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TECTONICS
PLATE
AND
NACCUMUHTION
HYDROCARBO
Dy
Dr Villiom R Dicl<inson
P r o f e s s oor f G e o l o g Y
5 t o n f o r dU n i v e r s i t Y
ond
1
HunterYorborough
Inc'
Globol ExolorotionAnolYsts,
ond Associotes
First Printing, November,1976
S e c o n dP r i n t i n g , M a r c h , 1 9 7 7
'l'hird Printing, August, 1977
l ' o u r t h P r i n t i n g , S e p t e m b e r ,1 9 7 8
(ReuisedEdition)
Fifth Printing, March, 1979
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PLATE TECTONIC EVOLUTION OF SEDII"GNTARYBASINS
by
Geology D.epartment
William R. Dickinson,
94305
SLanford, California
Stanford University,
ABSTRACT
motions of
inherent in the scheme of lateral
The vertical
tectonics
plates of lithosphere
affords a coherent logic for the analysis of sedi-thqrmotecattenuation,
Subsidence may stem from crustal
mentary basins.
or combinations of these influencels in
Lonics, flexure of lithosphere,
include geometric configKey facets of basin evolution
space or time.
fill,
the types of strucEural
uration, the nature of the stratigraphic
hydrocarbons in space and time.
features,
and the location of fluid
favorable to hydrocarbon occurrence include the
attributes
Critical
of thermal flux apPropresence of organic-rich
source beds, a history
migration paths to a1low conpriate for thermal maturation,
effective
traPs.
capacity within suitable
and adequate reservoir
centration,
tectonBoth divergent and convergent plate motions embody vertical
At
but pure transforms do not.
ics wj-thin the zone of plate inLeraction,
which are associated with the generation of
divergent plate junctures,
causes eventual subsidence
crustal
attenuation
new oceanic lithosphere,
effects but may later be enhanced by
that is delayed by thermotectonic
adjustment.
plate flexure under sedimentary loading that forces isostatic
which are associated with the consumption
At convergent plate junctures,
of subducof old oceanic lirhosphere,
crustal thickening causes uplift
orogens, but plate flexure assotion complexes and of arc or collision
ciated \^/ith plate subduction and rqith tectonic or sedimentarv loading
induces subsidence in basins that lie along the flanks of orogenic belts.
Most sedimentary basins can thus be grouped generally into those in
A given basin may
rifted
settings and those in orogenic settings,
in time, and gradaoccupy several settings of either kind sequentia|ly
tional
examples also occur.
basins and
settings include (f) infracratonic
Basins in rifted
(2) margj.nal aulacogens where continental
separation is incomplete;
(3) protoceanic rifts
emplacement of fresh oceanic
where the initial
crust occurs; (4) miogeoclinal prisms of terrace, slope, and rise
margins and (5) continental
assemblages that mask rifted
continental
edge is
of the continental
embankmentswhere sedimentary progradation
(6) nascent ocean basins in which expansion by accretion of
important;
new lithosphere
at midoceanic rise crests is dominant; (7) transtenor
sional basins along complex transform systems where pull-apart
basins formed as marginal
faulE-wedge features occur; and (8) interarc
systems from which remnant arc
arc-trench
seas behind intra-oceanic
struccures have been calved.
Basins in orogenic settings
include (9) oceanlc trenches where
plate consumption occurs, (10) slope basins forroed above accretionary
g"p
subduction complexes, and (11) forearc basins in the arc-trench
basins of (12) peripheral
related to subduction zones; pericratonic
-1-
::.'
:4':7:-.7.
orogens, (13) retroarc forelands adjacent
::relands adjacent to collision
basement
io drC orogens, and (14) broken forelands where differential
(15) transpressional
basins along complex
i-s significant;
:efornation
features occur; and (16)
:ransforn systems where wrench or fault-warp
re:nant ocean basins in which shrinkage by consumption of o1d lithosysEems is dominant.
sphere at bounding arc-trench
Useful for comparative basin analysis are plots of fhe following
paleolatitude,
nrrrneters asainst fime:
subsidence rate (maximal or
heat
net cumulative subsidence (rnaximal or volumetric),
i,clunetric),
and temperatule at key source horixons.
f1u:<, geothermal gradient,
r
J
r
eur e
INTRODUCTION
These short-course notes are based on the proposit,ion that plate
tectonics affords a coherent logic for the analvsis of basin evolution.
The line of thought runs as follows:
(a) The developmenl of a sedimentary basin, in the sense of an
requires subsidence of the basin floor,
accumulated prism of strata,
b
a
s
i
n
m
argins.
of confining
or uplift
theory focus
(b) Although rhe fcrmal postulates of plate tectonic
m
otions of
v
e
r
E
i
c
a
l
p
l
a
t
e
s
'
o
f
t
h
e
m
o
t
i
o
n
s
especially on the lateral
inherent
a
r
e
e
q
u
a
l
l
y
b
a
s
i
n
s
to form sedimentary
magnitudes sufficient
m
o
untainous
u
p
l
i
f
t
o
f
i
n
d
u
c
e
t
h
e
a
l
s
o
in the scheme. Plate interactions
i
s
d
e
r
i
v
e
d
.
s
e
d
i
m
e
n
t
belts from which most clastic
processes of basin
into overall
(c) Therefore, valuabie insights
of various plate
g
e
n
e
r
a
l
c
o
n
s
i
d
e
r
a
t
i
o
n
g
a
i
n
e
d
f
r
o
m
a
evolution can be
tectonic settings.
that is
Of course, each indirzidual basin has its own uniqlre history
p
l
a
t
e
i
n
t
e
ractions
o
f
a
n
d
c
o
m
b
i
n
a
t
i
o
n
p
a
r
t
i
c
u
l
a
r
s
e
q
u
e
n
c
e
dependent upon a
n
o
t
u
p
o
n
s
P
e
c
i
f
ic hisi
s
h
e
r
e
e
m
p
h
a
s
i
s
T
h
e
conditions.
and depositional
pert
h
a
t
c
a
n
b
e
g
e
n
e
r
a
l
i
n
s
i
g
h
t
s
u
p
o
n
r
a
t
h
e
r
tories of this kind, but
o
f
l
o
c
a
l
d
e
t
a
i
l
.
ceived through webs
as an aid to inquiry by the
I think of Lhese notes, therefore,
I have
c
a
t
a
logue of basin types.
a
n
e
x
h
a
u
s
t
i
v
e
reader, rather than as
each thought or
prepared them in an informal style, without referencing
is a guide
The attached bibliography
suggestion in the formal manner.
inquiry.
to further
I
In the past few years, many besides myself have taken a turn at
framer.rork.
a plate tectonic
sedimentary basins within
trying
to classify
r
e
l
e
v
a
n
t
a
l
l
t
h
e
talks
a
n
d
h
e
a
r
d
p
a
p
e
r
s
p
e
r
t
i
n
e
n
t
I have read all the
f
o
l
l
o
w
a
n
y
t
o
s
c
h
eme other
h
e
r
e
a
t
t
e
m
p
t
m
a
k
e
n
o
that I could,
Although I
I
t
h
e
i
n
s
i
g
h
ts
o
w
n
m
i
n
d
,
f
o
m
y
tiran the one that comes most forcefully
p
a
r
t
i
c
u
l
a
r
,
g
r
a
t
eI
I
n
a
r
e
l
e
g
i
o
n
.
have gained from the work of others
m
a
n
u
s
c
r
i
p
t
s
p
e
r
u
s
e
u
n
p
u
b
l
i
s
h
e
d
t
w
o
to
fully
acknowledge the opportunity
in the biblioby A. W. Bally and L. L. Sloss, which I am unable to list
a
n
d foreland
graphy.
I owe many of my ideas about subduction systems
P
e
t
e
r
C
o
ney and
of extended discussions with
systems to the fruits
of many
Warren Hamilton over the years. I have also been the beneficiary
of sedimentary basins
setting
ranbling discussions about the tectonic
Steve Graham, Ray IngerGreg Davis, Ray Fletcher,
with Clark Burchfiel,
and George Viele.
soll,
Dan Karig, Casey Moore, Don Seely, Eli Silver,
-2-
BASIN EVOLUTION
facets
The evoluLion of a sedimentary basin has four interdependent
prirne interest
to petroleun geology:
1.
The geometric shape and size of the basin as a whole is conof the bounding basement rocks
srrained by the evolving configuration
The patcern and timing of
that form the floor and. flanks of the basin.
of
tilts
control regional
changes in the gross shape of the basin largely
features that strongly influence migration
strata and other structural
In general, basin configuraanC entrapment of fluids within the basin.
tectonic setting.
tions directly
reflect
of the basj-n is the product
fill
2.
The nature of the stratigraphic
The nature
evolution.
b
a
s
i
n
d
u
r
i
n
g
s
y
s
t
e
m
s
of the depositional
4ctive
t
h
e
i
n
terplay
o
f
p
a
r
t
l
y
a
r
e
s
u
l
t
a
n
t
i
s
s
y
s
t
e
m
s
of these depositional
p
revail
at
t
h
a
t
o
f
s
e
d
i
m
e
n
t
a
t
i
o
n
a
n
d
r
a
t
e
s
between rates of sub6idence
i
n
i
t
i
a
l
s
u
b
s
i
d
ence
o
n
e
e
x
t
r
e
m
e
,
A
t
e
v
o
l
u
t
i
o
n
.
various times during basin
f
u
r
t
h
e
r
i
s
o
s
t
a
tic
i
n
d
u
c
e
s
f
i
l
l
i
n
g
t
h
a
t
f
o
l
l
o
w
e
d
b
y
to form a deep hole is
s
e
d
i
m
e
n
t
a
t
i
o
n
o
t
h
e
r
e
x
t
r
e
m
e
,
A
t
t
h
e
l
o
a
d
.
subsidence under the sediment
D
e
p
o
s
i
e
v
e
r
h
o
l
e
i
s
e
m
p
t
y
a
n
d
n
o
keeps pace with subsidence
Present.
tional
systems are also influenced strongly by paleographic factors,
(fig. 1).
including paleolatitude
that develop as folds and faults within
The types of structures
3.
and partly
evolution
p
a
r
t
l
y
b
y its tectonic
the basin are conditioned
c
o
r
m
nonly produces
d
e
f
o
r
m
a
t
i
o
n
E
x
t
e
n
s
i
o
n
a
l
by its sedimentary evolution.
d
e
f
o
r
mation comc
o
n
t
r
a
c
t
i
o
n
a
l
w
h
e
r
e
a
s
blocks,
normal faults
and tilted
h
a
n
d
,
the presence
o
t
h
e
r
O
n
t
h
e
f
a
u
l
r
s
.
monly produces folds and thrust
a
function
i
s
l
a
r
g
e
l
y
g
r
o
w
t
h
f
a
u
l
t
s
f
o
l
d
s
a
n
d
or absence of diapiric
f
i
J
I
.
of the sedimentary
of the properties
4.
The amount, nature, and location of fluid hydrocarbons within
Ehe basin is governed in part by the three previous facets of basin
by the thermal history of the
evolution, but perhaps most critically
p
l
a
te tectonic settings may be
(
f
i
g
.
d
i
f
f
e
r
e
n
t
2).
Basins in
basiir
f
l
u
x
e
s
.
Moreover, the sarne basin
heat
exposecl to markedly different
times during its
a
t
d
i
f
f
e
r
ent
heat fluxes
may experience different
evolution.
that can be observed
of styles of basin evolution
The diversity
p
a
r
t
t
h
e vari-ety of Patterns
f
r
o
m
g
o
o
d
in lhe geologic record stems in
p
r
o
c
e
sses of subsidence,
ttrrbugh time followed by these interrelated
I
n
e
x
a
m
ining the plate tectonic
and heating.
structurj-ng,
sedimentation,
of the settings
i
m
p
l
i
c
a
t
ions
of basins. we need to focus on the
settlng
The manner
considered for
each of these facets of basin evolution.
c
o
m
b
i
n
e
d in different
aspects of evolution may be
in which the different
to seek.
instances is the key insight
o:
OCCURRENCE
HYDROCARBON
hydrocarbons depends
Stated most simply, the occurrence of fluid
of a sedimentary basin:
upon four critical
attributes
source
there must be organic-rich
requirement,
As an essential
1.
fineSource beds are generally
beds within the sedimentary sequence.
dilution
grained sedj-rnent deposited in black-bottom areas lrhere clastic
is low, winnowing of fines that include organic
of organic constituents
debris is minor, and oxidatio-n by aerobic decay during early diagenesis
of the organic debris enhances its chances
is limited.
Rapid burial
-3-
No90
ffi
APPALACHIAN
ffi
coRDrr-LERAN
0
(WESTN O. AM)
z
a
m
ii!iii
45
NORTH
SEA
i:i::i
i:iV
O
UJ
F
(J
IJ
J
r!
a
30
G U LF
COAST
t5
PERSIAN
G UL F
o
LL
o
t5
UJ
O
:f
30
F
45
L
tfU'A).4
J
o
r!
60
o_
75
J
ARTESIAN
KARROO
S og o
n
roo 200 3 0 0 4 0 0
T I ME I N M Y B P
500
Figure 1.
Approximate paleolatitudes
o f s e l e c t e d sedimentary basins
through Phanerozoic tine.
Data from Briden, J . C . , G . E . D r e w r y ,
and A.G. Smith, L974, phanerozoic equal-area world maps:
Jour.
Geology, v. 82, p. 555-574.
-4-
include oxygen-minimum
Favorable sites of deposition
for preservation.
silled
marine
low-oxygen zones within
zones on open marine slopes,
Basins
n
o
n
m
a
r
j
n
e
o
r
m
a
r
g
i
n
a
l
r
n
a
r
i
n
e
e
n
v
i
r
o
n
m
e
n
t
s
.
basins, and saline
pref
a
c
i
e
s
t
h
e
s
e
k
i
n
d
s
of
whose sedimentary fill
includes widespread
p
o
t
e
n
t
i
a
l
hydrocarbons.
sources of
sumably harbor the largest
2.
For generation of fluid
hydrocarbons, there must be appropriate
hydrocarbons or therural gas.
Relaheat for thermal maturation
of liquid
g
i
v
e
n
o
f
to achieve a
degree
tions of time and temperature required
are clear.
Ideally,
maturation are complex, but the guiding principles
source beds should undergo maturation during a time span in the evolution
hydrocarbons into traps is feasible
of the basin when migration of fluid
without escape to the surface.
As either underheating or overheating can
is
spoil potential
hydrocarbons, special attention
sources for liquid
drawn to Lime-dependent variati-ons
in the heat flux experienced by a
basin in relation
to times of subsidence, sedimentation and structuring.
hydrocarbons, there must be perneable
For concentration
of fluid
3.
paths to gather any hydrocarbons produced.
The most effective
nigration
sandy strata contai-ned
carriers
are tilted
conduit beds of well-sorted
Possibilities
beneath impermeable sealing beds of finer grained rock.
connections are
for concentrationate
thus enhanced where porous stratal
beds and have an
continuous latera1ly
from source beds to reservoir
for conduit beds
these conditions
unbroken regional dip.
Satisfactionof
j-s more critical
of fluid
than simple distance alone for the migration
hydrocarbons.
4.
For containment of fluid
hydrocarbons, there must be porous
reservoir
by impermeable
beds confined within some trapping configuration
sandy strata,
capping beds.
well-sorted
Reservoir beds are typically
whether clastic
or carbonaLe,
Favorable sites of deposition are most
abundant in shallow-marine
environments near basin
or marginal-marine
margins and within
proximal turbidite
assemblages along basin margins.
Traps may be formed either by stratigraphic
enclosure or by structural
features of tectonic
or sedirnentar:y origin.
of sedimentary basins should thus
Analysis of the plate tectonics
seek to identify
and times during basin evolustyles of basin evolution
tion that embody favorable combinations of these four critical
attributes
for hydrocarbon occurrence (fig.
Conceivably, plate tectonics may
3).
point the way toward a comprehensive theory of hydrocarbon genesis.
implies understanding of the
Understanding plate interactions
fully
causes of subsidence, the sequencing of depositional
events, the development of sEructural
Perhaps
features,
and the timing of thermal f1ux.
with adequate analysis we can now specify the most favorable combinations
of subsidence, sedimentation,
and deformation required to create desirable
juxtapositions
paths, and reservoirs
of sources, migration
upon which the
requisite
thermal flux is superimposed.
If so, we can therr seek these
conditions
in the geologic record of sedimentary basins.
PLATE INIEMCTIO}'IS
are spherical
caps, or arcuat.e slabs,
The plates of plate tectonics
of the earthts lithosphere
which is thicker
or tectosphere,
than Ehe
crusL as defined by M and extends dor.m to the so-called
1ow-velocity
zone
of the upper mantle.
degree, the plates are rigid
To a surprising
blocks.
Alrhough some internal
does occur, it is much less significant
deformation
in terms of nagnicude or rate than the relative
motions of the plates.
The
plates apparently rest upon a mobile layer call-ed the asthenospherewiEhln
B.P
M.Y.
O C E A N I CS C A L E
zo
a
too
60
40
BRIAN
PRECAM
PLATFORMS
AND SHIELDS
2.5
:
z
C E N O Z O I CR I F T S
l
OROGENS
MESOZOIC
2.O
3
o
r20
t
t
P A L E O Z O I CO R O G E N S
J
LL
I
O C E A N I C
F
t-rJ
I
%_lnr_
400
200
o
600
SC A L E I N
CONTINENTAL
t200
looo
800
MYB P
Data after Sclater,
decay of heat f 1 u x .
General logaritlimic
Figure 2.
'Jour' R o y . A s t r o . S o c - , v . 2 O '
J . G . a n d . i . F r a n c h e t e : r u ' ( ( J e - o p h y' s
p.509-542, 1970).
