Sediments and Sedimentary Rocks Chapter 5

1
Sediments and Sedimentary RocksChapter 5
2
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")

3

• Lecture Outline
• Sedimentary rocks
• 2. Your sedimentary environment and Burial and
  diagenesis
• 3. Interpretation of clastic texture
• 4. Sedimentary structures
• 5. Sedimentary Rock classification

4
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 gt weathering and/or erosion
• e.g., (2) Southern Louisiana gt
• e.g., (3) offshore Louisiana gt

5
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 gt weathering and/or erosion
• e.g., (2) Southern Louisiana gt transportation or
  deposition or erosion
• e.g., (3) offshore Louisiana gt

6
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 gt weathering and/or erosion
• e.g., (2) Southern Louisiana gt transportation or
  deposition or erosion
• e.g., (3) offshore Louisiana gt erosion or
  sedimentation

7
erosion
weathering
transportation
Erosion includes BOTH weathering and
transportation
8
Sedimentary rocks are typically layered,
(although layering is not diagnostic of only
sedimentary rocks)
9

• 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

10
A sedimentary environment is a geographic
location that has a peculiar combination of
geological processes
11
(No Transcript)
12
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.

13
Bedding sequences--- are successions of rock ( in
a vertical profile) that help geologists work out
the past environment
14
(No Transcript)
15
Where do you live?

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

16
(No Transcript)
17
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.
18
(No Transcript)
19
(No Transcript)
20
(No Transcript)
21
DIAGENESIS
compaction
22
DIAGENESIS
compaction
dewatering
23
DIAGENESIS
compaction
dewatering
Cementation mineral changes
24

• 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

25
Geological FUZZY rulesfor determining degree of
weathering and transport a rock or sediment has
experienced respectively
26
(1) Product composition
27
(2) Degree of sorting
28

• 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.

29
(3) Angularity or roundness (antonym) is a
measure of the distance of transportation
30

• 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

31
(No Transcript)
32
(No Transcript)
33
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.
34
(No Transcript)
35
(No Transcript)
36
2 directions of fluid movement
37
Fossil example of the past activity of organisms
mixing sediment --- an example of fossil
BIOTURBATION
38

• 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

39
Three types of sedimentary Rocks

• Clastic
• Biochemical
• Chemical

40
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.
41
Clst size indicates ancient relative current
velocity
gt1.8 km/hr (strong currents)
weak
moderate
42
(No Transcript)
43
(No Transcript)
44
(No Transcript)
45
(No Transcript)
46
(No Transcript)
47
(No Transcript)
48
(No Transcript)
49
(No Transcript)
50
(No Transcript)
51
(No Transcript)
52
The End of Chapter 5
53
(No Transcript)
54
(No Transcript)
55
(No Transcript)
56
(No Transcript)
57
(No Transcript)
58
(No Transcript)
59
(No Transcript)
60
(No Transcript)
61
(No Transcript)
62
(No Transcript)
63
(No Transcript)