Gravity Flow 1

7/23/2019 Gravity Flow 1

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SEDIMENT GRAVITY

FLOW


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Sediment Gravity FlowSediment Gravity Flow

MechanismsMechanisms Sediment Gravity Flows:Sediment Gravity Flows: 20%-70% suspended sediment20%-70% suspended sediment High density/viscosity luidsHigh density/viscosity luids

! suspended sediment charged luid within a lower density" am#ient luidsuspended sediment charged luid within a lower density" am#ient luid

! mass o suspended particles results in the potential energy or initiation omass o suspended particles results in the potential energy or initiation o

low in a the lower density luid $clear water or airlow in a the lower density luid $clear water or air

mgh = PEmgh = PE mm= mass= mass gg= force of gravity= force of gravity hh= height= height PE= Potential energyPE= Potential energy


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Sediment Gravity FlowSediment Gravity FlowClassification :Classification :

1. Fluidal !ewtonian" Flow1. Fluidal !ewtonian" Flow

Mechanism : Fluidi#ed FlowMechanism : Fluidi#ed Flow

$ur%idity Current$ur%idity Current

&. Mass non'!ewtonian" Flow&. Mass non'!ewtonian" Flow

Mechanism : Mud()e%ris FlowMechanism : Mud()e%ris Flow

Grain FlowGrain Flow


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FourFour $$y*ey*essof Sedimentof Sediment GGravityravity FFlowslows


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FourFour $$y*ey*essof Sedimentof Sediment GGravityravity FFlowslows

Grain lows-occursGrain lows-occurs

when cohesionlesswhen cohesionlesssediments $e&'sediments $e&' ddryrysand movessand movesdownward under thedownward under the

pull o gravity'pull o gravity' (lthough there is air(lthough there is air

or water trappedor water trapped#etween the grains"#etween the grains"

it merely acts as ait merely acts as alu#ricant and doeslu#ricant and doesnot actually propelnot actually propelthe grains'the grains'


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What is a turbidity current ?


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What are the gravity deposits ?


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GrainGrain FFlowlow

)he most amiliar)he most amiliar

e&amples o graine&amples o grain

low are sandlow are sand

avalanches' )heyavalanches' )heyoccur whenever aoccur whenever a

sand dunesand dune

#ecomes steeper#ecomes steeper

than the angle othan the angle o

repose $2*+-,0+'repose $2*+-,0+'


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GrainGrain FFlowlow

Grain lows move #y dispersive pressureGrain lows move #y dispersive pressure

#etween grains'#etween grains'

eposits are thin" well sorted and showeposits are thin" well sorted and show

inverse graded #edding'inverse graded #edding'

Grain lows also occurs in the deep sea"Grain lows also occurs in the deep sea"

where sand avalanches down the sides owhere sand avalanches down the sides o

steep su#marine canyons'steep su#marine canyons'


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Fluidi#ed Sediment FlowsFluidi#ed Sediment Flows

.oncentrated dispersions o grains.oncentrated dispersions o grains

supported #y pore water in #etween'supported #y pore water in #etween'

)hey #egin to low when something)hey #egin to low when something

increases the pressure on the interstitialincreases the pressure on the interstitial

pore water" turning the once-irm sand intopore water" turning the once-irm sand into

a soupy liuid" e&' uicsand'a soupy liuid" e&' uicsand'

1uicsand - grain shit and settle past one1uicsand - grain shit and settle past one

another liueaction' ( person should notanother liueaction' ( person should notcontinue to sin $as in a swimming poolcontinue to sin $as in a swimming pool

#eyond your point o #uoyancy' )o get out#eyond your point o #uoyancy' )o get out

swim as you would in a pool' 3ie lat'swim as you would in a pool' 3ie lat'


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Fluidi#ed Sediment FlowsFluidi#ed Sediment Flows Mechanism forms when unsta%le masses of sediment areMechanism forms when unsta%le masses of sediment are

sha+en %y eart,ua+e.sha+en %y eart,ua+e.

Can flow down very gentle slo*e with tremendous s*eeds.Can flow down very gentle slo*e with tremendous s*eeds.

)uration of flows de*end on amount of fluid availa%le and)uration of flows de*end on amount of fluid availa%le and

only %e im*ortant very near the source.only %e im*ortant very near the source.