RA P ___+-l
F_T
///
/,/1'
.z'.2
----:-
S E A L I N GBEDS
.x-\
\
,/z
\ \
\\
RESERVOIR
B ED S
SOURCE
----
BEDS
CONDUCT
BEDS
M IGRATION
SCHEME
Idealized
Figure 3.
accumulation.
HEAT
scheme for
hydrocarbon
-6-
orr.3l ll]1
generation,
migration,
The geothermal
which rhe geothermal gradienE is probably adiabatic.
between
mainly by conductivity
gradient across the plates is controlled
tema
n
d
t
h
e
s
u
r
f
i
c
i
a
l
o
f
a
s
t
h
e
n
o
s
p
h
e
r
e
,
t
h
e
t
h
a
t
t
e
m
p
e
r
a
t
u
r
e
,
the basal
In general, plate
perarure, that of the atmosphere and hydrosphere.
blocks
boundaries do not coincide with boundaries betr.reen continental
elements can be joined
Both types of crustal
and oceanic basins.
together as parts of rhe same plaLe.
From a kinematic standpoint, there are three kinds of plate junctures (fig.4),
and these are analogous to the three classes of faults
At divergent plate junctures,
displacements.
as defined by relative
At convergof trvo plates occurs.
f
a
u
l
t
s
,
s
e
p
a
r
a
t
i
o
n
analogous to normal
p
l
a
t
e
o
n
e
d
e
s
cends at
j
u
n
c
t
u
r
e
s
,
f
a
u
l
t
s
,
t
h
r
u
s
t
p
l
a
t
e
t
o
analogous
ent
m
a
n
t
l
e
.
A
t transform
t
h
e
d
g
w
n
i
n
t
o
a
n
d
d
i
v
e
s
an angle benea[h the other,
p
l
a
t
e
o
n
e
j
u
n
c
t
u
r
e
s
,
s
l
i
des laterf
a
u
l
r
s
,
t
o
plate
strike-sllp
analogous
p
a
s
t
ally
the other.
old lithoinvolve rupture of intacr
Incipient
divergent junctures
b
l
o
c
k
,
intraconc
o
n
t
i
n
e
n
t
a
l
a
rift
crosses
sphere.
!{here an incipient
a
n
i
n
c
ipient
a
n
e
a
r
l
y
s
t
a
g
e
,
a
t
If arrested
tinenLal rifting
occurs.
If
b
l
o
c
k
.
g
r
a
b
e
n
r
^
r
i
f
h
l
n
a
c
o
n
t
i
n
e
n
t
a
l
rift
may t|us form a complex
a
o
c
e
anic
i
n
t
o
n
e
w
c
a
n
d
e
v
e
l
o
p
rift
allowed to proceed, the incipient
c
r
u
s
t
o
f
m
a
f
i
c
i
g
n
e
o
us
i
t
s
t
h
i
n
vrith
basin.
The oceanic lithosphere
p
r
o
c
e
s
s
e
s
m
a
g
m
a
t
i
s
m
f
r
o
m
upo
f
rocks is then constructed by combined
a
l
o
n
g
a
s
t
h
e
n
o
s
p
h
e
r
e
of depleted
welling asthenosphere and chilling
thus formed is emplaced
The new lithosphere
midoceanic rise cresfs.
blocks,
incrementally
between the receding pair of separating continental
s
e
p
a
r
a
t
i
on of
Con[inental
and is accreted to both receding plate edges.
extension of branches
this kind is normally achieved by the longitudinal
of
system, rather rhan by random iniriation
of the world midoceanic rift
a wholly new divergent plate juncture.
Convergent plate junctures are sites of plate consumPtion where
at a divergent plate juncture
oceanic lithosphere
formed previously
Just as a midoceanic rise crest is the
descends into the mantle.
morphologic signature of a fully
developed divergent plate juncture, an
developed conarc-crench system is the morphologic signature of a fully
vergent plate juncture.
The trench marks the subduction zone where
magmatic arc, which may
The parallel
is]consumed.
oceanic lithosphere
elements, marks the line
crustal
stand upon either oceanic or continental
into the
along the surface above the place where descent of lithosphere
Owing to the buoyancy of
mantle triggers
magmatism of orogenic type.
cannot descend into the mantle,
continental
lithosphere
continental
crust,
block at a subduction zone instead causes
The arrival
of a continental
Convergent plate
a crustal
collision
between it and the arc structure.
juncture-s are thus the sites of arc orogens where oceanic lithosphere
orgens where plate consumption
may be continuously
consumed or collision
collision.
is arrested by crustal
anelr in tvro ways at convergent
crust is probably built
Continental
(a) by the tectonic stacking of crustal elements in
plate junctures:
subduction zones \^rhere sedimentary layers are scraped off the top of
and (b) by the magmatic emplacedescending slabs of oceanic lithosphere,
piles
ment. of igneous cruscal elements added as plutons and volcanogenic
Some ancient continental
to the arc structures
associated with trenches.
processes operative
frorn unfamiliar
deep in
crust rnay also be inherited
crust and lithosphere
the Precambrian.
ln any case, continental
-7-.
e
DIVERGENT JUNCTURES
,-.
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O CE A N I C
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A ' r
CRUSTAL COLLISION
R E MN A N T O C E A N
Figure4.PrincipalkindsofplateinteracEionsaEdivergent(above)
of lithojunctures
showing relations
and convergent (below) plate
(
o
r
n
a
r
n
e
nted) '
as crust
sphere (L) and asthenosphere 1A) as well
-8-
apparently conserved while oceanic crusE and lirhosphere are continually
recycled .
in the
development is thus involved
A grand scheme of crustal
j
u
n
c
t
u
r
e
s
.
C
o
nceptually'
p
l
a
t
e
funcEioning of divergent and convergent
g
e
n
e
s
i
s
o
f
n
a
scent ocean
leads to
rift
rupture of continent at incipient
system leads
consumplion of such ocean at arc-trench
at rnidoceanic rise;
to reweldin arc orogen, and finally
first
of new continent
to building
ocean is
orogen as intervening
together at collision
ing of continents
oestroyed.
By contrast,
transform plate junctures are neutral with resPecl
plates slide
Ideally,
to the mass balance of crust and lithosphere.
past one another without accretlon or consumpti-on. However,
laterally
just as oblique-slip
faulfs occur, hybrid plate boundaries also occur in
motion
Where some component of extensional or contractional
sone areas.
ate
and ttansptession
the terms transtensicn
occurs along a transform,
ccnvenient to describe the interaction.
VERTICAL TECTONICS
of new lithosphere
that involve construction
All plate interactions
motions
as a result of large horizontal
or consumptlon of old lithosphere
Verrnotions of lithosphere.
vertical
of plates also involve significant
of seditical
tectonics of the general sort needed to explain the origin
mentary basins are thus inherent in the basic concepts of plate tectonics.
as a result of plate
There are three root causes of subsidence or uplift
thermal expansion or conthickness,
interactions:
ctranges in crustal
in
and broad flexure of plates of lithosphere
traction
of lithosphere,
response to local tectonic or sedimentary loading.
Crustal
Thickness
(fig.
5).
blocks
of the surfaces of the continental
elevations
The contrasting
block
and the ocean floors are well known. The rupture of a continental
and subsequent developmerpt of a ne\^/oceanic basin along a divergent
Plate
juncture
fhus forms a fresh receptacle for sediment between the two seParin thickness and compoThe great contrasts
ating continental
fragments.
and standard oceanic crust also imply that
sition
between continental
form
thickness will
crust wiLh some intermediate
belts of transitional
blocks.
The region of the continentcontinental
along the edges of rifted
thus stand, in the
margins will
continental
ocean interface
along rifted
between those of
intermediate
absence of sedimentation,
at elevations
continental
blocks and ocean floors.
crust that bridges betveen the two domains may have
The transitional
depending on derails of the process of contineither of two characters,
ental separation,
On Lhe one hand, it may be attenuated continental
crust, with the same composition but with lesser nec thickness than continental
On the other hand, it may be composed of oceanic nafic
basement.
with sediments of continigneous rocks mixed as flows, dikes, and sills
and quasiental derivation.
Complex mixtures of the quasicontinental
oceanic types of transitional
crusE also seem 1ike1y to form frour calving
margfns.
continental
of microcontinental
fragments off the edges of rifted
-9-
MIN
r-l
M
l +* t I
t.;+l
M
SMT
IS
STD
r*l
ffi
M
IS
ARC
rrilil
[ilililll
rHH
Hzo
Seds
Loy 1
t-J-;l
Loy 2
M
O C E A N I CF L O O R
M
OCEANIC
I SLANDS
" U p p g r"
Lower
SUBDUCTION
C O MP L E X
30 KM
CRATON
OROGEN
Figure 5.
Representative crustal
(below) regions.
continental
:
-t
I
I-
TYPICAL
CRUSTAL
PROFILES
profiles
-10-
in
oceanic
(above)
and
of new lifhosphere
at rivergent plate junctures
The construction
profiles
thus forros crustal
that are thinner than. those present localfy
before, and thereby induces wliolesale subsidence in belts along continental margins.
On the oEher hand, processes related to plate consumptlon
at arc-trench
systems along convergent plate junctures
construct crustal
profiles
that are thicker
than those present loca11y before, and thereby
induce uplift
within arc and collision
orogens.
Such uplifts
comrnonly
form new sediment sources and locally
form the si1ls or flanks of adjacent
residual sedimentary basins.
The processes that form crust of anomalous thickness at convergent
plate junctures may serve to thicken profiles
that r^/erepreviously
either
oceanic or continental.
Thickening processes include (a) the addition
of
tectonic increments of oceanic elernents to growing subduction complexes,
(b) the addition of magmatic increments to either oceanic or continental
profiles
of magmatic arcs, which occur in both j-ntra-oceanic and
continental-margin
setfings,
and (c) the tectonic overlapping or telescoping of continental elements along the sture belts of collision
orogens.
Where the resulting
thickness of paraoceanic or paracontinental
crust initially
exceeds that of normal continental crust, isostatic
uplifL
and accompanying erosion will
tend to reduce it to normal values
with the passage of time.
Thermal Effects
(fie.6)
Thermotectonic uplift
and erosion are displayed most clearly
in
oceanic basins where new lithosphere
is formed.
Near midoceanic rise
cresLs, the lithosphere
is thin, heat- flux is high, the geotherrnal gradient near the surface is steep, and \nrater depths are comparatively
shallow.
As lithosphere
passes farther
away from the rises,
it first
thickens
rapidly
and then contracts slowly as it cools.
As several have noted,
the net effect at the surface is gradual subsidence of the ocean floor
at a rate tirat is remarkably regular on a logarithmic
time scale.
A
simple linear equation can be written relating
depth of water to the
square root of the age of the igneous oceanic substraturn.
The equation
holds to an age between 75 and 100 million
years, beyond which a steadystate heat flux and stable geothermal gradient are apparently attained.
Where cont,inental separations occur at divergent plate junctures,
analogous thermotectonic
uplift
and subsidence can be expected to occur.
uplifts
along incipient
and juveni,le rifts
occur prior to and during
seParation evenrs when the effects
of high local heat flux can offset
the opposing effects of crustal thinning.
Erosional truncation of
uplifted
d o m . e sa n d a r c h e s a t t h i s t i r n e m a y c o n t r i b u t e
to crustal
thinning
during rifting.
Following cornpletion of rifL
separation,
subsidence
occurs as Ehe distance between midoceanic rise cresf and rifted
continental margin increases.
Although the isostatic
subsidence of transj-tional
crust in response to crustal
thinning may cause an appropriate
amount of
rapid subsidence, further
slow subsidence in response to thermal decay
of previously
heaEed lithosphere
will
be prolonged for perhaps 100 rnillion
years if the behavior in oceanic regions affords a proper analogy.
The high heat flux in magrnatic arcs can also be expected to induce
thermotectonic uplift
of parts of orogenic belts.
Behavior of this kind
is not well documented and ful1 understanding will
not. come easily,
for
the governing conditions
are much more complex.
Also clearly
related in
some manner to the arc heat flux are the rnarginal seas in which some form
-1t-
\*%q
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froo,rvsr
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uJ
1€oo
-5
4
9 16 25 36 49 64 8r rOO
AGE
M.Y.
IN
plot of oceanic depths vs'
lithosphere;
Subsidence of rifled
Figure 6.
(
E
a
r
t
i
r and Planetary Science
s q u a r e r o o L o f a g e a f t e r A . 1 1. ' T r 6 i r u
3
0
4
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L e t t e r s , v . 2 7, P . 2 8 7
;i$1t
L
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.- .-..--
S E D I M E N TF I L L
RIFTED-BASIN
SUBDUCTION
COMPLEX
--//
R I F T E-DM A R G I NS E D I M E NPTR I S M
FORELAND
F O L D _ T H R U SBTE L T
of
concept of broad'flexure
Figure 7.
Schematic diagrams depicting
(
a
b
o
v
e
)
o
r
t
e
c
t
o
n
ic
s
e
d
i
m
e
n
t
a
r
y
1
o
c
a
l
u
n
d
e
r
d
o
r
.
m
w
a
r
d
lithosphere
(below) loads.
- L 2 -^
Although this type of oceanic basin develops in
of spreading occurs.
is the
step in its evolution
m
a
g
m
a
tic arcs' the earliest
the main behind
c
a
n be
m
a
n
n
e
r
t
h
a
t
a
b
e
l
t
i
n
a
r
l
f
t
a
l
o
n
g
s
t
r
u
c
t
u
r
e
of an arc
splitting
s
e
p
a
r
a
t
i
o
n
.
c
r
u
s
t
a
l
o
f
viewed as a sDecial case
Flexural
Bending (fig.
l)
weak asthenosphere beneath the
The presence of hot and relatively
makes the flexure of lithoplates of cooler and stronger lithosphere
asthenosphere is readily
m
o
b
i
l
e
sphere an i:nportant phenomenon. The
abl-e to mold its upper surface to the shape adopted by the base of the
deformations
Because of broad flexures of the lithosphere'
lithosphere.
f
o
r
l
a
r
g
e lateral
e
f
f
e
c
t
s
can exert
tectonics
associated with vertical
dis tances .
are the
The most aDDarent loci of bending of slabs of lithosphere
b
e
g
i
n their
a
n
g
l
e
t
o
turn downward at an
where consume<l plates
flexures
The great depths of oceanic trenches, whose
descent into the mantle.
are
floors stand well below the ordinary level of the open ocean floor'
of
thinning or by thermal decay, but as the result
not reached by crustal
to
and heat flow in trenches are similar
plate flexure.
Crustal profiles
those of the ocean floors except for the influence of ponded trench sedi! r r e
^ r , v v
e
_ r t
of
Other important flexures of plates are caused by the imposition
1oca1 loads that induce broad dovrnbowing as a means to balance the load.
Classic examples are the annular j-sostatic moats that surround some
aprons of sediment far out in
volcanic islands and their archipelagic
cases of 1ocal loads are the vast sediment
More significant
the oceans.
pr|sms that are dumped into the edges of oceanic basins as conlinental
As this sediment displaces
margins.
continental
rises along rifted
subsidence beyond that resulting
water, its loacl can induce isostatic
rather than
By flexuring
from crttstal thinning and thermotectonics.
is able to deform into
the lithosphere
through 1ocal fracture,
failing
a broad regional downwarp. Not only does the basement beneath the conblock may
rise subside, but the edge of the nearby continental
tinental
tilt
d o v , r n w a r da s w e l l .
stacking of thrusE sheets
Tectonic loads formed by the structural
involves
Wherever deformation
downwarps.
or nappes can induce similar
d6collement that peels cover rocks off basement and mounds them into a
slab of
load can depress the underthrust
the resulting
telescoped welt,
disturbed beltover broad areas beyond the structurally
lithosphere
Settings where this mechanistn can operate include subduction complexes
and fold-thrust
that pile up above moving slabs of oceanic littrosphere,
lithosphere.
belts that pile uD above foreland slabs of continental
also
BASIN TYPES
that sedimentary
Consideratj-on of the causes of subsidence indicates
s
e
E
t
i
n
gs:
g
e
o
d
y
n
a
m
i
c
o
f
g
e
n
e
r
a
l
k
i
n
d
s
t
w
o
o
c
c
u
r
i
n
basins can
extensional
a
n
d
p
l
a
t
e
m
o
t
i
o
n
s
1.
d
i
v
e
r
g
e
n
t
w
h
e
r
e
Rifted settings
r
e
s
p
onse to
i
n
o
c
c
u
r
s
i
n
i
t
i
a
l
l
y
slructures
are dominant; subsidence
t
h
e
r
m
a
l decay as
b
y
e
n
h
a
n
c
e
d
l
a
t
e
r
i
s
attenuational
thinning of crust,
r
e
sponse to
f
l
e
x
u
r
e
i
n
b
y
e
v
e
n
t
u
a
l
l
y
time passes, and may be augmented
sedimentary loading.
