Embed Size (px)
Citation preview
Stratigraphic constraints on suture models for eastern Indonesia
J. Milsom
Department of Geological Sciences, University College London, London WC1E 6BT, UK
Received 10 May 2000; accepted 29 June 2000
Abstract
Although collision in eastern Indonesia is now accreting the Australian continent to Southeast Asia, the small North and South Bandaoceanic basins within the suture zone are interpreted as Late Cenozoic extensional features. Stratigraphic columns from the surroundingislands conform to one of three generalised patterns, two of which can be related to the margins of SE Asia (Sundaland) and the Australiancontinent, respectively. The third system, which is dominant in the outer Banda Arc and eastern Sulawesi, is associated with a microcontinentthat was rifted from Australia in the Jurassic, drifted northwards ahead of Australia in the Cretaceous and collided with the Sundaland Marginin the Paleogene. Subsequent collapse of the resulting collision orogen led to rapid extension and the formation of the Banda Sea behind theOuter Banda Arc thrust belt. Eastern Indonesia thus duplicates a pattern familiar in the Mediterranean. The Tertiary compressional structuresof the region cannot be explained solely in terms of the most recent collision, which began only in the Pliocene.q 2000 Elsevier Science Ltd.All rights reserved.
Keywords: Eastern Indonesia; Banda Arc; Eurasian Plates
1. Introduction
Suturing of northern Australia to SE Asia takes placewithin a diffuse and still poorly understood region (Fig. 1)where relative motions between the Indo-Australian andEurasian Plates are absorbed by subduction beneath theSunda Arc and collision around the strongly curved BandaArc. The plate boundary, which south of the Sunda Arc ismarked by a deep trench, is replaced in the Banda Arc by aseries of relatively shallow troughs. There is no significantoffset in the line of active and recent volcanoes but the twoforearcs are very different. Except in the area to the west ofSumatra, the Sunda forearc ridge is entirely submarine, butthe Banda forearc (Outer Banda Arc) is capped by largeislands such as Timor, Tanimbar, Seram and Buru (Fig.1). The origin of the back-arc Banda Sea is still unclear,with some authors (e.g. Silver et al., 1985) regarding theoceanic parts as trapped slices of Indian Ocean or MoluccaSea crust, while others (Hamilton, 1979; Re´hault et al.,1994) have argued in favour of Neogene extension. Apattern of local extension in an overall collisional environ-ment suggests analogies with the Mediterranean, wherecontinental collision has produced deep basins floored byattenuated continental crust in the Alboran and Aegean seasand by oceanic crust in parts of the Tyrrhenian Sea (Dewey,
1988). The Mediterranean basins resemble the Banda Sea,not merely in size, but also in being partly enclosed byorogens with total curvatures approaching 1808 (Fig. 2).
Many of the allochthonous terranes which make up east-ern Indonesia are of Australasian origin. This is true notonly of the large landmass of New Guinea, which is stilllinked to Australia, but of many of the smaller islands on theAsian side of the collision suture. Some of this material hasbeen transferred from Australasia to Eurasia during thePleistocene and continuing Banda Arc collision, but otherfragments must have been accreted earlier. Two important‘Australian’ elements are Buton Island, southeast of Sula-wesi, and the Banggai and Sula Islands, which form theSula Spur (Fig. 1). There is a wide measure of agree-ment (Hamilton, 1979; Milsom, 1985; Silver et al.,1985) that the Sula Spur is a fragment of New Guineawhich was transported west along transcurrent faultsduring the late Tertiary. Observations made in thecourse of oil exploration programmes have dated itscollision with the East Arm of Sulawesi to between5.2 and 3.8 Ma (Davies, 1990).
The history of Buton, which collided with the SundalandMargin much earlier, in the Early or Middle Miocene, ismore controversial (Davidson, 1991). One school of thoughtconsiders it to have also come from the Birdshead (Smithand Silver, 1991), but the correlations with New Guinea areless convincing, whereas the Mesozoic sediments are
Journal of Asian Earth Sciences 18 (2000) 761–779
1367-9120/00/$ - see front matterq 2000 Elsevier Science Ltd. All rights reserved.PII: S1367-9120(00)00035-3
www.elsevier.nl/locate/jseaes
E-mail address:[email protected] (J. Milsom).
virtually identical to those on the northern Banda Arcislands of Buru and Seram.
The Australian-derived fragments listed above allcontrast strongly with Sumba, the westernmost island inthe Outer Banda Arc (Fig. 1), which resembles SW Sula-wesi. Thus, and in very simple terms, the geology of easternIndonesia can be summarised by three generalised associa-tions of sedimentary, metamorphic and igneous rocks, ofwhich two are related to the continental margins of South-east Asia (Sundaland) and Australasia, respectively. Thethird, Banda, association is dominant in and around theBanda Sea. The stratigraphic data, while not defining theentire history of the suture zone, can be used to constrain therange of acceptable hypotheses.
2. Sundaland Margin Association
Subduction at the Sundaland Margin can be traced backinto the Cretaceous, and the exposed metamorphic rocks arethought to represent Cretaceous accretionary complexes.Conditions changed in the Oligo-Miocene as a result ofcollision with a microcontinent and many of the youngerrocks record extension rather than compression.
2.1. SW Sulawesi
SW Sulawesi is the end product of a series of volcanicepisodes that began in the late Mesozoic, when the blockwas joined to eastern Borneo, but continued after the Eoceneopening of the Macassar Straits (Polve´ et al., 1997). Meta-morphic basement complexes exposed in the Barru andBantimala areas of SW Sulawesi (Wakita et al., 1996) andfarther north in the Latimojong area (Bergman et al., 1996)are in thrust or depositional contact with weakly metamor-phosed deep marine clastics of the Upper CretaceousBalangbaru Formation. Carbonates were deposited in twomain periods, in the Eocene–Oligocene and Miocene(Wilson and Bosence, 1996). Volcanogenic sediments arewidely distributed, especially in the fault-bounded Walanaedepression that developed following the Late Oligocene orEarly Miocene collision, which sutured western and easternSulawesi. Volcanic rocks with ages ranging from 2 to18 Ma, but concentrated around 8 Ma, were interpreted byBergman et al. (1996) as evidence for orogenic collapse andextension, their chemistries being consistent with partialmelting at the base of an extending, collision-thickenedand possibly delaminating lithosphere. This conclusionwas endorsed by Polve´ et al. (1997), who noted the
J. Milsom / Journal of Asian Earth Sciences 18 (2000) 761–779762
1
122 Eo 126 Eo 130 Eo 134 Eo
2 So
6 So
10 So
Timor
Wetar
AlorFlores
Buton
Misool
OninPeninsula
KomewaPeninsula
TBJ-1X
Buru
Tanimbar
RidgesBanda
Flores SeaIslands
BANDA
BANDASOUTH
BASIN
BASINBASIN
WEBER
BayU.P.
Bone
SULAWESI
Seram
BIRDSHEAD(Irian Jaya)
Sumba
Sula Is.
Banggai
Kai
Aru
Obi
Aru
Trou
gh
SeramTrough
Timor Trough
NORTH WEST SHELF
Lawanopo
Fault
71
1
3
3
5
400 km2000
9a
4a
5a5b 4b
NORTH
9b
3a
3b
6a
6b8b
8a
Fig. 1. The East Indonesia suture zone. Numbers enclosed in triangles, inverted triangles and circles refer to figure numbers for stratigraphic columns for,respectively, stratigraphies of the Australian Margin association, the Banda association and the Sundaland Margin association. The thick line with triangles (onupper plate) indicates the approximate present-day location of collision suture. UP� Ujung Pandang.
comparative scarcity of conventional subduction-type calc-alkaline rocks with Neogene ages. The geological evolutionof western Sulawesi is summarised by the stratigraphiccolumn of Fig. 3a, which does not, however, include theimportant but controversial Lamasi Complex. The date ofemplacement of this deformed, metamorphosed and thrustbounded ophiolite (Bergman et al., 1996) is not known butthe mid-Tertiary orogenic phase is an obvious possibility.
2.2. Flores Sea Islands
Bouguer gravity levels indicate that the northern part ofthe Flores Sea, south of Sulawesi, is underlain by thinnedcontinental crust, but that there is oceanic crust further south(Silver et al., 1986). The small and scattered islands withinthe sea have been described by Guntoro (1995) as closelyrelated to the longitudinally corresponding areas of Sula-wesi, with acid igneous rocks in the west and more basicigneous rocks in the east. A volcanic sequence (Old Volca-nic Breccia) in the western islands is equivalent to the LangiVolcanics of SW Sulawesi, and the unconformably over-lying bioclastic limestones, reliably dated as Oligocene,are equivalent to the upper, bioclastic, units of the TonasaLimestone described by Wilson and Bosence (1996). Wide-spread calc-alkaline and alkaline, granitic to rhyolitic pluto-nic and volcanic rocks have not been dated, and their
contacts with other rocks have not been seen, but theycontain dioritic xenoliths interpreted as belonging to theOld Volcanic Breccia. These suggest an age no greaterthan Eocene and a probable correlation with the Early toMiddle Miocene granites of SW Sulawesi.
Volcanic activity recommencing in the Pleistocene,produced the Young Volcanic Breccia, which consists ofconglomerate, volcanic tuff and volcanic breccia of andesi-tic and basaltic composition. Alkaline andesitic and basalticdykes and sills intrude all units except the Quaternary corallimestones. As in western Sulawesi, the combination ofcalc-alkaline and alkaline chemistries suggests both subduc-tion and extension.
2.3. Sumba
The Flores Sea Islands form a partial link between SWSulawesi and the Outer Banda Arc island of Sumba (Fig. 1),which lies to the west of the region of current arc-continentcollision. The position of Sumba, and the absence there ofany Australasian material, is evidence that the large islandsof the Outer Arc do not owe their existence solely to accre-tion in the course of the present-day collision.
