Sedimentology- Pak Sugeng

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PRINCIPLES OFPRINCIPLES OFSEDIMENTOLOGYSEDIMENTOLOGY

Dr.Dr. SugengSugeng SS Sur Sur j jonoono

[email protected]@ugm.ac.id

Lab. Sedimentografi

Jurusan Teknik Geologi, Fakultas Teknik

Universitas Gadjah Mada



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IntroductionIntroduction

DefinitionsDefinitions

•• SedimentologySedimentology = the study of the processes of= the study of the processes of

formation, transport and deposition of material whichformation, transport and deposition of material which

accumulates as sediment in continental and marineaccumulates as sediment in continental and marine

environments and eventually forms sedimentary rocksenvironments and eventually forms sedimentary rocks

•• StratigraphyStratigraphy = the study of rocks to determine the= the study of rocks to determine the

order and timing of events in Earth historyorder and timing of events in Earth history

•• SedimentarySedimentary geologygeology ≈≈ sedimentologysedimentology ++

stratigraphystratigraphy



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SEDIMENTARY CICLES



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Sedimentary ciclesSedimentary cicles

WeatheringWeathering

(Erosion)(Erosion)

TransportationTransportation --DepositionDeposition Lithification (diagenesis)Lithification (diagenesis)



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WeatheringWeathering

Physical Weathering

• Frost wedging: caused by freezing and thawing of water in rockfractures.

• Alternate expansion and contraction of rock surfaces as a result of

diurnal changes in temperature

• Release of overburden pressure owing to erosion to overlying stratacauses the development of rock fractures

Chemical Weathering

It involves changes that can alter both the chemical andmineralogical composition of rocks. Minerals in the rocks areattacked by water, oxygen and carbon dioxide of the atmosphere,causing some component of the minerals to dissolve and be removein solution.



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Sedimentary ciclesSedimentary cicles WeatheringWeathering

(Erosion)(Erosion)

TransportationTransportation DepositionDeposition

Lithification (diagenesis)Lithification (diagenesis)



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EROSI

Proses lepasnyasuatubagianbatuandari tubuhbatuan induknya.Bagianyang terlepas tersebut bisamerupakanbagianyang lapuk

ataupunyang masihsegar, akibat benturan, hempasan, goresan

danataukorosi

HASIL EROSI :

Erosi menghasilkanmaterialhancuran

yang teronggokdekatdenganbatuan induknya : ENDAPAN KLASTIK

Endapanklastik dipindahkandari tempat asalnyake tempat lain

olehprosesyang disebut prosesTRANSPORTASI

AGEN EROSI :

AIR MENGALIR

ANGIN BERTIUP

GLETSER YANG BERGERAK



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Sedimentary ciclesSedimentary cicles

WeatheringWeathering ((ErosionErosion))

TransportationTransportation -- DepositionDeposition Lithification (diagenesis)Lithification (diagenesis)



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Sediment transportSediment transport

mechanismmechanism

CurrentsCurrents

WavesWaves

TidesTides

GravityGravity



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in laminar flow , waterparticles are all movingnearly parallel to eachother downflow

Two types of flows: Laminar and turbulent flows

in turbulent flow , waterparticles are movingmore chaotically, wherein local areas watermight be moving up,

down, in, out, or evenupstream

Highly turbulent water masses are referred to as eddies



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LAMINAR VS TURBULENT FLOW

Schematic representation of laminar vs turbulent fluid flowa) Laminar flow over a smooth stream bedb) Laminar flow over a spherical particle on a smooth bedc) Turbulent flow over a smooth bed. The arrows indicate flow

paths of the fluid

Boggs, 1995



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Reynolds numberReynolds number (laminar vs. turbulent flow)(laminar vs. turbulent flow)

u=flow velocity; l=characteristic length (flow depth);u=flow velocity; l=characteristic length (flow depth); υυ==kinematickinematic

viscosity (dynamic viscosity/fluid density)viscosity (dynamic viscosity/fluid density)

•• Turbulence is promoted by high flow velocities and flowTurbulence is promoted by high flow velocities and flow

depths, and low viscosities (Re>2000); laminar flowdepths, and low viscosities (Re>2000); laminar flow

occurs when the reverse is the case (Re<500)occurs when the reverse is the case (Re<500)•• Air and water are nearly always turbulent Air and water are nearly always turbulent

υ

ulRe =



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Types of particle movements in a turbulent currentTypes of particle movements in a turbulent current



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FroudeFroude numbernumber ((subcriticalsubcritical vs. supercritical flow)vs. supercritical flow)

u=flow velocity; d=flow depth;u=flow velocity; d=flow depth; √√gdgd=celerity (wave velocity)=celerity (wave velocity)