-13-
Ii
Table 1:
Types of
Rifted
Settings
INFRACRATONIC
BASIN
Intracontinental
rift
continental
basement
MARGINAL
AULACOGEN
Rift
trough elongate inward loward continental
interior
from re-entrant
in adjacent continental
margin
PROTOCEANIC
RIFT
ftncipienJt oceanic basin flanked by uplifts
nearby rifted
conlinental
margins
I'lIOGEOCLINAL
PRISM
Continental
s1ope, and rise association
terrace,
developed along continent-ocean
interface
CONTINENTAL
EMBANKMENT
Progradational
sediment pile
edge of a rifted
continental
NASCENT
OCEAN
Growing oceanic
system building
TRANSTENSIONAL
BASIN
Local pull-apart
and fault-wedge
a complex transform system
INTERARC
BASIN
Oceanic basin formed by backarc spreading
a migratory intra-oceanic
island arc
Table 2:
OCEANIC
TRENCH
SLOPE
BASIN
basin
floored
bv attenuated
constructed
margi-n
basin with a midoceanic
new lithosphere
Tvpes of Orogenic
along
off
the
rise
features
along
behind
Settings
Deep trough formed by plate descent at a
subduction zone related
to plate consumption
II
Local structural
depression developed between
trench axis and trench slope break
FOREARC
BASIN
Basin located within arc-trench
gap between
trench slope break and magmatic or volcanic
front
PERIPHERAL
BASIN
Foreland basin adjacent to fold-thrust
belt
associated with suture belt of collision
orogen
RETROARC
BASIN
Foreland basin adjacent to fold-thrust
associated vith infrastructure
of arc
BROKEN
FORELAND
Local structural
ment deformation
TRANSPRESSIONAI
BASIN
Local wrench and fault-warp
complex transform system
REMNANT
OCEAN
Shrinking
oceanj.e basin
sumption along flanking
- L.+-
belt
orogen
depressions isolated
by basewithin
orogenic foreland
region
features
undergoing
arc-Erench
along
a
plate consysEems
2,Orogenicsettingswhereconvergentplatemotionst"d"ot'ttactional
by plate flexure reare dominant; subsidence occurs initially
structures
of
thickening
t
e
c
t
o
n
i
c
1
o
c
a
l
t
o
o
r
c
o
n
s
u
m
p
t
i
o
n
p
l
a
t
e
lated either to
r.y also be augmented by sedimentary loading, and is
crustal profiles,
effects.
subject lo influence by more varied thermotectonic
repreg
r
o
s
s
categories
t
.
s
t
o
s
u
c
h
i
n
t
o
Grouping sedimentary basins
ground
c
o
u
r
n
o
n
p
o
s
s
i
b
l
e
b
r
o
a
d
e
s
t
t
h
e
t
o
s
e
e
k
attempt
sents a deliberate
to focus
i
s
s
o
d
o
i
n
g
p
u
r
p
o
s
e
i
n
M
y
and masks a great deal of variability.
o
f sedg
r
o
u
p
i
n
g
A
n
y
b
a
s
i
n
e
v
o
l
u
t
i
o
n
.
o
f
on certain key themes
attention
types
d
i
f
f
e
r
e
n
t
t
h
a
t
t
h
e
a
s
s
u
m
p
t
i
o
n
imentary basins risks the unwarranted
howI
n
t
r
u
t
h
,
t
i
m
e
.
i
n
a
s
a
s
w
e
l
l
in space
entities
are wholly distinct
a
r
i
fted
i
n
l
o
c
a
t
e
d
b
e
t
i
m
e
o
n
e
a
t
may
ever, the same pi-ece of lithosphere
T
h
u
s'
v
e
r
s
a
'
v
i
c
e
o
r
s
e
t
t
i
n
g
,
time in an orogenic
setting and at a later
t
h
e
a
t
o
p
o
n
e
different kinds of sedimentary basins may be superimposed,
sedimentary basins may be
To use a better emphasis, individual
other.
The
setting.
and cournonly are composite basins in terms of plate tectonic
o
f
n
a
t
u
r
e
t
h
e
a
n
d
is rapid in geologic terms
pace of plate interactions
the evolution of a given basin may change
that affect
the interactions
several
Rifted
times during
Settings
life.
its
(faUte
t)
plate
is dominated by extensional
Basins whose tectonic evolution
(
g
r
a
dasubgroups
include three idealized
rifting
motions and crustal
tional exanrples also exist):
blocks along incipient
Basins where ruPture of continental
A.
these include two related types:
is incomplete;
d i v e r g-e n t p l a t e j u n c t u r e s
basins where clearcut structural
(1)
Infracratonic
the substratum
connections to ocean basins are doubtful;
crust but is not rruly oceanic
is attenuated transitional
in nature.
(2)Marginalaulacogensformedatre-entrantsinthe
margins as elongate or wedge-shaped
trends of continental
the aulacrust;
gashes floored by oceanic or transitional
cogenrePresentsthefailedarmofatriplejunction.
blocks is complete along
Basins where rupture of continental
B.
separation is pchieved and
hence continental
divergent plate junctures,
area; thesel include four
true oceanic crust is forrned in the intervening
plate
types which can be formed in sequence by the operation of the same
juncture:
where a narrow belt of initially
(3)
Protoceanic rifts
ftagforms between two continental
hof oceanic lithosphere
be influenced
can still
ments; sedimentation across the rift
blocks'
continental
by both flanking
continprisms deposited along rifted
(4)
Miogeoclinal
i
n
c
l
u
de
t
h
e
s
e
b
a
s
i
n
s
;
o
c
e
a
n
i
c
o
P
e
n
b
e
s
i
d
e
ental margins
c
o
ntino
f
t
h
e
e
d
g
e
t
h
e
a
l
o
n
g
d
e
p
o
s
i
t
s
conEinental terrace
e
dge of
t
h
e
a
l
o
n
g
d
e
p
o
s
i
t
s
r
i
s
e
c
o
n
t
i
n
e
n
t
a
l
ental block and
b
etween.
s
l
o
p
e
c
o
n
t
i
n
e
n
t
a
l
s
t
a
r
v
e
d
t
h
e
w
i
t
h
the oceanic basin
a
c
c
r
etion
s
e
d
i
m
e
n
t
a
r
y
w
h
e
r
e
(5)
e
m
b
a
n
k
r
n
e
n
t
s
Continental
p
r
o
g
r
a
d
e
d the
h
a
s
m
a
r
g
i
n
c
o
n
t
i
n
e
n
t
a
l
to the edge of a rifted
a
s the
b
a
s
i
n
;
o
c
e
a
n
i
c
a
d
j
a
c
e
n
t
t
h
e
i
n
t
o
slope out
continental
r
e
a
c
h a
c
a
n
b
r
e
a
k
t
h
e
s
l
o
p
e
toe of the embankment advances,
b
a
s
i
n
'
o
c
e
a
n
i
c
t
h
e
liithin
point that was initially
-15-
GULFPHASE
PROTO.OCEANIC
RIFT VALLEY PHASE
L A V A S +S E D I M E N T S
POTENTIAL
EROSION
S T A N D A R D OUASIOCEANIC
CRUST
OCEANIC
CRUST
BASALCLASTIC
PHASE
20 -t
MSL
,,lg
ffi,'i(
j_f)rlAo--<i;',1':!-,"^"s
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FULL CRUSI
-
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C A R B O N A T ES H A L E
P
SHELFAL HASE
CONT I NE NTAL
TERRACE
MSL
ruRBlolTES coNTtNENTALRtSE
ffilw
AL
T R A NS I T I O N
C R US T
<--FULL
sl;
OCEANIC
CRUST
OCEANICCRUST
CRUST----i
I
MSL
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w g(ffi
OCEANIC
CRUST
>i;i'),1?7ISiZ.,t
t)''rt<
1l-i>laX
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(r>l,l
'
/'
riluu'cnusr
g
'
T R A NS I T I O N A L
CR U S T
,go
-
z?o
rF
q?o
5F
KILOMETERS
F i g u r e B . S c h e m a t i c d i a g r a m s ( v e r t i c a l e x a g g e r a t i o n l 0 X r) itfot ei ldl u s ct roanttei n e n t a l
general evolution of rifted--"rgr"-prisi-along
m a r g i n : ( A ) i n c i p i e n t o " " a ' ' i " " I " g " ' s h o w i n g p i t - o " " "t thtei cr rdnea p
e nl c e i s
l o ss ui tbi soind a
when
phases; (B) end of narrow-oc"""-"Iugt
during
configuration
t.it.".-"Iop.-tise
complete; (C) continent.f
a later
a
t
.orrai.r"nta1 ernbankment
(D) orogrrjfig
open ocean stage;
u
l
t
i
m
ately
i
s
unless sediment delivery
state of growtt not reached
voluminous enough'
-16-
(6)
Nascent oceanic basins where gradual subsidence
of the oceanic lithosphere
between a midoceanic rise crest
and the trailing
edge of a continental
block forms a broad,
elongate depression in which abyssal plains of turbidites
can form above oceanic crust;
seamounts and archipelagic
aprons may occupy parts of such a basin.
occurs in association
C.
Basins where rifting
with transform or
convergent plate junctures;
examples of each case can be identified:
(7)
Pull-apart
and fault-wedge
basins along transtensional fault systems where loca1 attenuation
of crust occurs
to form depressions between subparallel
branches of a transform system; such basins may be associated with yoked uplifts.
(8)
apart of a magmatic
Interarc
basins where splitting
arc leads to development of oceanic crust between an inactive
remnant arc and a frontal
arc w[rere active magmatism continues;
iinception as downdropped graben
interarc
basins mav have their
within arc structures.
Orogenic Settings
(Table
2)
Basins whose tectonic
plate
evolution
is dominated by contractional
motions and orogenic deformation
subgroups (grainclude three idealized
dational
examples also exist):
Basj-ns related
A.
to the development of subduction complexes along
the trench flank of arc orogens; these are the three main sedimentary
components of arc-trench
systems:
(9)
Oceanic trenches whose substratum is the descending
oceanic lithosphere
of a plate being consumed; the inner flank
front of the subof the trench is marked by the defornation
duction complex.
(10) Slope basins formed as fault-bounded depressions on
the deforming submarine slopes between trench axes and trench
slope breaks; sediments of these basins are eventually
incorporated into subduction complexes along with trench sediments.
(1f) Forearc basins formed within the arc-trench
gap bethe trench
tv/een the trench slope break and the magmatic arc;
slope break marking the edge of the active subduction zone
serves as thelsill
for such a basin.
B.
Basins formed in pericratonic
foreland settings
adjacent to the
deforming flanks of orogenic belts;
these basins are systematically
asymmetric, with their deepest keels adjacent to fold-thrust
belts at the
flanks of the adjacent orogens, but three distinct
types occur:
(L2) Peripheral
basins formed where the surface of a
continental
b l o c k i s d r a w n d o v m w a r da g a i n s t t h e s u t u r e b e l t
of a collision
orogen; the polarity
of che adjacent orogen
faces this type of foreland basin, hence the ophiolitic
suture belt lies closer to the basin than the magmatic
belt of batholiths
and volcanogenic rocks.
(13) Retroarc basins formed where the surface of a
continental
block is drawn downward against the rear flank
of an arc orogen; the polarity
of the adjacent orogen faces
away from this type of foreland basin (really
a hinterland
basin!),
hence the ophiolitic
subduction complex lies farther from the basin than the magmatic belt of batholiths
and volcanogenic
rocks.
TRENCH
EREAK
I N T R A- A R C
I N T ER AR C
BASIN
FOREARC
VOLCANO EASIN
B A SN
I
(octive)
TRENCH
REMNANT
ARC
L
Ex;fJ+6*+.1
+++l
,2 Y
r . +, . + . + . + . +
l:
.++++
+ + + +
l++ + ++
+ + + + +
S P RE A O N
I G
C EN T E R
m
S U BO U C TOI N
ZONE
( m e l o n g e s e fc )
//
a
I
I
T R E NC H
SLOPE
8 R EA K
I
I
I
I
,I
TRENCH
I
cRusr
,27 '/
u
VOL
FOREARC
8ASIN
/y
t1i/
/ \\. E/i
.
ARC /
STRUCTURE
INTRA-ARC BASINS
I
to,IN
'eifi*
T E R A- R c[ c o * r , ner u -',
t
eoer]
D
G
t
J
BASIN
I
(inoctive)_irsL_J_
Ir nnr usr r r or .r al
l 7N ;
cRusr,,,.j)ii
FOREL.AND
F O L O- T H R U S T
8E LT
RE T R O A R C
BASIN
a\t{.h<r-\/-!lnfnn)n*
ffi#5:iilllll
/
MSL
ffii
rffi';ii(jt;iijiit)i)
isi'+?Vii.i i . ),rli,r!)_t'
i),(
BATHOLITH
'I
i
BELT
;i
*
i
j
:t
i
:
5?ii2,\'5Y
<r7,,i
c2
()'v
exaggeration
intraoceanic
:::":'::.:::?"1::':l:it
"'"'=:u?;."?:5'T
arcs'
margin (betow) magmatic
ental
fOX) to illustrate
(above) and contin-
R i aT t D - M A R G I N
P R IS M
MSL
r 1/r )l--[
R E M N A N TO C E A N
B A S I Nr.
T
f---
A R C - T ! ? EN C H S Y S TE M
R
SZ
O C E A NI C C R U S T
+
PERIPHERAL
BASIN
tt-r o
**l
CONTN
I ENTAL
CRUST
t- 2 0
I
L
o
L
30
too 200 300
l
l
KM
l
PERIPHERAL
EASIN
FT8
C R U S T A LS U T U R E
e
uJ
(,
c\
G"
sediexaggeration 10X) to illustrate
Figure 10.
Schematic diagrams (vertical
to form intercontinental
mentary basins associated with crustal collision
orbgen. Symbols: TR, trench; SZ, subduction
suturebelcwith
collision
basin; FTB, foreland fold*thrust
zone; FAB, forearc basin: RAB, retroarc
Diagrams A-B-C represent a sequence of events in time at one place
be1t.
along a collision
orogen marked by diachronous closure; hence, erosion in
join is
one segment (C) of the orogen where the sutured intercontinental
past a migrating
tecEonic
complete could disperse sediment longitudinally
fans of flysch in a remnant
point (S) to feed subsea turbidite
transition
ocean basin (A) along tectonic
strike.
- L 9 -
basins formed where basement is
(14) Broken-foreland
Eo cause block uplifts
deformation
in foreland
involved
basinal deisolated
f
o
l
d
s
s
e
p
a
r
a
t
i
n
g
and basement-cored
o
c
c
u
r in either
m
a
y
o
f
d
e
f
o
r
m
a
t
i
o
n
s
t
y
l
e
t
h
i
s
pressions;
s
e
t
t
i
n
g
s
.
or retroarc
peripheral
basinal evolution
control
effects
Basins where contractional
C.
orogens:
outside arc or collj-sion
fault
(15) Downwarped basins along transpressional
s
t
r
uctures
o
t
h
e
r
f
a
u
l
t
w
a
r
p
f
o
l
d
s
a
n
d
systems where wrench
f
e
atures
f
l
e
x
u
r
e
;
r
e
g
i
o
n
a
l
and
thickening
cause tectonic
d
e
formai
n
c
i
p
i
e
n
t
o
f
of this kind may occur as evidence
f
a
ults.
t
r
a
n
s
f
o
r
m
d
e
v
e
l
o
p
e
d
tion in the absence of fu1ly
s
hed
c
l
a
s
t
i
c
s
i
n
t
o
w
h
i
c
h
(16) Remnant ocean basins
p
r
o
p
a
g
a
t
i
n
g
c
o
l
l
i
s
i
o
n
o
f
from the ends
longitudinally
these deposits
orogens rnay build subsea fans and deltas;
'are probably the typical
of classic
m
o
l
a
s
s
e
and
flysch
terminology.
BASIN COMPARISONS
sequences of
indicates
that certain
The logic of plate tectonics
In the
g
e
o
l
o
g
i
c
record.
in the
should recur frequently
basinal settings
d
i
ctates
o
c
e
a
n
s
c
l
o
s
i
n
g
simplest case, the governing cycle of opening and
p
h
a
s
e
s
d
o
m
i
n
ated
from nascent
that oceanic basins must evolve regularly
c
o
n
t
r
a
c
t
i
o
n
a
l
to remnant phases dominated by
tectonics
by extensional
continthe sedimentary assemblages along rifted
Similarly,
tectonics.
p
r
o
t
o
ceanic
B) must include phases deposited within
ental margins (fig.
prism, which may in turn be
the younger miogeoclinal
rifts
underlying
emconti-nental
of a progradational
covered and flanked by the deposits
may later be
sedimentary associations
These rifted-margin
bankment.
covered in part, with the onset of orogenY, bY the foreland deposits of
(ffg.10)
9) or collision
retroarc or peripheral basins as arc (fig.
Special variants
margin.
orogens develop along the deformed continental
can lead to other successions of
of the gpiding plate interactions
basinal
development.
mechanisms of subsidence must operate
that dlfferent
The inference
suggests that the pattern of
and orogenic settings
in the various rifted
in
One difference
types of basi-ns.
subsidence may vary in different
shapes of the
cross-sectional
pattern
is apparent in the contrasting
may also exist in the timing of
Differences
varj-ous types of basins.
For basins where water
of the basins.
subsidence during the history
history,
shallow throughout the depositional
depths are consistently
subsidence rates and net subsidence can be estimated closely on ei-ther
or isopach maps.
basis from columnar sections
a maximal or volumetric
hisduring the depositional
For basins where water depths vary greatly
into an
of changing bathymetry must be incorporated
estimates
tory,
11) and net
Maximum subsj-dence rates (fig.
analysis of subsidence.
12) have been plotted
through tirne (fig.
maximum subsidence integrated
here.
many of the types distinguished
for a number of basins representing
basi-ns, where rapid
is suggested between rifted
A elearcut
difference
early subsidence rates decline with time, and orogenic basins, where
The former pattern
climax.
toward a final
subsidence rates tend to build
inifollowing
probably reflects
effects
the dominance of thermotectonic
progressively
may reflect
whereas the latter
tial
crustal
attenuation,
movements cease.
more intense flexuring
until
contractional
-20-
P R E -A N T L E R
CORDILLERIAN
MI O G E O C L I N E
MODERN
OCEAN
O UA C HI T A
S E Q U EN C E
loo
=
lrJ
F
50
I L LI NO I S
25
E.