The oldest rocks exposed on Sumba are Cretaceous openmarine sediments of the Lasipu Formation, described byWensink (1997) as identical to the Balangbaru of SW
J. Milsom / Journal of Asian Earth Sciences 18 (2000) 761–779 763
Tethyan Oroclines
Banda Sea
Aegean
Alboran
CarpathianTyrrhenian
0 500 km
Fig. 2. The Banda, Tyrrhenian, Alboran, Aegean and Carpathian oroclines, at common scale.
J.M
ilsom
/Jo
urn
alo
fA
sian
Ea
rthS
cien
ces
18
(20
00
)7
61
–7
79
764
EA
RL Y
EA
RL Y
CR
ET A
CE
OU
S
CR
ET A
CE
OU
S
ME
SO
ZO
IC
ME
SO
ZO
IC
CE
NO
ZO
IC
CE
NO
ZO
IC
LA
TE
LA
TE
PLIOCENE PLIOCENE
MIO-CENE
MIO-CENE
OLIGO-CENE
OLIGO-CENE
PALEO-CENE
PALEO-CENE
EOCENE EOCENE
100 100
50 50
0 0
BALANGBARU FORMATION LASIPUFORMATION
BARRU, BANTIMALA ANDLATIMOJONG COMPLEXES
LANGIVOLCANICS
JAWILAVOLCANICS
SW SULAWESI SUMBA
MALAWAFORMATION MASU
FORMATION
TONASALIMESTONE
PAUMBAP AFORMATION
TACIPIMEMBER
QUATERNARY REEF
CAMBAFORMATION
KANANGGAR
WAIKABUBAK
WALANAEFORMATION
Tectonic melange;sandstones, shales,
cherts, basaltultramafics and
schists
Deep marineclastic sediments
Turbidites andsubmarine fan
deposits
Tholeiitic andcalc-alkaline
volcanics
Tholeiitic andcalc-alkaline
volcanics
Carbonate platform withredeposited marginal facies
Shallow marine sedimentsincluding platform carbonates
Volcaniclastics
Carbonateplatform
Shallow marineclastics
Reef limestones
Shales
Coals
? ??
Neritic
Sediments
Chalk andreef limestones
Volcaniclastics
3a 3b
Fig. 3. (a) Stratigraphic column for SW Sulawesi, after Bergman et al. (1996) and Wilson and Bosence (1996). (b) Stratigraphic column for Sumba, afterFortuin et al. (1997) and Wensink (1994). Numbers ininverted triangles refer to locations shown in Fig. 1. Vertical scale in m.y.
J.M
ilsom
/Jo
urn
alo
fA
sian
Ea
rthS
cien
ces
18
(20
00
)7
61
–7
79
765
BATHURST ISLANDGROUP
ASHMORELIMESTONE
Marine siltstoneand shales
Marine shalesand sandstones
Marine glauconitic shales
Continental redbeds
Non-marine siliciclastic
Paralic to shallow marine clasticsand carbonates
Marine clastics depositedat a wide variety of depths
TR
OU
GH
TO
NG
RO
UP
TIMOR GAP IRIAN JAYA
MT. GOODWINFORMATION
PLOVER FORMATION
WONWOGISANDSTONE
EKMAISANDSTONE
KOPAIFORMATION
NEW GUINEALIMESTONE
MALITAFORMATION
CAPE LONDONDERRYFORMATION
FLAMINGO GROUP
TIPUMAFORMATION
AIFAMGROUP
KE
MB
EL
AN
GA
NG
RO
UP
IMSKIN
Thickly-bedded micaceous andglauconitic orthoquartzite
Massive to thickly-beddedquartz sandstone and siltstone
Dense, well beddedcalcilutite
Micaceous glauconitic andmicaceous sands and silts
Argillaceous, glauconitic andcalcarous quartz sandstone
and silty mudstone
Continental redbeds
Nonmarine, lacustrine andparalic sediments, some coals
Shallow water platformcarbonates with isolated reefs
Sandstonesand claysSTEENKOOL FORMATION
Semi-consolidated pelagicand nanno chalks
Radiolarian chalk
MIO-CENE
OLIGO-CENE
PALEO-CENE
EOCENE
PA
LE
OZ
OI
C
PLIOCENE
EA
RLY
CR
ETA
CE
OU
SJU
RA
SSIC
TR
IASS
ICPE
RM
IAN
ME
SO
ZO
IC
CE
NO
ZO
IC
EA
RL Y
EA
RL Y
MID
DL
EL
AT
EL
AT
EL
AT
E
M
L
E
100
200
300
100
200
300
MIO-CENE
OLIGO-CENE
PALEO-CENE
EOCENE
PA
LE
OZ
OI
CPLIOCENE
EA
RLY
CR
ETA
CE
OU
SJU
RA
SSIC
TR
IASS
ICPE
RM
IAN
ME
SO
ZO
IC
CE
NO
ZO
IC
EA
RLY
EA
RL Y
MID
DL
EL
AT
EL
AT
EL
AT
E
M
L
E
4 a 4 b
? ? ?
? ? ?
? ? ?
? ? ?PINYA
MUDSTONE
Fig. 4. (a) Stratigraphic column for the Timor Gap region of the Northwest Shelf, after Brown (1992). (b) Stratigraphic column for Irian Jaya, after Pieters et al. (1983). Numbers in triangles refer to locationsshown in Fig. 1. Vertical scale in m.y.
J.M
ilsom
/Jo
urn
alo
fA
sian
Ea
rthS
cien
ces
18
(20
00
)7
61
–7
79
766
CRYSTALLINEBASEMENT
BANGGAIGRANITE
TANAMUFORMATION
BUYAFORMATION
Continental redbeds
Paralic to shallow marineand fluvial clastics
Sandy paralic tonearshore clastics
Deepwater clays
Clays (limestoneson Misool)
Slates,schists and
gneisses
Acid tointermediate
intrusives
Calcilutite/calcarenite
? ? ? ? ?
? ? ?
? ? ?
SULA SPUR MISOOL
MANGOLEVOLCANICS TIPUMA
FORMATION
AIFAMGROUP
KABAU WFORMATION
BOBONG FORMATIONINANWATAN
POLYSEQUENCEYEFBISHALE
ROABIBAPOLYSEQUENCE
SEBYARPOLYSEQUENCE
PELENG FORMATION
PANCORAN FORMATION
SALODIC FORMATION
Nonmarine, lacustrine andparalic sediments, some coals
FAFANLAP FORMATION
DARAM SANDSTONE
ZAAG LIMESTONE
KASIM MARLSTONE
ATKARI LIMESTONE Fine-grained calcarenite
Calcarenite with minor oolite
FACETLIME-STONE
BOGALLIME-STONE
Calcareniteand coralgal
limestone
LIGUMETA-
MORPHICS
Sandstone, calcareoussiltstone
Siltstone
Tuff-aceouscalci-lutiteand
clayeylime-stone
Intr
usiv
es
Restricted shallow marineanoxic and highly
fossiliferous shales
Highly fosilliferous pelagiclimestones
Shallow water platformcarbonates with isolated reefs
Shallow marine carbonateswith localised reefs
Subaerial acidvolcanics
Continental redbeds
Paralic to shallow marine clasticsand carbonates
JASSPOLYSEQUENCE
MIO-CENE
OLIGO-CENE
PALEO-CENE
EOCENE
PA
LE
OZ
OI
C
PLIOCENE
EA
RLY
CR
ETA
CE
OU
SJU
RA
SSIC
TR
IASS
ICPE
RM
IAN
ME
SO
ZO
IC
CE
NO
ZO
IC
EA
RL Y
EA
RLY
MID
DL
EL
AT
EL
AT
EL
AT
E
M
L
E
MIO-CENE
OLIGO-CENE
PALEO-CENE
EOCENE
PA
LE
OZ
OI
C
PLIOCENE
EA
RLY
CR
ETA
CE
OU
SJU
RA
SSIC
TR
IASS
ICPE
RM
IAN
ME
SO
ZO
IC
CE
NO
ZO
IC
EA
RL Y
EA
RL Y
MID
DL
EL
AT
EL
AT
EL
AT
E
M
L
E
100
200
300
100
200
300
5 b5 a
Fig. 5. (a) Stratigraphic column for the Sula Spur, after Garrard et al. (1988). (b) Misool. In the Mesozoic and Paleozoic, the formations and polysequences identified on the left are after Fraser et al. (1993). Allother data from Rusmana et al. (1989). Numbers in triangles refer to locations shown in Fig. 1. Vertical scale in m.y.
Sulawesi. Mid-Cretaceous dinoflagellates suggest a NorthTethys affinity (Fortuin et al., 1997). The upper age limit ofthe Lasipu is uncertain, but there was widespread igneousactivity in the Late Cretaceous and Paleogene. The JawilaVolcanics, originally thought to be Early Miocene, havenow been dated as Late Eocene (Fortuin et al., 1997) andcan be regarded as part of a belt that includes the LangiVolcanics of Sulawesi and the Old Volcanic Breccia ofTanahjumpea. Also in the Eocene, a platform developedand, as with the Tonasa of SW Sulawesi, remained a siteof carbonate sedimentation (Paumbapa Formation) into theEarly Miocene (Fortuin et al., 1997). The Paleogene sedi-ments are truncated by a Middle Miocene angular uncon-formity above which reef carbonates, chalks andvolcanoclastic turbididites were deposited. The stratigraphyof Sumba is summarised in Fig. 3b; the similarities to SWSulawesi are clear and are enhanced in both areas by thepresence of Eocene granodioritic intrusions.
Extensive paleomagnetic work (Wensink, 1997) hasprovided additional support for a Late Mesozoic positionof Sumba close to western Sulawesi, followed by detach-ment and a complicated series of rotations, the net effect ofwhich has been some 908 of clockwise rotation. Thiscontrasts with the mounting evidence for counter-clockwiserotation of Kalimantan and western Sulawesi (Fuller et al.,1999).