•• Flow velocities exceeding wave propagation velocitiesFlow velocities exceeding wave propagation velocities(Fr>1) yield supercritical flow, lower velocities (Fr<1)(Fr>1) yield supercritical flow, lower velocities (Fr<1)

causecause subcriticalsubcritical flowflow

••

A spatial transition from A spatial transition from subcriticalsubcritical to supercritical flowto supercritical flow(or vice versa) is characterized by a(or vice versa) is characterized by a ‘ ‘hydraulic jumphydraulic jump’ ’

gd

uFr =



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StokesStokes’ ’ LawLaw (settling velocity in a static fluid)(settling velocity in a static fluid)

vvgg=settling velocity; D=grain diameter;=settling velocity; D=grain diameter; ρρgg=grain density;=grain density;

ρρf f =fluid density;=fluid density; µµ=dynamic viscosity=dynamic viscosity

•• StokesStokes’ ’ Law only applies to fine (<100Law only applies to fine (<100 µµm)m), quartz, quartz--

density grains in waterdensity grains in water

µ18)ρ(ρgDv f g

2

g −=



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Based on the equation and realize: a slight increase ingrain size leads to normal grading an increase in viscosity

and/or an increase in ρρf can lead to a matrix-supported

deposit (i.e. large clasts appear to be floating in a matrixof fine grained mud) as opposed to grain-supported

deposit where each large clast is resting on another large

clast.

Suspended Load vs. Bed Load: grains will stay in

suspension if the upward motion of water, due to

turbulence, is larger than the grain's settling velocity.

Therefore, the smaller or less dense grains will tend to by

carried in a flow up in suspension and settle down to the

bed, to become bedload, once the flow's turbulence

becomes less (i.e. the flow slows down).

StokesStokes’’ LawLaw



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•• TheThe BernouilliBernouilli effecteffect is the reduction of pressure,is the reduction of pressure,

proportional to the increase of flow velocity as the flowproportional to the increase of flow velocity as the flow

encounters an obstacle (sediment particle), leading to aencounters an obstacle (sediment particle), leading to alift force and entrainment of the particlelift force and entrainment of the particle

•• Drag forces and lift forces act together to causeDrag forces and lift forces act together to cause

entrainment of sediment grainsentrainment of sediment grains

•• TheThe boundary layerboundary layer is that part of the flow influencedis that part of the flow influenced

by frictional effectsby frictional effects



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Transport modes in a turbulent fluidTransport modes in a turbulent fluid

Coarse sediment (sand and gravel) moves on or very close to thebed during transport : bedload.

Finer material (clay to silt) carried higher up in the main flow abovethe bed makes up the suspended load

Types of bedload transport:

•• TractionTraction (rolling over the(rolling over the

bed surface)bed surface)

•• SaltationSaltation (jumping over(jumping overthe bed surface)the bed surface)

SuspensionSuspension (permanent(permanent

transport within the fluid)transport within the fluid)

PARTICLE TRANSPORT BY FLUIDS



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PARTICLE TRANSPORT BY FLUIDSHjulstrom Diagram : show the critical current velocity and sedimenterosion, transport and deposition (deduced experimentally from flows required to

move quartz grain on a plane bed at a water depth of 1 m



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Flow Competence: faster moving flows cancarry larger particles

Flow Capacity : faster moving flows can also

carry more particles



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Current ripplesCurrent ripples

•• Once movement of sand grains (<0.7 mm) occurs, current ripples aOnce movement of sand grains (<0.7 mm) occurs, current ripples arereformed as a result of boundary layer separation, commonlyformed as a result of boundary layer separation, commonly

accompanied by a separation vortexaccompanied by a separation vortex

•• Current ripples have aCurrent ripples have a stossstoss side (erosion and transport) and lee sideside (erosion and transport) and lee side

(deposition), the latter with a slope of ~30(deposition), the latter with a slope of ~30°° (angle of repose)(angle of repose)•• Current ripples only form under moderate flow velocities, with aCurrent ripples only form under moderate flow velocities, with a graingrain

size <0.7 mmsize <0.7 mm

•• Height: 0.5Height: 0.5 – –3 cm; wavelength: 53 cm; wavelength: 5 – –40 cm40 cm

DunesDunes

•• Dunes are distinctly larger than current ripplesDunes are distinctly larger than current ripples

•• There is a relationship between boundaryThere is a relationship between boundary--layer thickness (layer thickness (≈≈flow depth in rivers) and the dimension of dunesflow depth in rivers) and the dimension of dunes

