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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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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 Classes of sediments and sedimentary
rock: -based on grain size -based on chemical composition, e.g.,
carbonate rocks ("carbonates") and evaporitic rocks ("evaporites")
Lecture Outline Sedimentary rocks 4. Sedimentary structures
2. Your sedimentary environment and Burial Diagenesis 3.
Interpretation of clastic texture 4. Sedimentary structures 5.
Sedimentary Rock classification 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 => 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 => 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 erosion weathering transportation
Erosion includes BOTH weathering and transportation Sedimentary
rocks are typically layered, (although layering is not diagnostic
of only sedimentary rocks) Lecture Outline Sedimentary rocks;
surface processes
2. Your sedimentary environment and Burial and diagenesis 3.
Interpretation of clastic texture 4. Sedimentary structures 5.
Sedimentary Rock classification A sedimentary environment is a
geographic location that has a peculiar combination of geological
processes Walthers Rule (1894) 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. Bedding
sequences--- are successions of rock ( in a vertical profile) that
help geologists work out the past environment Where do you live?
What dominant sedimentary process is at work where you live? If
deposition is the dominant process, e. g
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. DIAGENESIS compaction DIAGENESIS
compaction dewatering DIAGENESIS compaction dewatering Cementation
& mineral changes Lecture Outline 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 Geological FUZZY rules for
determining degree of weathering and transport a rock or sediment
has experienced respectively (1) Product composition (2) Degree of
sorting Sorting 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. (3) Angularity or roundness (antonym) is a
measure of the distance of transportation Lecture Outline
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 Cross-bedding 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. 2
directions of fluid movement Fossil example of the past activity of
organisms mixing sediment --- an example of fossil BIOTURBATION
Lecture Outline Sedimentary rocks; surface processes
2. Your sedimentary environment and Burial and diagenesis 3.
Interpretation of clastic texture 4. Sedimentary structures 5.
Sedimentary Rock classification Three types of sedimentary
Rocks
Clastic Biochemical Chemical Major Classes of sediments and
sedimentary rocks
For clastic sedimentary rocks there is a classification scheme
based on the SIZE of their clasts, (or rock fragments) that
comprise them. Clst size indicates ancient relative current
velocity
weak moderate >=1.8 km/hr (strong currents) The End of Chapter
5
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