Download Turning Sediment into Rock

퇴적물, 퇴적암
퇴적암 구성 비율
Sedimentary rocks cover about 75% of the world's land area
퇴적암으로부터의 정보
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Paleoclimate Conditions
Paleoenvironment – Arid and Tropical Belts (presence of
seas, deltas, beaches, rivers, lakes, glaciers, coral reefs,
swamps, mountains, deserts, etc.)
Source Material
History of Transport and Deposition
Relief
Latitude – Climate Belts
Climate / Temperature
Sea Level
Changes in Atmospheric Chemistry
Plate Movements
Tectonic Setting – Evolution of Earth
Fossils – Evolution of Organisms
Relative and Absolute Age Dating
암석의 순환
• Sedimentary
Rocks are
formed from
sediments.
퇴적암은?
• Composed of sediment = loose particulate
material – Chemical and Physical weathering
– clay, silt, sand, gravel, etc.
• Sediment derivation by weathering
– Chemical (decomposition)
– Physical (disintegration)
• Sediment becomes sedimentary rock through
diagenesis(속성작용), which involves:
– Lithification (암석화작용)
• Compaction (다짐작용)
• Cementation (교결작용)
– Recrystallization (재결정작용) (of carbonate sediment)
퇴적물에서 퇴적암으로
(Turning Sediment into Rock)
• Diagenesis (속성작용) – all of the
chemical, physical, and biological
changes that take place after
sediments are deposited.
• Occurs within the upper few
kilometers of Earth’s crust at
temperatures generally less than 150
to 200 ºC (metamorphism occurs
beyond this threshold).
Turning Sediment into Rock
• Diagenesis Includes:
• Recrystallization – development of more
stable minerals from less stable ones.
Example = CaCO3 to CaMg(CO3)2
• Lithification – unconsolidated
sediments are transformed into solid
sedimentary rock by compaction and
cementation.
Turning Sediment into Rock
• Diagenesis Includes
• Compaction: 입자와 입자 사이 공극이
줄면서 공극을 채우고 있던 물이 짜여져 나옴
– Sediment accumulates.
– Weight of overlying material compresses
deeper sediments.
– Deeper sediment is further buried
becoming more compacted and firm.
– Grains are pressed increasingly closer
reducing pore space by as much as 40%
(clays).
– Most significant lithification process in
fine-grained sedimentary rock (shales).
속성작용(Diagenesis): Lithification
Sediment
Rock
Turning Sediment into Rock
• Diagenesis Includes
• 교결작용(Cementation): 공극수에 용해된
물질이 입자 사이의 공간에 침전하여 입자들을 엉겨
붙게 하는 작용
– Most important process by which sediments
are transformed to sedimentary rocks.
– Chemical diagenesis that involved the
precipitation of minerals carried in solution
into the open pore spaces between individual
grains.
– Natural Cements include calcite, silica, and
iron oxide.
Cementation
Typical Cements:
• Calcite
• Quartz
• Iron Oxide
퇴적암의 분류
• Rock types are based on the source of
the material.
• 쇄설성암(Detrital Rocks) – Derived from
both the chemical and mechanical
weathering of pre-existing rock forming
detritus that is then transported and
deposited in another location.
• 탄산염암(Carbonate Rocks) – Sediment
that was once in solution and precipitated
by organic or inorganic processes.
퇴적암 분류 기준
• Sedimentary rocks are classified based on
their texture (grain size and shape) and
composition (mineral content).
• Detrital rocks are subdivided primarily based on
particle size and composition.
– The chief constituents of detrital rocks include:
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Clay minerals
Feldspars
Quartz
Micas
• Chemical rocks are subdivided primarily based
on composition.
– The chief constituents of chemical rocks include:
– Calcite
– Microcrystalline Quartz
– Gypsum, Halite, and Sylvite
Classification of Sedimentary Rocks
• Two major textures are used in the
classification of sedimentary rocks.
• Clastic
– Discrete fragments and particles.
– All detrital rocks have a clastic texture.
– Some chemical rocks – coquina and
oolitic limestone – also posses clastic
textures.
• Nonclastic (or Crystalline)
– Pattern of interlocking crystals.