)e*osits are massive or show vague *lanar laminae and)e*osits are massive or show vague *lanar laminae anddish'*illar structure.dish'*illar structure.

-i,uefaction occurs in others instances for e/am*le in-i,uefaction occurs in others instances for e/am*le in

shoc+waves sent through saturated soil %y an earth,ua+eshoc+waves sent through saturated soil %y an earth,ua+e..


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)lm sistem aliran ini sedimen terdu+ung oleh)lm sistem aliran ini sedimen terdu+ung olehaliran fluida +e atas melalui sedimen yangaliran fluida +e atas melalui sedimen yang

mem%uat %utiran menga*ung.mem%uat %utiran menga*ung.

$er0adi *ada saat massa sedimen yang tida+ sta%il$er0adi *ada saat massa sedimen yang tida+ sta%il

digoncang oleh gem*a.digoncang oleh gem*a. liran air +e atas menye%a%+an *enguranganliran air +e atas menye%a%+an *engurangan

+e+uatan massa +arena %utiran tida+ terdu+ung+e+uatan massa +arena %utiran tida+ terdu+ung

lagi oleh +onta+ antar %utir shg aliran d*t %ergera+lagi oleh +onta+ antar %utir shg aliran d*t %ergera+

*d lereng landai 23' 143".*d lereng landai 23' 143". )*t ter0adi di ling+ungan darat atau air dg)*t ter0adi di ling+ungan darat atau air dg

+ece*atan tinggi+ece*atan tinggi''


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)urasi dari aliran tergantung *ada 0umlah)urasi dari aliran tergantung *ada 0umlah

+andungan air.+andungan air.

5anya ter0adi di daerah de+at sum%er +rn5anya ter0adi di daerah de+at sum%er +rn

tida+ mem*unyai cu+u* wa+tu untu+tida+ mem*unyai cu+u* wa+tu untu+

menem*uh 0ara+ 0auh.menem*uh 0ara+ 0auh.

Gera+an air +e atas mem%entu+ dish danGera+an air +e atas mem%entu+ dish dan

*illar structures yg ter%entu+ s%g +olom air*illar structures yg ter%entu+ s%g +olom air

yg melalui sedimen selama dewatering".yg melalui sedimen selama dewatering".


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)ish'*illar structure generated)ish'*illar structure generated

%y fluidi#ed flow%y fluidi#ed flow


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-i,uified-i,uified FlowsFlows Sama dg fluidi#ed flow teta*i hanya se%agianSama dg fluidi#ed flow teta*i hanya se%agian

%utir yg terdu+ung oleh gera+an fluida +e atas.%utir yg terdu+ung oleh gera+an fluida +e atas. $er0adi selama taha* a+hir dari de*osisi$er0adi selama taha* a+hir dari de*osisi highhigh

density turbiditedensity turbidite atau sedimen terair+an +rnatau sedimen terair+an +rn

*roses luar se*erti gem*a" dimana sedimen*roses luar se*erti gem*a" dimana sedimen

%ergera+ menuruni lereng dan air yang%ergera+ menuruni lereng dan air yang

di+andungnya %ergera+ +e atas.di+andungnya %ergera+ +e atas.

6i+a lereng cu+u* curam aliran d*t %eru%ah men0adi6i+a lereng cu+u* curam aliran d*t %eru%ah men0adi

arus tur%id dan d*t %eru%ah +em%ali men0adiarus tur%id dan d*t %eru%ah +em%ali men0adi

li,uified flow *d saat aliran %ergera+ lam%at.li,uified flow *d saat aliran %ergera+ lam%at.


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-i,uified-i,uified FlowsFlows

Mem%entu+Mem%entu+ dish dan pillar structures.dish dan pillar structures. )e*osit masiv +adang'+adang mem%entu+)e*osit masiv +adang'+adang mem%entu+

planar laminaeplanar laminae yang tida+ 0elas.yang tida+ 0elas.

$d+ d*t mengerosi la*isan di %awahnya +rn$d+ d*t mengerosi la*isan di %awahnya +rn alirannya lam%at.alirannya lam%at.


