraphy Core
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Superposition in the Stratigraphic Column
Law of Superposition
• Original Horizontality
• Lateral Continuity
• Superposition
• Cross-cutting Relationships
• Inclusions
• Faunal Succession
• Igneous intrusions and geological structures must be younger than the rocks they affect or cut across
• If things deposited horizontally have an igneous intrusion, then those rocks have been there before intrusions occurred
• If the rocks are faulted or folded, they have been there horizontal to begin with and were deformed after they were deposited
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Law of Cross-Cutting Relationships
Law of Superposition
• Original Horizontality
• Lateral Continuity
• Superposition
• Cross-cutting Relationships
• Inclusions
• Faunal Succession
• Rock fragments (clasts) from another rock must be older than the rock containing the fragments
• For example, a sandstone that is made up of bits of igneous rock, indicates that the igneous rock was there first, got eroded, and the particles of the igneous rock make up the sandstone
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Law of Superposition
• Original Horizontality
• Lateral Continuity
• Superposition
• Cross-cutting Relationships
• Inclusions
• Faunal Succession
• Fossils can be used to correlate sedimentary rocks
• Certain fossil groups are preceded or succeeded by other fossil groups. This allows for the development of a fossil stratigraphy that can be used around the world
• Fossils used for age dating and correlation of strata from one region to another are called Index Fossils.
Using Fossils for Correlation
Correlation of strata exposed at three localities many kilometres apart. The fossils show that at locality 3 stratum D is missing. Either D was never deposited there, or it has been removed by erosion before deposition of E.
Courtesy of John Wiley and Sons, Inc.
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Using Fossils for Marine / Non-Marine
Learning Objectives
Describe the six basic Laws of Stratigraphy (i.e. the study of Strata or Layers of the Earth):
Original Horizontality
Lateral Continuity
Superposition
Cross-cutting Relationships
Law of Inclusions
Law of Faunal Succession
You are now able to:
Basic Geology_________________________________________________________________________________________________________Time and Stratigraphy Core
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Geologic Time and Stratigraphy
Time and Stratigraphy Core
Learning Objectives
By the end of this lesson, you will be able to:
Differentiate between relative and absolute geological time
Use the geological time scale
Relate deposition to stratigraphic concepts
Differentiate between: Lithostratigraphy – based on rock type
Chronostratigraphy – based on time equivalence
Biostratigraphy – based on fossils Magnetostratigraphy – based on the rocks magnetic properties
Explain the connection between correlation, stratigraphy, and reservoirs
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The Standard Geologic Column
Principal Methods of Radiometric Age Determination (Absolute Time)
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Determining Relative Time using Radiometrics
Use Radiometric dating of Uranium, Thorium or Potassium in Igneous Intrusions for determining Relative Time
Standard Geologic Column with Atomic Dates
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Correlation
Correlation is:• The process of making the link between rocks from one area
with rocks from another area• The equivalence in the character and stratigraphic position
of the geological characteristics in two or more separate areas
If we measure geological formations in one place, how does it compare to
formations in another place?
Correlation of Stratigraphic Sections
Basic Geology_________________________________________________________________________________________________________Time and Stratigraphy Core
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Log Correlation Across Peco Field, Alberta, Canada
Stratigraphy
Stratigraphy is:• The science of rock strata, considering their:
– Original succession– Age relations– Form– Distribution– Lithology– Fossils– Geophysical and geochemical properties– Mode of origin– Geological history
• The study of the layering of rocks
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Stratigraphic Concepts
Lithostratigraphy Chronostratigraphy Biostratigraphy
Lithostratigraphy
Lithostratigraphy Chronostratigraphy Biostratigraphy
Description and organization of rocks into distinctive named units based on lithology and stratigraphic relations
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Example: Lithostratigraphic Correlation
Lithostratigraphic Correlation Independent of Time
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Chronostratigraphy
Lithostratigraphy Chronostratigraphy Biostratigraphy
Deals with the age of strata and their time relations
Chronostratigraphically Events, Independent of Lithostratigraphic Correlation
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Cross-Section Showing Geographic Distribution of Formations and Facies Changes
View of Fluvial Sand Outcrop and Facies Changes
Basic Geology_________________________________________________________________________________________________________Time and Stratigraphy Core
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View of Fluvial Sands in Electric Log Cross Section
View of Fluvial Sands in Electric Log Cross Section showing Facies Changes
Facies Changes
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Biostratigraphy
Lithostratigraphy Chronostratigraphy Biostratigraphy
The distribution of fossils in the stratigraphic record and the organization of strata into units based on their contained fossils
Subsurface Correlation Between Wells Using Fossils
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Examples of MicroFossils used in Correlation
Typical Size of MicroFossils used in Correlation
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Selected Other Types of Stratigraphy
Magnetostratigraphy• Plate tectonics is based on magneto stratigraphy
• The iron-rich minerals in magma orient themselves to magnetic north. When ready to turn solid, those crystals will get locked in place and can be used as an indicator of north or south.
