Modul 9 - Sedimentary Rocks

7/28/2019 Modul 9 - Sedimentary Rocks

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Module 9Module 9

SedimentarySedimentary RocksRocks


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Rocks formed from material derived fromRocks formed from material derived frompreexisting rocks bypreexisting rocks by surfacialsurfacial processesprocesses

followed byfollowed by diagenesisdiagenesis

There are two main classes of sedimentary rocksThere are two main classes of sedimentary rocks ClasticClastic ((detritaldetrital) sedimentary rocks) sedimentary rocks

are formed from bits and pieces of previously

are formed from bits and pieces of previouslyexisting rocks, calledexisting rocks, called clastsclasts or detritusor detritus

Chemical sedimentary rocksChemical sedimentary rocksare formed in several ways

are formed in several ways

By precipitation from aqueous solutionBy precipitation from aqueous solution

From plant materialFrom plant material

From animal materialFrom animal material

SEDIMENTARY ROCKSSEDIMENTARY ROCKS


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Processes Leading to Formation ofProcesses Leading to Formation of

Clastic Sedimentary RocksClastic Sedimentary Rocks

ClasticClastic Sedimentary RocksSedimentary Rocks

Weathering:Weathering: the processes that change rocksthe processes that change rocks size andsize and

composition at or near Earthcomposition at or near Earths surfaces surface

Erosion and Transportation:Erosion and Transportation: removal of rock particlesremoval of rock particles

(clasts) from their source by water, wind, or glacial ice(clasts) from their source by water, wind, or glacial ice

Deposition:Deposition: the settling of clasts on Earththe settling of clasts on Earth s surface ass surface assediments, leads to formation of a sedimentary bedsediments, leads to formation of a sedimentary bed

Compaction:Compaction: pressing together of clasts, squeezing outpressing together of clasts, squeezing out

pore water, by pressure exerted by overlying bedspore water, by pressure exerted by overlying beds

LithificationLithification:: cementation of clasts together to form acementation of clasts together to form a

sedimentary rocksedimentary rock

DiagenesisDiagenesis:: a process of conversion of unconsolidateda process of conversion of unconsolidatedsediments to coherent sedimentary rockssediments to coherent sedimentary rocks


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Formation of Metamorphic RocksFormation of Metamorphic Rocks

Uplift and exposure

Weathering

Transportation

Deposition

Compaction and

Lithification

All rocks exposedAll rocks exposed

at earthat earths surfaces surface

undergoundergo

Rocks CycleRocks Cycle


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Where do the sediments form?Where do the sediments form?


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Temperaturedecreases

SiO2

ofliquidincreases

Olivine

Pyroxene

Amphibole

Biotite

Ca-rich

Na-rich

Ca-Na-rich

Na-Ca-rich

Quartz

Mus

covite

K-feldspar P

lag

ioc

lase

fel

dspar

D

iscontinuo

usbranch

Continuousbranch

BOWENS REACTION SERIES

Resistance of Minerals to WeatheringResistance of Minerals to Weathering

Most readily

to weathering

More resistant

to weathering

Most resistant

to weathering

Most resistant of

all to weathering

the effect of mineral composit ionthe effect of mineral composit ion

on the resistance to weatheringon the resistance to weathering


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Effect of Weathering, Gradient, Distance from SourceEffect of Weathering, Gradient, Distance from Source--RockRock

on Clast Size, Shape, Sorting, and Compositionon Clast Size, Shape, Sorting, and Composition

Close to source Far from source

clast size large clasts small clasts

clast shape angular clasts rounded clasts

sorting poorly sorted

sediments

well sorted

sedimentscomposit ion rich in mafic minerals

and feldspar

quartz sands andclays


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07_18.jpgEffect of Weathering, Gradient, Distance from SourceEffect of Weathering, Gradient, Distance from Source--RockRock

on Clast Size, Shape, Sorting, and Compositionon Clast Size, Shape, Sorting, and Composition

Eff f C i C i S diEff t f C ti C t ti S di t


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Effects of Compaction, Cementation on SedimentsEffects of Compaction, Cementation on Sediments

On mudOn poorly-sorted

sediments

On well-sorted sediments

F di t t di t kF di t t di t k


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From sediments to sedimentary rocksFrom sediments to sedimentary rocks

clayclaysiltsiltsandsandgravelgravel

conglomerateconglomerate sandstonesandstone siltstonesiltstone claystoneclaystone

C SCl ti S di t R k T t


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Clastic Sedimentary RockClastic Sedimentary Rocks Textures Texture