UJ
O
ATLA NTI C
COAST
z
lrJ
o
a
(D
f
a
(9
o
J
ALBERTA
FORELAND
APPALACHIAN
\
M I O G E O C L I Ni E
I
L_\
2.5
\ A NA D A R K O - AD
RM O R E
AULACOGEN
500
400
300
TIME IN
Figure ll.
rhrough
positive
tory of
200
loo
M.Y.B.P
Estimated subsidence rates for selected sedimentary basins
basins'
Phanerozoic time; note negative slopes for rifted
hisslopes for orogenic basins, and trough shape for full
aulacogens and oceanic Ouachita sequence.
-2L-
ME IN
M E S O Z O I C - C E N O Z OTIIC
roo
200
300
k
2500
MY'B'P
AAA
=
t!
O
z
5000
ACA DI AN
EVENT
UJ
o
a
(D
f
7500
a
lrl
F
AAA = ANADARKO-ARDMORE
AULACOGEN
J
= t z
l
O
4uu
5OO
PALEOZOIC TIME IN
M.Y.B.P
Figure12.Approximatecumulativesubsidenceinselectedsedimentary
basinsthroughPhanerozoictime;noteconcave-upshapeforrifted
and S-shape for full
basins'
basins, convex-up shape for orogenic
of aulacogens and oceanic Ouachita sequence'
history
-22-
"
coNc
(uo,'/ v'-o)
"ofl
g
M
s
los
VS
\
\
81 o
lo4
lo3
m - From
F o l d Thrust
Bt e l t
K
\
tao
qc"\o
oA
\,
M Al N - /
TREND
USA
I NL A ND
BASINS
\
o\
\
t.o
\
B A R R E NB A S I N S
x2.5
o
o
Z
o
500
]-,
KM
rooo
Figure 13.
Plot of "0i1 Concentrationr"
expressed as oil volume in
per cubic kilometer
barrels
of total
sedimenL, as a function
of
distance inward from craton margin as defined by distance from
(Appalachian, Ouachitan, or Cordilleran).
nearest fold-thrust
belt
potential
Data fron estimates of ultimate
for 20 U.S. interi-or
basins from MPG Memoir 15 (I.H. Cram, editor).
-23-
'-
to plot changing geothermal grainformative
would be especially
against time for examples
h
o
r
izons
k
e
y
s
o
u
r
c
e
at
dients and temperatures
data'
d
o
so with available
t
o
u
n
a
b
l
e
I
a
m
of varj-ous types of basins.
p
e
t
r
o
leum
(
f
i
g
.
o
f
o
f
v
o
l
u
m
e
1
3
)
p
l
o
t
one special
I have included
c
o
n
tinp
r
e
s
e
n
t
t
h
e
i
n
b
a
s
i
n
s
sediment for various
per volume of fotal
Future
o
n
V
o
l
u
m
e
s
C
r
a
u
r
M
P
G
f
r
o
m
t
h
e
The data are taken
ental interior.
d
i
s
tance
t
o
a
c
c
o
r
d
i
n
g
a
r
r
a
n
g
e
d
The basins are
u.S. Petroleum Provinces.
b
asin
t
h
e
o
f
c
e
n
t
e
r
t
h
e
f
r
o
m
from the nearest orogenic belt as measured
n
e
c
e
s
s
a
r
ily
a
r
e
M
e
a
s
u
r
e
m
e
n
t
s
belt.
to the closest foreland fold-thrust
j
n
v
o
l
v
e
d
o
f
u
n
c
ers
a
g
s
supracratonic
include
The basins
rough values.
f
o
r
e
l
a
n
d
a
n
d
v
a
r
i
o
u
s
basins, aulacogens,
infracratoni-c
tain origin,
to support
The plot is interpreted
basins, some of composite origin.
f
r
om the dec
r
a
t
o
n
t
h
e
the concept that migrati-on of oil updip toward
j
s
phenomenon'
i
m
p
o
r
t
a
n
t
a
n
regions
pressed orogenic flanks of foreland
concentration
o
v
e
r
a
l
l
t
h
e
increases,
As di-stance from the orogenic fronts
of petroletrm appears to decline logarithmically'
It
INCIPIENT RIFTS
blocks have
of continental
rifting
to incipient
Basins related
o
f
t
h
e substratum
(
a
)
attenuation
crustal
several aspects in common:
(b) high heat
o
f
s
u
b
s
i
d
e
n
c
e
;
j-s characteristic
and is the prime trigger
p
r
i
o
r
t
o
s
u
b
s
idence and
doming
flux is associated with thermotectonic
trans(
c
)
o
v
e
rall
t
h
e
continues during the early stages of subsidence;
(
d
)
o
r
o
g
enic
a
n
d
symmetric;
of the basins are generally
verse profiles
ina
r
e
b
a
s
i
n
s
o
f
t
h
e
Two major features
is not intense.
deformation
of
p
r
o
f
i
l
e
(
a
)
c
r
u
s
t
a
l
the atEenuated
to evaluate:
difficult
herently
be
c
a
n
n
a
t
u
r
e
i
t
s
hence
covered by sediment'
the substratum is entj-rely
g
r
a
d
i
e
nts
(
b
)
g
e
o
t
h
e
r
m
a
l
the
only by geophysical methods; and
established
i
n
f
e
r
e
n
c
e
s
f
r
o
m
must be hindcast
early in basin evolution
that prevailed
t
h
e
o
f
heat flux and of the influence
of the magni-tude of the initial
during thermal decay'
growing sedimentary blanket
Infracratonic
Basins (fig.14)
infrabasins represent
The i-nference that major intracontinental
prior
o
c
c
u
r
r
e
d
separation
continental
r^rhere partial
structures
cratonic
P
e
r
h
a
ps
hypothesis.
an unsubstantiated
to subsidence remains largely
g
e
o
p
h
ysical
w
h
e
r
e
to the North Sea basin,
the best documentation pertains
b
e
n
e
a
th
n
o
r
m
a
l
than
that the crust is thinner
studies have established
b
a
sin'
o
f
t
h
e
p
o
r
t
i
o
n
s
the major graben trends that represent the deeper
s
ims
u
g
g
e
s
t
b
a
s
i
n
of basal grabens in tl-e West Siberian
patterns
Similar
rocks
d
e
n
s
e
u
n
u
s
u
a
l
l
y
The presence of
attenuation.
belts of crustal
ilar
h
i
nts
b
a
s
i
n
s
I
l
l
i
n
o
i
s
in the substratum beneath the Michigan and
locally
cons
t
r
u
c
t
u
r
a
l
d
i
r
e
c
t
btit
attenuation,
at analogous processes of crustal
is generallY lacking.
firmation
basins appear to be broad,
infracratonic
typical
From the surface,
gentle and merge with surare typically
roughly equant downbows; flanks
In the subsurface,
margins.
sharp structural
without
rorrndi.rg platforms
thickness of lower horizons may reflect
abrupt changes in the stratal
during the early stages
by normal faulting
controlled
graben 3tructures
trilete
branching
Buried graben trends corrnonly display
of subsidence.
on thermotectonic
as branching rifts
patterns
that. suggest initiation
for
with the processes responsible
domes that developed in association
S
e
a and
The importance of thermal gas in the North
attenuation.
crustal
-24-
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Figure 14.
Schematic diagrams to
infracratonic
basin in profile
illustrate
development of rifted
vlew.
Time runs top to bottom.
-25-
high heat flux early in
a corresponding
basins may reflect
West Siberian
tend to be gentle folds and
structures
Later tectonic
basin evolution.
either minor contractional
that probably reflect
faults
with modest offset
load.
to the growing sedimentary
adjustments
or isostatic
deformation
shallowbasins are typically
of infracratonic
The sedirnent fills
with non-marine beds present in the lowermost and uPpermosf
marine strata
Contrasts with
in marginal areas.
parrs of the column as well as locally
The
and not in facies.
regions are mainly in thickness
adjacent platform
blocks coupled with
easy access Eo sediment sources on nearby continental
combined proeesses of clastic
modest rates of subsidence apparently allow
with sediment
basins filled
to keep i-nfracratonic
and carbonate deposition
Shelf deposits of well sorted mature sands and various
during subsidence.
with
Periods of temporary starvation
carbonate types are thus connon.
also a1low, however, for the development of stagnant
silled
conditions
source beds can accumulate in the basin
basins in which organic-rich
Deltaic
complexes or carbonate buildups
local grabens.
or within
interior
and
reservoirs
Attractive
shelves or horst blocks.
may form on adjacent
origin
thus tend to cluster
and stratigraphic
traps of combined structural
Geometric patterns
tectonic
trends.
around basin margins or along internal
may
attenuation
amounts of crustal
by irregular
of subsidence controlled
be complex, but the subsequent sedi-ment load tends to induce centripetal
Updip migrabeneath the basin as a whole.
of the lithosphere
downflexure
toward marginal parts of the basins.
tion paths thus tend to be centrifugal
Marginal
Aulacogens
(fig.
15)
to describe
in the Soviet literature
The term aulacogen originated
pattern
radial
troughs disposed in a generally
fault-bounded
long-lived,
The features
areas of cratons.
as wedge-shaped flaws in the marginal
sequences or orogenic magfrom geosynclines in lacking ophiolitic
differ
of the same style.
o
r
d
i
n
a
r
y
o
r
o
g
e
n
e
s
i
s
e
x
p
e
r
i
e
n
c
e
matism, and do not
a
s
aborted oceans; that ist
a
u
l
a
c
o
g
e
n
s
v
i
e
w
Plate tectonic
interpretations
other rnembers continued
r
i
f
t
s
y
s
t
e
m
s
w
h
o
s
e
as the failed
arms of branching
m
a
rgins of those ocean
b
a
s
i
n
s
.
T
h
e
o
c
e
a
n
i
c
to evolve into full-fledged
i
n
t
o
w
h
i
ch the aulacogens
c
r
a
t
o
n
s
t
h
e
e
d
g
e
s
o
f
t
h
e
basins then define
m
o
uth of an aulacogen
s
i
d
e
o
f
t
h
e
m
a
r
g
i
n
s
t
o
e
i
t
h
e
r
extend.
The craton
and eventually
i
n
t
h
e
i
r
h
i
story,
m
a
r
g
i
n
s
e
a
r
l
y
are thus rifted
continental
conis later
l
i
t
h
o
s
p
h
e
r
e
a
d
j
a
c
e
n
t
o
c
e
a
n
j
c
w
h
e
n
t
h
e
o
r
o
g
e
n
i
c
b
e
l
t
s
become
the
t
o
r
e
l
a
t
e
d
a
u
l
a
c
o
g
e
n
i
s
a
M
e
s
o
z
o
i
c
o
f
N
i
g
e
r
i
a
T
h
e
B
e
n
u
e
t
r
o
u
g
h
sumed.
Atlantic
Ocean, and the Anadarko-Ardmore basin of Oklahoma j-s a Paleozoic
to the Ouachita orogeni-c be1t.
aulacogen related
between those of infraof aulacogens is intermediate
The structure
cratonic
basins and oceanic basins, to each of which aulacogens are gradaThe nature of
and oceanic ends, respectively.
tional
at their continental
to oceanie, and
the crust beneath the floor of aulacogens is transitional
of igneous rocks emplaced at the time the
may include
several kilometers
infracratonic
basins, aulacogens
aulacogen first
developed.
Unlike typical
are markedly elongate,
although roughly symmetrical in transverse profile.
hinge lines where
Their flanks commonly are prominent fault-controlled
Actiintermittently
active fault
scarps serve as 1oca1 sediment sources.
vity
early in the history
on these bounding fault
trends is most significant
of the aulacogen when rapid subsidence of the floor accmpanies initial
may occur
thermotectonic
A second period of major activity
subsidence.
late i-n the history
of the aulacogen when deformation related
to orogenesis
along the associated
geosynclinal
trend causes reactivation
of t.he fracture
-26-
R I F T E DC O N T I N E N T AML A R G I N
o
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H I N G E F A U L TZ O N E
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P L A T F O R MS E D I M E N T
S E D I M E N TD I S P E R S A L
AULACOGEN
REACTI VATED
FAULT ZONE
S E D I M E N TD I S P E R S A L
AULACOGEN
Figure 15'
schematic diagrams to illustrate
d.evelopment of aulacogen
in plan view.
Transverse profile
of cratonic
end of aulacogen is
similar
to infracratonic
basin (fig.
14), and transverse prJrile
of
oceanic end of aulacogen is similar
to protoceanic
(iig.
rift
16).
Time runs top to bottom.
- 2 7-
Systems.TheearlierfaultstendEobenormalblock-faulEs,whereasthe
laterfaultstendtobereversefaulEsassociatedwithbasement_cored
foldsandblock-uplifts.Bothsetsoffaultstendtobreaktheaulacog e n i n t o s u b p a r a l l . l " . t " o f l i n e a r , f a u l t - c o n t r o l l e d S t r u c t u r a l e l e m e n t st h. i c k
sedirniddle period of aulacogen evolution'
During the intervening
of
k
e
e
l
E
h
e
a
l
o
n
g
its axis
forms an elongate dovrnflexure wiLh
mentation
t
h
e
t
i
l
t
s
This enhanced subsidence
is thin.
the aulacogen wher.
" r rp
, ,liat t f o r m s . d o w n w a r d
toward the aulacogen structure'
edges of the bounding
Undertheseconditions,depositiontendstomasktheStructuralmargins
ot tn;n:"131?3!l;
firls
of auracosensare mainly sharrow-marineshelf
than the nearby plarform
thicker
to but several titl"
similar
strata
S e q u e n c e s . P r o m i n e n t s e d i m e n t a r y c o m p o n e n t s m a y i n c l u d e m a t ua rcet sc l aasst i ca d r a i n
into the aulacogen, which
sediment dravrn preferentially
fortheadjacentcontinentalblock,orcarbonatesedimentdeposited
duringgradualsubsj-dence.Additionalcomponentsarealsoimportant.
LavasassociatedwiththeextensiveriftingrhatesrablishestheStructuremaybeinterbeddedatlowerhorizons.Coarse,immatureclastics
thatarenon-marineinpartmaybeassociatedwithactivityom
n laoyc bael s h e d u p t h e
Marine or non-marine clastics
scarps.
fault
marginal
a u l a c o g e n f r o m t h e o r o g e n i c b e l t t h a t e v e n t u a l l y c l o s e s ipt rsem
v aol eu nt th . Tdhui rsi n g t h e
to tirat
is opposite
of sediment delivery
direction
Conis open to an oceanic basin'
time that the mouth of the aulacogen
of
t
i
l
t
s
e
a
w
a
r
d
the
of such Jrogenic'clastics,
current with the arrival
t h e a u l a c o g e n a x i s m a y b e e n h a n c e d b y f l e x u r e o f t h e c o n t i n eb ne ltta' l m a r g i n
orogenic
of the developing
downward beneath th" il"t'k
an aulacogen or
w
ithin
b
e
d
s
s
o
u
r
c
e
paths from
Updip migration
beyonditsmouthliealongthetrendofthefeatureandoutwardtor^lard
i r s f l a n k s . R e s e r v o i r s i n s u i t a b l e t r a p s m a y b e a s s o c i a t e d etiht eh e ar uwl ai tcho g e n '
or
of
defined hinges along the margins
the structurally
c
l
ose
t
h
e
may occur toward
-rumpling
the aulacogen where tectonic
within
of its evolution.
Protoceanic
Rifts
(fig'
f6)
D e e p r i f t v a l l e y s a n d p r o t o c e a n i c g u l f s t h a t f o r m d u r i n g t h e e a r l y rift
symmetric
*.y foirn persistenE
separatiol
stages of contin.r,a"i
if the
A
lternately,
s
t
a
g
e
.
e
a
r
l
y
a
n
a
t
is arresred
basins if separation
S
t
a
ge are
deposits of the protoceanic
oceanic basin continues to broaden,
presentasauniqueassemblage.ofStrataformingthelowerhorizonsof
t h e r e s u l t i n g r i f t e d _ m a r g i n s e d i m e n t p r i s m . C h a r a c t e r i s t i c f e a t u r e sl a
o vf a s a n d
interstratified
sedimentary issernblages include
protoceanic
of igneous oceanic crust
aid the building
sediments formed as deposition
associated with large
Lxtensive piedmont clastics
proceed concurrently,
fault blocks, and massive evaporites
scarps bounding tilled
buried fault
that
and desiccation
circulation
of restricted
formed under conditions
'
seaways that occupy the basins
commonly develop in the narrow
the
that control
effects
Because of the intense thermotettonic
e l e v a t i o n o f t h e s u b s t r a t u m , t r u e s a b k h a e v a p o r i t e s m a y r e s t d i r e c t l yu n d e r g o e s
oceanic crusL that later
or even truly
attenuated
on strongly
dovmward beneath
the evaporites
dramatic subsidence capable of carrying
Therof younger sediment'
great depths of water or immense thicknesses
motectonicupliftoftheedgesofthecontinentalblocksborderinga
shoulders
protecEive
forms bounding uplands that act as
rift
protoceanic
toscreenmajorriversawayfromthecrustalcleft,andthustohelp
-28-
REDBEDS.
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Figure 16.
Schematic diagrams to illustrate
protoceanic rifts
quas ic ont inental
(above) and quasioceanic
(be1ow) floors.
