sedimentary rocks ii sedimentary rock ii. characteristics of clastic rocks sedimentary rock types 5....
TRANSCRIPT
Characteristics of clastic rocks
Sedimentary Rock Types
5. Color:
• presence of key components
(can be minor by volume)
Characteristics of clastic rocks
Sedimentary Rock Types
5. Color:
• BLACK: organic carbon, iron sulfide
Characteristics of clastic rocks
Sedimentary Rock Types
5. Color:
• BLACK:abundant dead organismsand stagnant water
(not enough oxygen for decomposition)
Characteristics of clastic rocks
Sedimentary Rock Types
5. Color:
• BLACK:
still water:
swamp, lake, deep marine
Characteristics of clastic rocks
Sedimentary Rock Types
5. Color: Red or Brown:
Iron Oxide
high O2
(continental)
htt
p://
ww
w.v
isito
rtip
s.co
m/im
ag
es/g
alle
ry/d
est
ina
tions
/usa
/co
lora
do/d
en
ver/
fulls
ize
/de
nve
r12.
jpg
Characteristics of clastic rocks
Sedimentary Rock Types
6. Lithification:
• transformation of loose sediment into a rock
Characteristics of clastic rocks
Sedimentary Rock Types
6. Lithification:
• transformation of loose sediment into a rock
• compaction: degree
(packing and fusion)
Characteristics of clastic rocks
Sedimentary Rock Types
6. Lithification:
• transformation of loose sediment into a rock
• cementation: composition
silica, calcite, hematite SiO2 CaCO3 FeO2
htt
p://
facu
lty.g
g.u
wyo
.ed
u/h
elle
r/S
ed%
20S
tra
t%2
0C
lass
/Se
dS
tra
tL1
/Se
dst
rat%
20g
ifs/s
d1-
p1
1.jp
g
Plagioclase grains - Calcite cement
http
://fa
culty
.gg.
uwyo
.edu
/hel
ler/
Sed
%20
Str
at%
20C
lass
/Sed
Str
atL1
/slid
esho
w_1
_16.
htm
q-quartz grains, o-quartz cement, c-calcite cement
Characteristics of clastic rocks
Sedimentary Rock Types
7. Texture:
size, shape and arrangement
of clasts.
Characteristics of clastic rocks
Sedimentary Rock Types
Three components:
• grains: the larger particles (sand and larger)
Characteristics of clastic rocks
Sedimentary Rock Types
Three components:
• grains: the larger particles (sand and larger)
• matrix: fine clastic particles deposited with grains
Characteristics of clastic rocks
Sedimentary Rock Types
Three components:
• grains: the larger particles (sand and larger)
• matrix: fine clastic particles deposited with grains
• cement: chemical precipitate that fills voids after deposition
Characteristics of clastic rocks
Sedimentary Rock Types
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
Characteristics of clastic rocks
Sedimentary Rock Types
8b. Compositional Maturity:
Immature - least stable
• rock fragments
• iron/magnesium minerals
• feldspars
• quartz
Mature - most stable
Sedimentary Rock Types
most mature least mature
well rounded angular grains
well sorted poorly sorted
fine grained pebbles & sand
quartz rock fragments
Summary
Characteristics of Clastic Rocks
Sedimentary Rock Types
1. Grain size2. Composition of grains3. Sorting of grains4. Shape of grains5. Color of rock6. Lithification process7. Texture8. Maturity
a. texturalb. compositional
Sedimentary Rock Types
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
Environmental significance of sandstones
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
Quartz arenite: tectonic setting
• Beach, far from the mountains
Environmental significance of sandstones
Sedimentary Rock Types
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
Environmental significance of sandstones
Arkose
htt
p://
smcc
d.n
et/a
cco
unts
/han
d/g
eol
og
y101
/se
dim
en
tary
/ima
ge
s/ar
kose
2.jp
g
Sedimentary Rock Types
Arkose: tectonic setting
• Physical weathering near granitic mountain
Environmental significance of sandstones
Sedimentary Rock Types
Wacke:
• matrix 30% of rock (dark minerals)
• little or no cement
• grains supported by matrix
Environmental significance of sandstones
Wacke
htt
p://
ww
w.s
mcc
d.n
et/
acc
oun
ts/h
an
d/g
eo
log
y10
1/s
edim
ent
ary
/ima
ges
/gre
ywa
cke1
.jpg
Sedimentary Rock Types
Wacke: tectonic setting
• Rapid uplift near continent margin
Environmental significance of sandstones
Sedimentary Rock Types
Lithic sandstone:
• quartz, mica, chert, rock frag.
• little feldspar
• 15% matrix or less, rest cement
• intermediate rounding & sorting
Environmental significance of sandstones
Sedimentary Rock Types
Lithic sandstone: tectonic setting
• delta on the edge of a coastal plain
Environmental significance of sandstones