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MudMudFFlows and )e%rislows and )e%ris FFlowslows

MudMudflowsflowsare composed o a slury-lie mass oare composed o a slury-lie mass oliueied mud that move downhill under the orceliueied mud that move downhill under the orceo gravity'o gravity'

4 there are large particles" ranging up to #oulder4 there are large particles" ranging up to #ouldersi5e" they are nown assi5e" they are nown as )e%ris flows)e%ris flows'' MudMudflows and )e%ris flowsflows and )e%ris flows are most commonare most common

in steep mountain canyons during heavyin steep mountain canyons during heavy

rainstorm'rainstorm' -ahars-ahars are mud/de#ris lows in the volcanicare mud/de#ris lows in the volcanic

area'area'


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epend on the cohesive strength o the matri&"epend on the cohesive strength o the matri&"larger grains are supported #y the high densitylarger grains are supported #y the high densityand viscousity o the matri&-water mi&ture'and viscousity o the matri&-water mi&ture'

)he te&ture can #e varies depending on the)he te&ture can #e varies depending on theconcentration o coarse grain $mud supported orconcentration o coarse grain $mud supported orgrain supported'grain supported'

)he #ed is generally massive" inverse grading is)he #ed is generally massive" inverse grading is

common eaturecommon eature'' eposition occurs when internal stress iseposition occurs when internal stress is

overcome #y cohesion o the matri&'overcome #y cohesion o the matri&'


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)hese lows)hese lows

have thehave the

consistency oconsistency owet cement andwet cement and

can move ascan move as

ast as water inast as water in

a lash lood'a lash lood'


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(n e&otic #loc(n e&otic #loc

can #e transportedcan #e transported#y lahar due to the#y lahar due to the

high viscousityhigh viscousity

and density oand density o

ash-water mi&ture'ash-water mi&ture'


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Some #eds e&hi#itSome #eds e&hi#it

reverse $inversereverse $inverse

grading" with thegrading" with the

coarsest materialcoarsest materialat the top and theat the top and the

iner at the #ottom'iner at the #ottom'

)he pressure push)he pressure push

the largest grainsthe largest grainsto the top" whento the top" when

stop they settle'stop they settle'


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$ur%idity Currents$ur%idity Currents

)ur#idity)ur#idity ccurrents are gravity lows in which theurrents are gravity lows in which thesediment is supported #y upward tur#ulence o thesediment is supported #y upward tur#ulence o theluid within the low'luid within the low'

4t is trigger #y gravity'4t is trigger #y gravity' )he mass o suspended sediment is denser than)he mass o suspended sediment is denser thanwater'water'

6ccures in areas where sediments is6ccures in areas where sediments is

accumulating su#aueously a#ove or near aaccumulating su#aueously a#ove or near aslope" so that as the sediments move downslope itslope" so that as the sediments move downslope itcan mi& with water and low tur#ulently withcan mi& with water and low tur#ulently with

tremendous speedtremendous speed''


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22 -- 8eerence" date" place8eerence" date" place

Delta front offlap

x10 to >100m

Delta plain Delta front Prodelta shelf

Shelf break

Difference of 2 orders of magnitude

Slope 1000 - 2000 m

Many types of environment can be observed in the shelf

They are conditioned by :

- the fluid dynamics

- physiography of the basin

- latitude

- climatic conditions- clastic input in the system etc.


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Idealized passive continental margin


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2929-- 8eerence" date" place8eerence" date" placeModel for Miocene sand deposition during lowstands of sea

level in the Kutei Basin

Slope and Basin Floor Deposits


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2727 -- 8eerence" date" place8eerence" date" place

A profile of experimental high-density turbidity current showing density

stratification. Note a lower laminar inertia-flow and an upper turbulent flow.

From Postma et al. (1988).

It is the deposit of a more complex flow whose final state is that of a fully turbulent

turbidity current.

