The Plate Tectonics of Cenozoic SE Asia and The Distribution of Land and Sea
The Plate Tectonics of Cenozoic SE Asia and The Distribution of Land and Sea
The Plate Tectonics of Cenozoic SE Asia and The Distribution of Land and Sea
99
Abstract
Introduction
100
R. Hall
20oN
PHILIPPINE
SEA
South
China
Sea
EURASIA
PACIFIC
10oN
Sulu
Sea
Celebes
Sea
CAROLINE
0o
Bismarck
Sea
Banda
Sea
Solomon
Sea
Woodlark Basin
INDIA
90oE
100oE
10oS
INDIA-AUSTRALIA
110oE
120oE
130oE
140oE
150oE
20oS
Fig.1. The larger tectonic plates of SE Asia and the SW Pacific. The many small ocean basins and the major strike-slip fault
systems at the margins of SE Asia and Australia are manifestations of the complexity of plate tectonics in the region which
requires a description in terms of many more plates than those shown.
101
AvalonianCadomian
terranes
Cimmerian
terranes
AFRICA
SOUTH
AMERICA
PrePalaeozoic
Gondwana
core
INDIA
AUSTRALIA
ANTARCTICA
Pacific margin
102
R. Hall
0 Ma
30Ma
45Ma
0Ma
30Ma
90Ma
45Ma
90Ma
120Ma
120Ma
120Ma
Fig.3. India and Australia separated from Gondwana in the Cretaceous. The map shows the late Cretaceous and Cenozoic
movement of these two major continental fragments north with respect to Asia and SE Asia, both of which are shown in their
present day positions for reference.
predicted by early plate tectonic models. Instead, India continued to move northwards, albeit at a slower rate than during the Cretaceous.
There is considerable disagreement amongst geologists about how the continued northward
movement was accommodated during the
Cenozoic, and its consequences. According to
Tapponnier and colleagues (e.g. Tapponnier et
al., 1982, 1986, 1990; Peltzer and Tapponnier,
1988; Briais et al., 1993) the impact of a rigid
Indian indentor on an Asian margin weakened
by subduction-related heating and magmatism
caused eastward extrusion and rotation of continental fragments, and opening of some of the
small oceanic marginal basins of SE Asia. The
progressive extrusion of continental fragments
to the east and consequent rotation of crustal
blocks has been simulated in laboratory experiments using plasticine (Fig.4), and the strike-slip
103
D
ASIA
SOUTH
CHINA
SOUTH
CHINA
SEA
INDIA
INDOCHINA
Fig.4. The impact of a rigid Indian indentor with Asia has been postulated to have caused the development of major strike-slip
faults as India progressively penetrated Asia (A to D). Analogue models produced during experiments (redrawn from Peltzer
and Tapponnier, 1988) show striking similarities to the major features of SE Asia.
collision with a composite SE Asia, which includes some of the earlier Gondwana fragments
to arrive, and also includes the island arcs
formed due to the subduction of oceanic crust
north of Australia. In east Indonesia the northward movement of Australia during the
Cenozoic has been marked by arc-continent collision and major strike-slip motion within the
north Australian margin. Further east, arc-continent collisions have been the result of elimination of marginal basins formed above subduction zones as Australia has moved north, and
this system of arcs and marginal basins can be
traced east along the margin of the Pacific plate
in Melanesia.
During the late Mesozoic and Cenozoic there
was subduction of the Pacific ocean to the east
of Asia, although the eastern margin of Asia and
SE Asia was probably a region of small plates
104
R. Hall
0 Ma
EURASIA
Present Day
40oN
PHILIPPINE
SEA
PLATE
INDIA
20oN
H
PACIFIC
PLATE
INDIAN
PLATE
AUSTRALIA
20oS
NEW
ZEALAND
40oS
120oE
90oE
150oE
180oE
60oS
ANTARCTICA
Fig.5. Present-day tectonic features of SE Asia and the SW Pacific. Light straight lines are selected marine magnetic anomalies. and
active spreading centres. White lines are subduction zones and strike-slip faults. The present extent of the Pacific plate is shown
in mid grey. Labelled filled areas are mainly arc, ophiolitic, and accreted material formed at plate margins during the Cenozoic, and
submarine arc regions, hot spot volcanic products, and oceanic plateaus. Pale grey areas represent submarine parts of the Eurasian
continental margins. Dark grey areas represent submarine parts of the Australian continental margins. See pages 126-131 for colour
plates of Figs.5 to 10. Letters represent marginal basins and tectonic features as follows:
Marginal Basins
A Japan Sea
B Okinawa Trough
C South China Sea
D Sulu Sea
E Celebes Sea
F Molucca Sea
G Banda Sea
H Andaman Sea
J West Philippine Basin
K Shikoku Basin
L Parece Vela Basin
M Mariana Trough
N
P
Q
R
S
T
U
V
W
X
Y
Z
Ayu Trough
Caroline Sea
Bismarck Sea
Solomon Sea
Woodlark Basin
Coral Sea
Tasman Sea
Loyalty Basin
Norfolk Basin
North Fiji Basin
South Fiji Basin
Lau Basin
Tectonic features
Ba Banda Arc
BH Birds Head
Ca Cagayan Arc
Fj Fiji
Ha Halmahera Arc
IB Izu-Bonin Arc
Ja Japan Arc
Lo Loyalty Islands
Lu Luzon Arc
Mk
Mn
NB
NC
NH
NI
Nng
Pa
Pk
Makassar Strait
Manus Island
New Britain Arc
New Caledonia
New Hebrides Arc
New Ireland
North New Guinea
Terranes
Papuan Ophiolite
Palau-Kyushu Ridge
Ry
Sa
Se
So
Sp
Su
TK
Ryukyu Arc
Sangihe Arc
Sepik Arc
Solomons Arc
Sula Platform
Sulu Arc
Three Kings
Rise
To Tonga Arc
Tu Tukang Besi
Platform
105
may not have existed, both for arc and continental terranes. Thus, the plate model can only be
an approximation. Some of the elements of the
model are deliberately represented in a stylistic
manner to convey the processes inferred rather
than display exactly what has happened, for example, the motion of the terranes of north New
Guinea.