_29_
with
Such conditions
depositon.
for evaporite
suitable
promote conditions
w
here thick NeoS
e
a
in the modern Red
rppu"r to reach ideal expresion
at sea 1eve1 upon thin crust'
were laid down essentially
gene evaporites
are thick along the flanks of rnajor ocean
evaporites
Wh"t" protoceanic
subsequent
within
structuring
diapiric
they may cause attractive
basins,
or embankments.
terraces
continental
however, the Colorado River
t
h
e Gulf of California,
l
i
k
e
In a case
through a breach in the bounding
rift
is able to enter a protoceanic
Major evaporite deposits are
s
t
r
u
c
t
u
r
e.
o
f
t
h
e
e
n
d
o
n
e
highlands near
has advanced longitudinally
c
o
m
p
l
e
x
d
e
l
t
a
i
c
p
r
o
g
r
a
d
a
t
i
o
n
a
l
A
lacking.
of
s
e
d
i
m
e
nts shed off the front
c
l
a
s
t
i
c
a
n
d
r
i
f
t
dor^m the protoceanic
d
e
ep
i
n
t
o
c
u
r
r
e
n
f
s
t
u
r
b
i
d
i
t
y
a
s
f
a
r
t
h
e
r
e
v
e
n
the delta have travelled
s
p
r
e
a
d
i
n
g
s
y
s
t
e
m
'
d
i
s
p
e
r
s
a
l
c
l
a
s
t
i
c
o
f
t
h
i
s
Within the reach
\,/ater.
a blanket
centers where igneous oceanic crust is forming are covered with
and
s
i
1
l
s
'
d
i
k
e
s
,
l
a
v
a
s
,
m
i
n
g
l
e
d
o
f
c
r
u
s
t
A transitional
of sediment.
r
i
f
t
.
p
r
o
t
o
c
e
a
n
i
c
t
h
e
b
e
n
e
a
t
h
sediments is thus being formed
is composed of
rifts
crust 1n protoceanic
Other transitional
basement rocks'
c
o
n
t
i
n
e
n
t
a
l
and fault-fragmented
greatly
attenuated
f
l
a
n
ks of the rift,
b
o
t
h
s
c
a
l
l
o
p
f
a
u
l
t
s
arrays of normal
Subparallel
and calving
platforms
u
p
l
i
f
t
e
d
o
f
a
d
j
a
c
e
n
t
stepping down the broken flanks
1
ocal shield
v
o
l
c
a
n
i
s
m
,
F
i
s
s
u
r
e
g
r
o
w
i
n
g
c
l
e
f
t
.
horst blocks away into the
the
w
i
t
h
a
s
s
o
c
i
a
t
e
d
a
r
e
f
a
n
c
o
m
p
l
e
x
e
s
and broad alluvial
volcanoes,
t
r
a
n
s
i
t
i
o
n
a
l
t
h
e
o
f
f
o
u
n
d
e
r
i
n
g
c
a
u
s
e
s
As thermal decay
deformation.
h
igh
o
n
t
h
e
o
r
b
l
o
c
k
s
o
n
h
o
r
s
t
d
e
v
e
l
o
p
carbonate buildups may
crust,
c
o
m
plex
s
t
r
u
c
t
u
r
a
l
l
y
I
n
t
i
m
e
,
t
h
i
s
fault blocks.
shoulders of tilted
t
r
a
n
s
g
r
e
s
s
i
v
e
b
y
i
s
b
u
r
i
e
d
t
y
p
e
s
sediment
terrane with varied local
of the edges
sedimentary loading of the deep rift,or
marine deposits.
the edges of
t
i
l
t
s
i
t
,
e
v
e
n
t
u
a
l
l
y
f
r
o
m
of the ocean basin that develops
The
belt'
r
i
f
t
t
h
e
t
o
w
a
r
d
d
o
v
m
w
a
r
d
p
l
a
t
f
o
r
m
s
continental
the adjacent
d
r
a
p
e
d
a
s
m
o
o
t
h
l
y
b
e
n
e
a
t
h
m
a
s
k
e
d
i
s
t
h
e
n
broken terrane
structurally
sediment cover.
sabkha
algal
source beds may include organic-rich
Protoceanic
and
b
u
i
l
d
u
p
s
C
a
r
b
o
n
a
t
e
u
n
c
e
r
t
a
i
n
.
1
s
sediments, but the likelihood
great
t
h
e
b
u
t
r
e
s
e
r
v
o
i
r
s
,
f
o
r
m
s
u
i
t
a
b
l
e
m
a
y
sand facies
local shoreline
sedim
a
r
i
n
e
y
o
u
n
g
e
r
b
e
n
e
a
t
h
b
u
r
i
e
d
depths to which they are ordinarily
S
u
b
o
r
d
j
n
a
te
i
n
s
t
a
n
c
e
s
.
m
a
n
y
i
n
t
a
r
g
e
t
s
ments makes them unattractive
b
l
o
c
k
s
f
a
u
l
t
t
i
l
t
e
d
g
r
a
b
e
n
s
a
n
d
redbed basins that occur as elongate
belts are less deeply buried but
rift
in the outer parts of protoceanic
The Triassic
h
y
d
r
o
c
a
rbon occurrences.
to harbor important
are unli-kely
examples.
a
p
t
a
r
e
A
m
e
r
i
c
a
N
o
r
t
h
e
a
s
t
e
r
n
and Jurassic redbed basins of
CONTI}IENTAL SEPAMTIONS
that fragments continental
separation
Basins formed by continental
m
a
r
g
i
ns of the continental
t
h
e
those developed along
blocks include
Basins in
basin itself.
o
c
e
a
n
a
d
j
a
c
e
n
t
the
fragments and those within
(
a
)
s
u
b
s
i
d
ence of
i
n
i
t
i
a
l
i
n
c
o
m
m
o
n
:
both areas have several aspects
(
b
)
additional
l
i
t
h
o
s
p
h
e
r
e
;
h
e
a
t
e
d
o
f
d
e
c
a
y
thin crust stems from thermal
s
e
d
i
m
ent loads;
t
h
i
c
k
o
f
a
c
c
u
m
u
l
a
t
i
o
n
t
h
e
b
y
subsidence is caused
flexural
(
d
) oroa
n
d
o
r
o
n
e
s
i
d
e
d
;
a
s
y
m
m
e
t
r
i
c
(c) the depositional
systems are
to a
c
o
n
t
i
n
u
i
t
y
g
r
o
s
s
s
t
r
a
t
a
l
d
i
s
r
u
p
t
genic deformation can ultimately
difi
n
h
e
r
e
n
t
l
y
a
r
e
t
h
e
b
a
s
i
n
s
o
f
f
e
a
t
u
r
e
s
Two major
remarkable degree.
c
o
n
t
i
n
e
n
t
o
c
e
an
t
h
e
a
l
o
n
g
(
a
)
c
r
u
s
t
the transitional
ficult
to evaluate;
b
e
c
a
n
n
a
t
u
r
e
i
t
s
h
e
n
c
e
c
o
v
e
r
,
interface
is masked by thick sediment
after orogenesis has
only by geophysical rnethods; and (b)
established
strata must be hindcast
t
h
e
o
f
r
e
l
a
t
i
o
n
s
h
i
p
s
facies
occurred, the original
must be
c
onstraints
a
d
e
q
u
a
t
e
f
o
r
w
h
i
c
h
reconstructions
by palinspastic
inferred
frorn liurited
control.
-30-
b.-
Miogeoclinal
Prisms(fig.17)
sequences of past usage are regarded
The classic miogeosynclinal
margins
contj,nental
prisms deposited along rifted
now as miogeoclinal
the
Modern analogues include
ocean.
open to a neighboring
in settings
Mesozoic and Cenozoic sequences along the eastern edge of the Americas,
where the upper part of the sediment pile is well understood but the
Paleozoic analogues include
details
of the lower parts are obscure.
to the
miogeoclines
as developed prior
the Appalachi-an and Cordilleran
respectively.
Within these successions,
Taconic and Antler orogenies,
but facies relathroughout,
local sequences can be observed in detail
hence
disrupted by major thrusts,
tions on a large scale are structurally
of both are known by inference on1y.
configurations
overall
the initial
prisms extend as continuous elongate belts for long
Miogeoclinal
margins, although cross-sectional
continental
distances along rifted
of sedivolumes may vary markedly from place to place with the vagarles
may be broken at intervals
Their continuity
ment delivery
and bypass.
where
in the edge of the continent,
by the presence of marginal offsets
separation leads to a
of transform rather than rift
an early history
of sedimentation.
Along marginal offsets,
different
subsequent history
attenuation
is suppressed to some degree, and volcanogenic
crustal
positive
features
These long-lived
marginal fracture
ridges may form.
sediment to deeper sites elsewhere and may
thereafter
deflect
clastic
serve instead as loci of organogenic carbonate deposition.
prisms have an overall
lensoid
miogeoclinal
In transverse section,
bein elevation
form, but the depositional
relief
spans the difference
The ourter part of
surface and the ocean floor.
tween the continental
rise.
The
beneath the contlnental
the lens is composed of turbidites
coalesced subsea fans of this region grade to the abyssal plains of the
The inner part of the lens is composed of shelf
oceanic basin beyond.
terrace.
These strata grade
and paralic
deposits of the continental
Between contlnlaterally
to non-marine deposits of the coastal p1ain.
slope, located
ental rise and continental
terrace is the continental
interface.
Reduced sedimentation on
roughly along the continent-ocean
typical
starved,
shaly slopes lends an hourglass shape to the prism as
a whole.
Terrace and rise deposits form the bulk of the prism.
The lower part
terrace has two major components.
The continental
phase whose accumulation
is commonly a rapidly
deposited basal clastic
probably reflects
quick subsidence of attenuated basement
the initial
margin during the early period of developalong the rifted
continental
During this phase,
ment when thermal decay was a dominant influence.
highlands along the edge of the continencal
the stripping
of residual
to high sedimentation rates.
This phase is brought
block may contribute
crust and
to a close when local isostatic
balance of the transi-tional
its overlying
terrace is achieved.
continental
of shelf sediments that may include
Subsequent slower deposition
probably only proceeds as
abundant carbonates as well as clastics
flexural
block occurs in response to
downwarping of the continental
the sedimentary load of the continental
rise offshore.
Wedge-shaped
bodies of sediment deposited as part of the continental
terrace during
prograded regressive
this time may i-nclude successively
cycles of
deltaic
clastics
or a1ga1-bank carbonates as well as marine shelf
deposits.
Disconformities
may separate successive wedges of sediment.
-31
P R O T O C E A NP
I CH A S E S
CONTIN E NTAL
CRUST
B A S A L- C L A S T I C
PHASE
)-XX,i':Bi:)lr
I
E
C O N T I N E N T ATLE R R A C
S H E L F A LP- A R A L I C
SEDIMENTS
CONTINENTAL
SLOPE
CONTI NENTAL
R I SE
TURBIDITES
ffia
+
+
+,+1+1
t 3 )$ t$(D f J..l-i+ +l+
))'V2l,}5ili;iit:-{,
J'>D<AiZSl'V
ER ACq
SLOP
E- R I S E
O NF I GU RATI oN
Figure 17.
Schematic diagrams to illusLrate
development of miogeoclinal
prism from basal clastic
phase (above) duri-ng early thermotectonic
subsidence of transi-tional
crust to mature phase (be1ow) vrhen flexural
subsidence is dominant.
-32 -
The inner lirnit
may form near the shelf break.
buildups
r:ronate
m
a
y
t
o
s
tand well within
come
terrace
: ;he downwarped continental
occurred during
attenuation
block where no crustal
:-e continental
r:rtinental
separation.
prisms include diapiric
folds
features of miogeoclinal
Structural
protoceanic
;:.ose development depends upon the presence of underlying
facies should be overlapped
Faults Ehat cut the protoceanic
='.-aporites.
may continue,
strata,
but some growth faulting
miogeoclinal
--.- overlying
phase.
Moreover,
of the basal clastic
:specially
during rapid deposition
interface
is imperfect,
:: structural
coupling across the continent-ocean
of
rise may cause reactivation
:re sedimentary load of the continental
as well as simple
:lder fractures,
including
those of marginal offsets,
terraces underlain by protoceanic
:lexure of lithosphere.
Continental
basins
at depth may even develop constituent
rorst-and-graben
structures
horizons as
and arches vrith structural
closure at higher stratigraphic
'*'e11. Orogenesis brings miogeoclinal
evolution
to a close by forming
rajor fold-thrust
belts composed of crumpled and imbricated miogeoclinal
strata.
miosource beds rnight occur within
Several kinds of organic-rich
(a) shaly continental
laid down within
geocli-nal prisms:
slope deposits
the oxygen minimum zone, (b) carbonate or shale beds of the continental
and (c) phosphorterrace deposited in si11ed depressions on the shelf;
water is
ites deposited on shelves where upwelling of nutrient-rich
and gentle
strong.
Reservoi-rs may be abundant in both stratigraphic
terrace.
the continental
However, the total
structural
traps within
paths updip
migration
volume of source beds may be 1ow, and effective
from slope sources to terrace reservoirs
may be rare owing to the lack
of continuous stratal
connections through starved facies.
Continental
Embankments (Fig.
18)
of the edge of the
In areas where massive sedimentary progradation
of the rj-fted-margin
sediment prism
continent
occurs, the configuration
to that of
terrace-slope-rise
triad
changes from that of the continental
a continental
embankment.
The shelf break advances from the original
it reaches a position
above oceanic
continent-ocean
interface
until
is then burj-ed, of course, beneath an immense
basement.
The latter
probably the thickest
kind of stratal
succession possible.
sediment pile,
to
1ens, extending
from sea level
The embankment is an immense unstable
downoceanic depths and havj-ng a deep keel made possible
by isostatj-c
flexure of the lithosphere.
The Gulf Coast and the Niger Delta are
outstanding
extent along their
modern examples.
Both have restricted
respective
continental
margins.
and related
Internal
of an embankment is intricate
strucfuring
gravitational
failure
may produce
mainly to loading processes.
Overall
pseudotectonic
growth faults
folds and thrusts near the toe.
Listric
and associated
folds may scar many parts of the pile but commonly are
fed by underlying
concentrated near prominent delta lobes.
Salt diapirs
protoceanic
facies are also cofitrnon.
Sediment associ-ations
within
an embankment consist
of a series of
overlapping
lenses,
each with stratal
continuity
laterally
from shallowest to deepest facies.
Fluvio-deltaic
and shoreline assemblages with
numerous potential
reservoir
to organic-rich
sand bodies grade offshore
prodelta and slope facies that in t.urn grade to turbidite
associations.
As progradational
growth of the embankment occurs,
each successive
-33-
B
a
z
tJ.J
J
t!
F
C)
rre
'/9'
)\
OJ
'ri
q)
.-t
.J
tl-.1
O
=r
d
.Fl
Hs
+J
at.
a)
v.
d.
1,/@i i
a
t-rJ
()
l!
o
z
(r
F
(n
F
L,"7','
o
d
;'l,'9'/,
'll
,l
,' ,6r'
,'9'/
"fl
AJ
-.
J
.rt
+J
z
d.
o
Or.
(/)
o0
d.
'rl
aE
z<)
3
o
tr
oo
(r
+
(J
F
J
IJ
d
!
0)
F
]J
]J
+ +
a
+
+ + ' \
+ + + + +
+ ' + '
++ + + + + + + +'+
I
r-l
F-l
.-l
+J
F
T,gdliBxp
'59:-i<,!,*,i/
J
F F
o z
> o
(L(L
i9t)'irt55!)i,
F
Z ;
w a
z =
,-(r
$gffrf${
|<:
o
>a).-rrlfzt'/)tD'ij
-J4-
L)
o0
d
.rl
1,
r l
'rl
1J
a l
a
r-l
CJ
lr
I
.r{
loaded by more and more overlyi-ng
is progressively
increment of strata
tilted
to higher and higher dips by the flexure
beds and progressively
offshore.
associated with sedimentary loading farther
of lithosphere
combine to pump any hydrocarbons generated continually
These actions
which form
associations,
in shoreline
updip toward favorable reservolrs
1id across the top of the embankment. Diaa diachronous stratigraphic
traps.
piric
combine to produce abundant attractive
and growth structures
and shoreline
Stratigraphic
traps are also common in fluvio-deltaic
extent.
assemblages where sand bodies have lj-mited individual
sediment prisms'
During the later phases of growth of rifted-margin
In continental
embankments, adequate maturheat flux is low to normal.
Fluid
ation can still
be achieved because of the great depths involved.
overpressures are characteristic
because of the rapid sedimentation.
Nascent
Oceans
The sedirnent cover in nascent oceanic basins \,rith midoceanic rises
of the ocean
elevations
varies in nature and thickness for different
oceanic layers
The characteristic
floor corresponding to different
ages.
to each increment of oceanic
build diachronous facies added successively
lithosphere
as it is formed and moves away from the rise crest.
The i-gneous oceanic crust forms at the rise crest as an ophiolite
and metaPillow
lavas near the top pass dovmward into altered
sequence.
The latter
dikes and sills.
rnorphosed lavas cut by s!,/arms of dolerite
to form
crustal
magma chambers that solidify
are fed from underlying
Igneous
bodies of massj-ve gabbro, 1oca11y converted to amphibolite.
within
the magma chambers forms cumulus gabbros and peridodeposition
of the
tectonites
near their base.
Underneath are ultramafic
tites
takes place in an
mantle.
The emplacement of all
these rocks obviously
hydrotherrnal
activity.
environment of high heat flux and pervasive
Sediment cover at the rise crest is sparse, but on the upper flanks
can
of the rise,
accumulation of carbonate sediment, mainly pelagites,
siliceous
b e r a p i d a b o v e t h e C C D . F a r t h e r d o v , r nt h e f l a n k s o f t h e r i s e ,
pelagites
hemipelagites
are added to the growing sucand argillaceous
Finally,
turbidites
of abyssal plains may cover
cession.
the terrigenous
or j-nterfinger
with pelagic and hemipelagic sediment in the broad oceanic
margins.