•• Dunes only form in grain sizes >0.2 mmDunes only form in grain sizes >0.2 mm

•• Sand waves constitute the largest category ofSand waves constitute the largest category of subaqueoussubaqueous

dunesdunes



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Current ripples (gelembur gelombang)



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Sediment transport mechanismSediment transport mechanism

CurrentsCurrents WavesWaves

TidesTides GravityGravity



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WavesWaves

Waves are windWaves are wind--generated oscillatorygenerated oscillatory

motions of watermotions of water Wave height is dependent on windWave height is dependent on wind

strength and fetchstrength and fetch

The depth to which the oscillatoryThe depth to which the oscillatorymotion due to wave action extends ismotion due to wave action extends isknown as theknown as the wave basewave base; shallow; shallowwater leads to breaking waveswater leads to breaking waves

Wave ripples are distinct from currentWave ripples are distinct from currentripples due to their symmetry, andripples due to their symmetry, andinclude lowinclude low--energyenergy ‘ ‘rolling grain ripplesrolling grain ripples’ ’ and highand high--energyenergy ‘ ‘vortex ripplesvortex ripples’ ’



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Tidal currentsTidal currents

Tides are formed by theTides are formed by the

gravitational attraction of the Moongravitational attraction of the Moonand Sun on the Earth, combinedand Sun on the Earth, combined

with the centrifugal force causedwith the centrifugal force caused

by movement of the Earth aroundby movement of the Earth aroundthe center of mass of the Earththe center of mass of the Earth--

Moon systemMoon system

•• SemiSemi--diurnal or diurnal tidal cyclesdiurnal or diurnal tidal cycles

•• NeapNeap--spring tidal cyclesspring tidal cycles

•• Annual tidal cyclesAnnual tidal cycles



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Ocean currentsOcean currents•• The circulation of sea water in the worldThe circulation of sea water in the world’ ’ ss

oceans is driven by wind and contrasts inoceans is driven by wind and contrasts in

density due to variable temperature anddensity due to variable temperature and

salinity (salinity (thermohalinethermohaline circulation),circulation),

combined with thecombined with the CoriolisCoriolis effecteffect•• Ocean currents transport clay and silt inOcean currents transport clay and silt in

suspension, and sand as bed load, andsuspension, and sand as bed load, and

their effects are especially important intheir effects are especially important indeep waters, where storms and tides aredeep waters, where storms and tides are

less importantless important



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Sediment transport mechanismSediment transport mechanism

CurrentsCurrents

WavesWaves

TidesTides

GravityGravity

PARTICLE TRANSPORT BY SEDIMENT GRAVITY FLOWS



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•• Debris flowsDebris flows have a high (>50%) proportion of sediment tohave a high (>50%) proportion of sediment to

water and can be both subaerial andwater and can be both subaerial and subaqueoussubaqueous

•• Low Reynolds numbersLow Reynolds numbers

•• Turbidity currentsTurbidity currents have a higher proportion of water, arehave a higher proportion of water, are

alwaysalways subaqueoussubaqueous, and move due to density contrasts, and move due to density contrasts

•• Higher Reynolds numbersHigher Reynolds numbers

PARTICLE TRANSPORT BY SEDIMENT GRAVITY FLOWS



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Below left: Ideal Bouma Sequence On right: Illustration of concept that with



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Below left: Ideal Bouma Sequence. On right: Illustration of concept that with

increasing distance downflow, the lower parts of the Bouma Sequence are

not found.

DiagenesisDiagenesis



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sediment is covered by successive layer of younger sediment;increased temperature and pressure leading to consolidation andlithification of the sediment into sedimentary rocks

diagenesis is anychemical, physical, orbiological changeundergone by

sediments after itsinitial deposition andduring and after itslithification, exclusiveof surface alteration

(weathering) andmetamorphism.

Depositional environmentsDepositional environments



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Depositional environmentsDepositional environments

Fluvial environmentsFluvial environments



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•• Bedrock riversBedrock rivers essentially do not contribute to the stratigraphicessentially do not contribute to the stratigraphicrecord, contrary torecord, contrary to alluvial riversalluvial rivers

•• Alluvial fans Alluvial fans are relatively steep (>1are relatively steep (>1--22°°) cones consisting of) cones consisting of

coarsecoarse--grained facies and constitute the most proximal fluvialgrained facies and constitute the most proximal fluvial

depositional environments (usually at the break of slope on thedepositional environments (usually at the break of slope on theedge of a floodplain)edge of a floodplain)

•• Debris flows dominate on small and steep alluvial fansDebris flows dominate on small and steep alluvial fans

•• SheetfloodsSheetfloods are common on larger and gentler alluvial fansare common on larger and gentler alluvial fans

