lecture 1 ua sedimentary basins

7/29/2019 Lecture 1 UA Sedimentary Basins

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http://eqsun.geo.arizona.edu/geo5xx/geos517/


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Sedimentarybasinscanbeclassifiedbasedonthetypeofplate

motions(divergent,convergent),typeofthelithosphere,distance

fromplatemargins.

http://eqsun.geo.arizona.edu/geo5xx/geos517/


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Basinsrelatedtoconvergent marginsPeripheral

foreland

system

Convergentmargins:collisional andnoncollisional

RetroarcForearcBackarc


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AfterDickinson(1974):

Riftedcontinental

margins

Arctrenc system

Suturebelts

Intracontinental basins


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TOFORMASEDIMENTARYBASINYOU

NEEDACCOMODATION

SPACE

Subsidenceof

the

crust

is

caused

by:

erosion(divergentmargins);

(divergentmargins);

epress ono

ot

crust

an

t osp ere

y

sedimentaryortectonicloading(convergent

marg ns .


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Primarymechanismsofbasin

subsidence

thicknessand/or

density)

Flexure(loading)


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Abody

immersed

in

a

fluid

is

buoyed

up

by

a

displacedfluid.

Isostasy assumeslocalcompensation:i.e.the

earthis

composed

of

free

floating

pistons


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,

sealevel

is

supported

below

sea

level,

and

weightperunitareaisequalallaroundthe

.

.


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topographichighs

are

accommodatedbychangesin

thickness

Pratt:.bychanges

in

density

Adjacentblockswithdifferentdensitiesorthicknesswillhave

differentrelativerelief


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AfterAngevine etal.,1990


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Typicallithospheric structureunder

thecontinents

and

the

oceans


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AfterAngevine etal.,1990


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lithosphereso

that

the

isostatic balance

is

Initialcoolingofthelithosphereby

After10sthelithospherewillcool

exponent a y

su s ence:

ecauseco er

rocksaredenser.)


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A.Ifeverythingelseisequalthetotalamount

of

uplift

duringheating(e.g.intrusiondoming)isequa tot eamount

ofsubsidence

during

cooling.

B.Subsidencecanoccurincaseoferosion;

thickeningof

the

mantlelidduringcoolingorstretching.

AfterAngevine et

al.,

1990


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FollowingMcKenzie( Intime2the

t osp erew

subsidebecauseofisostatic

(youreplace

densermantlelidwithlessdenseasthenosphere.

In time3thelithosphere

cools

andthickensaswarmasthenosphere

conver s

n

coo

lithosphere(thermal


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Examplesofdivergentmargins


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Examplesofconvergentmargins

Peripheralforelands

Retroarcforelands


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The

Al ine

oro enForeland

AlpsProwedge

AfterStampflietal.(2002)Foreland

Retrowedge

TheAlpineorogeny

istheresultofthe

collisionbetween

Europeand

Adria

~50Myago,

followingclosureof

theAlpineTethys.


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TheHimalayanorogeny

orogenyisthe

resultofthe

TibeteanPlateauN

co s on

betweenIndia

andAsia~50My

Himalaya

Foreland

ago,following

closureofthe


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Exampleofoceancontinentcollisionandretroarcforeland:

TheAndes

TheAndesaretheresultof

magmaticprocesses

related

tothesubductionofthe

Altiplano

Puna

Cordillera

Foreland

azcap a eun er e ou

AmericanPlate.

Plateau

CourtesyIsabelleCoutand


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Mechanismsofforelandbasinformation

ModifiedafterDeCellesandGiles(1996)


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Mechanismsofforelandbasinformation

ModifiedafterDeCellesandGiles(1996)


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Slide 2 8

c1 dynamic slab load is caused by viscous coupling between the subducting slab, overlying mantle-wedge materil and the base of theoveridding continental platecarrapa, 1/5/2006


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Sedimentaryfaciesanddepositionalenvironmentin

heri heral

basins

Shallowing

upwar ren

upsection


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andthe

magnitudeof

subsidencelargely

dependonthe

a eand

thickness

oftheunderlying

crust(i.e.closing

oldcontinental

margin=highD).D=flexuralstrength


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inassociation

with

thin

skinned

thrust

belts:

. .

byfoldingandthrustingaboveundeformed

basement.


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andLaramide

style)

develop

associated

with

crystallinebasementrockstranslatealong

.


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Preconditionstoformacontinuous

ore an

asin

horizontalshortening;

strata.


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Inferredpreconditionstoformabroken

ore an

asin

horizontalshortening;

lowangleofdescentintothemantle(i.e.flat

.


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Componentoftectonicsubsidencein

ro en

ore an

asins

intoshort

beams

that

can

rotate

about

.

rotationisaprincipalcomponentoftectonic


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Whatarethecontrollingfactorsforthe

ang eo

su uction

epreex s ng ec on c s oryo an

orogenicbeltandtheshapeofitsplatemargin


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Exampleofflatslabandbrokenforeland:Sierra

Pampeanas

An es

In out Amer caa ongstr e

variabilitiesinthestructureof

theAndes

generates

along

strikevariationsingeometryof

forelandbasins

E l f b k f l d


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Exampleofbrokenforeland:

andtheLaramideforelandsystem

ThedepocenteroftheupperCretaceous(A) ineastern

Wyomingistoofarfromthethrustbelttohavebeen

simplycausedbyloadingandflexure. B)Eocenebasinand

ranges;upliftandsubsidencearecontemporaneous;C)

thicknessof

the

Green

River

Basin

reflects

tilting

and

bendingofthecrustalblocks.


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LaramideandSierraPampeanas

comparison


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Seismicexercise:

t ins inne

or

t ic

s inne


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Seismicexample:

t ins inne

or

t ic

s inne

AfterRamosetal.(2002)

lecture 1 ua sedimentary basins

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