Special facies
basins between midoceanic rises and continental
islands,
todeveloped locally
include lavas of seamounts and volcanic
gether with the reef carbonates that may surmount them and the archipelagic aprons of turbidites
that may surround them.
assemblage
During orogenesis,
scraps or slices of the ophiolitic
facies
of the ocean floor may be carried by thrusts across the contrasting
fn favorable instances,
as in Oman,
of rifted-margin
sediment prisms.
an intact
ophiolitic
slab may be thrust across slope assemblages that
in turn are thrust across shelf assemblages.
Where orogenic disruption
of a continental
margin is severe, care must be taken with detailed
interpretations
of the nature of basement beneath various successions,
for even the thick continental
rise sequences rest on an oceanic and
presumably ophiolitic
basement.
HYBRID RIFTS
where
Local plate divergence along or near complex plate junctures
transform moti-ons or convergence are dominant regionally
also give rise
locally
to rifted
basins.
Transtensional
basins along complex transforms
-35-
R i g h t - s l i p foult conlinues
on to norlhwest
lrregulor
bosin morgin
D et o c hm e nt
f o ul l s
l r r e g u l o rn o r m o l -s l i O
F o ul t s
S l r e l c h e do n d o t t e n u ot e d m o r g i n o l
floor
C o m p l e xu n c o n f o r m r t i e os n
o v e r l o o s i n s u b s u r f o ce
Slroighf
bostn
m o r gi n
d
C o m p l e xi n i e r s e c l i o n
\
L L - APART
ft-.t
t
Volconic
-
floor
BA S I N
C o mp l e x
corner
O l d e s li n t o c t b o s r n f i l l
R e m n o n t so f m o r g i n o l
r o c k s w i t h i n v o l c o ni c s
o bI r q u e -
T o l u s b r e c c i o so n d r o p r d
f o c r e s c h o n g e s b o s i n w or d
I
t \
! r
S m ol l t h r u s t p l o t e s
foults
Slrde blocks
il
il
B r o i d e dr i g h t- s l
z0ne
lrregulor bosin
m or g i n - f o l d s
resull of convergence
belweenboundory
r i g h f- s l i p f o u l l s
-N-
R r g h t-
f o u l t c o n t i n u e st o S E
MAP
pu11-apart basin
transtensional
Sketch map of idealized
Figure 19.
(from J.C. Crowell, I914, Origin of late Cenozoic basins in southern
Special
and Mineralogists
Soc. Econ. Paleontologists
California:
Pub. No. 22, p. L90-204).
-36-
\
rift,
whereas interarc
of incipient
3re a variety
of truly
are a variety
convergent plate junctures
crustal
separation i-s complete.
iranstensional
plex
1er
ueJlts
1s
ce
s
Basins
(fig.
basins formed near
oceanic basin where
f9)
basins may occur along the trend of transform sysTranstensional
or branching
segments, curving faults,
tems wherever en echelon fault
orienrather than a constraining,
faults
are arranged in a releasing,
plate motion.
Approxiof relative
tation with respect to the direction
segments
basins between en echelon transform
rrately equant pu1l-apart
llore elongate fault-wedge basins between
are perhaps most typical.
of the same
are variants
branching faults
or beside curving faults
behavior.
essential
of overall
tectonic
Pull apart basins may occur in a variety
rise-to-rise
transforms
settings.
Some depressions along intra-oceanic
probably have this basic origin.
Spreading centers along the Cayman
lie between en echelon transform
trend in the Caribbean also apparently
slippage
occur, continued lateral
collisions
Where continental
segments.
pu11-apart
after subduction has stopped may form local post-orogenic
the case for Carboniferous redbed basins in
basins, as was apparently
Perhaps the most-discussed transtensional
the marj-time Appalachians.
to developrelated
basins of Californla
basins, however, are the Tertiary
T
h
e deep
ment of both Paleogene and Neogene continental
borderlands.
of the
f
i
l
1
e
d
b
a
s
i
n
a
n
d
t
h
e
f
u
l
1
y
basins within
the Gulf of California
same group
a
r
e
m
e
m
b
e
r
s
o
f
t
h
e
m
o
d
e
r
n
Salton Depression at its northern end
of basins.
of the late
to the inception
Miocene transtensional
basins related
r
a
p
i
d
l
y
f
o
r
m
d
e
e
p
w
a
ter into which
t
o
Cenozoic San Andreas sysLem subsided
f
o
r
m
c
o
a
rse subsea
turbidites
to
were shed from nearby basement uplifts
p
a
r
t
l
y
floors
f
o
r
m
e
d
v
o
l
c
a
n
ic
fan complexes.
Contemporaneous volcanj-sm
stratia
b
b
r
e
v
i
a
t
e
d
Shallow si11s marked by starved,
within
some basins.
graphic sections led to stagnant conditions
o
r
g
a
n
o
g
e
n
i
c
d
e
p
o
s
i
t
s over
and
m
a
t
u
ration
f
l
u
x
f
a
v
o
r
e
d
r
a
p
i
d
High heat
that
large parts of some basins.
p
r
o
b
a
b
l
y
c
o
n
d
u
cive
s
e
e
m
e
s
p
e
c
i
a
l
l
y
was
Such conditions
characteristic.
p
r
o
x
i
m
a
l
r
e
s
e
r
voirs
r
.
^
r
i
t
h
i
n
t
u
r
b
i
d
i
t
e
to the concentratlon
of hydrocarbons
p
i
n
c
h
o
u
t
s
n
ear
1
o
c
a
l
in traps delineated
or
structures
by stratigraphic
t
h
e
i
n
t
e
r
i
o
r
b
y
w
r
e
n
ch
whole basin
basin margins.
Later deformation of
e
x
p
e
c
t
e
d
.
structures
to continued transform motions can also be
related
Interarc
Basins
(fig.
20)
Interarc
basins are one of the most puzzling types because they
related
to arc-trench
systems
represent clearly
extensional
tectonics
p
l
a
t
e
where the dominant
motion is convergent.
The key to understanding
that the high heat flux j-n magmatic arcs
their
origin
is to appreciate
High
spoils the integrity
of the lithosphere
across arc structures.
temperature at shallow depths below the magmatic arc softens the rigid
lithosphere
in the region behind the arc to move
and allorvs lithosphere
gap.
independently of lithosphere
a thermal
in the arc-trench
In effect,
curtain
into two separate
along the belt of magmatism saws the lithosphere
slabs.
Once this detachment is achieved, various relative
molions are
possi-ble.
In Sumatra, for example, transform-1ike
motion
strike-s1ip
occurs along the Semangko fault
dovrn the length
system that extends right
of the Barisan volcanic
occur
chain.
Even 1ocal pull-apart
structures
as unusually large volcano-tectonic
depressions along the trend of the
magmatic arc.
-37-
C O N TNI E N T A L
INTRA-ARC
MARGINz
BASIN
MARGINAL
/
,
- i-r\ / ',-\
\ /-1
\/
r\ lz
- : - , \ | 1| ,\
z1i7
|
- \l
. \ ,., 7/)
)/
ta,7
z-A
\
\/
/ r t l:r r z
sEAT
2
\
\
/
T R ENcH/
'
7
r
ffih
NNC STRUCTURE
^'"
OCEANTC
CRUST
REMNANT
ARC
I N T E R F A C E FRONTAL
ARC
BASIN
+ + +'+
+ + + + +
+ + + + + +
+ + + + +
Figure 20.
Schematic diagrams to illustrate
incipl-ent
developed (be1ow) interarc
basins in profile
view.
-38\
(above) and fu1ly
i
j-n the backarc
Elsewhere, divergence occurs betrveen lithosphere
.rea and that in the arc-trench
gap.
The geodynamic forces involved
3re not well understood, but the kinematics are c1ear.
Young, bare
:ceanic crust occurs in the Lau Basin west of Tonga, and also west of
:he active Marianas arc.
The Sea of Japan contains two main rift
structures
with the microcontinental
block of the Yamato Bank sandi;iched between.
The style of sea-f1oor spreading in these interar:c
rasins seems less regular than at midoceanic rise crests, for magnetic
,nomalies caused by magnetic reversals
cannot be identified
clearly.
Sti1l,
the structure
of the oceanic crust seems from present data to
:e the same as that in the open oceans, and is thus presumed to be an
ophiolite
sequence.
Interarc
basins probably begin their evolution
as complex grabens
along the volcanic chain, and may at that intra-arc
stage resemble the
Nicaraguan depression along the arc trend in Central America.
Mixed
volcanic and volcaniclastic
fill
of either non-marine or marine origln
rvould be expected initially.
A later phase of separation may be represented in the New Hebrides where a deep marj-ne trough has developed from
which large volcanoes emerge as islands loca11y.
When the frontal
arc
and remnant arc have separated fu11y, the flanks of each face the interarc basin as compound normal fault
scarps.
Volcaniclastic
debris shed
backward from the frontal
arc where magmatism continues will
in time
mask one flank of the basin with a rhick sediment cover, but in general
only pelagic sediment can be draped over the remnant arc.
The interior
of the interarc
basin will
undergo pelagic sedimentatlon
similar
to that
of the open ocean unless turbidite
wedges extending backward from the
active frontal
arc eventually cross it.
Special conditions
exist where one side of an interarc
basin is a
continental
margin, as is the case along the Sikhote-A1in
coast of the
Sea of Japan.
The evolution
of such a basin margin should resemble that
of a more normal rifted
continental
margin.
One significant
detail
of
geologic history
should differ;
namely, orogenic arc magmatism should
prevail
just before its
along the site of the continental
margin until
formation.
Such is the case for Sikhote-Alin.
Even the eastern flank of the Sea of Japan bears some resemblance
to a rifted
continental
margin because the Japanese arc is such a massive
crustal
element.
Faulted Neogene basins of considerable extent are
developed Lhere on crust of continental
or transitional
thickness.
Unlike those along rifted
continental
margins, horvever, these basins have
undergone pronounced local contractional
deformation quite early i-n
thpi
r
hi
cf nrrz
In summary, the interior
parts of interarc
basins are similar
to
other nascent oceanic basins, except perhaps for relative
proximity
to
sources of airborne ash.
The flanks are structurally
similar
to ri,fted
continental
margins but commonly receive much less sediment except in
special cases.
The clastic
sediment ordinarily
is markedly less mature.
There is probably a higber heat flux initially,
as the arc splits,
and
a likelihood
of prolonged high heat flux along the rear flank of the
frontal
arc r.+herecontinued deformation may also occur.
The ful1 implications of these conditions
for hydrocarbon genesis are not clearrbut
rapid maturation might be expected.
However, widespread source beds and
adequate reservoirs
seem unlikely
in most cases.
Duri-ng orogenesis that
results
in oceanj-c closure,
interarc
basins and intra-oceanic
arcs are
severely deformed and metamorphosed together as integral
parts of socalled eugeosynclinal
terranes,
and thereby become who11y unattractive
for exploration.
-3 9-
Where
Aleutians,
an interarc
cover older
are sPread
across oceanic areas, as in the
island arcs are iniEiated
the oceanic basin behind the arc is a marginal sea but not
shed from the new are may
turbidites
Volcaniclastic
basin;
aprons
the basi,n rouch as archipelagic
oceanic sediment within
seamount chains.
from basaltic
S U B D U C T I O NP R I S M S ( f i g .
2L)
related to the accretion of subduction comsettings
Depositional
(a) crustal
from
thickening
plexes have several aspects in cormon:
telescoping tends to counteract subsidence related to Plate
tectonic
(b) low heat flux that is associated
consumption and sedimentary loading;
prevails
during basin evolution;
with subduction of cool lithosphere
of the basins are asymmetric; and
(c) the overall
transverse profiles
Two major
is significant.
(d) flexural
subsidence of lithosphere
(a) the
to evaluate:
difficult
featirres of the basin are inherently
m
a
g
matic arcs
a
n
d
t
r
e
n
c
h
e
s
b
e
t
w
e
e
n
b
e
l
t
i
n
t
h
e
o
f
t
h
e
s
u
b
s
t
r
a
t
u
m
nature
i
s
a
n
d
conl
o
a
d
s
,
a
n
d
t
e
c
t
o
n
i
c
s
e
d
i
m
e
n
t
a
r
y
t
h
i
c
k
is hidden beneath
(b) the
a
n
d
c
o
n
t
i
n
u
e
s
;
s
u
b
d
u
c
t
i
o
n
p
a
r
t
w
h
i
l
e
a
c
t
i
v
e
i
n
changing
stantly
t
h
eir
m
o
d
i
f
i
e
d
d
u
r
i
n
g
i
s
c
o
n
t
i
n
u
a
l
l
y
b
a
s
i
n
s
t
h
e
g
e
o
m
e
t
r
y
o
f
original
their
b
e
f
o
r
e
m
o
d
i
f
i
e
d
i
s
f
u
r
t
h
e
r
a
n
d
t
e
c
t
o
n
i
s
m
,
evolution by concurrent
uplift
w
i
t
h
a
s
s
o
c
i
a
t
e
d
d
e
f
o
r
m
a
t
i
o
n
a
d
d
i
t
i
o
n
a
l
b
y
exposure to view on land
after
subduction
has ceased.
Oceanic Trenches
of trenches where plate consumption occurs
The sedimentary fills
as severely deb
u
t instead are incorporated
are not preserved intact,
m
o
r
p
h
o
l
o
gic crest of
T
h
e
c
o
m
p
l
e
x
e
s
.
subduction
formed strata within
s
u
bduction complex
u
p
l
i
f
t
e
d
a
n
d
i
s
o
s
t
a
t
i
c
a
l
l
y
thickened
fhe tectonically
i
n
n
e
r
s
l
ope of the
T
h
e
s
t
e
e
p
b
r
e
a
k
.
s
l
o
p
e
is located at the trench
a
n
d
t
h
e
Lrench axis is
z
o
n
e
s
u
b
d
u
c
t
i
o
n
a
c
t
i
v
e
trench thus represents the
t
r
e
n
c
h
f
l
oor at any
p
o
n
d
e
d
t
h
e
a
l
o
n
g
S
e
d
i
m
e
n
t
the deformation front.
a
d
y
n
a
m
ic balance
[
l
i
a
t
r
e
p
r
e
s
e
n
t
s
v
o
l
u
m
e
given tj-me is a steady-state
r
a
t
e
s
u
b
d
u
c
t
i
o
n
.
o
f
a
n
d
between rate of sedimentation
by flexure associThe deep water of the trench is formed primarily
u
p
b
ow of the ocean
b
r
o
a
d
A
c
o
m
p
e
n
s
a
t
o
r
y
afed with plate consuurption.
f
r
o
n
t
o
f the trench.
i
n
o
u
t
e
r
s
w
e
l
l
o
r
o
u
t
e
r
a
r
c
h
floor occurs as an
o
ffsets
oclanic
c
o
n
m
o
n
l
y
f
e
a
t
u
r
e
t
h
i
s
w
i
t
h
associated
Normal faulting
i
g
n
e
o
u
s
c
r
u
st just
r
n
a
f
i
c
o
f
s
u
r
f
a
c
e
sediment layers and the underlying
z
o
n
e
.
F
a
ult
s
u
b
d
u
c
t
i
o
n
i
n
t
o
t
h
e
of lithosphere
prior to insertion
o
f
t
h
e
t
r
e
n
c
h
r
eflect
o
u
t
e
r
s
l
o
p
e
g
e
n
t
l
e
on the
scarps present locally
d
i
s
p
ersed
t
u
r
b
i
d
i
t
e
s
t
r
e
n
c
h
,
o
f
t
h
e
Along the floor
this deformation.
o
f
o
n
t
o
P
d
e
p
o
s
i
t
e
d
a
r
e
t
r
e
n
c
h
o
f
t
h
e
d o r , r nt h e a x i s
longitudinally
c
r
u
s
t
t
h
a
t
i
s
o
c
e
a
n
i
c
o
f
t
h
e
or other sediments
oceani-c pelagites
passes
As oceanic lithosphere
carried into the trench by plaCe motion.
h
ave
l
a
y
e
r
s
t
h
a
t
s
e
d
i
m
e
n
t
beneath the inner slope of the trench, the
of
o
l
d
e
r
c
o
m
p
o
n
e
n
t
s
beneath
accumulated on it tend to be underthrust
o
f
f
t
h
e
b
e
s
c
r
a
p
e
d
to
the subduction complex, and simultaneously
descending slab of lithosphere.
feature
tectonic
The:subduction complex is thus an accretionary
profiles
of
Revealing reflection
complexity.
of immense structural
Japanese, and Sunda
Middle America, Aleutian,
the Lesser Antilles,
geometry appears to
The gross internal
Lrenches have been published.
deforrned
wedges of intensely
be dominated by a series of underlapping
zones that merge downward into a
thrust
separated by imbricate
strata
surface of d6collement at the top of the descending slab of lithosphere.
between igneous
near the interface
The d6collement surface is apparently
A R C- T R E N C H
GAP
ARC
TRENCH
O U T E RA R C H
z l!:
@
I
SLOPE
BASIN
FOREARC
BASIN
ONLAP
FOREARC
BASN
I
TRENCH
FILL
S U B D U C T I OC
NO M P L = E X
-\A,XfiQ.:;:s:::; lf :;i;,i':
i A{-)\t<N:";"ri:;j;i"":;5
"",r(
)O'sV,arxru##
l)iira)</,Wi't-6Ct)]
S'';
)>'61>',
);OO'.;'"
of oceanic
association
Schernatic diagrams to illustrate
Figure 21.
trench'slopebasin,andforearcbasinwithgrowingsubduction
Time runs toP to bottom'
complex.
-4Lt
sequence at the top of
and sedimentary components of Lhe ophiolite
r
n
ay form between pelagites
i
t
h
o
w
e
v
e
r
,
Locally,
oceanic lithosphere.