•• Ephemeral rivers are dry during a significant part of the year,Ephemeral rivers are dry during a significant part of the year,

contrary to perennial riverscontrary to perennial rivers

•• Floodplains are the areas occupied by river channels, as well asFloodplains are the areas occupied by river channels, as well as

the surrounding, flat (the surrounding, flat (overbank overbank ) areas that are subject to flooding) areas that are subject to flooding•• Discharge is confined to the channel untilDischarge is confined to the channel until bankfullbankfull discharge isdischarge is

reached; from that point onreached; from that point on overbank overbank flow can occur, submergingflow can occur, submerging

the entire floodplainthe entire floodplain




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•• Channel patterns (fluvial styles) are commonlyChannel patterns (fluvial styles) are commonlyclassified as:classified as:•• Braided riversBraided rivers

•• Meandering riversMeandering rivers•• Straight riversStraight rivers

•• Anastomosing Anastomosing riversrivers

•• Fluvial style is primarily controlled by specific streamFluvial style is primarily controlled by specific stream

power (W mpower (W m--22) and grain size, but also by bank) and grain size, but also by bankstability and the amount of bed loadstability and the amount of bed load

ρρ=fluid density; Q=discharge; s=slope (gradient); w=channel=fluid density; Q=discharge; s=slope (gradient); w=channelwidthwidth

w

ρgQsω =




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•• BarsBars are sandy or gravellyare sandy or gravelly macroformsmacroforms in channelsin channels

that are emergent, mostlythat are emergent, mostly unvegetatedunvegetated features atfeatures at

low flow stage, and undergo submergence and rapidlow flow stage, and undergo submergence and rapid

modification during high dischargemodification during high discharge

•• Point barsPoint bars form on inner banks and typically accreteform on inner banks and typically accrete

laterally, commonly resulting in laterallaterally, commonly resulting in lateral--accretionaccretion

surfaces; midsurfaces; mid--channel orchannel or braid barsbraid bars accrete bothaccrete bothlaterally and downstreamlaterally and downstream

•• Braided rivers are characterized by a dominance ofBraided rivers are characterized by a dominance of

braid bars; meandering rivers primarily contain pointbraid bars; meandering rivers primarily contain pointbars; in straight (and mostbars; in straight (and most anastomosinganastomosing) rivers bars) rivers bars

are almost absentare almost absent



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•• Channel beltsChannel belts consist ofconsist of channelchannel--barbar andand channelchannel--fillfill

depositsdeposits; the proportion of the two generally decreases; the proportion of the two generally decreases

markedly from braided rivers to straight ormarkedly from braided rivers to straight or anastomosinganastomosing

riversrivers•• The geometry of a channel belt (width/thickness ratio) is aThe geometry of a channel belt (width/thickness ratio) is a

function of the channel width and the degree of lateralfunction of the channel width and the degree of lateral

migration; values are typically much higher for braidedmigration; values are typically much higher for braided

systems (>>100) than for straight orsystems (>>100) than for straight or anastomosinganastomosing

systems (<25)systems (<25)

•• ResidualResidual--channel depositschannel deposits are predominantly muddyare predominantly muddy

(occasionally organic) deposits that accumulate in an(occasionally organic) deposits that accumulate in anabandoned channel where flow velocities are extremelyabandoned channel where flow velocities are extremely

smallsmall




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•• Overbank Overbank environmentsenvironments are dominated byare dominated byfinefine--grained facies (predominantlygrained facies (predominantly mudsmuds))•• NaturalNatural--levee depositslevee deposits are wedges of sedimentare wedges of sediment

that form adjacent to the channel, dominated bythat form adjacent to the channel, dominated byfine sand and silt exhibiting planar stratification orfine sand and silt exhibiting planar stratification or(climbing) ripple cross stratification(climbing) ripple cross stratification

•• CrevasseCrevasse--splay depositssplay deposits are usually cones ofare usually cones of

sandy tosandy to siltysilty facies with both coarseningfacies with both coarsening--upwardupwardand finingand fining--upward successions, and are formed byupward successions, and are formed bysmall, secondary channels during peak flowsmall, secondary channels during peak flow

•• FloodFlood--basin depositsbasin deposits are the most distal facies,are the most distal facies,consisting entirely of sediments deposited fromconsisting entirely of sediments deposited fromsuspension, and are volumetrically very importantsuspension, and are volumetrically very important(mainly in low(mainly in low--energy fluvial settings)energy fluvial settings)



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•• PaleosolsPaleosols (well drained conditions) and(well drained conditions) and peatspeats

(poorly drained conditions) occur frequently(poorly drained conditions) occur frequentlyinin overbank overbank environments and are importantenvironments and are important

indicators of variations ofindicators of variations of clasticclastic aggradationaggradation

rates and the position relative to activerates and the position relative to activechannelschannels

