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)
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