Sediments and sedimentary rocks chapter 5
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Sediments and Sedimentary Rocks Chapter 5. Concepts you will need to know for the exams. Weathering Erosion Transportation Sorting Angularity Sedimentary environments, Cross-bedding (sedimentary structures) Bioturbation, bedding sequences, diagenesis

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Concepts you will need to know for the exams l.jpg
Concepts you will need to know for the exams

  • Weathering

  • Erosion

  • Transportation

  • Sorting

  • Angularity

  • Sedimentary environments,

  • Cross-bedding (sedimentary structures)

  • Bioturbation, bedding sequences, diagenesis

  • Classes of sediments and sedimentary rock:

  • -based on grain size

  • -based on chemical composition, e.g., carbonate rocks ("carbonates") and evaporitic rocks ("evaporites")


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  • Lecture Outline

  • Sedimentary rocks

  • 2. Your sedimentary environment and Burial and diagenesis

  • 3. Interpretation of clastic texture

  • 4. Sedimentary structures

  • 5. Sedimentary Rock classification


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1. Sedimentary Rocks

  • Cover most of the land surface and seafloor

  • Your physical geography determines the dominant process at work in the sedimentary rock cycle

  • e.g. (1) Mountains => weathering and/or erosion

  • e.g., (2) Southern Louisiana =>

  • e.g., (3) offshore Louisiana =>


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1. Sedimentary Rocks

  • Cover most of the land surface and seafloor

  • Your physical geography determines the dominant process at work in the sedimentary rock cycle

  • e.g. (1) Mountains => weathering and/or erosion

  • e.g., (2) Southern Louisiana => transportation or deposition or erosion

  • e.g., (3) offshore Louisiana =>


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1. Sedimentary Rocks

  • Cover most of the land surface and seafloor

  • Your physical geography determines the dominant process at work in the sedimentary rock cycle

  • e.g. (1) Mountains => weathering and/or erosion

  • e.g., (2) Southern Louisiana => transportation or deposition or erosion

  • e.g., (3) offshore Louisiana => erosion or sedimentation


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erosion

weathering

transportation

Erosion includes BOTH weathering and transportation


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Sedimentary rocks are typically layered, (although layering is not diagnostic of only sedimentary rocks)


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  • Lecture Outline is not diagnostic of only sedimentary rocks)

  • Sedimentary rocks; surface processes

  • 2. Your sedimentary environment and Burial and diagenesis

  • 3. Interpretation of clastic texture

  • 4. Sedimentary structures

  • 5. Sedimentary Rock classification


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A is not diagnostic of only sedimentary rocks)sedimentary environment is a geographic location that has a peculiar combination of geological processes


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Walther’s Rule (1894) is not diagnostic of only sedimentary rocks)

“The different (sedimentary) rocks (types) were formed beside each other in space, but in a crustal profile we see them lying on top of each other….”


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Bedding sequences--- is not diagnostic of only sedimentary rocks)

are successions of rock ( in a vertical profile) that help geologists work out the past environment


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Where is not diagnostic of only sedimentary rocks) do you live?

  • What dominant sedimentary process is at work where you live?


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If deposition is the dominant process, e.g., offshore Lousiana then rocks are in the process of being formed:

Diagnesis includes

(1) compaction = volume loss (mechanical squeezing)

and is accompanied by dewatering (= water loss) (by chemical or physical means)

(2) changes in mineral composition (chemical process with heat and or fluids)

(3) cementation (physical)

If a sediment eventually becomes a rock we say it is lithified.


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DIAGENESIS Lousiana then rocks are in the process of being formed:

compaction


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DIAGENESIS Lousiana then rocks are in the process of being formed:

compaction

dewatering


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DIAGENESIS Lousiana then rocks are in the process of being formed:

compaction

dewatering

Cementation &

mineral changes


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  • Lecture Outline Lousiana then rocks are in the process of being formed:

  • Sedimentary rocks; surface processes

  • 2. Your sedimentary environment and Burial and diagenesis

  • 3. Interpretation of clastic texture

  • 4. Sedimentary structures

  • 5. Chemical and biological classification


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Geological FUZZY rules Lousiana then rocks are in the process of being formed:for determining degree of weathering and transport a rock or sediment has experienced respectively


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(1) Product composition Lousiana then rocks are in the process of being formed:


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(2) Degree of sorting Lousiana then rocks are in the process of being formed:


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  • Sorting Lousiana then rocks are in the process of being formed: is a measure of how similar grain sizes are within a sediment or rock and tells us about the relative strength of the current before it dropped (deposited) it cargo.

  • In a current of water or air, the larger and denser grains fall faster than the smaller grains. That is, for the same density, size determines settling velocity.



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  • Lecture Outline distance of transportation

  • Sedimentary rocks; surface processes

  • 2. Your sedimentary environment and Burial and diagenesis

  • 3. Interpretation of clastic texture

  • 4. Sedimentary structures

  • 5. Chemical and biological classification


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Cross-bedding distance of transportation

Cross-bedding: sets of bedded material within rock layers that are inclined at angles as large as 35 degrees from the horizontal. These latter indicate wind-blown conditions in either a desert or a beach.


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2 directions of fluid movement distance of transportation


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Fossil example of the past activity of organisms mixing sediment --- an example of fossil BIOTURBATION


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  • Lecture Outline sediment --- an example of fossil BIOTURBATION

  • Sedimentary rocks; surface processes

  • 2. Your sedimentary environment and Burial and diagenesis

  • 3. Interpretation of clastic texture

  • 4. Sedimentary structures

  • 5. Sedimentary Rock classification


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Three types of sedimentary Rocks sediment --- an example of fossil BIOTURBATION

  • Clastic

  • Biochemical

  • Chemical


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Major Classes of sediments and sedimentary rocks sediment --- an example of fossil BIOTURBATION

For clastic sedimentary rocks there is a classification scheme based on the SIZE of their clasts, (or rock fragments) that comprise them.


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Clst size indicates ancient relative current velocity sediment --- an example of fossil BIOTURBATION

weak

moderate

>=1.8 km/hr (strong currents)


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The End of Chapter 5 sediment --- an example of fossil BIOTURBATION


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