Previous reconstructions which cover all or
parts of the region discussed here include those
of Katili (1975), Crook and Belbin (1978), Hamilton (1979), Briais et al. (1993), Burrett et al.
(1991), Daly et al. (1991), Lee and Lawver (1994),
Rangin et al. (1990), and Yan and Kroenke (1993)
who also produced an animated reconstruction
of the SW Pacific. The reader is referred to the
original papers for accounts of the earlier models. Some differences between the model here
and other models result from the choice of reference frames; some use the hotspot reference
frame, and others use a fixed Eurasia, whereas
these reconstructions use a palaeomagnetic reference frame. These choices result in different
palaeolatitudes and can cause other differences.
There have also been improvements in our
knowledge of global plate motions since the
earlier regional reconstructions. However, in
many cases the principal differences between
the different models result from different interpretations of geological data.
This paper gives an account of a plate tectonic
model for the Cenozoic development of the region based on my interpretations of a large
range of geological data. It summarises the regional tectonic development of SE Asia using a
plate model which has been animated using 1
Ma time-slices. Below is a brief account of the
model and its major features, which is followed
by a discussion of its principal implications for
biogeographers relating to the distribution of
land and sea during the last 30 million years.
Reconstructions
The model discussed here includes that developed earlier for SE Asia (Hall, 1996) which has
been extended to include the SW Pacific (Hall,
1997). Reconstructions of SE Asia and the SW
Pacific (Fig.5) shown on a global projection are
presented at 10 Ma intervals for the period 50-10
Ma (Figs.6-10). The reader is referred to Hall
(1995, 1996) for a more complete account of the
assumptions and data used in reconstructions of
SE Asia and for maps showing only SE Asia but
with more detail.
106
R. Hall
50 Ma
End Early
Eocene
EURASIA
40oN
PACIFIC
PLATE
20oN
INDIA
INDIAN
PLATE
AUSTRALIAN
PLATE
20oS
AUSTRALIA
40oS
90oE
180oE
ANTARCTICA
60oS
Fig.6. Reconstruction of the region at 50 Ma. The possible extent of Greater India and the Eurasian margin north of India are
shown schematically. Shortly before 50 Ma collision between the north Australian continental margin and an island arc had
emplaced ophiolites on the north New Guinea margin, and in New Caledonia, eliminating ocean crust formed at the former
Australian-Indian ocean spreading centre. Double black arrows indicate extension in Sundaland.
Configuration at 50 Ma
At 50 Ma (Fig.6) India and Australia were separate plates although their motions were not
greatly different. Transform faults linked the
slow-spreading Australia-Antarctic and the fast
spreading India-Australia spreading centres.
Some of the ophiolites of Sulawesi probably
formed at the India-Australia mid-ocean ridge.
107
spreading centre. Further east in the Pacific, Indian and Australian oceanic lithosphere had
been subducting northwards beneath the SepikPapuan arc in the early Tertiary. During the
Paleocene and early Eocene the New Guinea
Mesozoic passive margin collided with this intraoceanic arc causing emplacement of the Sepik
and Papuan ophiolites (Davies, 1971). Subsequently, most of the New Guinea margin was a
passive margin during the Paleogene but the
oceanic crust to the north is inferred to have
formed during the Mesozoic in an intra-oceanic
marginal basin behind the Sepik-Papuan arc.
The position and character of the east AustraliaPacific margin is also uncertain. Tasman and
Coral Sea opening had probably been driven by
subduction but the site of subduction must have
been considerably east of the Australian continent, beyond the Loyalty Rise and New Caledonia Rise. Spreading had ceased in both basins by
about 60 Ma (Paleocene). By the Paleocene it
appears that subduction east of New Caledonia
was to the east not to the west (Aitchison et al.,
1995). The history of this region remains poorly
known since it is almost entirely submarine, and
magnetic anomalies in this area are poorly defined.
