6
Chapter 1 Basin Classification
SUBDUCTION-RELATED BASINS
a INTRAOCEANIC
INTERARG (BAGKARG) BASIN
VOLGANIG ISLAND ARG
REMNANT ARG (INACTIVE)
FOREARG BASIN
- -k lr:SPREA()ING CENTER
INTERMEDIATE CRUST
(ARC STRUCTURE)
B· SI,IBOUCTION
ACCRETION
COMPlEX ( M~lANGE)
b
~
INTRA·ARG BASINS
100Kl1'
VOLGANIG ARG
AT CONTINENTAL MARGIN
OCEAN IC
CRUST
BATHOLITH BELT
Fig. 1.2a,b. Tectonic
classifieation of subduetion related basins
(Fig. 1.1 eontinued).
See text for explanation
often affeeted by subsequent convergenee along fault
zones. Basins similar to aulaeogens mayaiso be initiated during the closure of an oeean and during
orogenies.
Passive margin basins (Fig. l.1d). The initial stage of
a true oeeanie basin setting (or a proto-oeeanie rift system) is established when two divergent eontinents separate and new oeeanie ernst forms in the intervening
spaee. This does not neeessarily mean that such a basin
type fills with oeeanie sediments, but it does imply that
the eentral basin floor lies at least 2 to 3 km below sea
level. When such a basin widens due to eontinued divergent plate motions and aeeretion of oeeanie ernst
(drifting stage), its infilling with sediment tends to
more or less lag behind oeean spreading. Terrigenous
sediments are deposited predominantly along the two
eontinental margins of the growing oeean basin. The
marginal "basins" are eommonly not bordered by morphologieal highs. They develop on top of seaward thinning eontinental ernst with seaward inereasing (differential) subsidenee (Seet. 8.4). They therefore represent
asymmetrie depositional systems in whieh sediments.
eomrnonly build up in the form of a prism (Fig. 1.ld
and Seet. 12.2). Some ofthese marginal basins may be
affeeted and bordered by transform motions (tensionsheared basins). In a sediment-starved environment,
subsided transitional erust ean ereate deep plateaus
(sunk basins). In general, subsidenee of these marginal
basins tends to deerease with passing time, unless it is
reaetivated by heavy sediment loads.
Oceanic sag basins or nascent ocean basins oeeupy
the area between a mid-oeeanie ridge, including its rise,
and the outer edge of the transitional erust along a passive eontinental margin (Fig. 1.11). They eommonly
aeeumulate deep-sea fan or basin plain sediments. Due
to the advaneed eooling of the aging oeeanie erust, subsidenee is usually low, unless it is aetivated by thiek
sedimentary loading near the eontinental margin. Faultbounded basins of limited extent are eommon in eonjunetion with the growth of mid-oeeanie ridges
(Fig.l.1 e).
Basins related to subduction. Another group of basins is dominated by eonvergent plate motions and
orogenie deformation. Basins related to the development of subduetion eomplexes along island ares or aetive eontinental margins include deep-sea trenehes,
foreare basins, backare basins (Fig. l.2a and b), and
smaller slope basins and intra-are basins.
Deep-sea trench j/oors are eomposed of deseending
oeeanie erust. Therefore, some of them represent the
deepest elongate basins present on the globe. In areas
Chapter 1 Basin Classification
SUBDUCTION-RELATED BASINS
a INTRAOCEANIC
INTERARG (BAGKARG) BASIN
VOLGANIG ISLAND ARG
REMNANT ARG (INACTIVE)
FOREARG BASIN
- -k lr:SPREA()ING CENTER
INTERMEDIATE CRUST
(ARC STRUCTURE)
B· SI,IBOUCTION
ACCRETION
COMPlEX ( M~lANGE)
b
~
INTRA·ARG BASINS
100Kl1'
VOLGANIG ARG
AT CONTINENTAL MARGIN
OCEAN IC
CRUST
BATHOLITH BELT
Fig. 1.2a,b. Tectonic
classifieation of subduetion related basins
(Fig. 1.1 eontinued).
See text for explanation
often affeeted by subsequent convergenee along fault
zones. Basins similar to aulaeogens mayaiso be initiated during the closure of an oeean and during
orogenies.
Passive margin basins (Fig. l.1d). The initial stage of
a true oeeanie basin setting (or a proto-oeeanie rift system) is established when two divergent eontinents separate and new oeeanie ernst forms in the intervening
spaee. This does not neeessarily mean that such a basin
type fills with oeeanie sediments, but it does imply that
the eentral basin floor lies at least 2 to 3 km below sea
level. When such a basin widens due to eontinued divergent plate motions and aeeretion of oeeanie ernst
(drifting stage), its infilling with sediment tends to
more or less lag behind oeean spreading. Terrigenous
sediments are deposited predominantly along the two
eontinental margins of the growing oeean basin. The
marginal "basins" are eommonly not bordered by morphologieal highs. They develop on top of seaward thinning eontinental ernst with seaward inereasing (differential) subsidenee (Seet. 8.4). They therefore represent
asymmetrie depositional systems in whieh sediments.
eomrnonly build up in the form of a prism (Fig. 1.ld
and Seet. 12.2). Some ofthese marginal basins may be
affeeted and bordered by transform motions (tensionsheared basins). In a sediment-starved environment,
subsided transitional erust ean ereate deep plateaus
(sunk basins). In general, subsidenee of these marginal
basins tends to deerease with passing time, unless it is
reaetivated by heavy sediment loads.
Oceanic sag basins or nascent ocean basins oeeupy
the area between a mid-oeeanie ridge, including its rise,
and the outer edge of the transitional erust along a passive eontinental margin (Fig. 1.11). They eommonly
aeeumulate deep-sea fan or basin plain sediments. Due
to the advaneed eooling of the aging oeeanie erust, subsidenee is usually low, unless it is aetivated by thiek
sedimentary loading near the eontinental margin. Faultbounded basins of limited extent are eommon in eonjunetion with the growth of mid-oeeanie ridges
(Fig.l.1 e).
Basins related to subduction. Another group of basins is dominated by eonvergent plate motions and
orogenie deformation. Basins related to the development of subduetion eomplexes along island ares or aetive eontinental margins include deep-sea trenehes,
foreare basins, backare basins (Fig. l.2a and b), and
smaller slope basins and intra-are basins.
Deep-sea trench j/oors are eomposed of deseending
oeeanie erust. Therefore, some of them represent the
deepest elongate basins present on the globe. In areas