The
igneous layering.
t
h
e
p
e
n
e
t
r
a
t
e
m
a
y
or
clasEics,
and overlying
i
n
h
e
r
i
t
e
d
p
a
r
r
l
y
i
s
c
o
m
p
l
e
x
of the subduction
imbrication
internal
established between successively
from tecEonic boundaries initially
Also in part, however,
underthrusE components of the subduction complex.
of the
failure
s
t
r
u
c
tulal
l
a
t
e
r
is generated by
Lhe inter:nal imbrication
u
plifts
t
h
i
c
k
e
n
i
n
g
t
e
c
t
o
n
i
c
As
spreading,
growing mass by gravitational
of
d
r
a
g
t
h
e
t
r
e
n
c
h
,
t
h
e
deformed marerials beneath the inner slope of
o
v
e
r
s
t
e
e
Pen
t
o
t
e
n
d
s
at the toe of the slope
the descending lithosphere
o
f
a
n
g
l
e
t
h
e
The elevation of the trench slope break and
the slope.
bY internal
therefore,
the inner slope of the trench are controlled,
g
r
a
v
i
t
{
t
ionally
geornetry to a
that adjusts the overall
imbrication
load of the subduction complex may
The tectonic
stable configuration.
also tend to deepen the trench by plate flexure'
Tn strucof the subduction complex can be varied.
The materials
crumpled
i
s
o
c
l
i
n
a
l
l
y
s
l
a
b
s
,
L
h
r
u
s
t
i
n
t
a
c
t
i
n
c
l
u
d
e
m
a
y
t
h
e
y
tural style,
and
s
t
r
a
t
a
,
d
i
s
r
u
p
t
e
d
o
f
t
h
o
r
o
u
g
h
l
y
b
e
l
t
s
*
6
1
"
.
9
"
s
t
r
a
t
a
,
packets of
of these units include
Protoliths
tectonites.
metamorphosed blueschist
abyssal turbidites'
p
e
l
a
g
i
tes,
o
c
e
a
n
i
c
a
l
s
o
b
u
t
s
e
d
i
m
e
n
t
s
,
t
r
e
n
c
h
not only
c
o
m
p
lex is most
s
u
b
d
u
c
t
i
o
n
T
h
e
s
e
q
u
e
n
c
e
s
.
p
i
e
c
e
s
o
f
o
p
h
i
o
l
i
t
e
and
the most sediment
w
h
e
r
e
h
i
g
h
e
s
t
s
t
a
n
d
s
b
r
e
a
k
s
l
o
p
e
t
r
e
n
c
h
t
h
e
massive and
the
p
a
radoxically,
T
h
u
s
,
c
o
n
s
u
m
e
d
.
b
e
i
n
g
p
l
a
t
e
o
c
e
a
n
i
c
t
h
e
o
n
is present
subduction complex is most prominent where the trench is topographically
sequences
most subdued. The oceanic plate must carry thick turbidite
g
e
o
l
o
gic record
i
f
t
h
e
f
u
l
l
t
r
e
n
c
h
t
h
e
k
e
e
p
m
u
s
t
r
a
t
e
s
or sedimentation
is to be
c
o
m
p
l
e
x
s
u
b
d
u
c
t
i
o
n
i
n
t
h
e
p
r
e
s
e
r
v
e
d
a
s
z
o
n
e
of the subduction
r
e
c
o
r
d
'
1
i
t
t
l
e
l
e
a
v
e
t
r
e
n
c
h
e
s
Empty
impressive.
.Sf_ry_qBasins
Wittrin the active subduction zone along the inner slope of a trench,
p
resence of outcropping thrust faults or growing folds may give rise
the
to small depressions wtrere modest [hicknesses of slope strata can accumuThe substratum is deformed subduction complex rather than
late locally.
If the
s
equence upon r,rhich trench sediments are deposited'
the ophiolite
deu
p
l
i
f
t
t
o
t
r
y
i
n
g
e
s
c
a
l
a
t
o
r
i
m
p
e
r
f
e
c
t
a
s
a
n
r
e
g
a
r
d
e
d
i
s
trench slope
the
t
h
e
n
b
r
e
a
k
,
s
l
o
p
e
t
r
e
n
c
h
t
o
t
h
e
a
x
i
s
t
h
e
t
r
e
n
c
h
f
r
o
m
formed sediment
p
a
r
t
w
a
y
u
P
'
a
d
d
e
d
s
e
d
i
m
e
n
t
a
s
v
i
e
w
e
d
b
e
slope basins can
of slope basins is not rvell understood, but continued
The history
deformation probably deforms them quickly and adds them to fhe subduction
contacts within the complex, they
Although bounded by tectonic
complex.
folding or m6lange
by isoclinal
d
e
f
o
r
m
a
t
i
o
n
may well show less internal
to the
i
n
c
r
ementally
m
o
r
e
a
d
d
e
d
a
r
e
t
h
a
t
shearing than trench deposits
p
e
r
v
a
s
i
v
e deforf
o
r
o
p
p
o
r
C
u
n
i
t
y
n
o
r
e
subduction complex wilh accordingly
N
o
r
t
hwest
P
a
c
i
f
i
c
o
f
f
t
h
e
a
s
h
o
w
e
v
e
r
,
Cases apparently exist,
mation.
t
o
s
u
b
d
u
ction
r
e
l
a
t
i
o
n
i
n
h
i
g
h
a
r
e
s
o
today, where sedimentafion rates
build
d
e
p
o
s
i
t
s
c
a
n
s
l
o
p
e
a
s
s
o
c
i
a
t
e
d
a
n
d
rates that subsea fan complexes
r
i
ght
e
x
t
e
n
d
a
n
d
c
o
m
p
l
e
x
s
u
b
d
u
c
t
i
o
n
across the surface of the
steadily
you
i
f
o
r
,
t
h
e
n
e
x
i
s
t
n
o
t
d
o
e
s
across the subduction zone, The trench
d
i
s
t
i
n
c
t
i
o
n
a
n
Y
c
a
s
e
s
,
s
u
c
h
In
the trench is then overfilled.
will,
subduction
the resulting
and slope deposits within
between trench fill
structural
d
e
g
r
e
e
o
f
The overall
complex would be almost meaningless.
i
n
stances.
o
r
d
i
n
a
r
y
presumably would be less than in rnore
dislocation
-42-
subduction complexes would
of evolution,
Regardless of details
basins for hydrocarbon exploration.
Althougtr
appear to be unatLractive
the combination
organic-rich
source beds may occur within slope deposits,
disruption
conditions,
of migraof intense deforrnation, poor ieservoir
and low heat flux are discouraging
dislocation,
tion paths by structural
factors.
Forearc Basins
of slope basin, but are
Forearc basins can be regarded as a variety
treated separately here because they occur within the arc-trench
gap
between the trench slope break and the magmatic front of the arc.
They
are thus deposited outside the active subduction zone and do not undergo
of the subduction
the intensive and pervasive deformation characteristic
complex.
Nor do they experience the magmatism and metamorphism characteristic
of the magmatic arc terrane.
The late Mesozoic Great Va1ley Sequence
deposited in California
t
h
e
coeval Franciscan subduction complex
between
and the Sierra Nevada batholith
is a good example.
belt,
On the arc side of a forearc basin, sediments 1ap depositionally
upon eroded igneous and metamorphic rocks along the flank of the magmatic
arc.
During the evolution
of a forearc basin, there is commonly a progressive transgressive
enroachment of deposition across the eroded arc
terrane because the site of the magmatic belt tends to reatreat
with time.
This effect
is partly
h
o
w
e
v
e
r
,
b
y
m
o
v
e
m
e
n
f
s
o
n
a
f
a
ult
counteracted,
system that commonly lies along the flank of the arc structure
and sets the
basin side dor.m.
On the trench side of a forearc basin, the edge of the basin also
gradually away from i-ts center as the accretionary
tends to shift
subduction complex broadens, and the position
of the trench slope break
accordingly rnigrates.
The flank of the basin at the trench slope break
is essentially
defined tectonically
as the edge of the active subduction
zone.
Sediment deposited beyond the trench slope break is incorporated
within
the subduction complex by deformarion that is essentially
concurrent with sedimentation.
As the flank of the iorearc basin transgresses
across the growing subduclion complex, the basal contact of the undeformed
sequence with the subduction complex thus mav not develop as a simple
unconformity, but rafher as a time-transgressive
zone of tectonic dislocation mappable as a thrusf zone at any given place on the outcrop.
The substratum beneath the center of a forearc basin ls composed
1
of rock older than either the subducrion complex or the magmatic arc.
In
typical
cases, the floor of the forearc basin spans a continent-ocean
interface
and hence masks the transition
from continental
to oceanic
basement inherired
to establishment of the arc-trench
from a time prior
system.
I^lhere forearc basins are thickest,
the substratum is probably
oceanic crust.
A Paleozoic forearc basin in New ZeaIand, a Mesozoic
forearc basin in California,
and a Cenozoic forearc basin in Burma are
known to rest depositionally
on ophiolite
sequences along their oceanic
flanks.
Forearc basins are coinmonly elongate parallel
to the trend of the
arc-trench
system, but may occur as thick features only at intervals
along the length of an arc-trench
gap.
In effect, the sediment in a
forearc basin is ponded behind the threshold formed by the trench slope
break.
The amount that can accumulate is probably controlled
largely
by the local thickness of crust from place to place within
the arc-trench
gap.
The progressive expansion of a forearc basin across the flanks of
the adjacent arc terrane and subduction complex may be facilitated
by
-43-
t
-
H
f
:
in resPonse to the sediruent load
broad dovmflexure of lithosphere
of the forearc basin.
forearc basins are highly variable'
sedimentary facies within
dependentinpartupontheelevationofthebasinthresholdatthe
trenchslopebreakandinpartuponthesedimentationratewithinthe
of the trench sl0pe
to the rate of tectonic uprift
reration
basin,in
gaps include
arc-trench
of the ground within
configurations
break.
seas' deeps
h
e
l
f
lowlands'
terrestrial
mouhtainous tracts,
uplifted
f
o
rearc basins
o
f
Sediments
and deep-marine troughs.
marine terraces,
a
s
s
e
m
b
lages' shelf
complexes and shoreline
Ehus include fluvio-deltaic
andslopedeposits,starvedbasinplains,andsubseafanassociationsin
widelyvaryingproportions.ctasticsedimentiscommonlyirnmatureand
carbonates are rare.
Althoughthereareclearopportunitiesfordepositionoforganic_|
h"atl
depressiois,
*.tirr.
silled
rich source beds on marine stopes and in
fluxisabnormallylowandmaturationProcessesshouldbeslow.The
present
with magrnatic arcs is, apparently not
high heat flux aslociated
a
n
d refleca
s
s
e
m
b
l
a
g
e
s
mineral
oialenetic
far from the magmatic front.
Z
e
a
land and
o
f
N
e
w
of organic debris in ancient forearc basins
tivities
a
d
j
a
c
e
nt subf
o
r
t
h
o
s
e
as low as
irnply geothermal gradients
california
duction comPlexes.
Structureswithinforearcbasinsincludesomefoldsandfaults
thatapparentlyreflectdeformationconcurrentwithsedimentation.
deformation near the disl0caThese are related both to contractional
deformaand to extensional
tionar contact \"rith the subduction complex,
tionnearthefaultsystemmarkingtheflankofthearcstructure.
Progressiveregionaltilt,dowt'wardawayfromtheupliftedsubduction
complexandtowar<lthedovmfaultedzoneofthemagmaticarc,isalso
conmoninmanyforearcbasins.Ilajorstructuresareassociated,howof the subduction complex, perhaPs by isostatic
ever, with later uplift
At that
plate consumption end'
rebound when rhe glodynamic effects of
s
u
b
duction
t
h
e
above
time, the flank oi the forearc basin structurally
complexistiltedsteeplyupwardanderoded'Theremainingpartofthe
syncline
as)rrnmetric regional
a strongly
forearc basin then lies within
withitsgentlelimbdrapedacrosstheflankofthearc.Regional
toward the trench side of the basin
migration paths are thus Partly
updip migration plaths are later
but persistent
during sedimentation,
mainly toward the arc side of the basin'
FORELANDBASINS
Depositionalbasinsalongcontinentalflanksoforogenicbeltshave
belts
load of fold-thrust
several aspects in commont (u) the tectonic
of
s
u
b
s
i
d
e
n
c
e
to flexural
thaE lie adjacenL to the basins contributes
asyns
t
r
o
n
g
l
y
of the basins are
(b) the transverse profiles
the basins;
d
uring
(c) the orogenic flanks of the basins undergo deformation
metric;
g
r
a
dum
e
r
g
e
flanks of the basins
r.rJ {a) the cratonic
their evolution;
allywithplatformsequences.Tr,lomajorfeaturesofthebasinsare
importance of dif(a ) the relative
to evaluate:
difficult
inherently
ferentmechanismsofsubsidence;and(b)thegeothermalgradientsthaE
evolution'
in different
prevail
Parts of the basins during
b
e
n
e
a
t
h all pericratonic
s
u
b
s
E
r
a
t
u
m
that the
Isopachs indicatl
deposit
h
e
o
r
o
g
e
nic belt-during
t
o
w
a
r
d
dor^mvrard
foreland basins is tilted
d
e
v
e
l
o
p
rnent
s
t
r
u
c
t
u
r
a
l
l
a
t
e
r
t
h
a
t
contours indicate
Eion, but structure
t
e
ctonic
u
n
d
e
r
l
y
i
n
g
b
e
l
t
.
o
r
o
g
e
n
i
c
the substratum away from the
mav tirt
-44-
elements conmonly include Ehe margin of the craton and part of a
Composite foreland
prisrn older than the foreland basin.
miogeoclinal
o
r
o
genic episodes
s
u
c
c
e
s
s
i
v
e
o
f
e
f
f
e
c
t
s
the net
basins nay reflect
A
p
p
a
l
a
c
hian basin contains
t
h
e
F
o
r
e
x
a
m
p
l
e
,
margin.
along a continental
a
n
d Alleghenian
A
c
a
d
i
a
n
,
wedges from the Taconic,
separate clastic
c
a
s
e
s, both peripheral
s
u
c
h
I
n
b
e
l
t
.
orogenies in the adjacent orogenic
b
e
u
r
a
y
h
e
r
e
Present in the same
conponents as described
and retroarc
t
h
o
se two kinds of
b
e
t
r
,
r
e
e
n
Distinction
composite foreland basin.
of batholith
p
o
sitions
r
e
l
a
t
i
v
e
t
h
e
depends upon knowledge of
settings
o
r
o
gen.
n
e
a
r
b
y
i
n
t
h
e
a
g
e
s
belts of various
belts and ophiolite
Peripheral
Basins
(fig.
22)
foreland basins developed
foreland basins are the classic
Peripheral
margins have been
c
o
n
t
i
n
e
n
t
a
l
adjacenf to crustal lsuture belts where
oceanic crust
i
n
t
e
r
v
e
n
ing
t
h
e
a
f
t
e
r
subduction complexes
drarnm alainst
block
c
o
ntinental
t
h
e
o
n
f
o
r
m
e
d
i
s
basin
has been consumed. The foreland
F
o
r
t
a
n
d
A
r
k
o
m
a
T
h
e
z
o
n
e
.
dovmward toward the subduction
as it tilts
Worth basins adjacent to the Ouachita orogenic belt are examples'
basins may have two causes r'rhose
subsidence in peripheral
Flexural
with
flexure associated directly
First,
importance is unclear.
relative
n
o
r
t
h
ern
t
h
e
w
h
e
r
e
i
l
l
u
s
t
r
a
t
e
d
b
e
and may
plate consumption is possible,
i
n
to
d
o
w
n
w
a
r
d
t
i
l
t
e
d
n
o
w
p
l
a
t
f
o
r
m
i
s
continental
edge of the Australian
w
h
e
re
S
e
c
o
n
d
,
s
y
s
t
e
m
'
a
r
c
E
r
e
n
c
h
deep water near Timor along the Sunda
f
o
l
d
t
h
e
i
m
b
r
i
c
a
t
e
d
b
e
n
e
a
t
h
the edge of the continent is underLhrust
load of the latter
thrust belt of a subduction complex, the tectonic
o
f
that kind may have
l
o
a
d
A tectonic
flexure.
may induce additional
when Lhe Ouachita
b
a
s
i
n
for subsidence in the Arkoma
been responsible
over the edge of
n
o
r
t
h
w
a
r
d
sequence to the south ruas carried
overthrust
the Oklahoma platform.
basins
Folds and Lhrusts along the orogenic margin of peripheral
anaf
a
u
l
t
s
N
o
r
m
a
l
margin on one side'
<iefine an evolving structural
f
o
rm
m
a
y
t
r
e
n
c
h
e
s
to those on the outer slopes cf
logous in position
e
ither
f
r
o
m
b
a
s
i
n
t
h
e
sediment may enter
Clastic
side.
on the cratonic
a
s
s
o
c
i
a
t
e
d
c
o
m
m
o
n
l
y
wedges are most
side, although prominenE clastic
i
n
s
t
ances'
s
o
m
e
o
c
c
u
r
i
n
nay
Although turbidites
with the orogenic side.
m
a
y
be
t
r
a
n
s
p
o
r
t
Sediment
complexes are more typical.
fluvio-deltaic
m
a
r
i
n
e
o
f
p
r
o
p
o
r
t
i
o
n
The
locally.
either transverse or longitudinal
between subsidence rate
and non-marine beds is dependent on relations
marine
Source beds may be abundant where silled
rate.
and sedimentation
e
n
t
i
rely
i
s
s
e
c
t
i
o
n
depressions occur or may be nearly absent where the
clastics.
terrestrial
prisms buried beneath foreland
The fate of older miogeoclinal
basins.
facet of the development of peripheral
sediment is a critical
bumpers
l
i
k
e
b
l
o
c
k
s
prisms ride the edges of continental
Miogeoclinal
s
e
d
i
m
ent prism
occurs, Ehe marginal
collision
Where a crustal
on cars.
p
r
i
s
n
a
re tilted
t
h
e
Strata of
into the subduction zone.
is drawn first
a
nd
c
o
m
p
l
e
x
beneath the flank of the subduction
domward strongly
prism'
miogeoclinal
Within such a tilted
basin.
covered by the plripheral
basin, migration
foreland
Paths
asyrmetric
as well as in ti're overlying
T
he
b
e
l
t
.
o
r
o
g
e
n
i
c
t
h
e
o
f
f
l
a
n
k
f
r
o
m
t
h
e
a
w
a
y
are dominantly updip
l
o
ading
s
e
d
i
m
e
n
t
a
r
y
a
n
d
t
e
c
t
o
n
i
c
f
o
r
s
t
r
o
n
g
,
i
s
migr"iion
inducementfor
pror
e
m
a
r
k
a
b
l
e
t
h
e
t
h
a
t
e
l
s
e
w
h
e
r
e
a
r
g
u
e
d
I
h
a
v
e
both increase downdip.
such conmay reflecE
foreland
of the Persian Gulf peripheral
ductivity
p
r
i
sm of
s
e
d
i
m
e
n
t
r
i
f
t
e
d
m
a
r
g
i
n
i
r
u
n
e
n
s
e
a
n
In that region,
ditions.