Java and West Sulawesi were situated above a
trench where Indian plate lithosphere was
subducting towards the north. The character of
this boundary is shown as a simple arc but may
have included marginal basins and both strikeslip and convergent segments depending on its
local orientation. Extending plate boundaries
into the Pacific is very difficult. A very large area
of the West Pacific has been eliminated by subduction since 50 Ma which will continue to
cause major problems for reconstructions. However, there is clear evidence that this area resembled the present-day West Pacific in containing
marginal basins, intra-oceanic arcs and subduction zones. The Java subduction system linked
east into Pacific intra-oceanic subduction zones
required by the intra-oceanic arc rocks within
the Philippine Sea plate; parts of the east Philippines, the West Philippine basin and Halmahera
include arc rocks dating back at least to the Cretaceous. North of the Philippine Sea plate there
was a south-dipping subduction zone at the
southern edge of a Northern New Guinea plate.
50-40 Ma
Whatever the timing of India-Asia collision, a
consequence was the slowing of the rate of
108
plate convergence after anomaly C21 and a major change in spreading systems between
anomaly C20 and C19 at about 42 Ma. India and
Australia became one plate during this period
(Figs.6 and 7) and the ridge between them became inactive. Northward subduction of IndianAustralian lithosphere continued beneath the
Sunda-Java-Sulawesi arcs although the direction
of convergence may have changed. Rift basins
formed throughout Sundaland, but the timing of
their initial extension is uncertain because they
contain continental clastics which are poorly
dated, and their cause is therefore also uncertain. They may represent the consequences of
oblique convergence or extension due to relaxation in the over-riding plate in response to
India-Asia collision, enhanced by slowing of
subduction, further influenced by older structural fabrics.
The Java-Sulawesi subduction system continued into the West Pacific beneath the east Philippines and Halmahera arcs. Further east, the
direction of subduction was southward towards
Australia and this led to the formation of a
Melanesian arc system. During the Eocene the
extended eastern Australasian passive margin
had collided with the intra-oceanic arc already
emplaced in New Guinea resulting in emplacement of the New Caledonia ophiolite (Aitchison
et al., 1995; Meffre, 1995) followed by subduction polarity reversal. Subduction began beneath Papua New Guinea with major arc growth
producing the older parts of the New Britain,
Solomons and Tonga-Kermadec systems, leading to development of major marginal basins in
the SW Pacific whose remnants probably survive only in the Solomon Sea. This model postulates the initial formation of these arcs at the
Papuan-east Australian margin as previously
suggested by Crook and Belbin (1978) following
subduction flip, rather than by initiation of intraoceanic subduction within the Pacific plate outboard of Australia as suggested by Yan and
Kroenke (1993). The evidence for either proposal is limited but this model has the simplicity
of a single continuous Melanesian arc.
During this interval there were major changes
in the Pacific. The Pacific plate is widely said to
have changed its motion direction at 43 Ma,
based on the age of the bend in the HawaiianEmperor seamount chain, although this view
has recently been challenged by Norton (1995)
who attributes the bend to a moving hotspot
which became fixed only at 43 Ma. Subduction
of the Pacific-Northern New Guinea ridge
(Fig.7) led to massive outpouring of intra-oce-
R. Hall
anic volcanic rocks (Stern and Bloomer, 1992)
which formed the Izu-Bonin-Mariana arc system, and the Philippine Sea plate was a recognisable entity by the end of this period. There
was significant rotation of the Philippine Sea
plate between 50 and 40 Ma and the motion history of this plate (Hall et al., 1995) provides an
important constraint on development of the
eastern part of SE Asia. The West Philippine basin, Celebes Sea, and Makassar Strait opened as
single oceanic basin within the Philippine Sea
plate although the reconstructions probably underestimate the width of the Makassar Strait and
Celebes Sea, which may have been partially
subducted in the Miocene beneath west
Sulawesi.
The opening of the West Philippine-Celebes
Sea basin required the initiation of southward
subduction of the proto-South China Sea beneath Luzon and the Sulu arc. It is this subduction which caused renewed extension along the
South China margin, driven by slab-pull forces
due to subduction between eastern Borneo and
Luzon, and later led to sea-floor spreading in the
South China Sea, rather than indentor-driven
tectonics.
40-30 Ma
In this interval (Figs.7 and 8) the spreading of
the marginal basins of the West and SW Pacific
continued. Indian ocean subduction continued
at the Sunda-Java trenches, and also beneath the
arc extending from Sulawesi through the east
Philippines to Halmahera. Sea floor spreading
continued in the West Philippine-Celebes Sea
basin until about 34 Ma. This spreading centre
may been linked to backarc spreading of the
Caroline Sea which formed from about 40 Ma
due to subduction of the Pacific plate. The
Caroline Ridge is interpreted in part as a remnant arc resulting from Caroline Sea backarc
spreading, and the South Caroline arc ultimately
became the north New Guinea arc terranes. By
30 Ma the Caroline Sea was widening above a
subduction zone at which the newly-formed
Solomon Sea was being destroyed as the
Melanesian arc system migrated north. The
backarc basins in the SW Pacific were probably
very complex, as indicated by the anomalies in
the South Fiji basin, and will never be completely reconstructed because most of these basins have been subducted.