2.4. Sundaland Margin summary
The diagnostic features of the Sundaland Margin strati-graphy include Upper Cretaceous–Paleogene deep-waterclastic sediments, volcanics which are of island arc typein the Paleogene but extensional in the Neogene, and thedevelopment of large carbonate platforms in the Eocene–Early Miocene. The type area is the South Arm of Sulawesiand, in particular, the region northeast of Ujung Pandang(Fig. 1). Similar, although not always complete, Mesozoicand Paleogene sections can be recognised in the Flores SeaIslands and Sumba. Sediments above the mid-Mioceneangular unconformity, which is a feature of the association,show fewer common characteristics, which is unsurprisingif dispersion began during the unrecorded interval. Disper-sion, and the generation of oceanic crust in the Flores Sea,must predate the Late Neogene development of the easternSunda/Banda volcanic arc, because this lies to the north ofSumba. Since the volcanic islands from Flores to Wetarseparate two Sunda-related blocks, it is possible, andperhaps even probable, that they are themselves built onSundaland basement, although this is nowhere exposed.
3. Australasian Margin Association
Sediments were deposited along the Australian Marginunder terrestrial or marginal marine conditions in the Trias-sic and Jurassic and in deeper water during and after theCretaceous. Basement rocks in the east belong to a Late
Paleozoic orogenic belt and in the west to a craton coveredby Paleozoic platform sediments. Anomalously, ‘eastern’granitic basement crops out in the Banggai Islands (Fig.1), the most northwesterly Australasian fragment. Neogenesediments vary widely due to differences in setting in rela-tion to the collision orogenies.
3.1. The Northwest Shelf
During the Paleozoic, north-western Australia formedpart of the interior of the Gondwana super-continent, butrifting in the Triassic and Jurassic detached India andother blocks and created new passive margins along theNorthwest Shelf. Sediments deposited at these margins arealmost nowhere seen in outcrop but are known from numer-ous wells. The stratigraphy of the shelf to the south of Timorhas been described and compared with stratigraphies inadjacent areas by Brown (1992). Three major sedimentarygroups were recognised, these being the Triassic–JurassicTroughton Group, the Jurassic–Cretaceous Flamingo Groupand the Middle and Upper Cretaceous Bathurst IslandGroup (Fig. 4a). Troughton group sediments are predomi-nantly siliciclastic and include red beds in the Malita Forma-tion, which is of latest Triassic and earliest Jurassic age.Marine transgression followed, with deposition of thefluvio-deltaic sediments of the Jurassic Plover Formation.There are no sediments which can be unequivocallyassigned to a rift/break-up setting before the Late Jurassicwhen, as a result of rifting, an unconformity developed onwhich the sandstones and shales of the Flamingo Groupwere deposited under deeper marine conditions. Generallysimilar sediments characterise the Bathurst Group, depos-ited following an Early Cretaceous hiatus, but the sea hadevidently deepened still further. Radiolarian shales weredeposited in the Aptian to Early Albian and a black clays-tone with high gamma-ray signature represents a condensedsequence in the Turonian to Coniacian. Chalks were thendeposited, which were dominantly radiolarian in the LateCretaceous and foraminiferal in the Paleocene through tothe Pliocene (von Rad and Exon, 1983). Harris (1991) notedstrong similarities between these sediments and the LowerCretaceous Kolbano Series of Timor.
3.2. New Guinea
Island arcs, which accreted to the northern margin ofAustralia during the Tertiary, now form mountain rangesalong the north coast of New Guinea (Dow, 1977). Theseterranes can be tentatively correlated with Halmahera,where Indonesia borders on the Pacific, but are remotefrom the Banda Arc and are therefore not further consideredhere. Southern and central New Guinea have also been inter-preted in terms of large numbers of allochthonous or‘suspect’ terranes (Struckmeyer et al., 1993), but most ofthe geological features of northern Australia can be traced atleast as far north as the watershed in the central ranges. Thewestern peninsula (Birdshead), which forms the link
J. Milsom / Journal of Asian Earth Sciences 18 (2000) 761–779 767
between the main body of New Guinea and the smallerislands of eastern Indonesia, presents particular problems.It is widely thought to have moved independently for muchof its history (cf. Hamilton, 1979) and some movementrelative to New Guinea continues to the present day (Punto-dewo et al., 1994). The core of the peninsula is formed bythe Birdshead/Kemum Terrane of Struckmeyer et al. (1993),in which metamorphosed Siluro-Devonian turbidites havebeen intruded by Carboniferous and Permo-Triassic grani-toids and are overlain by Late Paleozoic shallow marineclastics and Triassic to Lower Jurassic continental redbeds.Marginal marine conditions were re-established in the earlyMiddle Jurassic and continued throughout the Mesozoic andinto the early Tertiary, interspersed with periods of erosionand non-deposition (Dolan and Hermany, 1988). Sedimentsdeposited during this long interval have traditionally beenassigned to the ‘Kembelangan Formation’ (Visser andHermes, 1962) but the term has been used in such a varietyof contexts that it has become virtually meaningless (Fraseret al., 1993). The stratigraphic column of Fig. 4b is based onthe more westerly of the New Guinea stratigraphiespresented by Pieters et al. (1983).
Shelf carbonates (New Guinea Limestone, Visser andHermes, 1962) dominate the Tertiary throughout NewGuinea but deposition on the Birdshead was interruptedby a period of folding and erosion in the Late Oligocene.
3.3. The Sula Spur
The Banggai and Sula Islands, which lie immediately tothe north of the North Banda Basin and the northern limb ofthe Banda Arc, were transported from the New Guinearegion to their present position by transcurrent movementsalong strands of the Sorong Fault System (Hamilton, 1979;Pigram et al., 1985). Basement consists of poorly knownmetamorphics but there are also granitic rocks of assumedPaleozoic age. The Triassic is dominated by the acidMangole Volcanics and by probably co-magmatic Permo-Triassic granites. Sedimentation, generally in marine basinswith restricted circulation and water depths of less than200 m, was almost continuous throughout the Jurassic buta ‘break-up unconformity’ (Garrard et al., 1988) occupiesmuch of the Cretaceous. Following this break, bathyal sedi-ments were deposited during the Late Cretaceous and Paleo-cene (Garrard et al., 1988). A second hiatus occupied muchof the Eocene but thereafter carbonate platform sedimenta-tion continued almost uninterrupted until the onset of colli-sion with East Sulawesi in the latest Miocene (Davies,1990). Davidson (1991), amongst others, has suggestedcorrelations between the Sula Spur and Buton and theOuter Banda Arc but the statigraphic sequence describedabove and summarised in Fig. 5a has virtually nothing incommon with either of these areas.
3.4. Kai Besar
Seismic reflection surveys near the Kai islands (Fig. 1)
have shown that the plate suture runs between Kai Besar andKai Kecil, rather than through the Aru Trough (Milsom etal., 1996). The oldest rocks exposed on Kai Besar, on theAustralian side of the suture, are Eocene flat-beddedcalcilutites and marls. Shallow-water carbonates weredeposited from the Oligocene almost to the present day.This stratigraphy is not significantly different from theend-Cretaceous to Late Miocene succession on the SulaSpur.
3.5. Misool–Onin–Komewa
The Late Oligocene compression widely observed in theBirdshead was interpreted by Struckmeyer et al. (1993) asdue to a collision with a Misool–Onin–Komewa Terrane.On Misool island a Paleozoic basement of folded and meta-morphosed turbidites is overlain by an almost completeMesozoic passive margin sequence of Triassic turbidites,Upper Triassic shallow-water limestones and Lower Juras-sic to Upper Cretaceous bathyal clastics and carbonates(Rusmana et al., 1989). Outcrop information on the geologyof Misool and the related Onin and Komewa peninsulas ofthe New Guinea mainland (Fig. 1) has been supplementedby drilling, and Fraser et al. (1993) used subsurface datafrom both the Misool–Onin–Komewa province and adja-cent parts of the Birdshead to develop a new scheme toreplace the Kembelangan nomenclature. In this schemethe Mesozoic sediments were divided into a Lower toMiddle Jurassic shallow marine to fluvial ‘Inanwatan Poly-sequence’, a Middle to Upper Jurassic paralic to nearshore‘Roabiba Polysequence’, an Upper Jurassic–Lower Cretac-eous deepwater open marine ‘Sebyar Polysequence’and anUpper Cretaceous to Paleocene, ‘Jass Polysequence’, sepa-rated by major unconformities (Fig. 5b). In the crucial TBJ-1X well (Fig. 1) off the Onin Peninsula (and therefore withinthe Misool–Onin–Komewa Province), section is missingfrom the Middle Triassic to the base of the Toarcian, fromthe top of the Bajocian to the base of the Oxfordian, from theLower Kimmeridgian to the mid Tithonian and from theLower Valangian to the Cenomanian. Jass sediments havealso largely been removed from the well section by erosion.Elsewhere, the Cenomanian base of the Jass is marked by avolcanic event and the overlying sediments are mainlydeepwater clays, although shallow water rudists outcrop inthe Misool archipelago.
Fig. 5b shows that there are considerable differencesbetween the rocks outcropping on Misool and those inter-sected in TBJ-1X. Whereas the well section fits into thepattern of the Australian Margin Association, Misool hasmuch in common with the Banda Association describedbelow, although it reportedly lacks the characteristic Juras-sic unconformity. Moreover, palaeomagnetic data indicatesthat the island was more than 1000 km north of Australia inthe Cretaceous (Wensink et al., 1989). There is thus a clearpossibility that Misool was detached from the AustralianMargin as an independent fragment in the Mesozoic and
J. Milsom / Journal of Asian Earth Sciences 18 (2000) 761–779768
J.M
ilsom
/Jo
urn
alo
fA
sian
Ea
rthS
cien
ces
18
(20
00
)7
61
–7
79
769
LAKANSAIFORMATION
TOBELO FORMATION
TOBELO FORMATION
Dark shales, limestones,occasional massive sandstone
Fossiliferous red calcareousmudstone
Argillaceous limestone
Bathyal fine-grained limestonesand argillaceous limestone
Pelitic phyllite and slatewith subordinate quartzoseand micaceous sandstone
White to pink nannofossil-microfossil pelagic
limestones, some cherts
Well laminated calcilutitewith local clastic detritus
Reef LimestonePelagic foraminiferal marly chalk
Coarse to fine grainedterrigenous clastics
SAMPOLAKOSA FORMATION
WAPULAKA FORMATION
Possible hiatus? ? ? ? ?
