Types of sedimentary rock

1

• Types of sedimentary rock
• Sedimentary structures

2
Types of sedimentary rocks

• Sediment originates from mechanical and/or
  chemical weathering
• Rock types are based on the source of the
  material
• Clastic rocks transported sediment as solid
  particles
• Chemical/Biochemical rocks sediment that was
  once in solution

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Chapter 8
Sedimentary rocks

• Clastic
• sedimentary rocks

• Size of clasts (particles)

common name
size
Detrital rock

• gravel bigger than 2 mm
  conglomerate
• (1/10 inch)
  or breccia

• sand sand-sized (1/16-2)
  sandstone

• silt, clay very fine-grained (lt1/16)
  shale, mudstone,siltstone

See Table 8.3
4
sediments
sedimentary rocks
5
Chapter 8
Sedimentary rocks

• Clastic sedimentary rocks

• Siltstone, Mudstone Shale

• silt clay-sized particles (clay, silt),
  particles too small to identify w/ eye

• over 1/2 of all sedimentary rocks

• shale beds often underlay groundwater
• conduits

• shale may contains fossils, oily organics,
  breaks along bedding planes

• raw material for brick, tile, pottery, china

• shalelimestone Portland cement

Shale w/plant remains
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Chapter 8
Sedimentary rocks

• Clastic sedimentary rocks

• Sandstone

• composed of sand grains

• 2nd most abundant sedimentary rock

• deposited by moderate currents
• - rivers deltas
• - beaches
• - wind (sand dunes)

• mostly quartz (strong chemically stable, but
  may also contain volcanic rock)

See Fig. 8.15 for major groups of sandstone
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Chapter 8
Sedimentary rocks

• Clastic sedimentary rocks

• Sandstone

• sorting

degree of similarity in particle size
8
Chapter 8
Sedimentary rocks

• Clastic sedimentary rocks

• Sandstone

• shape

degree of roundedness
9
Chapter 8
Sedimentary rocks

• Clastic sedimentary rocks

• Conglomerate

• composed mostly of gravel
• pebbles to boulders

• poorly sorted

• deposited by strong, turbulent currents
• - big flooding rivers
• - steep streams (near mountains)
• - glaciers

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Chapter 8
Sedimentary rocks

• Clastic sedimentary rocks

• Breccia

• conglomerate with angular grains

• didnt travel far

11
Chapter 8
Sedimentary rocks

• Chemical
• sedimentary rocks

• derived from material carried in solution to
  lakes/seas

• precipitation from solution to form chemical
  sediments

• 2 types of precipitation
• - chemical
• - biochemical

See Table 8.4
12
Chapter 6
Sedimentary rocks

• Chemical sedimentary rocks

• Limestone

• 10 of all sedimentary rocks (by volume)

• most abundant chemical sedimentary rock

• composed primarily of calcite (calcium carbonate
  CaCO3)

• Marine biochemical limestones form as coral
  reefs, coquina (broken shells), and chalk
  (microscopic organisms)

• Inorganic limestones include travertine (caves)
  and oolitic limestone (tropical beach environment)

• Dolostone dolomiteCaMg(CO3)2 Typically formed
  secondarily from limestone

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Chapter 6
Sedimentary rocks

• Chemical sedimentary rocks

Organic rock of biochemical origin

• coquina (rock of shell fragments) bioclastic

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Chapter 6
Sedimentary rocks

• Chemical sedimentary rocks

Fossiliferous limestone
15
Coral reef
Limestone cliff (Guadalupe Mountains Natl Park,
TX)
16

• How to build a carbonate platform

See Figure story 8.16
17

• How to build an atoll

Darwins theory on atolls (1831)
See Box 8.1
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Chapter 8
Sedimentary rocks

• Chemical sedimentary rocks

• Common chemical sedimentary rocks

• Chert
• Made of microcrystalline silica (SiO2)
• Varieties include flint and jasper (banded form
  is called agate)

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Chapter 8
Sedimentary rocks

• Chemical sedimentary rocks

• Evaporites

• water evaporates and triggers the deposition of
  salts

• sequence of precipitation calcite (calcium
  carbonate), gypsum (calcium sulfate), rock salt
  (halite, NaCl) bitter salts (potassium and
  magnesium salts)

20
Chapter 8
Sedimentary rocks

• Chemical sedimentary rocks

• Evaporites

• water evaporates and triggers the deposition of
  salts

• sequence of precipitation carbonate, gypsum
  (calcium sulfate), rock salt (halite, NaCl)
  bitter salts (potassium and magnesium salts)

• ancient seawater basins evaporated and deposited
  salt

21
Chapter 8
Sedimentary rocks

• Chemical sedimentary rocks

• Evaporites- the story of the Mediterranean

During the Miocene, lower sea level almost shut
down the inflow of Atlantic surface water into
the Mediterranean over the Strait of Gibraltar.
Evaporation removed vast quantities of water and
left behind evaporative sediments that underlay
the sediments in the Mediterranean today.
Fig. 8.19
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Chapter 8
Sedimentary rocks

• Chemical sedimentary rocks

• Coal

• buried and compacted plant material

• different kinds of coal, depending on formation
  process

23

• Sedimentary structures

(Physical features)
1. Layers (bedding, or strata)
2. Cross-bedding
3. Graded beds
4. Ripple marks
5. Mud cracks
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• Sedimentary structures

(Physical features)
1. Layers (bedding, or strata)

• deposited horizontally

• each layer is unique

• separated by bedding planes

25

• Sedimentary structures

(Physical features)
2. Cross-bedding

• tilted bedding

• commonly ancient sand dunes

• river deltas, flow channels

26

• Sedimentary structures

(Physical features)
3. Graded beds

• rapid deposition from
• water w/ varying sed. sizes

Colorado River
27

• Sedimentary structures

(Physical features)
4. Ripple marks

• wavy surfaces in sand current
• ripple marks

• tell direction of current because
• they are perpendicular to flow

See Fig. 8.8
28

• Sedimentary structures

(Physical features)
5. Mud cracks

• sediment alternatively
• wet/dry

• shallow lakes,
• desert basins

• flood plains

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• Some MC questions

Which of the following sets of processes is
written in order of increasing temperature? A.
sedimentation, metamorphism, diagenesis B.
diagenesis, sedimentation, metamorphism C.
sedimentation, diagenesis, metamorphism D.
metamorphism, diagenesis, sedimentation
30

• Some MC questions

What type of sediments are accumulations of solid
fragments produced by weathering? A.
biochemical sediments B. chemical sediments C.
clastic sediments D. all of the above
31

• Some MC questions

Which of the following statements about
transportation of sediment is false? A.
Smaller particles settle faster than larger
particles. B. As a current slows, the largest
particles start to settle. C. Faster currents
carry larger particles than slower currents. D.
Rivers and ocean currents move much more material
than do air currents.
32

• Some MC questions

  In what type of environment did the ripples
depicted above most likely form? A. beach
(waves) B. desert (wind) C. alluvial
(stream) D. delta (river tides)
33

• Some MC questions

Which of the following minerals is least likely
to occur in a marine evaporite environment? A.
calcite B. gypsum C. halite D. quartz