The Philippines-Halmahera arc was stationary, so spreading in the West Philippine-Celebes
109
40 Ma
Middle Eocene
EURASIA
40oN
PACIFIC
PLATE
20oN
INDIA
INDIAN
PLATE
20oS
AUSTRALIA
40oS
90oE
180oE
ANTARCTICA
60oS
Fig.7. Reconstruction of the region at 40 Ma. India and Australia were now parts of the same plate. An oceanic spreading centre
linked the north Makassar Strait, the Celebes Sea and the West Philippine basin. Spreading began at about this time in the
Caroline Sea, separating the Caroline Ridge remnant arc from the South Caroline arc. Spreading also began after subduction flip
in marginal basins around eastern Australasia producing the Solomon Sea and the island arcs of Melanesia.
110
R. Hall
30 Ma
Mid Oligocene
EURASIA
40oN
PACIFIC
PLATE
INDIA
20oN
INDIAN
PLATE
20oS
AUSTRALIA
40oS
90oE
180oE
60oS
ANTARCTICA
Fig.8. Reconstruction of the region at 30 Ma. Indentation of Eurasia by India led to extrusion of the Indochina block by
movement on the Red River fault and Wang Chao-Three Pagodas (WC-TP) faults. Slab pull due to southward subduction of the
proto-South China Sea caused extension of the South China and Indochina continental margin and the present South China Sea
began to open. A wide area of marginal basins separated the Melanesian arc from passive margins of eastern Australasia, shown
schematically between the Solomon Sea and the South Fiji basin.
111
20-10 Ma
The clockwise rotation of the Philippine Sea
plate necessitated changes in plate boundaries
throughout SE Asia which resulted in the tectonic pattern recognisable today (Figs.9 and 10).
These changes include the re-orientation of
spreading in the South China Sea, and the development of new subduction zones at the eastern
edge of Eurasia and in the SW Pacific. Continued northward motion of Australia caused the
counter-clockwise rotation of Borneo. Northern
Borneo is much more complex than shown.
There was volcanic activity and build-out of
delta and turbidite systems into the proto-South
China Sea basin. Major problems include the
source of sediment in the basins surrounding
central Borneo and the location and timing of
volcanic activity in Borneo. The remaining oceanic crust of the western proto-South China Sea,
and thinned continental crust of the passive
margin to the north, was thrust beneath Borneo
thickening the crust, resulting in rapid erosion
of sediments into the Neogene circum-Borneo
deltas, and ultimately leading to crustal melting.
The rotation of Borneo was accompanied by
counter-clockwise motion of west Sulawesi, and
smaller counter-clockwise rotations of adjacent
Sundaland blocks. In contrast, the north Malay
peninsula rotated clockwise, but remained
linked to both Indochina and the south Malay
peninsula. This allowed widening of basins in
the Gulf of Thailand, but the simple rigid plate
model overestimates the extension in this region. This extension was probably more widely
distributed
throughout
Sundaland
and
Indochina on many different faults. The Burma
plate became partly coupled to the northwardmoving Indian plate and began to move north
on the Sagaing fault leading to stretching of the
Sunda continental margin north of Sumatra, and
ultimately to ocean crust formation in the
Andaman Sea.
North Sumatra rotated counter-clockwise with
south Malaya, and as the rotation proceeded the
orientation of the Sumatran margin changed
with respect to the Indian plate motion vector.
The consequent increase in the convergent
component of motion, taken up by subduction,
may have increased magmatic activity in the arc
and weakened the upper plate, leading to formation of the dextral Sumatran strike-slip fault
system taking up the arc-parallel component of
India-Eurasia plate motion.
East of Borneo, the increased rate of subduction caused arc splitting in the Sulu arc and the
112
R. Hall
20 Ma
Early Miocene
EURASIA
40oN
PACIFIC
PLATE
INDIA
20oN
INDIAN
PLATE
20oS
AUSTRALIA
40oS
90oE
180oE
ANTARCTICA
60oS
Fig.9. Reconstruction of the region at 20 Ma. Collision of the north Australian margin in the region between the Birds Head
microcontinent and eastern New Guinea occurred at about 25 Ma. The Ontong Java plateau arrived at the Melanesian trench at
about 20 Ma. These two events caused major reorganisation of plate boundaries. Subduction of the Solomon Sea began at the
eastern New Guinea margin. Spreading began in the Parece Vela and Shikoku marginal basins. The north Australian margin
became a major left-lateral strike-slip system as the Philippine Sea-Caroline plate began to rotate clockwise. Movement on splays
of the Sorong fault system led to the collision of Australian continental fragments in Sulawesi. This in turn led to counterclockwise rotation of Borneo and related Sundaland fragments, eliminating the proto-South China Sea. The Sumatra fault
system was initiated.