BUTON
WINTOFORMATION
RUMUFORMATION
OGENAFORMATION
TONDO FORMATION
High - very high gradeschists and gneisses
h i a t u s ?
h i a t u s ?
h i a t u s ?
erosional hiatus
LATE CRETACEOUSNIEF BEDS
PALAEOGENENIEF BEDS
KOBIPOTO COMPLEX
TAU NUSA COMPLEX
Coralli-genous
limestones
Chert-richlimestones,
locallybioclastic
Clays, shales,graywackes,
somelimestones
Weakly metamorphosed shales,graywackes, some limestones
Phyllites with graywackes,some limestones
Neritic shales
Argillaceouscalcilutites
Dense, brittle calcilututes,some cherts
Cream and white calcilutitesred and green marls
Medium - high gradeschists and gneisses.
POSSIBLE GRADATIONAL CONTACT
Neritic sediments
Bathyal sediments Tectonite
Grey argillaceous calcilututes
SAKU FORMATION
TEHORU FORMATION
NIE
FB
ED
S
EARLY NEOGENE NIEF BEDS
WAHAI BEDS SALASBLOCKCLAY
SERAM
KANIKEHFORMATION
SAMANSAMAN
LST
EARLY NIEF BEDS
MANUSELA
FORMATION
h i a t u s ?
KOLA SHALE
TOBELO FORMATION
FUFA FORMATION
MIO-CENE
OLIGO-CENE
PALEO-CENE
EOCENE
PA
LE
OZ
OI
CPLIOCENE
EA
RLY
CR
ETA
CE
OU
SJU
RA
SSIC
TR
IASS
ICPE
RM
IAN
ME
SO
ZO
IC
CE
NO
ZO
IC
EA
RLY
EA
RL Y
MID
DL
EL
AT
EL
AT
EL
AT
E
M
L
E
MIO-CENE
OLIGO-CENE
PALEO-CENE
EOCENE
PA
LE
OZ
OI
C
PLIOCENE
EA
RLY
CR
ETA
CE
OU
SJU
RA
SSIC
TR
IASS
ICPE
RM
IAN
ME
SO
ZO
IC
CE
NO
ZO
IC
EA
RL Y
EA
RLY
MID
DL
EL
AT
EL
AT
EL
AT
E
M
L
E
100
200
300
100
200
300
6 a 6 b
Fig. 6. (a) Stratigraphic column for Buton, after Davidson (1991). (b) Stratigraphic column for Seram, after Kemp and Mogg (1992). Numbers in circlesrefer to locations shown in Fig. 1. Vertical scale in m.y.
collided with the Birdshead in the Mid-Tertiary, when theolder sediments were folded. More detailed work is neededon the Mesozoic rocks, which are well exposed on the southcoast of Misool and the islands immediately to the south, toclarify their role in the regional evolution.
3.6. Australian Margin summary
The wide variations in Australian Margin stratigraphiesare not surprising in view of the vast area covered. The typearea for the association is taken to be the shelf south ofTimor (the ‘Timor Gap’). Western Irian Jaya, includingthe Birdshead, and the Sula Spur, are included in this asso-ciation but their basements of Late Paleozoic granites andassociated extrusive rocks have more in common withcentral Papua New Guinea than the Northwest Shelf. Misoolisland is different again and lacks the terrestrial Triassic ‘redbeds’ deposited elsewhere in the region prior to, and at thebeginning, of the break-up of this part of Gondwanaland.
The later Mesozoic in all areas records a steady increase inwater depth, from marginal marine in the Jurassic to openwater bathyal in the later Cretaceous. During the Tertiary,parts of the margin were fragmented and/or involved incollisions, and Tertiary stratigraphies therefore differconsiderably.
4. Banda Association
The Banda Association, which is found on the islandssurrounding the Banda Sea, progresses from Upper Triassicto Lower Jurassic shallow water clastics and carbonateswhich are richly fossiliferous and sometimes bituminous,via unconformity to an Upper Jurassic to Paleogenecondensed sequence of deep water carbonates and chertsfrom which clastic components are almost completelyabsent. The Middle to Late Jurassic hiatus is an importantdiagnostic feature. It is widely recognised on the Australian
J. Milsom / Journal of Asian Earth Sciences 18 (2000) 761–779770
Lawanopo Fault
Undifferentiated Mesozoic
Cretaceous limestone
Jurassic limestone
Jurassic/Triassic clastics
Fig. 7. Distribution of Mesozoic sedimentary rocks in eastern Sulawesi, after Sukamto (1975).
J.M
ilsom
/Jo
urn
alo
fA
sian
Ea
rthS
cien
ces
18
(20
00
)7
61
–7
79
771
POMPANGEOSCHIST
Low to highgrade metamorphics
Reef LimestoneREEF LIMESTONE
EAST SULAWESI
MELUHUFORMATION
TOKALAFORMATION
CELEBES MOLASSE
CELEBES LIMESTONE
BURU
MATANO FORMATION
WAHLUA COMPLEX
RANA COMPLEX
DALANFORMATION
KUMAFORMATION
MEFAFM.
Interbeddedsandstones, shales,
siltstones, someconglomerates
Basalticlavas
and tuffs
Cherty calcilutitesinterbedded with
conglomerates in thelower part and
marl and shale in theupper parts
Low grade (greenschistfacies) metamorphosed
clastics
Marls, calcilutites, conglomerates
Conglomerate, sst, lst
Coral andforam. lst
LEKO FORMATION
FTAU
WAEKEN FORMATION
WAKATIN
GHEGANFORMATION
HOTONG
Dolomites,shales, somebituminous,limestones
Medium-grade (greenschistto amphibolite)
metamorphosed clastics
Coral reef
SandstonesCoarse to fine grained
terrigenous clastics
Reefal and nummuliticlimestone
White to pinkporcellaneous pelagic
limestones
Bituminous limestones,and shales
Bathyal fine-grained limestonesand argillaceous limestone
MIO-CENE
OLIGO-CENE
PALEO-CENE
EOCENE
PA
LE
OZ
OI
CPLIOCENE
EA
RLY
CR
ETA
CE
OU
SJU
RA
SSIC
TR
IASS
ICPE
RM
IAN
ME
SO
ZO
IC
CE
NO
ZO
IC
EA
RL Y
EA
RLY
MID
DL
EL
AT
EL
AT
EL
AT
E
M
L
E
MIO-CENE
OLIGO-CENE
PALEO-CENE
EOCENE
PA
LE
OZ
OI
C
PLIOCENE
EA
RLY
CR
ETA
CE
OU
SJU
RA
SSIC
TR
IASS
ICPE
RM
IAN
ME
SO
ZO
IC
CE
NO
ZO
IC
EA
RL Y
EA
RLY
MID
DL
EL
AT
EL
AT
EL
AT
E
M
L
E
100
200
300
100
200
300
8 b8 a
Fig. 8. (a) Stratigraphic column for East Sulawesi, after Rusmana et al. (1993). (b) Stratigraphic column for Buru, after Tjokrosapoetro et al. (1993). Numbers in circles refer to locations shown in Fig. 1. Verticalscale in m.y.
Northwest Shelf, where it was termed ‘Wombat-type’ byGradstein (1992) following ODP drilling on the WombatPlateau. There are many similarities between the Mesozoicsediments of the Wombat Plateau and the Banda Associa-tion. However, whereas the Mesozoic of the plateau rests ona thick unmetamorphosed Paleozoic section, metamorphicrocks, upon which the Triassic sediments are said to restunconformably, are common in the Banda Association, asare Cretaceous–Paleocene ophiolites. Stratigraphies in thevarious Banda fragments diverge significantly only after theOligocene, when many of the blocks were deformed bythrusting.
4.1. Buton
Buton is one of the most important islands of the BandaAssociation because of its present close proximity to Sula-wesi (Fig. 1). Drawing in part on work by Fortuin et al.(1990) and De Smet and Hermanto (1991), Davidson(1991) deduced separation from Australia in the Late Trias-sic or Early Jurassic and a transition from pre-rift to syn-riftsedimentation in the Middle to Late Triassic. The Triassicrocks (Winto Formation) rest on pelitic phyllites and slates(Lakansai Formation) which are exposed over an area ofonly about 40 km2 in the northeast of the island (Smithand Silver, 1991). Both the Winto and the overlyingLower Jurassic Ogena Formation consist dominantly oflimestone, but the Ogena appears to have been depos-ited in deeper water. Clastic sediments, principallyshales, are common in the Winto of southern Buton.Both formations contain abundant organic material thatis generally considered to be the source of the island’sasphalt deposits.
The poorly exposed later Mesozoic on Buton begins withdeep marine siliceous and calcareous mudstones of theUpper Jurassic Rumu Formation and continues with thepelagic limestones with nodules and stringers of red chertof the Tobelo Formation. The Tobelo was originally classi-fied as entirely Upper Cretaceous but has now beenshown to extend from the end of Rumu deposition upinto the late Eocene or early Oligocene (Smith andSilver, 1991). Both the Rumu and the Tobelo wereevidently laid down very slowly and their lithologiesare consistent with deposition during the drift of anisolated continental fragment.
According to Davidson (1991), a hiatus at the top of theTobelo Formation can be attributed to collision with SESulawesi in the Early and Middle Miocene (N11). Ophio-lites in southern Buton were probably emplaced at about thistime, and compression led to uplift and the establishment ofan unconformity representing a hiatus of approximately3 m.y. The basal sediments of the coarse clastic TondoFormation, immediately above the unconformity, aremainly carbonate detritus but ultramafic and mafic frag-ments become dominant later, indicating uplift of the ophio-lites above sea level.