•• LacustrineLacustrine deposits can be important indeposits can be important in

overbank overbank environments characterized by highenvironments characterized by highwater tables, and are also found in distalwater tables, and are also found in distal

settingssettings



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•• Avulsion Avulsion is the sudden diversion of a channel to ais the sudden diversion of a channel to a

new location on the floodplain, leading to thenew location on the floodplain, leading to the

abandonment of a channel belt and the initiation of aabandonment of a channel belt and the initiation of a

new onenew one

•• Alluvial architecture Alluvial architecture refers to the threerefers to the three--

dimensional arrangement of channeldimensional arrangement of channel--belt depositsbelt deposits

andand overbank overbank deposits in a fluvial successiondeposits in a fluvial succession•• The nature of alluvial architecture (e.g., theThe nature of alluvial architecture (e.g., the

proportion of channelproportion of channel--belt tobelt to overbank overbank deposits) isdeposits) is

dependent on fluvial style,dependent on fluvial style, aggradationaggradation rate, and therate, and the

frequency of avulsionfrequency of avulsion



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Deltaic environmentsDeltaic environments



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•• Deltas form where a river enters a standing body ofDeltas form where a river enters a standing body ofwater (ocean, sea, lake) and forms a thick deposit thatwater (ocean, sea, lake) and forms a thick deposit thatmay or may not form protuberancesmay or may not form protuberances

•• TheThe delta plaindelta plain is theis the subaerialsubaerial part of a deltapart of a delta(gradational upstream to a floodplain); the(gradational upstream to a floodplain); the delta frontdelta front(delta slope and(delta slope and prodeltaprodelta) is the) is the subaqueoussubaqueous componentcomponent

•• Delta plains are commonly characterized by distributariesDelta plains are commonly characterized by distributariesand flood basins (upper delta plain) orand flood basins (upper delta plain) or interdistributaryinterdistributarybays (lower delta plain), as well as numerous crevassebays (lower delta plain), as well as numerous crevassesplayssplays

•• Upper delta plains containUpper delta plains contain faciesfacies assemblages that areassemblages that arevery similar to fluvial settingsvery similar to fluvial settings



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•• Mouth barsMouth bars form at the upper edge of theform at the upper edge of the

delta front, at the mouth of distributaries; theydelta front, at the mouth of distributaries; they

are mostly sandy and tend to coarsen upwardsare mostly sandy and tend to coarsen upwards

•• TheThe delta slopedelta slope is commonly 1is commonly 1--22°° and consistsand consists

of finer (usuallyof finer (usually siltysilty)) faciesfacies; the most distal; the most distalprodeltaprodelta is dominated by even finer sedimentis dominated by even finer sediment

•• ProgradationProgradation ((basinwardbasinward building) of deltasbuilding) of deltas

leads to coarseningleads to coarsening--upward successions, andupward successions, andprogradationprogradation rates depend on sediment supplyrates depend on sediment supply

and basin bathymetry (water depth)and basin bathymetry (water depth)



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•• Delta morphology reflects the relativeDelta morphology reflects the relativeimportance of fluvial, tidal, and wave processes,importance of fluvial, tidal, and wave processes,

as well as gradient and sediment supplyas well as gradient and sediment supply•• RiverRiver--dominated deltasdominated deltas occur inoccur in microtidalmicrotidal settingssettings

with limited wave energy, where deltawith limited wave energy, where delta--lobelobe

progradationprogradation

is significant and redistribution of mouthis significant and redistribution of mouth

bars is limitedbars is limited

•• WaveWave--dominated deltasdominated deltas are characterized byare characterized bymouth bars reworked into shoremouth bars reworked into shore--parallel sand bodiesparallel sand bodies

and beachesand beaches•• TideTide--dominated deltasdominated deltas exhibit tidal mudflats andexhibit tidal mudflats and

mouth bars that are reworked into elongate sandmouth bars that are reworked into elongate sandbodies perpendicular to the shorelinebodies perpendicular to the shoreline



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•• CoarseCoarse--grained deltas are composed of gravellygrained deltas are composed of gravelly

faciesfacies and form where alluvial fans or relativelyand form where alluvial fans or relatively

•• steep braided rivers enter a water bodysteep braided rivers enter a water body

•• Delta cycles are the result of repetitive switchingDelta cycles are the result of repetitive switching

of delta lobes, comparable to avulsion in fluvialof delta lobes, comparable to avulsion in fluvial

environments; this leads to characteristic verticalenvironments; this leads to characteristic vertical

successions withsuccessions with progradationalprogradational faciesfacies andand

transgressivetransgressive faciesfacies



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Coastal environmentsCoastal environments