113
10 Ma
Late Miocene
EURASIA
40oN
INDIA
PACIFIC
PLATE
20oN
AUSTRALIA
20oS
40oS
90oE
180oE
ANTARCTICA
60oS
Fig.10. Reconstruction of the region at 10 Ma. The Solomon Sea was being eliminated by subduction beneath eastern new Guinea
and beneath the New Hebrides arc. However, continued subduction led to development of new marginal basins within the period
10-0 Ma, including the Bismarck Sea, Woodlark basin, North Fiji basins, and Lau basin. The New Guinea terranes, formed in the
South Caroline arc, docked in New Guinea but continued to move in a wide left-lateral strike-slip zone. Further west, motion on
strands of the Sorong fault system caused the arrival of the Tukang Besi and Sula fragments in Sulawesi. Collision events at the
Eurasian continental margin in the Philippines, and subsequently between the Luzon arc and Taiwan, were accompanied by intraplate deformation, important strike-slip faulting and complex development of opposed subduction zones. Rotation of Borneo was
complete but motion of the Sumatran forearc slivers was associated with new spreading in the Andaman Sea.
wards this subduction zone. North of Luzon, sinistral strike-slip movement linked the
subducting west margin of the Philippine Sea
plate to subduction at the Ryukyu trench. Collision of Luzon and the Cagayan ridge with the
Eurasian continental margin in Mindoro and
114
duction resulting in local volcanic activity. At the
east edge of the Philippine Sea plate spreading
terminated in the Shikoku basin.
As a result of the change in plate boundaries,
fragments of continental crust were emplaced in
Sulawesi on splays at the western end of the
Sorong fault system. The earliest fragment to
collide is inferred to have been completely
underthrust beneath West Sulawesi and contributed to later crustal melting (Polv et al., 1997).
Later, the Tukang Besi platform separated from
the Birds Head and was carried west on the
Philippine Sea plate to collide with Sulawesi.
Locking of splays of the Sorong fault caused
subduction to initiate at the eastern margin of
the Molucca Sea, thus producing the Neogene
Halmahera arc. In this way the Molucca Sea became a separate plate as the double subduction
system developed.
After the collision of the Ontong Java plateau
with the Melanesian arc the Solomons became
attached to the Pacific plate. Westward subduction began on the SW side of Solomon Sea, beneath eastern New Guinea, eliminating most of
Solomon Sea and resulting in the formation of
Maramuni arc system. As the Solomon Sea was
eliminated, the South Caroline arc began to converge on the north New Guinea margin and the
arc terranes were translated west in the major
left-lateral shear zone, probably accompanied
by some rotation. In the southern part of the
Solomons Sea subduction was in the opposite
direction (eastward) and created the New Hebrides arc system. Spreading ceased in the South
Fiji basin.
10-0 Ma
At the beginning of this period SE Asia was
largely recognisable in its present form (Fig.10).
Rotation of Borneo was complete. This, with
collision in the central Philippines and Mindoro,
and continued northward movement of Australia, resulted in reorganisation of plate
boundaries and intra-plate deformation in the
Philippines. The Luzon arc came into collision
with the Eurasian margin in Taiwan. This may
be the cause of the most recent regional change
in plate motions at about 5 Ma. The Philippine
Sea plate rotation pole moved north from a position east of the plate; clockwise rotation continued but the change in motion caused re-orientation of existing, and development of new,
plate boundaries. Subduction continued at the
Manila, Sangihe and Halmahera trenches, and
R. Hall
new subduction began at the Negros and Philippine trenches. These subduction zones were
linked by strike-slip systems active within the
Philippines, and this intra-plate deformation created many very small fragments which are difficult to describe using rigid plate tectonics.
The Molucca Sea continued to close by subduction on both sides. At present the Sangihe
forearc has overridden the northern end of the
Halmahera arc, and is beginning to over-thrust
west Halmahera. In the Sorong fault zone, accretion of Tukang Besi to Sulawesi locked a strand
of the fault and initiated a new splay south of
the Sula platform. The Sula platform then collided with the east arm of Sulawesi, causing rotation of the east and north arms to their present
position, leading to southward subduction of
the Celebes Sea at the north Sulawesi trench.
The Eurasia-Philippine Sea plate-Australia triple junction was and remains a zone of microplates but within this contractional setting new
extension began in the Banda Sea. The Birds
Head moved north relative to Australia along a
strike-slip fault at the Aru basin edge. Mesozoic
ocean crust north of Timor was eliminated at the
eastern end of the Java trench by continued
northern motion of Australia which brought the
Australian margin into this trench as the volcanic
inner Banda arc propagated east. Seram began
to move east requiring subduction and strikeslip motion at the edges of this microplate. Since
5 Ma the southern Banda Sea has extended to its
present dimensions, and continental fragments
are now found in the Banda Sea ridges within
young volcanic crust. The Banda Sea is here interpreted to be very young as suggested by
Hamilton (1979) and others.
In west Sundaland, partitioning of convergence in Sumatra into orthogonal subduction
and strike-slip motion effectively established
one or more Sumatran forearc sliver plates. Extension on the strike-slip system linked to the
spreading centre in the Andaman Sea (Curray et
al., 1979). Within Eurasia reversal of motion on
the Red River system may have been one consequence of the regional change in plate motions.
Opening of the Ayu trough separated the
Caroline plate and Philippine Sea plate, although the rate of separation at this spreading
centre was very low. North of the Birds Head,
and further east in New Guinea, transpressional
movements were marked by deformation of arc
and ophiolite slivers separated by sedimentary
basins. Progressive westward motion of the
South Caroline arc within the left-lateral transpressional zone led to docking of the north New
115
30 Ma
Mid Oligocene
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10oN
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LAND
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PLATFORMS
DEEP SEA
100oE
10oS
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SHALLOW SEA
90oE
0o
110oE
120oE
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150oE
20oS
Fig.11. Postulated distribution of land and sea in SE Asia at 30 Ma. No attempt has been made to represent topography with Asia
and Indochina. Much of the area north and east of the Indian collision zone must have been highlands.