Tondo Formation deposition was ended by subsidence ofButon to bathyal depths at approximately 5 Ma and thedeposition of chalks and marls. Subsequent uplift wasaccompanied by the development of reefal carbonates.Minor compressional effects can be observed in UpperPliocene strata, and oblique compression and associatedstrike-slip faulting may continue to the present day.Quaternary uplift in southern Buton, where spectacularflights of coral terraces rise to almost 500 m above sealevel, has been estimated at 2.5 km, but the northernpart of the island is now subsiding (Davidson, 1991).The history of post-Middle Miocene molasse depositionand ophiolite emplacement on Buton is virtually identi-cal with that of eastern Sulawesi, and the 5 Ma subsi-dence seems much more likely to have been caused byextensional collapse of the entire Sulawesi orogen, ofwhich Buton formed a part (Milsom et al., 1999), thanby the choking of a subduction zone, as suggested byDavidson (1991).
4.2. Buru
The Mesozoic succession on Buru (Fig. 8b) is virtuallyidentical to that on Buton, even though the two islands areseparated by the oceanic North Banda Basin (Fig. 1). Bitu-minous Triassic source rocks which are abundantly presentin float in rivers in the northwest are directly comparablewith the Triassic of Buton, as is most of the Cretaceoussection. One distinctive feature of Buru, however, is thepresence of some Jurassic igneous material, which may becompared with the rift phase volcanics of the WallabyPlateau (Gradstein, 1992). Buru also differs from Buton inthe abundance of metamorphic rocks, which cover almostthe whole of the western two-thirds of the island. Thesemetamorphics were divided by Tjokrosapoetro et al.(1993) into the low grade Rana and higher grade WahluaComplexes. A recent reconnaissance along new roads intothe centre of the island confirmed this distinction (D.Roques, personal communication, 2000).
As on Buton, the depositional environment on Burubecame shallower in the Tertiary, but there is no directevidence for Middle Miocene orogeny. Tjokrosapoetro etal. (1993) described the island as characterised by theabsence of thrust faults, imbricated structures, melange orophiolites. The latest phase of the island’s history has beendominated by very rapid uplift and deposition of thick,coarse alluvial fans (Fortuin et al., 1988). However, steepgravity gradients recently mapped in the southeast of theisland are difficult to explain except by the presence ofconcealed, thrust emplaced, ophiolites.
4.3. Seram
Buru and western Seram were described by Hamilton(1979) as forming a single microcontinent, and certainlythe two islands are stratigraphically very similar. Forexample, parallels have been drawn between the Rana
J. Milsom / Journal of Asian Earth Sciences 18 (2000) 761–779772
Metamorphics of Buru and the Tehoru Metamorphics ofSeram (Linthout et al., 1989). The sediments of Seramwere divided into allochthonous and para-autochthonousunits by Audley-Charles et al. (1979) but this was renderedunconvincing by disagreement amongst the co-authors as towhether the key Nief Beds, which span the time intervalfrom the Jurassic to the Oligocene, were to be assigned tothe allochthon or the para-autochthon. A different viewbased in part on recent exploration drilling has been offeredby Kemp and Mogg (1992). In this scheme, the oldest unme-tamorphosed sediments of Seram belong to the Middle toUpper Triassic, clastic-dominated, near-shore KanikehFormation, which grades into Lower and Middle Jurassicdeep and shallow water limestones (Manusela and Saman–Saman Formations, respectively) both upwards and later-ally. If these relationships have been correctly interpreted,then all the sediments of Seram can be fitted into a singlestratigraphic sequence (Fig. 6b).
The Kanikeh and Saman–Saman are contemporaneouswith, and also strikingly similar to, respectively, theWinto and Ogena Formations of Buton. Only the ManuselaFormation appears to lack a direct Buton equivalent. In viewof the small area of Mesozoic outcrop on Buton, there maybe little significance in this absence, or in the apparentlydifferent durations of the Jurassic hiatus. The similaritiesbetween Buton and Seram continue above the mid-Jurassicunconformity, since the Late Jurassic Kola Shale of Seramresembles the Rumu Formation of Buton and both are over-lain by deep water condensed sequences dominated by fora-miniferal limestones and marls which extend from the EarlyCretaceous into the Paleogene (Nief Beds on Seram andTobelo Formation on Buton). In both the Nief and Tobelothere is evidence for shallower water conditions in thePaleogene and eventual termination of carbonate sedimen-tation in the Miocene.
4.4. Western Kai and the Banda Ridges
Silicic schists, gneisses and migmatites on the western-most islands of the Kai group have been correlated by Charl-ton et al. (1991b) with the Kobipoto Complex of Seram andwere considered by Honthaas et al. (1997) as uplifted partsof a former Banda forearc.
Dredging on the high standing ridges (Banda Ridges) inthe central Banda Sea has recovered igneous and meta-morphic rocks (Silver et al., 1985), Triassic sediments(Villeneuve et al., 1994) and Miocene reefs (Corne´e et al.,1998). The metamorphics were originally correlated withthose of the Birdshead (Silver et al., 1985) but the descrip-tions of the Triassic rocks are much more reminiscent ofButon, Buru and Seram.
4.5. Eastern Sulawesi
The geology of eastern Sulawesi is often described interms of a simple division into belts of schist and ophioliteseparated by the Lawanopo Fault (Fig. 1), but there are
schists to the north of this fault and ophiolites to thesouth. Patterns of metamorphism are complex. Parkinson(1998) considered that some of the metamorphic rocksformed a high temperature metamorphic sole to the ophio-litic thrusts but it is not clear how widely this interpretationcan be applied. Both blueschists and greenschists arepresent. Metamorphic facies vary and have been used todefine a number of distinct formations, but it is possiblethat these grade into each other. The prevalence of thrusting,and the reconnaissance nature of the mapping in many areas,leave this question open.
Gravity data indicate that the ophiolites overlie the schistson a thrust surface with variable but very shallow dip (Silveret al., 1978). Relatively small south-block up movementalong the Lawanopo Fault could have created the presentoutcrop pattern by exposing the southern parts of the ophio-lite belt to more intensive erosion. Ultramafics south of theLawanopo Fault, which might represent deep keels to apreviously extensive thrust sheet, are associated with occa-sionally strong but very local positive gravity anomalies. Ifschists, rather than ophiolites, predominate at depth, thentheir age and origin are important in any regional synth-esis. The most widely held view is that they representthe basement of a microcontinent which collided withwestern Sulawesi in the mid-Tertiary (Hamilton, 1979).If this is the case, then Australasia seems the mostlikely ultimate source, although Parkinson (1998) inter-preted the main metamorphic formation, the PompangeoSchist Complex, as the easternmost extension of theMesozoic Sundaland Margin, metamorphosed in theEarly Cretaceous under intermediate high-pressureconditions.
Mesozoic sediments, metamorphosed slightly or not atall, are often ignored in regional descriptions but are verywidely distributed in eastern Sulawesi (Fig. 7). The mainperiods represented are the Triassic–Lower Jurassic (terres-trial to marginal marine Meluhu Formation and deep waterTokala Formation) and Cretaceous (deep water carbonate-chert Matano Formation). Kundig (1956) estimated the totalMesozoic section as little more than one kilometre thick onthe East Arm, but it may be thicker in the Southeast Arm,where the outcrops are more extensive. He alsocommented on similarities between the Triassic sedi-ments along the southeastern margin of the East Arm,where they form isolated klippen and comprise bitumi-nous limestones and shales, and those of Buru. Surono(1998), in describing the Meluhu Formation, noted thatpalaeomagnetic determinations placed the site of deposi-tion close to the then latitude of the North AustralianMargin.
The Cretaceous deep water sediments are generallyspatially associated with the ophiolite and might besupposed to constitute its uppermost part. However,Parkinson (1998) cited age relationships and thereported existence of depositional contacts between theMatano Formation and the schists as arguments against
J. Milsom / Journal of Asian Earth Sciences 18 (2000) 761–779 773
J.M
ilsom
/Jo
urn
alo
fA
sian
Ea
rthS
cien
ces
18
(20
00
)7
61
–7
79
774
MIO-CENE
OLIGO-CENE
PALEO-CENE
EOCENE
PA
LE
OZ
OI
C
PLIOCENE
EA
RLY
CR
ETA
CE
OU
SJU
RA
SSIC
TR
IASS
ICPE
RM
IAN
ME
SO
ZO
IC
CE
NO
ZO
IC
EA
RL Y
EA
RLY
MID
DL
EL
AT
EL
AT
EL
AT
E
M
L
E
h i a t u s ?
h i a t u s ?
erosional hiatus
Claystone and shale withinterbedded limestones,calcilutites and siltstones
Interbedded calcilutites andthin shales with radiolaria,
foraminifera and chert nodules
Massive to thickly beddedcalcarenites, calcirudites
and recrystallised limestones
ATAHOCFORMATION
OFU FORMATION
VIQUEQUEGROUP BOBO-
NARO
TIMOR (PARA)-AUTOCHTHON TIMOR ALLOCHTHON
MAU BISSEFORMATION
AITUTULIMESTONE
BABULUFORMATION
NIOFFORMATION
WAI LULIFORMATION
OE BAAT FORMATION
NAKFUNUFORMATION
MENU FORMATION
MIO-CENE
OLIGO-CENE
PALEO-CENE
EOCENE
PLIOCENE
Limestone andradiolarian chert
withvolcanics and
tuffaceous clastics
Volcanics andtuffaceous clastics
Agglomerate and tuff
Basalts and tuffs
Shallow marinebioclastic limestone
EA
RLY
CR
ETA
CE
OU
S
ME
SO
ZO
IC
CE
NO
ZO
IC
LA
TE
LA
TE
METAN FORMATION
OCUSSI VOLCANICS
CABLAC LIMESTONE
HAU LASIFORMATION
NONI FORMATION
MUTIS/LOLOTOICOMPLEX
Radiolaria-richlimestones and
shales
Silts, shales andsandstones
Red crinoidal limestonesand basaltic pillowlavas
Shales with minorsandstones and tuffs. Weakly
metamorphosed at base.Slates, phyllites, meta-quartzites, schists, rare marble.