– May resemble an igneous rock.
Types of Sedimentary Rocks
• Detrital Sedimentary Rocks
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Conglomerate or Breccia
Sandstone
Siltstone
Shale or Claystone
• Chemical/Biochemical Sedimentary Rocks
– Evaporites
– Carbonate sedimentary rocks (limestones and
dolostone)
– Siliceous sedimentary rocks (chert, diatomite)
– Organic sedimentary rocks (Coals – peat, lignite,
bituminous, and anthracite)
Identification of Sedimentary Rocks
STOP
쇄설성 퇴적암의 특성
Detrital Sedimentary Rocks
• Detrial rocks have a clastic (broken or
fragmental) texture that may consist of:
– Clasts – larger pieces, such as sand or gravel.
– Matrix – mud or fine-grained sediment
surrounding the clasts.
– Cement – the chemical
“glue” that holds it all
together.
• Types of Cement:
– Calcite
– Iron Oxide
– Silica
역지지 역암
(Clast -Supported
Conglomerate)
(River Deposits)
기질지지 역암(Matrix-Supported
Conglomerate) (Glacial/Landslide Deposits)
2.2 Gyr Conglomerate
“Modern”
Glacial Sediments
입도에 따른 쇄설성 퇴적암의 분류
Particle size is used to distinguish among
the various types of detrital rocks.
• Gravel(자갈): Grain size greater than 2 mm.
– If rounded clasts = Conglomerate (역암)
– If angular clasts = Breccia (각력암)
• Sand(모래): Grain size 1/16 to 2 mm – Sandstone
• Silt(실트): Grain size 1/256 to 1/16 mm (gritty) –
Siltstone
• Clay(점토): Grain size less than 1/256 mm
(smooth)
– Shale (if fissile)
– Mudstone (if massive)
Grain Size
• Gravel ≥ 2 mm
• Sand – 2 mm to 1/16 mm
• Silt – 1/16 mm to 1/256 mm
• Clay ≤ 1/256 mm
Detrital Sedimentary Rocks
are Classified by Grain Size
Grain Size
Rock Name
Gravel
Conglomerate = Rounded Clasts
Breccia = Angular Clasts
Sand
Sandstone
Silt
Siltstone
Clay
Shale = Fissile
Mudstone = Massive
Detrital Sedimentary Rocks
Shale
Conglomerate
Sandstone
Breccia
입도(입자 크기)의 의미
• The energy of the environment and
media of deposition.
• Currents of water or air sort the
particles by size – the stronger the
current, the larger the particle size
carried.
Grain Size Interpretation
• Gravel
• High Energy
• Sand
• Silt
• Clay
STOP
• Low Energy
• River, Beach
• River, Beach,
Desert
• Delta, Shallow
Ocean
• Deep Ocean,
Lake, Swamp
분급(Sorting)
• Sorting refers to the distribution of
grain sizes in a rock.
– Well Sorted – All the grains are approximately
equal in size.
– Poorly Sorted – Particles of variable size are
mixed together.
Degrees of Sorting
분급의 의미
• The energy of the environment and media of
deposition.
Interpretation: Transport Agent
Poorly Sorted Gravity and Glaciers (and Rivers)
Well Sorted
Water and Wind
What Does the
Degree of Sorting Tell Us?
• 퇴적환경 별 에너지 수준 반영:
• Windblown sands are typically better
sorted than wave-washed sediments.
• Particles washed by waves are
commonly better sorted than materials
deposited by streams.
분급도의 의미
• 기원지로부터의 운반 거리와 퇴적률
반영:
• Poor sorting indicates sediments were
transported a short distance and
deposited rapidly.
– Examples: Alluvial Fans (선상충적지) and
Glacial Tillite (표석점토암) deposits
• Well-sorted sediments indicate the
sediments were transported a longer
distance and deposited more gradually.
– Examples: Deep-ocean deposits
입자의 모양(Grain Shape)
• Grain shape is described in terms of rounding
(원마도) of grain edges and sphericity(구형도)
(equal dimensions, or how close it is to a
sphere).
• When currents transport sedimentary particles,
the particles collide together breaking off sharp
edges.