TextureTexture::

the relationship between the grains of mineralsthe relationship between the grains of minerals

forming a rockforming a rock

a.a. grain sizegrain size

b.b. roundnessroundness

c.c. sortingsortingd.d. fabricfabric

e.e. ffragmenragment, matrix, & cementt, matrix, & cement

Cl ti S di t R kCl ti S di t R k T tT t


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a.a. Grain size:Grain size: Grain (Grain (particleparticle,, clastclast,, fragmentfragment) size) size isis primaryprimary

distinguishing factordistinguishing factorfor clastic sedimentaryfor clastic sedimentary

rocksrocks Size means diameter of rockSize means diameter of rocks grainss grains

Cl ti S di t R kCl ti S di t R k T tT t


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SizeSize (mm)(mm) Sedimentary clastsSedimentary clasts Sedimentary rocksSedimentary rocks

>256>256

128128 256256

6464 128128

3232 6464

1616 3232

88 1616

44 88

22 44

11 221/21/2 11

1/41/4 1/21/2

1/81/8 1/41/4

1/161/16 1/81/81/321/32 1/161/16

1/641/64 1/321/32

1/1281/128 1/641/64

1/2561/256 1/1281/128


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b.b. SphericitySphericity vsvs roundnessroundness SphericitySphericity is a degree of similarity to a ballis a degree of similarity to a ball

shapeshape

Roundness is a degree of roundedness of theRoundness is a degree of roundedness of theedges of a fragmentedges of a fragment

angularangular intermediateintermediate roundedrounded

HighHigh sphericitysphericity

LowLow sphericitysphericity

RoundnessRoundness


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Shapes of sand grains



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c. Sortingc. Sorting

Degree of similarity in particle sizeDegree of similarity in particle size



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Clastic Sedimentary RockClastic Sedimentary Rock s Textures Texture

This quartz grains are:This quartz grains are:

-well-sorted

-well-rounded



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d. Fabricd. Fabric Opened fabricOpened fabric Closed fabricClosed fabric


Closed fabricClosed fabric

Opened fabricOpened fabric



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e. Fragments, matrix, cemente. Fragments, matrix, cement Fragments (Fragments (clastsclasts)) MatrixMatrix

CementCement


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Clastic Sedimentary RockClastic Sedimentary Rocks Structures Structure


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Clastic Sedimentary RockClastic Sedimentary Rock s Structures Structure

Sedimentary Beds and Bedding PlanesSedimentary Beds and Bedding PlanesBeds represent distinct sedimentary event,Beds represent distinct sedimentary event,

times when deposition occurredtimes when deposition occurred

Bedding planes represent pauses betweenBedding planes represent pauses betweensedimentary events, times when deposition ceasedsedimentary events, times when deposition ceased

Bedding

plane

Bed



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Graded Sedimentary BedsGraded Sedimentary BedsForm in response toForm in response to

decrease in energydecrease in energyduring depositionduring deposition

Larger, heavier clastsLarger, heavier clasts ,,first pebbles then sand,first pebbles then sand,settle out first, in thesettle out first, in the

bottom of the bedbottom of the bedSmaller, lighter clastsSmaller, lighter clasts ,,

silt and finally clay,silt and finally clay,

settle out last in the topsettle out last in the topof the bedof the bed



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Cross BedsCross Beds

Cross beds areCross beds aredeposited in responsedeposited in responseto movement of ato movement of a

currentcurrent

Cross beds areCross beds areunidirectional if theunidirectional if the

current was constantcurrent was constantin directionin direction

Cross beds are biCross beds are bi--

directional if thedirectional if thecurrent was notcurrent was notconstant in directionconstant in direction

Note: these beds areNote: these beds aretilted

Current direction

tilted



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Mud CracksMud CracksMud cracks formMud cracks form

when mud drieswhen mud driesupup

Their shape andTheir shape andsize may varysize may varyconsiderablyconsiderably

Mudcracks in fresh sediment

MudcracksMudcracks

in ain a

sedimentarysedimentaryrockrock




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Ripple MarksRipple Marks

Are formed in response toAre formed in response tomovement of a currentmovement of a current

Symmetrical ripple marksSymmetrical ripple marksform if current is backform if current is back--andand--forth, biforth, bi--directionaldirectional

Asymmetrical ripple marksAsymmetrical ripple marksform if current is constant inform if current is constant in

directiondirection

Asymmetrical ripple marks

in fresh sediment

Symmetrical ripple marks

preserved in mudstone



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Raindrop Imprints and castsRaindrop Imprints and castsForm when big rain drops fall on mudForm when big rain drops fall on mud

Raindrop imprintsRaindrop imprints are depressions formed on theare depressions formed on the

bed upon which the raindrops fellbed upon which the raindrops fellRaindrop castsRaindrop casts are knobs formed on the bottom ofare knobs formed on the bottom of

the bed deposited on top of the bed upon which thethe bed deposited on top of the bed upon which theraindrops fellraindrops fell

Raindrop imprints

and mudcracks




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FossilsFossils

Are any evidence of life preserved in ancient rocksAre any evidence of life preserved in ancient rocks

Include bones, teeth, shells, molds and casts,Include bones, teeth, shells, molds and casts,petrified wood, impressions, footprints, etc.petrified wood, impressions, footprints, etc.