Shales with thin finegrained sandstones (turbidites)
Varied deep and shallowwater deposits Scaly
clay
Interbedded calcilutites andthin shales with radiolaria,
foraminifera and chert nodules
Massive glauconitic sandstoneMedium-grade metamorphics
and ophiolite
AILEU FORMATION
KO
LB
AN
OSE
QU
EN
CE
KE
KN
EN
OSE
QU
EN
CE
100
100
200
300
9 a9 b
Fig. 9. (a) Stratigraphic column for the Timor parautochthon and autochthon, after Sawyer et al. (1993) and Reed et al. (1996). (b) Stratigraphic column for the Timor allochthon, after Sawyer et al. (1993) andEarle (1983). Numbers in triangles refer to locations shown in Fig. 1. Vertical scale in m.y.
this assumption. The stratigraphic column for East Sula-wesi shown in Fig. 8a is compared with the column forBuru, where the proportions of outcrop of metamorphicrocks and sediments are similar, although ophiolites areabsent.
4.6. Banda Association summary
The Banda Association is characterised by a variety ofmetamorphic rocks, some of which may represent continen-tal basement and others which may be the metamorphicsoles to ophiolite sheets, and ophiolitic rocks which areonly occasionally strongly metamorphosed. The sedimen-tary record begins in the Triassic with deposition underfluvial or marginal marine conditions. Water depthsincreased, and carbonate deposition became more wide-spread, in the Early Jurassic. Sediments of this generallyconformable sequence are frequently bituminous. They arefound in outcrop on Buton (where they source asphaltdeposits; Davidson, 1991) and Buru, and source oil onSeram (Peters et al., 1999).
A characteristic feature of the Banda Association is thepresence of a major unconformity encompassing at least amajor part of the Late Jurassic and sometimes much of theMiddle Jurassic and Early Cretaceous. The sedimentsimmediately above this unconformity are generally shalesbut quickly give way to condensed sequences of carbonateswith cherts, deposited in environments remote from sourcesof clastic sedimentation. This type of sedimentation contin-ued into the Paleogene, when a second major unconformitydeveloped, interpreted here as a consequence of collisionbetween a microcontinent and the margin of Sundaland.The subsequent history of the association can be interpretedin terms of post-orogenic collapse and dispersal, with earlymolasse deposition and, in some cases, later collision withthe advancing Australian Margin around the Banda Arc.
5. Timor
Most discussions of the Outer Banda Arc begin withTimor, which is logical, since it is the largest and mostintensively studied of the islands, but unfortunate since itis probably also the most geologically complex (Charlton etal., 1991a). Moreover, at no time has it been equally easy tovisit both the eastern and the western parts of the island,which have been described rather differently even in themost recent publications (Sawyer et al., 1993; Reed et al.,1996). It is not clear whether the differences stem merelyfrom different approaches to mapping and interpretation orreflect real variations in geology.
It is common ground amongst all recent authors that mostof the Mesozoic sediments exposed on Timor are of Austra-lian origin (see discussion in Charlton et al., 1991a). Mostauthors also accept the presence on Timor of a forearc,formerly separated from Australia by an oceanic basin andreferred to by Carter et al. (1976) and Barber (1981) as the
allochthon and by Harris et al. (1998) as the ‘BandaTerrane’. Seismic lines across the arc near Timor haveprovided striking images of underthrusting by the thicklysedimented Australian continental margin (Hughes et al.,1996; Schlu¨ter and Fritsch, 1985) and suggest that coherentslices of the sedimentary cover have in some places beenstripped from the downgoing slab and incorporated in theoverlying collision complexes. In the same terminology,these continental shelf thrust slices constitute the parautoch-thon. Both allochthon and parautochthon are now overlainby post-orogenic sediments of the autochthon, depositedafter collision.
5.1. The allochthon
Charlton et al. (1991a) listed the allochthonous elementsof Timor, of which the most important were the Mutis/Lolo-toi Complex, the Palelo Group (Noni, Haulasi and MetanFormations), the Cablac Limstone and the Ocussi Volca-nics. Many authors have drawn attention to parallelsbetween some of these formations and rocks on Sumbaand Sulawesi. Earle (1983) and Haile et al. (1979) drewattention to localities in Timor where Noni Formation radi-olarian cherts of Late Jurassic or Early Cretaceous age restdirectly on the metamorphics, and to similar occurrences ofthis globally unusual pattern in SW Sulawesi. In both casesthe environment of deposition was interpreted as a forearcbasin. Elsewhere, the oldest unmetamorphosed sedimentswere considered by Earle (1983) to be the tuffs and agglom-erates of the Metan Formation, but these have now beenassigned to the Upper Eocene and Oligocene (Sawyer etal., 1993.). This discrepancy is some indication of the uncer-tainty that still surrounds the Palelo Series, an uncertaintycompounded by the strong similarities noted by Sawyer etal. (1993) between some outcrops normally mapped asPalelo Group and others mapped as part of the KolbanoSeries. A distinction can, however, be made on the basisof the presence of volcanic elements throughout the Palelo,as in similar and coeval rocks on both Sumba and SWSulawesi.
The Palelo Group is succeeded unconformably by theCablac Limestone and the Ocussi Volcanics. Harris (1992)considered the latter to be an upthrust part of the LateMiocene or Pliocene oceanic floor of the Savu Basin.
5.2. The parautochthon
Australian shelf rocks exposed on Timor range in agefrom Permian to Paleogene and have been divided intotwo main groups, termed the Kekneno and Kolbano series(Fig. 9a), separated by a hiatus occupying most of the LateJurassic (Sawyer et al., 1993). Three distinct PermianFormations have been recognised, these being the Lowerto Upper Permian Maubisse basalts and limestones, theAtahoc shales, which interfinger with the Maubisse lime-stones, and the Upper Permian (or possibly partly Triassic,Reed et al., 1996) Cribas sands, silts, shales and bioclastic
J. Milsom / Journal of Asian Earth Sciences 18 (2000) 761–779 775
limestones. The Aileu metamorphics of the north coast arenow recognised as metamorphosed equivalents of some orall of these formations.
The Triassic of Timor is composed of the Niof Formation,deposited as gravity flows in a range of water depths, andlater limestones and carbonate muds of the Aitutu Forma-tion. In western but not in eastern Timor, a massive butprobably local sandstone wedge has been given formationstatus (Babulu Formation). The top of the Kekneno Series isrepresented by the Late Triassic–Jurassic Wai Luli Forma-tion. In contrast to the other members of the Series, whichare generally confined to the northern mountains, the WaiLuli is found only in the south.
The Kolbano Series is exposed principally in thrust sheetsin the Kolbano Mountains of southern West Timor. It is notfound in the north and exposures in the east are very limited.The base of the series is represented by sandstones andconglomerates of the Lower Cretaceous Oe Baat Formation,but later sediments (the Nakfunu, Menu and Ofu Forma-tions; Fig. 9a) were deposited in clastic-starved marinesettings which were initially deep but became graduallyshallower in the Tertiary. The younger rocks of Timor areassigned to either the allochthon or the autochthon.
5.3. Timor controversies
Four major aspects of Timor geology continue to be
controversial. One of these, concerning the relationshipsbetween the various Permian formations, interpreted byAudley-Charles (1968) as having been deposited in widelyseparated areas but by many more recent authors as inter-fingering (cf. Barber, 1981), has only minor implications forlater orogenic development. More significant is the questionof when orogeny actually occurred. Reed et al. (1996) iden-tified folds in East Timor which pre-dated deposition of theEarly–Middle Miocene Cablac Limestone, but Sawyer et al.(1993) considered the earliest orogenic phase in West Timorto be Late Miocene. The timing of orogeny in Timor wouldhave been dictated by the exact shape of the AustralianMargin and would therefore have been diachronous (Harris,1991) but the time interval suggested above seems too longto be explained by this factor alone.
Another problem concerns the Kolbano Series, whichSawyer et al. (1993), following earlier authors, interpretedas accreted to Timor only in the latest Miocene or Pliocene.However, paleomagnetic studies by Wensink et al. (1987)placed the site of deposition of the Lower CretaceousNakfunu Formation at only 208S, and thus more than1000 km north of the Australian Margin (Smith et al.,1994). If this paleomagnetic datum is correct, the Nakfunumust have been deposited on a rifted fragment that driftednorth ahead of the main continent. The fossil evidence isambiguous and Clowes (1997) described a radiolarian faunaof mixed Tethyan and higher latitude affinities. Given strong
J. Milsom / Journal of Asian Earth Sciences 18 (2000) 761–779776
130 Eo
134 Eo
2 So
6 So
10 So
Banda Seaexpandseastward
Timor allochthon moves south-east from western Sulawesi
Halmahera block moves westto collide with Sangihe Arc
Buru and Seram moveeast from the collision
orogen and rotate
Sumba moves southfrom western Sulawesi
Sula Spur collides with theEast Arm of Sulawesi
W Sulawesi(remnantcollisionorogen)
126 Eo122 Eo
Aus tralian She lfAs s o c iat io n
Sundaland Marg inAs s o c iat io n
BandaAs s o c iat io n
400 km2000
Fig. 10. Dispersion and amalgamation in eastern Indonesia. The convergence of all three assemblages in Timor is unproven, and not essential to the basic postorogenic extension hypothesis, but a possibility meriting further investigation.
geological resemblances and the evidence for a pre-MiddleMiocene orogenic event in Timor, it seems unwise tocompletely discount the possibility that the Kolbanobelongs with the Banda Association as defined in this paper.
Uncertainty also surrounds the metamorphic rocks. Onthe basis of metamorphic grades indicating burial to depthsof more than 20 km, the Lolotoi Complex of East Timor wasoriginally described as continental basement (e.g. Audley-Charles, 1968), although the importance of basic igneousrocks was recognised by all early workers. In West Timorthe supposedly equivalent Mutis Complex has been moreintensively studied and comprehensively described, and isnow interpreted as a metamorphic sole overlain by a thrustmass of variably metamorphosed ophiolitic rocks similar tothe Lamasi Complex of west Sulawesi (Sopaheluwakan etal., 1989). It is not proven that continental metamorphicbasement outcrops in either West or East Timor.