116
R. Hall
25 Ma
End Oligocene
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117
20 Ma
Early Miocene
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extensive seismic surveys of SE Asia for hydrocarbons. New research could provide further
detail and biogeographers themselves could
also contribute by, for example, mapping distributions of fossil plants and interpreting their
environments.
Land and sea for 30-0 Ma
Figs.11 to 16 are an attempt to compile the general features of land and sea onto maps of the
tectonic reconstructions showing 5 million year
intervals between 30 and 5 Ma for the region of
SE Asia. The maps may be useful in indicating
the likely geographical connections and barriers
and the periods when these were in existence.
There are few studies that compile this type of
information and all cover limited parts of area
for limited times. Thus these maps are based on
118
R. Hall
15 Ma
Middle Miocene
aa
aa
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aaaa
aaaa
aaa
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aaa
VOLCANOES
HIGHLAND
aa
aa
aa
aa
aa
aa aa aa
aa
LAND
aa CARBONATE
aa PLATFORMS
SHALLOW SEA
DEEP SEA
aaaaaaa
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Asia down major river systems. Much of southern Sundaland was the site of deposition of alluvial, fluvial and deltaic sediments. There were
major embayments in the eastern Asian margin
formed by the South China Sea, the proto-South
China Sea and the Celebes Sea-Makassar Strait.
Separating these were elongate bathymetric features which were probably mainly shallow water with intermittent emergent areas, notably
where arc volcanoes were active. The southernmost promontory was the Sulawesi-PhilippinesHalmahera arc which could have provided a
pathway into the Pacific, via volcanic island
stepping stones, for organisms that could cross
seawater. The other promontories terminated in
the deep ocean area of the Pacific.
At about 25 Ma (Fig.12) the north Australian
margin came into contact with Sulawesi and the
Halmahera arc, and this could have created a
discontinuous land connection via the island
119
10 Ma
Late Miocene
aaa
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aa aaa
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aa aa aa
a aaa aa
aa
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a
aaaaa
aaaaa
VOLCANOES
HIGHLAND
aaaa
aaaa
aaaaaa
aaaaaa
aaaa
aaaa aaaaaa
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LAND
aa
aa CARBONATE
PLATFORMS
aa
aa aa
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aa
SHALLOW SEA
DEEP SEA
120
R. Hall
5 Ma
Early Pliocene
aa
aa
a
a
aa
aa
aaa
aaa
VOLCANOES
HIGHLAND
LAND
aa
aa CARBONATE
PLATFORMS
SHALLOW SEA
DEEP SEA
aa
aa
aa aa aa
a aaa aa
aa
aaaaa
aaaaa a
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aa aa
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gent and the central mountains on the SarawakKalimantan border extending into Sabah became wider and higher with time. It is important
to be aware that within this convergent setting
deep basins also formed (e.g., Sulu Sea, Banda
Sea) which must have represented new barriers
to dispersal which formed at the same time as
new land pathways were established.
Conclusions
There are three important periods in regional
development. At about 45 Ma plate boundaries
changed, probably as a result of India-Asia collision. From a biogeographical viewpoint the arrival of India would have led to a movement of
Gondwana plants and animals into Asia. Mountain building resulting from the collision led to
major changes in habitats, and climate, accom-
121
10 Ma
Equatorial
Undercurrent
16 Ma
20 Ma
South Equatorial
Current
22 Ma
30 Ma
Indonesian Seaway
South Equatorial
Current
Fig.17. Circulation patterns of surface and near-surface waters in the Pacific ocean inferred by Kennett et al. (1985) at
three stages during the Neogene as the Indonesian sea-way
closed. Black arrows indicate cold currents and unfilled arrows indicate warm currents
Fig.18. Possible circulation patterns of surface and near-surface waters in eastern Indonesia shown on the tectonic reconstructions of this paper. The currents postulated are
based on Kennett et al. (1985) and present-day circulation
patterns (Fine et al., 1994).
122
The second major period is around 25 Ma
when plate boundaries and motions changed
again, partly due to collision between the north
Australian margin and arcs to the north. This,
together with collision of the Melanesian arcs
and the Ontong Java plateau, changed the tectonics of the oceanic-arc region east of Asia
(Philippines, Celebes Sea, Sulu Sea, Philippine
Sea, Caroline Sea, north New Guinea, New Britain, Solomons, Tonga). The 25 Ma event was
probably the most important tectonic event
from the biogeographical point of view as it led
to new, albeit discontinuous, links between
Australia via Sulawesi into SE Asia across areas
which were mainly shallow marine and locally
included land. It also resulted in a very long discontinuous island arc link between Asia and
Melanesia. However, as the pathways between
Australia and Sundaland came into existence,
new barriers also formed. The central Borneo
mountains began to rise in the early Miocene
and became a regional drainage divide sending
sediment north into the Sarawak basins and
Baram delta, and southeast into the Tarakan and
Mahakam deltas. North of Borneo, as the protoSouth China Sea closed, the Oligo-Miocene
South China Sea widened and the Sulu Sea
opened. As the distance between Australia and
Sulawesi closed, the deep Banda Sea opened.