Chemical Sedimentary RocksChemical Sedimentary Rocks


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Chemical Sedimentary Rocksy

Chemical Sedimentary RocksChemical Sedimentary Rocks derived from material carriedderived from material carried in solutionin solution toto

lakes/ seaslakes/ seas

precipitationprecipitation from solution to formfrom solution to form

chemical sedimentschemical sediments

by precipitation from aqueous solutionby precipitation from aqueous solution

from plant materialfrom plant material

from animal materialfrom animal material



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Salt flats, UtahSalt flats, Utah

yy

EvaporitesEvaporites

water evaporates andwater evaporates and

dissolved stuff isdissolved stuff isdepositeddeposited

mostly marine rocks,mostly marine rocks,

but some lakes/ playasbut some lakes/ playas Salt, gypsum, potashSalt, gypsum, potash

Death Valley, CaliforniaDeath Valley, California


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LimestoneLimestone

formed by marine organismsformed by marine organisms

(corals, clams, algae)(corals, clams, algae) composed primarily of calcitecomposed primarily of calcite

(calcium carbonate CaCO3)(calcium carbonate CaCO3)

most abundant chemicalmost abundant chemicalsedimentary rocksedimentary rock

10% of all sedimentary rocks10% of all sedimentary rocks

(by volume)(by volume) some deposited directly out ofsome deposited directly out of

ocean or other watersocean or other waters

yy

Coral reefCoral reef

Coquina (rock of shell fragments)Coquina (rock of shell fragments)



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y

Limestone MountainLimestone Mountain



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Coal

CoalCoal

buried and compacted plant materialburied and compacted plant material

different kinds of coal, depending on formationdifferent kinds of coal, depending on formationprocessprocess

peatpeat lignitelignite coalcoal anthraciteanthracite

Classification of Sedimentary RocksClassification of Sedimentary Rocks


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Clastic

Clastic

Sedimen

taryRocks

Sedimen

taryRocks

Chemica

l

Chemica

l

SedimentaryR

ocks

SedimentaryR

ocks

ChertChert RadiolariteRadiolarite

DiatomiteDiatomite

SILICASILICAPeatPeat

LigniteLigniteCoalCoal

Anthraci teAnthracite

CARBONACEOUSCARBONACEOUS

HaliteHalite

GypsumGypsum

AnhydriteAnhydrite

EVAPORITEEVAPORITE

OoliteOolite

Coral limestoneCoral limestoneDolomiteDolomite

Crystalline l imestoneCrystalline limestone

BioclasticBioclastic limestonelimestone

Marl;Marl; ClasticClastic limestonelimestone

((CalcaruditeCalcarudite,, CalcareniteCalcarenite,, CalcelutiteCalcelutite))

CARBONATECARBONATE

SILICATESILICATEBrecciaBreccia SiltstoneSiltstone

Cong lomera teCong lomera te C lays toneC lays tone

Sandstone ShaleSandstone Shale

CLASTICCLASTIC

ANORGANICANORGANIC ORGANICORGANIC

Clastic Sedimentary Rocks:Clastic Sedimentary Rocks:


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yy

MudstonesMudstones



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SandstonesSandstones



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yy

ConglomeratesConglomerates


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Chemical Sedimentary Rocks:Chemical Sedimentary Rocks:


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Chemical Sedimentary Rocks:y

Formed by Precipitation from Aqueous SolutionFormed by Precipitation from Aqueous Solution

1. The Evaporites1. The Evaporites

a. Halite (NaCl)

b. Calcite (CaCO3)

c. Gypsum (CaSO4. H2O)

2. Precipitated Silica2. Precipitated Silica

Chert

Chemical Sedimentary Rocks:Chemical Sedimentary Rocks:Chemical Sedimentary Rocks:

F d f Pl t M t i l Th C l


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Formed from Plant MaterialFormed from Plants Material: The CoalFormed from Plants Material: The Coal

Inundated

swamp or

marsh

Bituminous coalBituminous coal

(soft coal)(soft coal)PeatPeat LigniteLignite

Coal seams in Mesa Verde National ParkCoal seams in Mesa Verde National Park Bituminous coalBituminous coal

Chemical Sedimentary Rocks:Chemical Sedimentary Rocks:

F d f A i l M t i l Th Li tF d f A i l M t i l Th Li t


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Formed from Animal Material: The LimestonesFormed from Animal Material: The Limestones

1. Limestone (a limey mudstone)

All contain CaCOAll contain CaCO3 All will fizz in contact with acidAll will fizz in contact with acid3

2. Fossil iferous limestone

3. Coquina

4. Chalk

Modul 9 - Sedimentary Rocks

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