6. Discussion
Although most aspects of the geological history of easternIndonesia are still controversial, there is consensus on a fewimportant points. It is generally agreed that eastern Sulawesiand Buton were sutured to western Sulawesi in the LateOligocene or Early Miocene and that their later historyhas been dominated by extensional and transcurrent fault-ing. This suturing was regarded as two separate events bySmith and Silver (1991) but Milsom et al. (1999) haveargued in favour of a single collision. Neogene compressionin Sulawesi has been confined to the north, where theCelebes Sea is now being subducted beneath the NorthArm and where the Sula Spur collided with the East Armin the Pliocene. Further south, Bergman et al. (1996) andPolve et al. (1997) have independently concluded, on thebasis of detailed geochemical studies, that Neogene volcan-ism was a consequence of orogenic collapse and extensionrather than of subduction.
It is also generally agreed that Sumba and the relatedTimor allochthon are of SE Asian origin and were closelylinked to western Sulawesi throughout the Mesozoic andPaleogene (Soeria-Atmadja et al., 1998; Wensink, 1997).It follows that the as yet undated oceanic crust of the FloresSea must be Neogene, which provides circumstantal supportfor the still controversial Late Neogene dating of the Northand South Banda Basins (Rehault et al., 1994). An almostinescapable corollary is that the Outer Banda Arc islands ofBuru and Seram, as well as the continental fragments in theBanda Ridges, were closer to Sulawesi prior to the LateMiocene than they are today and not further away, as inmany reconstructions (e.g. Silver et al., 1985). The virtuallyidentical Mesozoic stratigraphies of Buton, Buru and Seramstrongly suggest that they formed part of a single block and,somewhat more controversially, recent work (e.g. Surono,1998) suggests that this block included most of EastSulawesi.
In contrast, detailed stratigraphic comparisons argueagainst any correlation between these now dispersed frag-ments and the Sula Spur. Although they share an Australa-sian origin, there are significant differences in their times,places and modes of separation. The Sula Spur is closelyrelated to New Guinea, from which it has been detachedprincipally by transcurrent faulting. It remained part ofthat margin and a site of shallow water sedimentationuntil the Cretaceous, and collided with Sulawesi only inthe Pliocene. The rocks of the Banda Association, on theother hand, were rifted from Gondwanaland in the Jurassic,drifted north ahead of Australia during the Cretaceous andcollided with the SE Asian Margin at the end of the Oligo-cene. Their Mesozoic sediments resemble those of the mostdistal elements of the present Australian Margin, such as theWombat Plateau, but were deposited on metamorphic base-ment, instead of on older sediments. Direct correlation ofthe metamorphics with any known Australian province mayprove impossible, both because of distances involved (thenearest exposures of metamorphic rocks on the Australiancontinent are several hundred kilometres from any plausiblesites of rifting) and because of the later metamorphism asso-ciated with Tertiary collision, rifting and uplift.
The stratigraphic relationships outlined in this papersuggest a Late Neogene history for eastern Indonesiawhich is summarised in Fig. 10 and which is directlycomparable to hypotheses now being advanced to explainthe development of the western Tethys extensional basinsshown in Fig. 2. A number of propositions concerning theprocess of suturing are suggested by these relationships,which should be testable by detailed and focussedprogrammes of investigation. These are that:
1. The Cretaceous sediments of East Sulawesi are not partsof the ophiolite sequence but are direct equivalents of theCretaceous sediments of Buru, Buton and Seram;
2. The metamorphic rocks on which the Triassic sedimentsof Buru, Buton and Seram were deposited are equivalentsof the Pompangeo Schist of eastern Sulawesi;
3. The Wai Luli and Kolbano Series rocks of Timor,together with similar sediments on Buton, Buru, Seramand East Sulawesi, were deposited on a microcontinentwhich rifted away from the Australian continent in theLate Jurassic and collided with West Sulawesi in themid-Tertiary, and that similar and distinctive faunalassemblages will be found in all cases;
4. The main collision between the Timor ‘allochthon’(Sunda forearc) and the ‘parautochthon’ took placebefore, and not after, the Middle Miocene;
5. The palaeomagnetic inclinations in the Lower Cretac-eous rocks of Buton, Buru, Seram and East Sulawesiwill be similar to those already obtained for the NakfunuFormation of Timor; and
6. Triassic palaeomagnetic inclinations of Buton, Buru andSeram will be similar to those already obtained for theMeluhu Formation of East Sulawesi.
J. Milsom / Journal of Asian Earth Sciences 18 (2000) 761–779 777
In the light of the results of these tests it should be possi-ble to formulate a more detailed, more reliable (and perhapscompletely different) model.
References
Audley-Charles, M.G., 1968. The geology of Portuguese Timor. GeologicalSociety of London Memoir 4, 76pp.
Audley-Charles, M.G., Carter, D.J., Barber, A.J., Norvick, M.S., Tjokrosa-poetro, S., 1979. Re-interpretation of the geology of Seram: implica-tions for Banda Arc tectonics. Journal of the Geological Society ofLondon 136, 547–568.
Barber, A.J., 1981. Structural interpretations of the island of Timor, easternIndonesia. In: Barber, A.J., Wiryosujono, S. (Eds.). The Geology andTectonics of Eastern Indonesia, Geological Research and DevelopmentCentre Special Publication, vol. 2. Geological Research and Develop-ment Centre, pp. 183–197.
Bergman, S.C., Coffield, D.Q., Talbot, J.P., Garrard, R.A., 1996. Tertiarytectonic and magmatic evolution of western Sulawesi and the MakassarStrait, Indonesia: evidence for a Miocene continent–continent collision,Geological Society Special Publication, vol. 106. Geological Society ofLondon, London, pp. 391–429.
Brown, S., 1992. Mesozoic stratigraphy of the Timor Gap and its bearing onthe hydrocarbon potential of eastern Indonesia. Proceedings of the 21stAnnual Convention, Jakarta. Indonesian Petroleum Association, pp.553–574.
Carter, D., Audley-Charles, M.G., Barber, A.J., 1976. Stratigraphic analysisof island arc-continental margin collision in eastern Indonesia. Journalof the Geological Society of London 132, 179–198.
Charlton, T.R., Barber, A.J., Barkham, S.T., 1991a. The structural evolu-tion of the Timor collision complex, eastern Indonesia. Journal of Struc-tural Geology 13, 489–500.
Charlton, T.R., Kaye, S.J., Samodra, H., Sardjono, 1991b. The geology ofthe Kai Islands: implications for the evolution of the Aru Trough andthe Weber Basin. Marine and Petroleum Geology 8, 62–69.
Clowes, E., 1997. Micropalaeontological analysis of the Kolbano sequence(Jurassic to Pliocene), West Timor and its radiolarian fauna. PhDThesis, University College London, London, 433pp.
Cornee, J.-J., Butterlin, J., Saint-Marc, P., Re´hault, J.-P., Honthaas, C.,Laurent-Ribaud, A., Chaix, C., Villeneuve, M., Anantsena, Y., 1998.An early Miocene reefal platform in the Rama Ridge (Banda Sea,Indonesia). Geo-Marine Letters 18, 34–39.
Davidson, J., 1991. Geology and prospectivity of Buton Island, S.E. Sula-wesi, Indonesia. Proceedings of the 20th Annual Convention, Jakarta.Indonesian Petroleum Association, pp. 209–233.
Davies, I.C., 1990. Geological and exploration review of Tomori PSC,eastern Indonesia. Proceedings of the 19th Annual Convention, Jakarta.Indonesian Petroleum Association, pp. 41–67.
De Smet, M.E.M., Hermanto, B., 1991. The pre-Neogene of northern Butonand southeast Sulawesi. University of London Consortium for Geolo-gical Research in Southeast Asia, Unpublished Report, 145pp.
Dewey, J.F., 1988. Extensional collapse of orogens. Tectonics 7, 1123–1139.
Dolan, P.J., Hermany, 1988. Geology of the Wiriagar field, Bintuni Basin,Irian Jaya. Proceedings of the 17th Annual Convention, Jakarta. Indo-nesian Petroleum Association, pp. 53–84.
Dow, D.B., 1977. A geological synthesis of Papua New Guinea. AustralianBureau of Mineral Resources Bulletin 201, 41pp.
Earle, M., 1983. Continental margin origin for Cretaceous radiolariancherts in western Timor. Nature 305, 129–130.
Fortuin, A.R., De Smet, M.E.M., Hadiwasastra, S., Sumosusastro, S., vanMarle, L.J., Troelstra, S.R., Tjokrosapoetro, S., 1990. Late Cenozoicsedimentary and tectonic history of south Buton, Indonesia. Journal ofSoutheast Asian Earth Sciences 4, 107–124.
Fortuin, A.R., de Smet, M.E.M., Sumosusastro, P.A., van Marle, L.J.,
Troelstra, S.R., 1988. Late Cenozoic geohistory of NW Buru, Indone-sia, and plate tectonic implications. Geologie en Mijnbouw 67, 91–105.
Fortuin, A.R., Van der Werff, W., Wensink, H., 1997. Neogene basinhistory and palaeomagnetism of a rifted and inverted forearc region,on- and offshore Sumba, eastern Indonesia. Journal of Asian EarthSciences 15, 61–88.
Fraser, T.H., Bon, J., Samuel, L., 1993. A new dynamic Mesozoic strati-graphy for the West Irian microcontinent, Indonesia, and its implica-tions. Proceedings of the 22nd Annual Convention, Jakarta. IndonesianPetroleum Association, pp. 707–761.
Fuller, M., Ali, J., Moss, S.J., Frost, G.M., Richter, B., Mahfi, A., 1999.Paleomagnetism of Borneo. Journal of Asian Earth Sciences, 12.