This includes all those beds which appear to have formed through genetically relatedgravity flows the last of which is a waning and depleting turbidity current


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$ur%idity Currents$ur%idity Currents

))he composition is varied and they deposit a widehe composition is varied and they deposit a widerange o sediment types and sedimentary structuresrange o sediment types and sedimentary structuresdepending on the concentration and grain si5e o thedepending on the concentration and grain si5e o thesediments'sediments'

, populations o sediment si5es transported #y, populations o sediment si5es transported #ytur#idity currents : mud and ine to medium sands"tur#idity currents : mud and ine to medium sands"2 coarse sands to small pe##les" , pe##les to2 coarse sands to small pe##les" , pe##les toco##les'co##les'

2 types o tur#idity current :2 types o tur#idity current : 11''-ow density tur%idity current &.-ow density tur%idity current &.5igh density tur%idity current5igh density tur%idity current


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-ow )ensity-ow )ensity $ur%idity Currents$ur%idity Currents

))he sediment concentration is ; 20%he sediment concentration is ; 20% .an transport and deposit clay" silt and sand'.an transport and deposit clay" silt and sand'

eposition rom #edeposition rom #edload < suspended loadload < suspended load''

44nitial deposits are coarsest transported particlesnitial deposits are coarsest transported particlesdeposited $ideally under upper $plane #ed lowdeposited $ideally under upper $plane #ed lowregimeregime''

((s low velocity decreases $due to loss o minimums low velocity decreases $due to loss o minimum

mgh iner particles are deposited under lower lowmgh iner particles are deposited under lower lowregime conditionsregime conditions''

FFinal deposition occurs under suspension settlinginal deposition occurs under suspension settlingmode with hemipelagic layersmode with hemipelagic layers''


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An idealized

Bouma Sequence


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7utcro* of $ur%idite Se,uence7utcro* of $ur%idite Se,uence


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5igh )ensity5igh )ensity $ur%idity Currents$ur%idity Currents

))he sediment concentration is ? 20%he sediment concentration is ? 20% .an transport and support grains larger than sand'.an transport and support grains larger than sand' eposition romeposition rom traction load" traction carpettraction load" traction carpet

accretionaccretion < suspen< suspension'sion' eposits are sandy and gravelly'eposits are sandy and gravelly' 4nverse graded #edding orm during the traction4nverse graded #edding orm during the traction

carpet deposition and is caused #y dispersivecarpet deposition and is caused #y dispersive

pressure'pressure' @ormal graded #ed orms rom suspension@ormal graded #ed orms rom suspension

deposition as the velocity drops'deposition as the velocity drops'


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)raction carpet)raction carpet

deposition processdeposition processin high densityin high density

tur#idity currents'tur#idity currents'


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6utcrop o high-6utcrop o high-density tur#iditedensity tur#idite

pe##lype##ly

sandstonesandstone


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Geometry of submarine fans and theassociations of facies


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897-7G9C- P7CESS897-7G9C- P7CESS

A Aktivitas MetabolismeA Aktivitas Metabolisme


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A. Aktivitas MetabolismeA. Aktivitas Metabolisme

OrgaismeOrgaisme' 8e%era*a organisme menghasil+an CaC72' 8e%era*a organisme menghasil+an CaC72

s%g +erang+a luar cang+ang" ut+ melins%g +erang+a luar cang+ang" ut+ melindungidungi

%agian tu%uh yg luna+ dr serangan%agian tu%uh yg luna+ dr serangan*redator*redator

dan +ondisi e+ologis.dan +ondisi e+ologis.

' 7rganisme laut dang+al +oral" mr*+ *a%ri+' 7rganisme laut dang+al +oral" mr*+ *a%ri+

CaC72 dg cara mela+u+an +atalisaCaC72 dg cara mela+u+an +atalisaionion

+alsium dan +ar%onat yg terlarut dlm+alsium dan +ar%onat yg terlarut dlmairair

samodrasamodramen0adi cang+ang CaC72men0adi cang+ang CaC72*adat.*adat.'' Fotosintesa *Fotosintesa *aaddaaalga merah dan hi0aualga merah dan hi0au

mem*erce*at se+resi CaC72.mem*erce*at se+resi CaC72.

living coral'algal reef sheds %ioclastic sediment


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$he fore reef consists of coarse angular fragments of reef.

Coralline algae are the ma0or contri%utors of car%onate sand and mud

in the %ac+'reef environment. 8eaches and dunes = %ioclastic sand.

$he sediments in each area can lithify to form highly varied limestones.

living coral algal reef sheds %ioclastic sediment

into the fore'reef and %ac+'reef environments.


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Coralline algae on the seafloor off the Bahamas

can produce large quantities of carbonate mud.