원마도와 구형도(Rounding & Sphericity)
Spherical
Oblong
Degree of rounding is expressed using the following scale:
highly angular –> angular –> subangular –> subrounded –> rounded
–> highly rounded
(A) An angular particle (all edges sharp).
(B) A rounded grain that has little sphericity.
(C) A well-rounded, highly spherical grain.
Gravel Sized Detrital Rocks
(Subdivided Based on Grain Roundness)
Conglomerate
Breccia
Grain Shape
• Degree of rounding also indicates
distance from source and/or transport
time:
• Very well rounded sand
grains suggest that a
sand has traveled a great
distance from the source
over a long time period.
• They also may have
been recycled from older
sandstones.
STOP
Short
Interpretation:
Distance of Transport
Far
화학적 풍화
• Transport time also affects the
mineral composition of a
sedimentary deposit:
– Substantial weathering and long
transport leads to the gradual
destruction of weaker and less stable
minerals such as feldspars and
ferromagnesian minerals (Bowen’s
Reaction Series).
– Quartz – the most stable mineral at the
Earth’s surface survives.
퇴적암의 색
• Black and dark gray coloration in
sedimentary rocks generally indicates
the presence of organic carbon and/or
iron.
• Organic carbon in sedimentary requires
anoxic environmental conditions.
Color of Sedimentary Rocks
• Red coloration in
sedimentary rocks
indicates the presence of
iron oxides (Ferric Iron –
Fe+3) .
• Red beds typically
indicate deposition in
well-oxygenated
continental sedimentary
environments.
• May also be transitional
or marine.
Red siltstone w/ tracks
Hematite-cemented
Sandstone (Clinton Fm.)
Color of Sedimentary Rocks
• Green and gray coloration in
sedimentary rocks indicates the
presence of iron, but in a reduced
(rather than an oxidized) state.
• Ferrous iron (Fe+2) generally occurs in
oxygen-deficient environments.
STOP
쇄설성 퇴적암
유형별 특성
Detrital Sedimentary Rocks
• Common Detrital Sedimentary Rocks
(in order of increasing particle size)
• Shale
– A very fine-grained rock
composed of clay-sized
particles.
– Most common sedimentary
rock.
– Particles deposited in thin
layers commonly referred to
as laminae.
– Shale is fissile – splits readily
into thin, flat layers.
Detrital Sedimentary Rocks
• 이암(Mudstone)
• Composed of mud – a mixture of silt and clay.
• May exhibit fissility.
• Breaks into chunks or blocks.
Detrital Sedimentary Rocks
• Siltstone
– Composed of
largely of siltsized particles
with lesser claysized particles.
– Lacks fissility.
– Breaks into
chunks or blocks.
Formation of Shales to Siltstones
• Due to their Fine Grain Size:
– Clay and silt-sized particles tends to remain
suspended in the water column.
– Deposition occurs as the result of gradual settling
from relatively quiet, non-turbulent currents.
– Lithified predominantly via compaction.
– Clays and shales typically indicate low energy
environments, sheltered from waves and currents.
– Such environments include lakes (lacustrine),
river floodplains, lagoons, and portions of deep
ocean basins.
– Composition and color can further indicate the
environment of deposition (e.g., coaly shales).
Detrital Sedimentary Rocks
• 사암(Sandstone)
– Composed of sand-sized particles.
– Lithified predominantly via cementation.
– Forms in a variety of environments.
– Sorting, shape, and composition of the
grains can be used to interpret the rock’s
origin and history.
– Compositional components include:
• Quartz – predominant mineral
• Feldspar
• Rock Fragments
사암의 종류
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Quartz Sandstone – Dominated by quartz; mature
Arkose(장석질사암) – 25% or more feldspar;
immature
Graywacke(잡사암) – About 30% dark fine-grained
matrix; immature
Lithic Sandstone – Quartz, muscovite, chert, and
rock fragments. Less than 15% matrix. Immature
Four categories of sandstone as seen in thin section
under the microscope. Diameter of field is about 4 mm.
석영사암(Quartz Sandstone)
Composed of well-sorted, rounded quartz
grains suggests long-distance transport,
highly weathered, and moderate deposition
and burial rates.
