Transcript HistLecSedRx2

Sedimentary Rock II
Sedimentary Rocks II
Sedimentary Rock Types
Characteristics of clastic rocks
5. Color:
• presence of key components
(can be minor by volume)
Sedimentary Rock Types
Characteristics of clastic rocks
5. Color:
• BLACK: organic carbon,
iron sulfide
Sedimentary Rock Types
Characteristics of clastic rocks
5. Color:
• BLACK:
abundant dead organisms
and stagnant water
(not enough oxygen for
decomposition)
Sedimentary Rock Types
Characteristics of clastic rocks
5. Color:
• BLACK:
still water:
swamp, lake, deep marine
Sedimentary Rock Types
Characteristics of clastic rocks
5. Color:
Iron Oxide
high O2
(continental)
Red or Brown:
http://www.visitortips.com/images/gallery/destinations/usa/colorado/denver/fullsize/denver12.jpg
Sedimentary Rock Types
Characteristics of clastic rocks
6. Lithification:
• transformation of loose
sediment into a rock
Sedimentary Rock Types
Characteristics of clastic rocks
6. Lithification:
• transformation of loose
sediment into a rock
• compaction: degree
(packing and fusion)
http://www.grasp.ulg.ac.be/research/compaction/
PrePost-
Compaction - packing
http://www.grasp.ulg.ac.be/research/compaction/
Compaction - packing
http://www.gly.uga.edu/railsback/PDFimage0208a.jpeg
Compaction - grain fusion
Sedimentary Rock Types
Characteristics of clastic rocks
6. Lithification:
• transformation of loose
sediment into a rock
• cementation: composition
silica, calcite, hematite
SiO2
CaCO3
FeO2
Quartz grains - Calcite cement
http://faculty.gg.uwyo.edu/heller/Sed%20Strat%20Class/SedStratL1/Sedstrat%20gifs/sd1-p11.jpg
Plagioclase grains - Calcite cement
http://faculty.gg.uwyo.edu/heller/Sed%20Strat%20Class/SedStratL1/slideshow_1_16.htm
q-quartz grains,
o-quartz cement,
c-calcite cement
Sedimentary Rock Types
Characteristics of clastic rocks
7. Texture:
size, shape and arrangement
of clasts.
Sedimentary Rock Types
Characteristics of clastic rocks
Three components:
• grains: the larger particles
(sand and larger)
Sedimentary Rock Types
Characteristics of clastic rocks
Three components:
• grains: the larger particles
(sand and larger)
• matrix: fine clastic particles
deposited with grains
Sedimentary Rock Types
Characteristics of clastic rocks
Three components:
• grains: the larger particles
(sand and larger)
• matrix: fine clastic particles
deposited with grains
• cement: chemical precipitate
that fills voids after deposition
Levin - Earth Through Time 7th
Grains & Cement
Grains & Matrix
Sedimentary Rock Types
Characteristics of clastic rocks
8. Maturity:
a measure of how long/far
sediment was transported.
two kinds
Sedimentary Rock Types
8a. Textural Maturity:
Immature
• large grain size,
angular grains,
poorly sorted
• intermediates
• small grain size,
well rounded,
well sorted
Mature
Sedimentary Rock Types
Characteristics of clastic rocks
8b. Compositional Maturity:
Immature - least stable
• rock fragments
• iron/magnesium minerals
• feldspars
• quartz
Mature - most stable
Sedimentary Rock Types
Summary
most mature
least mature
well rounded
angular grains
well sorted
poorly sorted
fine grained
pebbles & sand
quartz
rock fragments
Sedimentary Rock Types
Characteristics of Clastic Rocks
1. Grain size
2. Composition of grains
3. Sorting of grains
4. Shape of grains
5. Color of rock
6. Lithification process
7. Texture
8. Maturity
a. textural
b. compositional
Sedimentary Rock Types
Environmental significance of sandstones
Sedimentary Rock Types
Environmental significance of sandstones
1. Quartz arenite:
• dominance of quartz
• little or no feldspar, mica, or matrix
• grains well rounded, well sorted
• calcite or silica cement
• wide spread thin sand beds
http://www.gly.uga.edu/railsback/sands/260Micro900.jpeg
Quartz sand
Sedimentary Rock Types
Quartz arenite :
http://nessus.gunslingers.org/2003-09%20-%20North%20Carolina%20Beach%20and%20California%20Hiking/0047%20More%20Beach-half.jpg
Sedimentary Rock Types
Environmental significance of sandstones
Quartz arenite: tectonic setting
• Beach, far from the mountains
Sedimentary Rock Types
Environmental significance of sandstones
Arkose: (feldspathic wacke)
• contain 25% or more feldspar (pink)
• quartz most abundant (angular)
• calcite, iron oxide cement, or clay matrix
• granitic source
• coarse sand, moderately well sorted
http://smccd.net/accounts/hand/geology101/sedimentary/images/arkose2.jpg
Arkose
Sedimentary Rock Types
Environmental significance of sandstones
Arkose: tectonic setting
• Physical weathering near granitic mountain
Sedimentary Rock Types
Arkose
Sedimentary Rock Types
Environmental significance of sandstones
Wacke:
• matrix 30% of rock (dark minerals)
• little or no cement
• grains supported by matrix
http://www.smccd.net/accounts/hand/geology101/sedimentary/images/greywacke1.jpg
Wacke
Sedimentary Rock Types
Environmental significance of sandstones
Wacke: tectonic setting
• Rapid uplift near continent margin
Episodes of deposition
Turbidites
Episodes of deposition
Turbidites
One
Turbidite
http://www.kickkleverlaan.com/ratab%20red.jpg
Turbidites
Turbidites & Deep Marine Shales
Sedimentary Rock Types
Environmental significance of sandstones
Lithic sandstone:
• quartz, mica, chert, rock frag.
• little feldspar
• 15% matrix or less, rest cement
• intermediate rounding & sorting
http://staff.aist.go.jp/sudo-gsj/sand/english/D-2444.html
Lithic sand
(Mekong river)
Sedimentary Rock Types
Environmental significance of sandstones
Lithic sandstone: tectonic setting
• delta on the edge of a coastal plain
Sedimentary Rock Types
Environmental significance of sandstones
Lithic sand
Sedimentary Rock Types
Environmental significance of sandstones
Beach
far from Mt
Continental
arid
Deep
Marine
Mature
River