-45-
II
j
1
m
+' + + +---\-+ l \ + + -1-,+
+ * + +
bo
o
tl
i* ** ++t
I
L
J
d
f.{
b
U)
.rl
I r!
.-l
r-{
m
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co
z
9
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O
l
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t!
J
o
o
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vll'l,
o-
9F
z (n
IJ
l
trJ E.
() ()
Cd
o
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o o
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o
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a
(D
a)
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tr
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a
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z
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a
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oo
rl
o
n
{J
d
0,
f
E
a
L)
6l
N
o
[.{
'r{
f..
has been drawn
Mesozoic age along the edge of the Arabian platforn
foreland basin'
T
e
r
t
i
ary
a
b
y
againsE the Zagros suture belt and covered
traps along
i
n
p
r
o
d
u
c
t
i
v
e
r
i
c
h
l
y
rocks are
BoEh llesozoic and Tertiary
a
long che
f
o
l
d
s
i
n
a
s
w
e
l
l
a
s
lirnb of the basin
the gentle foreland
orogenicflank.Deformationisjustsufficientrhowever,toimpose
If
and has not crumpled all the marine strata'
structuring
attractive
suturingproceedstoofaralongacollisionorogen,thefavorablecondeformation and
d.itions for hydrocarbon concenEration are destroyed by
m
igration paths
c
o
n
t
i
n
u
o
u
s
w
h
i
l
e
are oPtimal
metamorphism. conditions
z
o
n
e
s
'
exist updip away from subduction
still
Retroarc
Basins
(fig.
23)
magmatic
basins occur behind continental-margin
Retroarc foreland
by the
s
h
o
w
n
i
s
s
y
s
t
e
m
s
to arc-trench
Their clear relationship
arcs.
volcanic
c
o
m
p
l
e
x
,
s
u
b
d
u
c
t
i
o
n
o
r
maintained by trench
general parallelism
The
d
i
s
t
a
n
c
e
s
.
l
o
n
g
f
o
r
b
a
s
i
n
and foreland
belt,
chain or batholith
C
r
e
t
a
c
e
ous
m
a
r
i
n
e
t
h
e
a
n
d
A
n
d
e
s
Cenozoic Subandean basins east of the
s
a
l
ient
a
r
e
b
e
l
t
b
a
t
h
o
l
i
t
h
of the Rocky llountains east of the Mesozoic
s
u
bsidence
o
f
m
a
j
o
r
e
x
t
e
n
t
w
i
d
e
T
h
e
foreland basins'
examples of retroarc
b
lock
c
o
n
t
i
n
e
n
t
a
l
a
h
a
l
f
r
o
u
g
h
l
y
that
in the cretaceous basin indicates
a
c
o
n
t
i
n
e
n
t
a
l
m
a
r
g
i
n
i
n
by plate interactions
can be affected direcrly
sYstem.
arc-french
foreland basins is probably mainly
Flexural subsidence in retroarc
although a
belt,
the result of tectonj-c loading in a backarc fold-thrust
f
o
l
d-thrust
B
a
c
k
a
r
c
subduction occurs there.
amount of partial
limited
a
l
ong the
l
i
L
h
o
s
p
h
e
r
e
belts apparently develop when thermally softened
behind
l
i
t
h
o
s
p
h
e
r
e
a
s
motion
trend of the arc accoinmodates contractional
basins
R
e
t
r
o
a
r
c
g
a
p
'
in the arc-trench
the arc crowds toward lithosphere
the
a
c
r
o
s
s
k
i
n
e
m
a
t
i
c
s
overall
belts thus reflect
and backarc fold-thrust
b
a
cka
n
d
b
a
s
i
n
s
arc structure opPosite to that responsible for interarc
t
h
e
w
h
e
r
e
d
e
v
e
l
o
p
s
belt presurnably
The ioreland fold-thrust
arc rifts.
a
r
c
t
h
e
o
f
f
l
a
r
l
k
the rear
craton underthrusts
edge of the still-rigid
o
f
a
n older miogeoclinal prism
s
t
r
a
t
a
p
e
e
l
s
o
f
f
D
6
c
o
l
l
e
m
e
n
t
stiucture.
margin and stacks them into a telescoped pile of
along the continental
Parts of the flank of the retroarc basin are eventually
thrust sheets.
as well '
in the deformation
involved
complexes shed mainly from the orogenic flank but
Fltrvio-deltaic
strata
flank are perhaps the most characteristic
partly
from Ehe cratonic
d
e
eper
b
u
t
c
o
m
n
o
n
a
l
s
o
Shallow-marine deposits are
of reEroarc basins.
m
a
r
ine
s
i
l
b
e
d
w
h
e
r
e
Source beds may be common
marine strata are rare.
e
n
t
i
r
e
ly
i
s
s
e
c
t
i
o
n
depressions occur or may be nearly absent where the
s
t
r
u
c
t
ural
a
s
v
r
e
l
l
a
s
rraps
stratigraphic
Effective
clastics.
terrestial
b
a
s
ins'
r
e
t
r
o
a
r
c
flexures can be expected within
traps in gentle tectonic
b
a
s
i
n
s
r
e
t
r
o
a
r
c
prisms beneath
of older miogeoclinal
The tilting
as do
h
y
d
r
o
carbon concentration
o
n
i
n
f
l
u
e
n
c
e
a
n
,
t
r
o
.
r
g
u
"
may have
n
ot be so
m
a
y
Migration
basins.
conditions beneath peripheral
similar
b
e as draman
o
t
and loading may
because the amounts of tilting
forceful,
arc orogen
However, increased heat flux along the rear flank of the
tic.
Metamorphic mineral assemblages in the
may promote thermal maturation.
belt and fold-thrust
belt between batholith
infrastructural
so-called
basins'
within retroarc
d
e
b
r
i
s
o
r
g
a
n
i
c
o
f
be1t, as well as reflectivities
i
s
o
t
h
e
r
m
s
i
n
c
l
i
n
e
d
a
n
d
o
r
o
S
e
n
a
r
c
t
h
e
w
i
t
h
i
n
suggest a high heaE flux
t
h
ermal
m
o
v
i
n
g
a
C
o
n
c
e
i
v
a
b
l
y
,
b
e
1
t
.
the region of the fold-thrust
""io""
t
o
c
o
n
t
r
i
b
u
t
e
c
o
u
l
d
t
i
l
t
front as well as growing load and increasing
o
l
d
e
r
t
h
e
o
f
p
o
r
t
i
o
n
s
a
n
d
b
a
s
i
n
within the retroarc
updip misration
prisn below it.
mioglocllnal
-47-
B
0)
'r{
t
q)
< z
a{
(l-{
Y a
o
F <
t1
Ldm
E.
t
l
.
'
f
d
1
r
r{
o
F
a
^o
oo'
r
" o
o
l
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BROKEN FOREI.ANDS
basins have been discussed
foreland
and retroarc
Both peripheral
snooth
in terms of coherent as)rmmetric downbows with broad and generally
g
e
n
t
l
e
t
o
break
undulations
are comon, with only
floors.
Such features
p
l
a
t
e
s
o
f
l
i
thoof
integrity
to the overall
and attest
their continuity
the Laramide belt,
like
settings,
However, in some foreland
sphere.
involvement
basins reflect
fault-bounded
and local
baspment-cored uplifts
that promote this
The conditions
deformation.
of basement in foreland
sequences
Where rhin platform
understood.
kind of behavior are not fully
belt,
successions occupy the fold-thrust
rather than thick miogeoclinal
of
the tendency for d6collement nay be suppressed and the possibility
p
r
e
e
x
i
s
t
i
n
g
crustal
Where major
may be enhanced.
basement deformation
of
features like aulacogens exist in the foreland region, reactivation
and
blder fault
trends may also favor the bevelopment of block uplifts
local depressions rather than broad, continuous basins.
prequite heterogeneous conditions
regions,
Within broken foreland
Source beds
are possible with present data.
vail and few generalizations
silled
marine basins or even as non-marine sabkha demay occurinlocal
or
or wrench strucrures
posits in terrestrial
basins.
Local pull-apart
The
the region.
motions develop within
both may occur if transform-like
region
the same general foreland
of individual
basins within
character
greatly.
may well differ
OTITERBASINS
Two other kinds of basins are related to plate convergence, but
basins occur along
Transpressional
not in strictly
orogenic settings.
systems and remnant ocean basins lie along tectonic
complex transform
orogens.
suture belts of collision
strike from the,closing
Transpressional
Basins
(fig.
24)
Where a componenl of plate motion in a convergent sense is present
wrench folds may develop as en echelon features along
along a transforn,
The late Cenozoic folds of the
the margins of Lhe plates involved.
are examples.
central California
Coast Ranges beside the San Andreas fault
perhaps,
More significant,
basins.
Major synclines form local terrestrial
achieved by the formaLion of the en echelon
is che tectonic
thickening
to
is sufficient
where contraction
fold belt as a whole.r Especially
load that
the fold belt represents a tectonic
generate marginal thrusts,
basin along the flank of
may be sufficient
to down\rarp a foreland-like
Ehe fold belt awav from the transform.
Remnant Oce-ans (fig.
25)
orogen, sediment frorn
development of a collision
During sequential
basins, but also
is shed noE only into adjacent foreland
the highlands
The immense volumes of the
into remnant ocean basins.
longitudinally
Ganges delCa and the Bengal fan in the Bay of Bengal along tectonic
strike
fron the Hirnalayan Ranges are modern examples of Ehis phenomenon.
premay account for much of the so-called
Turbidites
wiEh this origin
i
s
on
f
l
y
s
c
h
d
u
m
p
e
d
S
u
c
h
o
r
o
g
e
n
i
c
b
e
l
t
s
.
orogenic flysch in classic
j
u
s
t
prior
o
c
e
a
n
i
c
b
a
s
i
n
p
r
e
v
i
o
u
s
l
y
s
t
a
r
v
e
d
older oceanic sediments in a
s
e
g
m
e
n
t
o
f
t
h
e
that sutures each suceessive
to the crustal
collision
Orogeny accompanies closure as the thick flysch
remnant lcean closed.
Subsequent post-orogenic
is deformed into a massive subduction complex.
-49-
t
i
L_
I
S+,
l:il
'.
:'t
:a
Ka.
l
t\
N
I
o
?fr
S A NJ O A O U I NV A L L E Y
SOUTHERN
"e
- : ; ^ , 1 . . . .!
C O N T O U B SO N T O P O F L O W E R P L I O C E N E
V A R I A E L E C O N T O U RI N T E R V A L
\
M A J O RS U F F A C E
S T R U C T UR E S
G E N E R A L I Z E OP O R O S I T Y
\
TERMINATIONS
[Y)
....)
t_
oose"err
OIL ANO
GASFIEL6
(AFTfR
HOOTS'
AEAR'
ANO
XL€M'ELL'
vrrench features
Sketch maP of generalized transpressional
Figure 24.
D ' R ' S e e l e y ' L 9 73 ' B a s i c
(f rorn Wj-lcox, R'E', T.i. Harding, and
8u11" V' 5J '
An. Assoc. Petroleum Geologists
wrench tectonics:
p. l4-9o).
t'"I
Y
FORELAND
B A S IN
SEDIMENT
DISPERSAL
D EL T AI C
DEPOCENTER
TURBIDITE
FLYSCH
FORELAND
BASIN
S U T U R EB E L T O F
D E F O R M EP
DR E - S U T U R E
FLYSCHWITH POST-SUTURE
M O L A S S EC O V E R
Schematic diagrarns to illusLrate
Progressive closure of
Figure 25.
remnant ocean basin by development of suture belt along collision
Time runs from top to bottom'
orogen seen in urap vlew'
-51-
...............
7
rqolasse is represented by fluvio-deltaic
couplexes that form a timetransgressive
facies most extensively
developed in the region marklng
the transition
frou fu1ly closed collision
orogen to remnant ocean
basin.
Both flysch and molasse are thus seen as time-transgressive
facies
whose age varies sequentially
along strike
within
the conpleted orogenlc
belt.
At any one place, however, molasse succeeds flysch,
and orogenic
events are sandwiched between their respective
times of deposition.
Settings
transitional
betr"reen pre-collision
reunant ocean basins and
post-collision
peripheral
foreland basins clearly
should exist during
early stages of collision
as subduction of a continental- m:1gin has just
besun.
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Atlantic
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r
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g
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s
y
n
c
l
i
n
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,
t
t
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(
e
d
.
)
,
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and
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a
l
e
o
n
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c
o
n
.
S
o
c
.
s
e
d
i
m
e
n
t
a
t
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o
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2
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,
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c
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o
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e
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r
n
e
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t
a
t
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:
a
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(
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,
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i
t
I
t ;
ti
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i
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Forearc
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-55-
t-----
ioreland
Basins
} i e c k e l , L . D . , l g T 0 , P a l e o z o i c a l l u v i a l d e p o s i t i oPnei tnt it jho eh cn e
pa
' l -R e e d ( e d s ' ) '
n dl AJp' C
' n t ar a
G'W'' F'J'
achians, p. 49-67 in Fisher'
Wiley InterCentral and Southern:
Studies of Appalachian Ceotogy;
,,.r*lli"ll3:,*iI;;,013.:;
andintrabasinderormaor,deltaic sedimenrarion
tion,UpperCretaceo''sofRockyllountainregi1
o 5n' : Spo' c '2E1c0o- 2n9' 2P' a l e o n t o l Paper No'
speciil
ogists ana ltineralogists
PoolerF.G.,LgT4rFlyschdeposirsofAntlerforelandbasin'westernUnited
S t a t e s , i n D i c k i n s o n ' W ' R ' t e a ' ) ' T e c t o n i c s a n d s e d Pi m
t ao t' i o2n2 ': SPo' c '5 8 - 8 2 '
u be' n N
special
and Mineraiogists
Econ. paleonrologists
*'B' CanpbeirL' lg74' Paleodrainage
Eisbacher, G.H., M'A' Carrigy ""i
in
basins of the Canadian Cordillera'
and late-o'ogt"i"
pattern
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RemnanEOceans
Curray,J.R-andD'G'Moore'LglL'GrowthofthA
en
Beer ni cgaa li du le1e' ,p - sve' a f8a2n' pa' 5n 6d3 - 5 7 2 '
Geol. soc.
Himalayas:
denudationinthe
IlorrisrR.C.rLgT4,CarboniferousrocksoftheOuachitaM
s ; flysch
s lo
o pu en t aainnds 'aAxri sk a no sf a a
,iorrg the unstable
a study of facies patterns
p
'
2
4
1
2
7
9
'
Paper 148'
Geol' Soc' Amerlca Speci"t
trough:
indicators
successions' polarity
A.H.G., Ig74, Flysch-opiriotit"
Mitchell,
i n a r c a n d c o l l i s i o n - t y p e o r o g " . " : N a t u r e , v . 2 4 B , p ' 7 4 7 -p1r o4b9l e' m o n T e t h y a n
melange' a world-wide
Gansser, A., Igl4, The ophiolitic
V ' 6 7 ' p - 4 1 9 - 5 0 7'
H
e
l
v
et''
ceotog'
examples: rtiog'
Collision
Orogens
GrahamrS.A.,W'R'Dickinson'andR'V'Ingersoll']^g'15'Him
y a: n - G
B e onlg' a l
s yaslt ae m
Appalachian-ouachita
model for flysch dispers.l-i;
' 213-286:
Soc. funerica Bull ' , V' 86' P
a n d t h e) H i m a l - a y a s :
C o n a g h a n' i l 9 l 3 ' P l a t e ^ t e c t o n i c s
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V' 2O' P' L-\?.
Earth Planet. Sci' Lettrs"
models
Guazzone' LITI' Plate teJtonic
C
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t
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d
I"l-, P' Elter,
Boccaletti,
forthedevelopmentofthe\testernAlpsandnorthernApennines:
p' 108-111'^-.
Nature Phys' Sci', v' 234'
:'gl4' Fragmentation of the Alpine
Wt'"t'
f
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l
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Alvarez' W., T' Cocozza' and
orogenicbeltbymicroplatedispersal:Nature'v'248'p'309-314'
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