Chemostratigraphy and Isotope Stratigraphy• Use specific minerals or chemical signatures that help
understand world temperatures and get a chronostratigraphic marker based on them
Basic Geology_________________________________________________________________________________________________________Time and Stratigraphy Core
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Key Concepts of Stratigraphy
Accommodation
• The space available for sediment accumulation between sea level and sea floor
Refs. SEPM Special Publication No. 42, 1988
Jackson, J., 1997, Glossary of Geology, American Geological Institute
Accommodation Envelope as a Function of Eustasyand Subsidence
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Key Concepts of Stratigraphy
Eustasy – (Sea level change) – a condition of worldwide sea level fluctuations influenced by:
• Global hydrologic balance, glaciation, ground water
• Ocean basin capacity, subsidence
• Plate tectonics, heat flow, subduction
Refs. SEPM Special Publication No. 42, 1988
Jackson, J., 1997, Glossary of Geology, American Geological Institute
First- and Second-Order Global Cycles of Relative Change of Sea Level During Phanerozoic Time
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Base Level and Stream Profile
Aggradation
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Sediment Loading on the Continental Shelf Results in Thick Sediment Wedges
Lowstand Base Level and Stream Profile
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Progradation
Highstand Base Level and Stream Profile
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Retrogradation
Learning Objectives
You are now able to:
Differentiate between relative and absolute geological time
Use the geological time scale
Relate deposition to stratigraphic concepts
Differentiate between: Lithostratigraphy – based on rock type Chronostratigraphy – based on time equivalence
Biostratigraphy – based on fossils
Magnetostratigraphy – based on the rocks magnetic properties
Explain the connection between correlation, stratigraphy, and reservoirs
Basic Geology_________________________________________________________________________________________________________Time and Stratigraphy Core
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Sequence Stratigraphy
Time and Stratigraphy Core
Learning Objectives
By the end of this lesson, you will be able to:
Define Sequence Stratigraphy terminology
Recall how to use Highstand and Lowstand system tracts in exploration
Relate deposition to stratigraphic concepts
Describe the connection between correlation, stratigraphy, and reservoirs
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Sequence Stratigraphy
The study of rock relationships within a chronostratigraphic framework of repetitive, genetically related strata bounded by surfaces of erosion or nondeposition, or their correlative conformities.