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•• ErosionalErosional coasts are commonly characterized by cliffs, whereascoasts are commonly characterized by cliffs, whereas

constructional coasts can be formed byconstructional coasts can be formed by clasticclastic, carbonate, or, carbonate, or

evaporiteevaporite faciesfacies

•• The morphology of constructional coasts is determined by sedimenThe morphology of constructional coasts is determined by sedimentt

supply, wave energy, and tidal range, as well as climate and seasupply, wave energy, and tidal range, as well as climate and sea--

level historylevel history

•• Beaches form when sand or gravel is available and wave energy isBeaches form when sand or gravel is available and wave energy is

significant, and result in lowsignificant, and result in low--angle crossangle cross--stratified deposits andstratified deposits andcross strata formed by wave ripplescross strata formed by wave ripples

•• Beaches can either be connected directly to the land and formBeaches can either be connected directly to the land and form

strand plainsstrand plains oror chenierchenier plainsplains (the latter consisting of beach(the latter consisting of beach

ridges separated byridges separated by mudsmuds), or be separated by), or be separated by lagoonslagoons oror tidaltidalbasinsbasins (the latter consisting of tidal channels, tidal flats, and salt(the latter consisting of tidal channels, tidal flats, and salt

marshes) and form eithermarshes) and form either spitsspits oror barrier islandsbarrier islands



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•• Barrier islands are especially prolific in environments with a hBarrier islands are especially prolific in environments with a highigh



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wave energy and a limited tidal range, that have experiencedwave energy and a limited tidal range, that have experiencedtransgression (relative seatransgression (relative sea--level rise)level rise)

•• The tidal inlets between barrier islands are sites of deepThe tidal inlets between barrier islands are sites of deep erosionalerosional

scour and are associated with floodscour and are associated with flood--tidal deltas (tidal deltas (lagoonallagoonal side) andside) and

ebbebb--tidal deltas (seaward side)tidal deltas (seaward side)•• WashoversWashovers can form during major storm events, and are foundcan form during major storm events, and are found

elsewhere across barrier islandselsewhere across barrier islands

•• Coastal dunes are common features associated with sandy beachesCoastal dunes are common features associated with sandy beaches

•• EstuariesEstuaries are semiare semi--enclosed coastal water bodies where fluvialenclosed coastal water bodies where fluvial

and marine processes interactand marine processes interact

•• TideTide--dominated estuariesdominated estuaries have tidal channels with bars and tidalhave tidal channels with bars and tidal

mudflats that contain tidal sedimentary structures (e.g., tidalmudflats that contain tidal sedimentary structures (e.g., tidal bundles,bundles,heterolithicheterolithic stratification)stratification)

•• WaveWave--dominated estuariesdominated estuaries are partly enclosed by a coastal barrierare partly enclosed by a coastal barrier

and have welland have well--developed baydeveloped bay--head deltashead deltas




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•• Carbonate coastal environments can exhibit comparableCarbonate coastal environments can exhibit comparable

characteristics ascharacteristics as clasticclastic coasts (i.e., barriers andcoasts (i.e., barriers and

lagoons), consisting of carbonate sands andlagoons), consisting of carbonate sands and mudsmuds,,

respectivelyrespectively•• StromatolitesStromatolites (algal or bacterial mats) commonly form on(algal or bacterial mats) commonly form on

carbonatecarbonate--rich tidal flatsrich tidal flats

•• Arid coastal environments are characterized by Arid coastal environments are characterized by sabkhassabkhas

andand salinassalinas, coastal plains frequently inundated by, coastal plains frequently inundated by

saline water andsaline water and hypersalinehypersaline lagoons, respectively,lagoons, respectively,

wherewhere evaporitesevaporites (notably anhydrite and gypsum) can(notably anhydrite and gypsum) canaccumulateaccumulate

Shallow marine environmentsShallow marine environments



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•• Shallow seas can be subdivided intoShallow seas can be subdivided into clasticclastic andand

carbonatecarbonate--dominated systems, dependingdominated systems, depending

mainly on sediment supply and climatic settingmainly on sediment supply and climatic setting•• Idealized models predict a general decrease ofIdealized models predict a general decrease of

grain size with water depth (i.e., away from thegrain size with water depth (i.e., away from the

shoreline); however, this simple picture isshoreline); however, this simple picture iscomplicated by a large number of factors (e.g.,complicated by a large number of factors (e.g.,

shelf bathymetry)shelf bathymetry)



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SS d i dd i d l il i h lh l id ll hibiid ll hibi