Thus, movement of plants and animals between
Australia and Sundaland would have remained
difficult. Perhaps it was this zone of barriers,
close to a region of deep and former deep
ocean barriers separating Borneo and Australia,
which is the origin of Wallaces line. The narrow
Makassar Strait, which at its south end terminates in a long-lived discontinuous carbonate
platform, could not alone have been a major
barrier to dispersal.
Plate motions and boundaries changed again
at about 5 Ma, possibly as a consequence of arccontinent collision in Taiwan, and in the last 5
Ma there has been renewed tectonic activity and
a significant increase in land and highlands all
round the margins of SE Asia. A number of new
dispersal pathways developed across the region, for example those linking Taiwan and
New Guinea through the Philippines and North
Moluccas, and connecting New Guinea to Thailand via the Banda and Sunda arcs. It is also
probable that there was an increase in the range
of habitats along these routes, due to elevation
of mountains, and likely associated variations in
rainfall.
Disentangling the contribution of geology to
biogeographic patterns is not simple. Geology
R. Hall
and tectonics could be a controlling factor in
some cases. Cicada distributions in New Guinea
suggest a geological control (Boer and Duffels,
1996), and slicing of crustal fragments from the
Birds Head could have caused influxes of faunas and floras into Sulawesi from Australia at
intervals in the last 20 Ma. However, geology
and tectonics also influence other variables
which are more subtle controls on biogeographic patterns. Sea-level, elevation of land areas, soil, wind and water movements, and climate are all examples of factors upon which
there is some geological influence. Climatic controls are too difficult to model at present, but at
some time in the future it will be possible to use
the tectonic models as the basis for simulation of
ancient climates in SE Asia. It is notable that at
present there are more highland areas, and a
greater area of land than at any time during the
last 30 million years. This is consistent with
rather restricted areas of modern carbonate platforms which are limited in part by clastic sediment influx. The present distribution and size of
shallow water carbonate areas may in part reflect a period of relatively low sea-level, but also
record the recent rise of mountains due to tectonic forces as the region is compressed between Asia and Australia.
Some of the biogeographic patterns in SE Asia
at present are difficult to relate simply to geology, for example, the distance between Borneo
and Sulawesi (Wallaces line and equivalents)
should have been as easy to cross as the barriers
between Australia and Sulawesi. This raises the
question of the longevity of biogeographic patterns, about which we currently lack adequate
information. During the last million years there
have been periods of low sea-level associated
with glacial intervals when far greater areas of
land were emergent than at present, and the
present areas are significantly greater than those
during the Neogene. Much of the Sunda shelf
would have been emergent although in eastern
Indonesia there are many narrow deep water
areas (such as the Makassar Strait) which would
have remained physical barriers. However, elsewhere large sea-level falls would have separated
some formerly connected ocean basins as shallow water areas became emergent, changing
oceanic circulation patterns and modifying
weather and climate (e.g. Huang et al., 1997).
Fluctuations in temperatures and rainfall are
likely to have been more extreme at intervals in
the last million years than in the preceding 30
million years. Therefore, the last period of geological history, perhaps one million years or
123
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125
Robert Hall
SE Asia Research Group, Department of Geology, Royal Holloway University of London
Captions
Fig.5. Present-day tectonic features of SE Asia and the SW Pacific. Yellow lines are selected marine magnetic anomalies. Cyan lines
outline bathymetric features. Red lines are active spreading centres. White lines are subduction zones and strike-slip faults. The
present extent of the Pacific plate is shown in pale blue. Areas filled with green are mainly arc, ophiolitic, and accreted material
formed at plate margins during the Cenozoic. Areas filled in cyan are submarine arc regions, hot spot volcanic products, and
oceanic plateaus. Pale yellow areas represent submarine parts of the Eurasian continental margins. Pale and deep pink areas
represent submarine parts of the Australian continental margins. Letters represent marginal basins and tectonic features as follows:
Marginal Basins
A Japan Sea
B Okinawa Trough
C South China Sea
D Sulu Sea
E Celebes Sea
F Molucca Sea
G Banda Sea
H Andaman Sea
J West Philippine Basin
K Shikoku Basin
L Parece Vela Basin
M Mariana Trough
N
P
Q
R
S
T
U
V
W
X
Y
Z
Ayu Trough
Caroline Sea
Bismarck Sea
Solomon Sea
Woodlark Basin
Coral Sea
Tasman Sea
Loyalty Basin
Norfolk Basin
North Fiji Basin
South Fiji Basin
Lau Basin
Tectonic features
Ba Banda Arc
BH Birds Head
Ca Cagayan Arc
Fj Fiji
Ha Halmahera Arc
IB Izu-Bonin Arc
Ja Japan Arc
Lo Loyalty Islands
Lu Luzon Arc
Mk
Mn
NB
NC
NH
NI
Nng
Pa
Pk
Makassar Strait
Manus Island
New Britain Arc
New Caledonia
New Hebrides Arc
New Ireland
North New Guinea
Terranes
Papuan Ophiolite
Palau-Kyushu Ridge
Ry
Sa
Se
So
Sp
Su
TK
Ryukyu Arc
Sangihe Arc
Sepik Arc
Solomons Arc
Sula Platform
Sulu Arc
Three Kings
Rise
To Tonga Arc
Tu Tukang Besi
Platform
Fig.6. Reconstruction of the region at 50 Ma. The possible extent of Greater India and the Eurasian margin north of India are
shown schematically. Shortly before 50 Ma collision between the north Australian continental margin and an island arc had
emplaced ophiolites on the north New Guinea margin, and in New Caledonia, eliminating ocean crust formed at the former
Australian-Indian ocean spreading centre. Double black arrows indicate extension in Sundaland.
