EA45CH13-Hall ARI 14 August 2017 13:28

40°N

in
a 150 Ma: b 90 Ma:

arg
ASIA ASIA
Late Jurassic Late Cretaceous

ry m

s
arc
South
China

nic
ona

Intraocea
20°N

reti
Meso-Tethys Viet
nam

Bu
A cc
Sea

rm
a
Incertus Arc Luconia–
Meso-Tethys Dangerous
Grounds

Sum
Sea

atr
I-A transform
EQ SW

a
Ceno- Borneo
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Inc Tethys East Java–

ert Sea West Sulawesi
us
Ar
c
Ceno-Tethys Sula
Sea
Woyla

20°S Greater Spur

Sula India
Spur
Arc

Banda Banda New

embayment Guinea
Greater
India Argo INDIA
INDIA
40°S
Latitude

AUSTRALIA AUSTRALIA
40°N
c 45 Ma: ASIA d 5 Ma: ASIA
Middle Eocene Pliocene
South Pacific South
China China
Ocean INDIA
20°N Vie

Burm
Greater
Burm

tna Vie Philippine

India m Proto- tna Sea

a
m
a

South China
Sea Dangerous
Grounds
INDIA es
Celeba
Sum

Cre- Luconia
nsform

es Se

Ninety East FZ
taceous Celeb Philippine
atra

Sum
EQ crust Borneo Borneo
Sea

atra
Sea

Investigator FZ
Java Java
Cenozoic North
I-A tra

New
crust Sulawesi H Wharton
al Guinea
ma Basin
he
st FZ

Sula Spur ra
20°S
ty Ea

Banda New Indian

FZ

AUSTRALIA
Nine

embayment Guinea Ocean

gator
Investi

40°S
AUSTRALIA d
50°E 70°E 90°E 110°E 130°E 50°E 70°E 90°E 110°E 130°E
Longitude

Figure 5
Reconstructions of Southeast Asia at (a) 150 Ma, (b) 90 Ma, (c) 45 Ma, and (d) 5 Ma. See Hall (2012) for a detailed discussion of the
tectonic development of the region. Modified from Hall (2012). Abbreviations: FZ, fracture zone; I-A, India-Australia.

metamorphic rocks similar to those of Sarawak. Hall et al. (2009) and Hall (2012) interpreted the
various igneous, metamorphic, and sedimentary rocks dredged offshore to be part of a Luconia–
Dangerous Grounds block with a Paleozoic basement, but new dating of the metamorphic rocks
in Sarawak casts doubt on proposals of collision of a single block in either the Cretaceous (Hall
2012) or the Eocene (Hutchison 1996). Instead, the metamorphic rocks of Sarawak, Semitau, the
offshore Luconia and Dangerous Grounds areas, and Palawan seem more likely to be part of a wide
accretionary complex, including ophiolitic/arc rocks and Cathaysian sedimentary rocks, formed at
a subduction margin at the Asia–Pacific plate boundary (Breitfeld et al. 2017) between the Triassic
and early Late Cretaceous (Figure 5a).

www.annualreviews.org • New Views of the Geology of the Malay Archipelago 339

 EA45CH13-Hall ARI 14 August 2017 13:28

3.5. East Java

Dating of zircons from East Java provided the earliest and greatest surprise in mapping the Sun-
daland basement. The few outcrops of basement rocks from East Java, and results from offshore
drilling by oil companies, seemed to support Hamilton’s (1979) suggestion that the basement was
Cretaceous or early Tertiary melange. However, recent studies show that the southern part of
East Java is underlain by continental crust and suggest that there is similar crust beneath the Java
Sea and in the forearc south of Java.
Zircons in Cenozoic sedimentary and igneous rocks of East Java range in age from Archean to
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Cenozoic (Smyth et al. 2007, 2008a). The Cenozoic zircons record contemporaneous magmatism.
The distribution of older inherited zircons reveals two different sources. Clastic rocks in the
northern and western parts of East Java contain Cretaceous zircons, which probably came from
SW Borneo. In contrast, abundant volcanic rocks and minor intrusions of dacites and rhyolites in
the Southern Mountains Paleogene volcanic arc contain only Archaean to Cambrian zircons.
The zircon U-Pb ages support an Australian origin of the deep crust below East Java.
Geochronological data (e.g., Neumann & Fraser 2007, Southgate et al. 2011) suggest that source
rocks for Archean zircons are common only in western Australia (Figure 6), in the Pilbara (3.5–
2.9 Ga) and Yilgarn cratons (2.7–2.6 Ga). The zircon populations of East Java are similar (Smyth
et al. 2007). The similarities indicate a Gondwana continental fragment at depth, which rifted
from Australia during the Late Jurassic (Figure 5a) and collided with Sundaland, resulting in
the termination of Cretaceous subduction (Figure 5b). Continental crust was therefore present
beneath the arc in South Java when Cenozoic volcanism began in the Eocene (Figure 5c).
Australian-origin continental crust has also been suggested to form the basement of the south-
ern Makassar Strait and East Java Sea on the basis of data from exploration wells (Manur &
Barraclough 1994). Offshore seismic data suggest that there may be similar crust north and south
of Java. In the Java Sea there is a broadly horizontal regional unconformity at the base of a Cenozoic
section, and beneath it are synforms containing 5–10 km of section interpreted as Precambrian
to Permian–Triassic (Granath et al. 2011). Below the Cenozoic section south of Java is a broadly
flat-lying sequence several kilometers thick, which Deighton et al. (2011) and Nugraha & Hall
(2012) suggest is Mesozoic or older. The lack of significant deformation of the Cenozoic section,
and the thick pre-Cenozoic section, suggests that this sequence is a fragment of strong Australian
lithosphere now incorporated within a weaker Sundaland.

3.6. Sabah–Northwest Sulawesi

Several authors (e.g., Wakita et al. 1996, Parkinson et al. 1998, van Leeuwen et al. 2007) have
suggested that Gondwana continental fragments were accreted to Sundaland in the Cretaceous in
SE Kalimantan and Sulawesi. Jurassic fossils from South Sulawesi (Sukamto et al. 1990, Sukamto
& Westermann 1993) suggest an Australian continental fragment. In parts of western Sulawesi
there is evidence from inherited zircons, and from geochemistry of Cenozoic igneous rocks, of
underlying continental basement (Priadi et al. 1994; Bergman et al. 1996; Polvé et al. 1997, 2001;
Elburg & Foden 1999; Elburg et al. 2003). In Mesozoic reconstructions (Hall et al. 2009, Hall
2012), western Sulawesi was included with East Java in a single block, which now appears too
simple. Plio–Pleistocene basalts and basaltic andesites from southern Sabah have isotopic charac-
teristics that suggest an ancient, possibly Archaean component in the crust below (Macpherson
et al. 2010). NW Sulawesi includes schists and gneisses of the Malino Complex (van Leeuwen
et al. 2007) and metagranites with Carboniferous zircons, and in the Sulawesi Neck (Figure 7)

340 Hall