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•• StormStorm--dominateddominated clasticclastic shelvesshelves ideally exhibit aideally exhibit atransition from predominantly wavetransition from predominantly wave--rippled sands in therippled sands in theupperupper shorefaceshoreface, to alternating sands and, to alternating sands and mudsmuds((tempestitestempestites with hummocky cross stratification) in thewith hummocky cross stratification) in the

lowerlower shorefaceshoreface, to muddy facies below storm wave base, to muddy facies below storm wave base•• TideTide--dominateddominated clasticclastic shelvesshelves may exhibitmay exhibit erosionalerosional

features, sand ribbons, and sand waves with decreasingfeatures, sand ribbons, and sand waves with decreasingflow velocities, commonly associated with mudflow velocities, commonly associated with mud--drapeddraped

subaqueoussubaqueous dunes; tidal sand ridges (tens of m high, manydunes; tidal sand ridges (tens of m high, manykm across) are characteristic of shelves with a high supplykm across) are characteristic of shelves with a high supplyof sandof sand

•• BioturbationBioturbation can obliterate many primary sedimentarycan obliterate many primary sedimentary

structures in shelf environmentsstructures in shelf environments



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•• Shallow seas within theShallow seas within the photicphotic zone are thezone are the

premierpremier ‘ ‘carbonate factoriescarbonate factories’ ’

•• Carbonate platformsCarbonate platforms can cover continentalcan cover continentalshelves orshelves or epicontinentalepicontinental seas, when theseas, when the

conditions for carbonate productionconditions for carbonate production

(temperature, salinity, light conditions) are(temperature, salinity, light conditions) are

favorablefavorable

•• Isolated platforms (atolls) are found in shallowIsolated platforms (atolls) are found in shallow

seas surrounded by deep water, like extinctseas surrounded by deep water, like extinctvolcanoesvolcanoes



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•• Carbonate rampsCarbonate ramps exhibit processes and characteristicsexhibit processes and characteristics

comparable tocomparable to clasticclastic shelves, with carbonate sands andshelves, with carbonate sands and

mudsmuds ultimately producing a seaward transition fromultimately producing a seaward transition from

grainstonegrainstone to mudstone, commonly with similarto mudstone, commonly with similarsedimentary structuressedimentary structures

•• Rimmed carbonate shelvesRimmed carbonate shelves consist of a coral reef orconsist of a coral reef or

carbonate sand barrier at some distance from thecarbonate sand barrier at some distance from the

mainland; the shelf lagoon can be up to many tens ofmainland; the shelf lagoon can be up to many tens of

kilometers widekilometers wide

•• BoundstonesBoundstones dominate the reef faciesdominate the reef facies

•• Shelf lagoon facies are mostly fineShelf lagoon facies are mostly fine--grained and ultimately lead tograined and ultimately lead tothe formation of mudstones andthe formation of mudstones and wackestoneswackestones

Deep marine environmentsDeep marine environments

h l l f d fTh i l l i j f di f



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•• The continental slope is a major source of sediment forThe continental slope is a major source of sediment for

the deep sea, and is a setting where slumps can occurthe deep sea, and is a setting where slumps can occur

•• Debris flows and turbidity currents are the mainDebris flows and turbidity currents are the main

mechanisms of transport from the continental slope intomechanisms of transport from the continental slope intothe deep sea; these processes can be triggered bythe deep sea; these processes can be triggered by

external forcing (e.g., an earthquake) or by the slopeexternal forcing (e.g., an earthquake) or by the slope

reaching a critical state as a result of ongoing depositionreaching a critical state as a result of ongoing deposition

•• DebrisDebris--flow deposits andflow deposits and turbiditesturbidites are often geneticallyare often genetically

relatedrelated

•• TurbiditesTurbidites can be bothcan be both clasticclastic (commonly leading to the(commonly leading to the

formation offormation of wackeswackes) or calcareous) or calcareous

Deep marine environmentsDeep marine environments•• Submarine canyons at the shelf edge (commonlySubmarine canyons at the shelf edge (commonly

related to deltas) are connected torelated to deltas) are connected to submarinesubmarine



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related to deltas) are connected torelated to deltas) are connected to submarinesubmarinefansfans on the ocean flooron the ocean floor

•• Contrary to debris flows,Contrary to debris flows, turbiditesturbidites exhibit aexhibit a

distinct proximal to distal finingdistinct proximal to distal fining•• Submarine fans share several characteristics withSubmarine fans share several characteristics with

deltas; they consist of a feeder channel thatdeltas; they consist of a feeder channel that

divides into numerousdivides into numerous distributarydistributary channelschannelsbordered by natural levees and are subject tobordered by natural levees and are subject toavulsionsavulsions•• Proximal fan (trunk channel)Proximal fan (trunk channel)