Arkose (장석질사암)
• Composed of quartz, feldspars, and micas indicates
granitic source rocks. Typically poorly sorted, angular
particles with minimal chemical weathering (indicated by
the presence of feldspar) suggests short-distance transport,
minimal chemical weathering in an arid climate, and rapid
deposition and burial.
Sandstone Close-Ups
• Quartz Sandstone (left)
• Arkose (Sandstone with >10% feldspar)
Detrital Sedimentary Rocks
• 역암과 각력암(Conglomerate and Breccia)
– Both are composed of particles greater than
2mm in diameter (gravel) with sand, silt, and
clay particles between.
– Particles are large enough to identify distinctive
rock types and therefore source rocks.
– Gravels accumulate in a variety of environments
and typically indicate steep slopes and/or very
turbulent currents.
– Examples: energetic mountain streams, strong
wave activity along rapidly eroding coastline,
and glacial and landslide environments.
Detrital Sedimentary Rocks
• Conglomerate and Breccia
– Conglomerate consists largely of rounded gravels.
– Breccia is composed mainly of large angular
particles.
역암 노두
Composition of variable materials, poorly sorted, and
rounded particles suggests relatively short-distance
transport (but long enough to have high degree of
abrasion), some mechanical and minimal chemical
weathering, and rapid deposition and burial.
Interbedded
Sandstone and
Conglomerate
사암과 역암의
교호층
Suggests distinctive
periods of alternating
depositional environments
of high and low energy.
Breccia
Composition of variable materials, poorly sorted,
and angular particles suggests short-distance
transport, minimal mechanical and chemical
weathering, and rapid deposition and burial.
화학적/생화학적
퇴적암
화학적 퇴적암
• Consist of precipitated material that
was once in solution.
• Precipitation of material occurs in two
ways:
• Inorganic Processes:
– Evaporation
– Hydrothermal
– Chemical Activity
• Organic Processes:
– Biochemical Origin from water dwelling
organisms
화학적, 생화학적 퇴적암의 분류
1. 탄산염암(Carbonate Rocks) – Form by
chemical processes and biochemical
processes (secreting shells).
2. 규질암(Siliceous Rocks) – Form from
chemical processes (silica replacing
limestone) or biochemical processes
(silica-secreting organisms).
3. 증발암(Evaporites) – Form from the
evaporation of seawater.
Carbonate Rocks
1. 석회암(Limestones)
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Most abundant chemical rock.
Composed of predominantly of calcite (CaCO3)
and secondarily aragonite (CaCO3).
Marine biochemical limestones form from preexisting organisms:
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Inorganic limestones form by inorganic
processes (evaporation, chemical activity):
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Reef Limestone(생물초석회암) – 생물초(reef)에 사는 생물들의
탄산염 골격이 교결되어 생성
Coquina(패각암 또는 코퀴나) – 부서진 조개껍질 조각들의 입자
Chalk(백악 또는 초크) – 미세한 부유성 바다미생물의 탄산염 껍질
Oolitic Limestone (어란상석회암)
Travertine (온천석회암)
Dolostones(백운암) (or Dolomites)
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Composed of Dolomite (CaMg (CO3)2)
해양성 탄산염암의 생성환경
• Some carbonate rocks form in lakes, caves,
and hot springs.
• Most carbonate rocks form in the shallow
marine environments:
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Marine
Warm Water
Shallow Water (less than 200 m deep)
Tropical Climate (30 ° N - 30 ° S of equator)
Clear Water (low to no terrigenous input)
Sunlight Required for photosynthesis by algae
유기화학적 퇴적암
• 백악(Chalk)
– Chalk is a soft, porous rock
composed of almost entirely of the
hard parts of microscopic
calcareous marine organisms.
유기화학적 퇴적암
• Coquina
– Coquina is a coarse-grained rock
composed of poorly-cemented
shells and shell fragments.
무기화학적 퇴적암
• Oolitic Limestone
– Oolitic limestone is composed of small
spherical grains of CaCO3 called ooids.
Origin of Ooids in
Oolitic Limestones
• Ooids are tiny spheres
composed of concentrically
laminated calcium carbonate.