Key terms:• Unconformity• Parasequence• Sequence• Systems Tract• Maximum Flooding Surface• Condensed Section
Unconformity
Unconformity: A surface separating younger from older strata, along which there has been subaerial erosion or exposure for a significant amount of time
Parasequence: A relatively conformable succession of genetically related beds bounded by flooding surfaces of their correlative surfaces
Sequence: A relatively conformable succession of genetically related strata (parasequences) bounded by unconformities of their correlative conformities
Systems Tract: A rock body linking contemporaneous depositional systems, i.e., highstand, lowstand, transgressive systems tracts
Maximum Flooding Surface: The surface corresponding to the greatest landward extent of a marine transgression
Condensed Section: A thin, very slowly deposited section of sediments laid down during rising sea level when there was very low input of terrigenous sediment on the shelf
Basic Geology_________________________________________________________________________________________________________Time and Stratigraphy Core
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Illustration of a Unconformity (Erosional Surface)
Parasequence
Unconformity: A surface separating younger from older strata, along which there has been subaerial erosion or exposure for a significant amount of time
Parasequence: A relatively conformable succession of genetically related beds bounded by flooding surfaces of their correlative surfaces
Sequence: A relatively conformable succession of genetically related strata (parasequences) bounded by unconformities of their correlative conformities
Systems Tract: A rock body linking contemporaneous depositional systems, i.e., highstand, lowstand, transgressive systems tracts
Maximum Flooding Surface: The surface corresponding to the greatest landward extent of a marine transgression
Condensed Section: A thin, very slowly deposited section of sediments laid down during rising sea level when there was very low input of terrigenous sediment on the shelf
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Parasequences
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Sequence
Unconformity: A surface separating younger from older strata, along which there has been subaerial erosion or exposure for a significant amount of time
Parasequence: A relatively conformable succession of genetically related beds bounded by flooding surfaces of their correlative surfaces
Sequence: A relatively conformable succession of genetically related strata (parasequences) bounded by unconformities of their correlative conformities
Systems Tract: A rock body linking contemporaneous depositional systems, i.e., highstand, lowstand, transgressive systems tracts
Maximum Flooding Surface: The surface corresponding to the greatest landward extent of a marine transgression
Condensed Section: A thin, very slowly deposited section of sediments laid down during rising sea level when there was very low input of terrigenous sediment on the shelf
Physical Boundaries of a Sequence
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When Sea Level Falls, a New Set of Conditions is Created, Starting a New Sequence
Systems Tract
Unconformity: A surface separating younger from older strata, along which there has been subaerial erosion or exposure for a significant amount of time
Parasequence: A relatively conformable succession of genetically related beds bounded by flooding surfaces of their correlative surfaces
Sequence: A relatively conformable succession of genetically related strata (parasequences) bounded by unconformities of their correlative conformities
Systems Tract: A rock body linking contemporaneous depositional systems, i.e., highstand, lowstand, transgressive systems tracts
Maximum Flooding Surface: The surface corresponding to the greatest landward extent of a marine transgression
Condensed Section: A thin, very slowly deposited section of sediments laid down during rising sea level when there was very low input of terrigenous sediment on the shelf
Basic Geology_________________________________________________________________________________________________________Time and Stratigraphy Core
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All Deposits are Genetically Related
Highstand Systems Tract
Package of Sedimentary Units Deposited When Sea Level is High
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Lowstand Systems Tract
Package of Sedimentary Units Deposited When Sea Level is Low
Lowstand Systems Tract
Lowstand Wedge – Type 1 Sequence
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Location of Shoreline, Gulf Coast During Last Lowstand
Transgressive Systems Tract
Package of Sedimentary Units Deposited as Sea Level Rises
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Highstand Systems Tract
Package of Sediments Deposited While Sea Level is High
Maximum Flooding Surface and Condensed Section
Unconformity: A surface separating younger from older strata, along which there has been subaerial erosion or exposure for a significant amount of time
Parasequence: A relatively conformable succession of genetically related beds bounded by flooding surfaces of their correlative surfaces
Sequence: A relatively conformable succession of genetically related strata (parasequences) bounded by unconformities of their correlative conformities
Systems Tract: A rock body linking contemporaneous depositional systems, i.e., highstand, lowstand, transgressive systems tracts
Maximum Flooding Surface: The surface corresponding to the greatest landward extent of a marine transgression
Condensed Section: A thin, very slowly deposited section of sediments laid down during rising sea level when there was very low input of terrigenous sediment on the shelf
Basic Geology_________________________________________________________________________________________________________Time and Stratigraphy Core
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Illustration of Maximum Flooding Surfaces and Condensed Section
Learning Objectives
You are now able to:
Define Sequence Stratigraphy terminology
Recall how to use Highstand and Lowstand system tracts in exploration
Relate deposition to stratigraphic concepts
Describe the connection between correlation, stratigraphy, and reservoirs
Basic Geology_________________________________________________________________________________________________________Time and Stratigraphy Core
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PetroAcademyTM Basic Geology Core
Earth Materials Core
Time and Stratigraphy Core
Plate Tectonics and Structure Core
Subsurface Investigation Core
Erosion and Subaerial Depositional Environments Core
Marginal Marine Depositional Environments Core
Marine Depositional Environments Core
Generation and Migration Core and Unconventionals
Basic Geology_________________________________________________________________________________________________________Time and Stratigraphy Core
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