•• Medial fan (lobes)Medial fan (lobes)

•• Distal fanDistal fan

•• BasalBasal BoumaBouma--divisions have the highestdivisions have the highest

preservation potentialpreservation potential updipupdip; upper; upper BoumaBouma



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preservation potentialpreservation potential updipupdip; upper; upper BoumaBouma--divisions are more commondivisions are more common downdipdowndip

•• TurbiditeTurbidite lobes characterize the medial fan andlobes characterize the medial fan and

may exhibit the most completemay exhibit the most complete BoumaBoumasequencessequences

•• TheThe BoumaBouma--model is increasingly challenged,model is increasingly challenged,

because manybecause many turbiditesturbidites do not conform to itdo not conform to it(e.g.,(e.g., ‘ ‘highhigh--concentrationconcentration turbiditesturbidites’ ’ ))

•• ContouritesContourites are formed by ocean currents andare formed by ocean currents and

commonly represent reworkedcommonly represent reworked turbiditesturbidites




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•• Pelagic sedimentsPelagic sediments primarily have a biogenic originprimarily have a biogenic origin•• Calcareous ooze (e.g., foraminifera) forms above the calciteCalcareous ooze (e.g., foraminifera) forms above the calcite

compensation depth (CCD) at ~4000 m depthcompensation depth (CCD) at ~4000 m depth•• Siliceous ooze (e.g., radiolarians, diatoms) forms betweenSiliceous ooze (e.g., radiolarians, diatoms) forms between

the CCD and ~6000 m depth where silica dissolves; itthe CCD and ~6000 m depth where silica dissolves; itlithifieslithifies intointo chertscherts

•• HemipelagicHemipelagic sedimentssediments consist of fineconsist of fine--grainedgrained(muddy)(muddy) terrigenousterrigenous material that is deposited frommaterial that is deposited fromsuspensionsuspension•• EolianEolian dust is an important component (~50%) ofdust is an important component (~50%) of

hemipelagichemipelagic (and pelagic) facies(and pelagic) facies•• BlackBlack shalesshales have a 1have a 1--15% organic15% organic--matter content and formmatter content and form

in anoxic bottom watersin anoxic bottom waters

Facies and depositional environmentsFacies and depositional environments



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•• TheThe faciesfacies concept refers to the sum of characteristicsconcept refers to the sum of characteristicsof a sedimentary unit, commonly at a fairly small (cmof a sedimentary unit, commonly at a fairly small (cm--m)m)

scalescale•• LithologyLithology

•• Grain sizeGrain size

•• Sedimentary structuresSedimentary structures

•• ColorColor•• CompositionComposition

•• Biogenic contentBiogenic content

•• Lithofacies (physical and chemical characteristics)Lithofacies (physical and chemical characteristics)

•• BiofaciesBiofacies (macrofossil content)(macrofossil content)•• IchnofaciesIchnofacies (trace fossils)(trace fossils)

•• Facies analysisFacies analysis is the interpretation of strata in termsis the interpretation of strata in termsof depositional environments (or depositional systems),of depositional environments (or depositional systems),

commonly based on a wide variety of observationscommonly based on a wide variety of observationsFacies associationsFacies associations constitute several facies that occurconstitute several facies that occur



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commonly based on a wide variety of observationscommonly based on a wide variety of observations•• Facies associationsFacies associations constitute several facies that occurconstitute several facies that occur

in combination, and typically represent one depositionalin combination, and typically represent one depositionalenvironment (note that very few individual facies areenvironment (note that very few individual facies arediagnostic for one specific setting!)diagnostic for one specific setting!)

•• Facies successionsFacies successions (or facies sequences) are facies(or facies sequences) are faciesassociations with a characteristic vertical orderassociations with a characteristic vertical order

•• WaltherWalther’ ’ s Laws Law (1894) states that two different facies(1894) states that two different faciesfound superimposed on one another and not separatedfound superimposed on one another and not separated

by an unconformity, must have been deposited adjacentby an unconformity, must have been deposited adjacentto each other at a given point in timeto each other at a given point in time

•• Sedimentary logsSedimentary logs are oneare one--dimensional representationsdimensional representationsof vertical sedimentary successionsof vertical sedimentary successions

•• Facies modelsFacies models are schematic, threeare schematic, three--dimensionaldimensionalrepresentations of specific depositional environmentsrepresentations of specific depositional environmentsthat serve as norms for interpretation and predictionthat serve as norms for interpretation and prediction



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is it time for lunch??is it time for lunch??



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Sedimentology- Pak Sugeng

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Transcript of Sedimentology- Pak Sugeng