• Ooids form in shallow marine
waters and begin as tiny
“seed” particles (commonly
shell fragments) are
constantly agitated by
currents.
• As the seeds are rolled
around in the CaCO3
supersaturated warm waters,
layers of CaCO3 are
concentrically precipitated
around the seed.
무기화학적 퇴적암
• Travertine
– Travertine forms in caves (stalagtites,
stalagmites, curtains, etc.) when groundwater
encounters air, CO2 comes out of solution and
causing CaCO3 to precipitate.
– Also forms from precipitation of calcite around
hot springs.
Carbonates: Dolomite
• Composed of dolomite
CaMg(CaCO3)2 – a calciummagnesium carbonate mineral.
• Dolomite (Dolostone) can form
by the direct precipitation of
seawater in a few areas of the
world where intense
evaporation of seawater
concentrates the magnesium.
• Typically formed secondarily
from limestone.
• Magnesium that has been
concentrated in sea water
replaces some of the calcium in
the CaCO3 structure
(diagenesis).
규질 퇴적암
• Chert
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Made of microcrystalline quartz (silica).
Massive and hard.
Often replaces limestone.
Varieties include the following:
• Flint – dark in color due to organic matter
• Jasper – red in color due to iron oxide
• Agate – banded form or chert
Siliceous Sedimentary Rocks
• Chert
– Chert has various modes of origin:
• Inorganic – Precipitated from groundwater
as nodules.
• Inorganic – Precipitated from groundwater
associated with the decomposition of lava
flows and layers of volcanic ash (silica-rich).
• Organic – Biochemical Sediment – Siliceous
ooze (gel) derived from silica skeletons of
marine organisms (diatoms and radiolarians).
규질 퇴적암
• Diatomite (규조토)
– Made of microscopic
planktonic organisms called
diatoms.
– Resembles chalk, but does
not fizz in acid.
증발암(Evaporites)
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Evaporation triggers deposition of chemical
precipitates.
Formed from dried basin areas that were
submerged by shallow arms of sea with little
or no connection to open ocean.
When seawater evaporates, minerals
precipitate in sequence according to their
solubility forming salt flats.
Gypsum precipitates before halite, which
precipitates before sylvite(칼리암염):
1.
2.
3.
Rock Gypsum – Composed of gypsum (CaSO4 . 2H2O)
Rock Salt – Composed of halite (NaCl)
Sylvite – Composed of potassium chloride (KCl)
Rock Salt (Halite)
Bonneville Salt Flats, Utah
Layered Rock Gypsum(석고)
유기적 퇴적암– Coal
• Composed of organic matter such as trees,
bark, wood, leaves, etc. buried for millions
of years.
• Stages in coal formation (in order) as a
function of increasing depth of burial
(increase in temperature and pressure):
• Plant Material
• Peat (토탄)
• Lignite (갈탄)
• Bituminous Coal (역청탄)
• Anthracite Coal (무연탄)
석탄의
생성단계
유기적 퇴적암– 석탄
•
Stages of Coal Formation
1. Plant Material – Accumulations of large
amounts of plant remains in a stagnant,
oxygen-deficient environment (늪지), where
oxidation and thus complete decomposition
of the plant remains is not possible.
Anaerobic bacteria (혐기성 박테리아) partially
decompose plant remains releasing oxygen
and hydrogen, thereby increasing the carbon
percentage and creating a layer of peat.
Organic Sedimentary Rocks – Coal
•
Stages of Coal Formation
2. Peat – A soft brown material in which
plant structures are still easily
recognizable
3. Lignite – With shallow burial, peat
slowly changes to lignite – a soft
brown coal
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Increase temperature and pressure
squeezes out the volatiles (water and
organic gases) increasing the proportion
of fixed carbon
The greater the carbon content, the
greater the coal’s energy ranking
석탄의 생성단계 (Successive Stages in Coal Formation)
Organic Sedimentary Rocks – Coal
•
Stages of Coal Formation
4. Bituminous – Deeper burial
transforms lignite to bituminous
coal – a soft black coal.
5. Anthracite – Forms during
regional metamorphism under
increased temperature and
pressure.
• Anthracite is a very hard, black,
shiny, metamorphic rock.
Successive Stages in Coal Formation
STOP