Fig.7. Reconstruction of the region at 40 Ma. India and Australia were now parts of the same plate. An oceanic spreading centre
linked the north Makassar Strait, the Celebes Sea and the West Philippine basin. Spreading began at about this time in the
Caroline Sea, separating the Caroline Ridge remnant arc from the South Caroline arc. Spreading also began after subduction flip
in marginal basins around eastern Australasia producing the Solomon Sea and the island arcs of Melanesia.
Fig.8. Reconstruction of the region at 30 Ma. Indentation of Eurasia by India led to extrusion of the Indochina block by
movement on the Red River Fault and Wang Chao-Three Pagodas (WC-TP) Faults. Slab pull due to southward subduction of
the proto-South China Sea caused extension of the South China and Indochina continental margin and the present South China
Sea began to open. A wide area of marginal basins separated the Melanesian arc from passive margins of eastern Australasia,
shown schematically between the Solomon Sea and the South Fiji basin.
Fig.9. Reconstruction of the region at 20 Ma. Collision of the north Australian margin in the region between the Birds Head
microcontinent and eastern New Guinea occurred at about 25 Ma. The Ontong Java plateau arrived at the Melanesian trench
at about 20 Ma. These two events caused major reorganisation of plate boundaries. Subduction of the Solomon Sea began at
the eastern New Guinea margin. Spreading began in the Parece Vela and Shikoku marginal basins. The north Australian margin
became a major left-lateral strike-slip system as the Philippine Sea-Caroline plate began to rotate clockwise. Movement on
splays of the Sorong Fault system led to the collision of Australian continental fragments in Sulawesi. This in turn led to counterclockwise rotation of Borneo and related Sundaland fragments, eliminating the proto-South China Sea. The Sumatra Fault
system was initiated.
Fig.10. Reconstruction of the region at 10 Ma. The Solomon Sea was being eliminated by subduction beneath eastern new Guinea
and beneath the New Hebrides arc. However, continued subduction led to development of new marginal basins within the period
10-0 Ma, including the Bismarck Sea, Woodlark basin, North Fiji basins, and Lau basin. The New Guinea terranes, formed in the
South Caroline arc, docked in New Guinea but continued to move in a wide left-lateral strike-slip zone. Further west, motion on
strands of the Sorong Fault system caused the arrival of the Tukang Besi and Sula fragments in Sulawesi. Collision events at the
Eurasian continental margin in the Philippines, and subsequently between the Luzon arc and Taiwan, were accompanied by intraplate deformation, important strike-slip faulting and complex development of opposed subduction zones. Rotation of Borneo was
complete but motion of the Sumatran forearc slivers was associated with new spreading in the Andaman Sea.
126
R. Hall
0 Ma
EURASIA
Present Day
40oN
PHILIPPINE
SEA
PLATE
INDIA
20oN
H
PACIFIC
PLATE
INDIAN
PLATE
AUSTRALIA
20oS
NEW
ZEALAND
40oS
90oE
120oE
ANTARCTICA
150oE
180oE
60oS
127
50 Ma
End Early
Eocene
EURASIA
40oN
PACIFIC
PLATE
20oN
INDIA
INDIAN
PLATE
AUSTRALIAN
PLATE
20oS
AUSTRALIA
40oS
90oE
180oE
ANTARCTICA
60oS
128
R. Hall
40 Ma
Middle Eocene
EURASIA
40oN
PACIFIC
PLATE
20oN
INDIA
INDIAN
PLATE
20oS
AUSTRALIA
40oS
90oE
180oE
ANTARCTICA
60oS
129
30 Ma
Mid Oligocene
EURASIA
40oN
PACIFIC
PLATE
INDIA
20oN
INDIAN
PLATE
20oS
AUSTRALIA
40oS
90oE
180oE
ANTARCTICA
60oS
130
R. Hall
20 Ma
Early Miocene
EURASIA
40oN
PACIFIC
PLATE
INDIA
20oN
INDIAN
PLATE
20oS
AUSTRALIA
40oS
90oE
180oE
ANTARCTICA
60oS
131
10 Ma
Late Miocene
EURASIA
40oN
INDIA
PACIFIC
PLATE
20oN
AUSTRALIA
20oS
40oS
90oE
180oE
ANTARCTICA
60oS