! Degra"asi #agkag! Degra"asi #agkag


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!. Degra"asi #agkag!. Degra"asi #agkag

#a#O$#a#O$' )egradasi +arena a+tivitas +onsumsi *ada' )egradasi +arena a+tivitas +onsumsi *ada

organisme %ercang+ang oleh verte%rata i+an"organisme %ercang+ang oleh verte%rata i+an"

; inverte%rata holothuroida gastro*oda".; inverte%rata holothuroida gastro*oda".

' )egradasi +rn' )egradasi +rn burrowingburrowing oleh organismeoleh organisme

%enthos *ada sedimen ta+ ter+onsolidasi ut+%enthos *ada sedimen ta+ ter+onsolidasi ut+

*erlindungan atau mencari ma+an.*erlindungan atau mencari ma+an.

' )egradasi +rn' )egradasi +rn boringboring oleh organisme %a+terioleh organisme %a+teri

molus+a echinodermata tanaman" *adamolus+a echinodermata tanaman" *adasu%strat +eras.su%strat +eras.

# % l ti i# %eletisasi


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#. %eletisasi#. %eletisasi

'' +tivitas meta%olisme organisme+tivitas meta%olisme organisme

cacing molus+a echinoid"cacing molus+a echinoid"menghasil+an *elet.menghasil+an *elet.

'


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D. Se"imet Tra&&igD. Se"imet Tra&&ig

' $er0adi di ling+ungan laut dang+al.' $er0adi di ling+ungan laut dang+al.

' lga mengeluar+an film yg mengandung' lga mengeluar+an film yg mengandung material organi+ %ergetah material organi+ %ergetah mucilagemucilage" yg" yg

da*at men0e%a+ *arti+el sedimen *rosesnyada*at men0e%a+ *arti+el sedimen *rosesnya

da*at ter0adi %erulang'ulang.da*at ter0adi %erulang'ulang.

' Mem%entu+ stromatolit enda*an dengan' Mem%entu+ stromatolit enda*an dengan

stru+tur laminasi terlitifi+asi yg tersusunstru+tur laminasi terlitifi+asi yg tersusun

oleh *erselingan la*isan yg ter%entu+oleh *erselingan la*isan yg ter%entu+

oleh mi+roorganisme %iasanya alga danoleh mi+roorganisme %iasanya alga dan *arti+el'*arti+el luar yg tersementasi".*arti+el'*arti+el luar yg tersementasi".


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Stromatolite yang di%entu+Stromatolite yang di%entu+

oleh sediment tra**ingoleh sediment tra**ing

E Se"imet !a'igE Se"imet !a'ig


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E. Se"imet !a'igE. Se"imet !a'ig

8e%era*a tum%uhan laut 8e%era*a tum%uhan laut thalasiathalasia" dan" dan

tum%uhantum%uhan marsh (spartina)marsh (spartina) d*t mem%entu+d*t mem%entu+

+ar*et di atas su%strat yg secara fisis+ar*et di atas su%strat yg secara fisis

da*at men0e%a+ *arti+el atau mem*erlam%atda*at men0e%a+ *arti+el atau mem*erlam%at

arus sehingga +om*etensinya %er+urang danarus sehingga +om*etensinya %er+urang dan

sedimen yg ditrans*ort mengenda*.sedimen yg ditrans*ort mengenda*.


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C5EM9C- P7CESSC5EM9C- P7CESS


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)iagenesis)iagenesis

Car%onateCemented

7ilStained

)iagenesis is the Post')e*ositional Chemical andMechanical Changes that7ccur in Sedimentary oc+s

Some )iagenetic Effects 9ncludeCom*actionPreci*itation of Cement)issolution of Framewor+ Grains and Cement

$he Effects of )iagenesis MayEnhance or )egrade eservoiruality

>hole CoreMisoa Formation ?ene#uela


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Lithification: Compaction and Cementation


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1) Compaction: reduction of pore space due to weight of overlying sediments. Porosity= percentage of voids : Loose sand : 30-50%

Lithified sand : 10-20%

Siltstone :


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Lithification2) Cementation : precipitation from pore

water (CaCO3, SiO2, Fe2O3, etc.).

Crystalline -imestoneCrystalline -imestone


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Crystalline -imestoneCrystalline -imestone

F.O.V. = 3 mm

Ch i l PCh i l P


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Chemical ProcessChemical Process

Documents

Gravity Flow 1