Garrard, R.A., Supandjono, J.B., Surono, 1988. The geology of the Bang-gai-Sula microcontinent, eastern Indonesia. Proceedings of the 17thAnnual Convention, Jakarta, Indonesian Petroleum Association, pp.23–52.
Gradstein, F.M., 1992. Legs 122 and 123, northwestern Australia margin-astratigraphic and palaeogeographic summary. In: Gradstein, F.M.,Ludden, J.W. et al. (Eds.), Proceedings ODP, Scientific Results.Ocean Drilling Program, College Station, TX, pp. 801–816.
Guntoro, A., 1995. Tectonic evolution and crustal structure of the CentralIndonesian Region from geology, gravity and other geophysical data.PhD Thesis, University College London, 335pp.
Haile, N.S., Barber, A.J., Carter, D.J., 1979. Mesozoic cherts on crystallineschists in Sulawesi and Timor. Journal of the Geological Society ofLondon 136, 65–70.
Hamilton, W., 1979. Tectonics of the Indonesian region. US GeologicalSurvey Professional Paper 1078.
Harris, R.A., 1991. Temporal distribution of strain in the active Bandaorogen: a reconciliation of rival hypotheses. Journal of SoutheastAsian Earth Sciences 6, 373–386.
Harris, R.A., 1992. Peri-collisional extension and the formation of Oman-type ophiolites in the Brooks Range and Banda Arc. In: Parsons, L.M.,Murton, B.J., Browning, P. (Eds.). Ophiolites and their Modern OceanAnalogues, Geological Society Special Publication, vol. 60. GeologicalSociety of London, London, pp. 103–127.
Harris, R.A., Sawyer, R.K., Audley-Charles, M.G., 1998. Collisionalmelange development: geologic associations of active melange-form-ing processes with exhumed melange facies in the western Bandaorogen, Indonesia. Tectonics 17, 458–479.
Honthaas, C., Villeneuve, M., Re´hault, J.-P., Bellon, H., Corne´e, J.-J.,Saint-Marc, P., Butterlin, J., Gravelle, M., Burhanuddin, S., 1997.Lile de Kur: geologie du flanc oriental du bassin de Weber (Indonesieorientale). Comptes Rendus Academie des Sciences 325, 883–890.
Hughes, B.D., Baxter, K., Clark, R.A., Snyder, D.B., 1996. Detailed proces-sing of seismic reflection data from the frontal part of the Timor troughaccretionary wedge, eastern Indonesia. In: Hall, R., Blundell, D.J.(Eds.). Tectonic Evolution of Southeast Asia, Geological SocietySpecial Publication, 106. Geological Society of London, London, pp.75–83.
Kemp, G., Mogg, W., 1992. Reappraisal of the geology, tectonics andprospectivity of Seram Island, eastern Indonesia. Proceedings of the21st Annual Convention, Jakarta, Indonesian Petroleum Association,pp. 521–552.
Kundig, E.H., 1956. Geology and ophiolite problems of East-Celebes.Verhandelingen van het Koninlijk Nederlandsch Geologisch Mijn-bouwkundig Genootschap 16, 210–235.
Linthout, K., Helmers, H., Sopaheluwakan, J., Surya Nila, E., 1989.Metamorphic complexes in Buru and Seram, northern Banda Arc. Neth-erlands Journal of Sea Research 24, 345–356.
Milsom, J., 1985. New Guinea and the western Melanesian arcs. In: Nairn,A.E.M., Stehli, F.G., Uyeda, S. (Eds.). The Ocean Basins and Margins,The Pacific Ocean, vol. 7A. Plenum Press, New York, pp. 551–605.
Milsom, J., Kaye, S., Sardjono, 1996. Extension, collision and curvature inthe eastern Banda arc. In: Hall, R., Blundell, D.J. (Eds.). TectonicEvolution of Southeast Asia, Geological Society Special Publication,106. Geological Society of London, London, pp. 85–94.
J. Milsom / Journal of Asian Earth Sciences 18 (2000) 761–779778
Milsom, J., Ali, J., Sudarwono, 1999. Structure and collision history of theButon continental fragment, eastern Indonesia. American Associationof Petroleum Geologists Bulletin 83, 1666–1689.
Parkinson, C., 1998. Emplacement of the East Sulawesi Ophiolite: evidencefrom subophiolite metamorphic rocks. Journal of Asian Earth Sciences16, 13–28.
Peters, K.E., Fraser, T.H., Amris, W., Rustanto, B., Hermanto, E., 1999.Geochemistry of crude oils in eastern Indonesia. American Associationof Petroleum Geologists Bulletin 83, 1927–1942.
Pieters, P.E., Pigram, C.J., Surono, Supandjono, J.B., 1983. Stratigraphy ofwestern Irian Jaya. Bulletin of the Geological Research and Develop-ment Centre, Bandung 8, 14–48.
Pigram, C.J., Surono, Supandjono, J.B., 1985. Origin of the Sula Platform,Eastern Indonesia. Geology 13, 246–248.
Polve, M., Maury, R.C., Bellon, H., Rangin, C., Priadi, B., Yuwono, S.,Joron, J.L., Soeria Atmadja, R., 1997. Magmatic evolution of Sulawesi(Indonesia): constraints on the Cenozoic geodynamic history of theSundaland active margin. Tectonophysics 272, 69–92.
Puntodewo, S.S.O., McCraffrey, R., Calais, E., Bock, Y., Rais, J., Subarya,C., Poewariadi, R., Stevans, C., Generich, J., Fauzi, C., Zwick, P.,Wdowinski, S., 1994. GPS measurements of crustal deformation withinthe Pacific-Australia plate boundary zone in Irian Jaya, Indonesia.Tectonophysics 237, 141–153.
Reed, T.A., de Smet, M.E.M., Harahap, B.H., Sjapawi, A., 1996. Structuraland depositional history of East Timor, Proceedings of the 25th AnnualConvention, Jakarta, Indonesian Petroleum Association, pp. 297–308.
Rehault, J.-P., Maury, R.C., Bellon, H., Sarmilli, L., Burhanuddin, S.,Joron, J.-P., Cotten, J., Malod, J.A., 1994. La Mer de Banda Nord(Indonesie): un bassin arriere-arc du Miocene superieur. ComptesRendues Academie des Sciences de Paris, Serie, 2 318, 969–976.
Rusmana, E., Hartono, U., Pigram, C.J., 1989. Geology of the Misool Sheetarea, Irian Jaya. Geological Research and Development Centre,Bandung.
Rusmana, S., Sukido, Sukarna, D., Haryanto, E., Simandjuntak, T.O., 1993.Geological Map of the Lasusua-Kendari Quadrangle, Sulawesi. Geolo-gical Research and Development Centre, Bandung.
Sawyer, R.K., Sani, K., Brown, S., 1993. The stratigraphy and sedimentol-ogy of West Timor, Indonesia. Proceedings of the 22nd AnnualConvention, Jakarta, Indonesian Petroleum Association, pp 534–574.
Schluter, H.U., Fritsch, J., 1985. Geology and tectonics of the Banda arcbetween Tanimbar Island and Aru Island (Indonesia). GeologischesJahrbuch E30, 3–41.
Silver, E.A., Breen, N.A., Prasetyo, H., Hussong, D.M., 1986. Multibeamstudy of the Flores back arc thrust belt, Indonesia. Journal of Geophy-sical Research 91, 3489–3500.
Silver, E.A., Gill, J.B., Schwarz, D., Prasetyo, H., Duncan, R.A., 1985.Evidence for a submerged and displaced continental borderland, northBanda Sea, Indonesia. Geology 13, 687–691.
Silver, E.A., Joyodiwiryo, Y., McCaffrey, R., 1978. Gravity results andemplacement geometry of the Sulawesi ultramafic belt, Indonesia.Geology 6, 527–531.
Smith, A.G., Smith, D.G., Funnell, B.M., 1994. Atlas of Mesozoic andCenozoic coastlines. Cambridge University Press, Cambridge, UK99pp.
Smith, R.B., Silver, E.A., 1991. Geology of a Miocene collision complex,Buton, eastern Indonesia. Geoogical Society of America Bulletin 103,660–678.
Soeria-Atmadja, R., Suparka, S., Abdullah, C., Noeradi, D., Sutanto, 1998.Magmatism in western Indonesia, the trapping of the Sumba block and
the gateways to the east of Sundaland. Journal of Asian Earth Sciences16, 1–12.
Sopaheluwakan, J., Helmers, H., Tjokrosapoetro, S., Surya Nila, E., 1989.Medium pressure metamorphism with inverted thermal gradient asso-ciated with ophiolite nappe emplacement in Timor. Netherlands Journalof Sea Research 24, 333–343.
Struckmeyer, H.I.M., Yeung, M., Pigram, C.J., 1993. Mesozoic to Caino-zoic plate tectonic and palaeogeographic evolution of the New GuineaRegion. In: Carman, G.J., Carman, Z. (Eds.), Proceedings of the 2ndPNG Petroleum Convention, Port Moresby, pp. 261–290.
Sukamto, R., 1975. Geological map of Indonesia, Ujung Pandang sheet.Geological Research and Development Centre, Bandung.
Surono, 1998. A palaeogeography study of the Meluhu Basin, southeastarm of Sulawesi, eastern Indonesia. Abstracts — Ninth RegionalCongress on Geology, Mineral and Energy Resources of SoutheastAsia (GEOSEA’98). Geological Society of Malaysia, Kuala Lumpur,Malaysia.
Tjokrosapoetro, S., Budhitrisna, T., Rusmana, D., 1993. Geology of theBuru Quadrangle, Maluku (with 1:250,000 map). Geological Researchand Development Centre, Bandung.
Villeneuve, M., Corne´e, J.-J., Martini, R., Zaininetti, L., Re´hault, J.-P. ,Burhanuddin, S., Malod, J., 1994. Upper Triassic shallow-water lime-stones in the Sinta Ridge (Banda Sea, Indonesia). Geo-Marine Letters14, 29–35.
Visser, W.A., Hermes, J.J., 1962. Geological Results of the Exploration forOil in Netherlands New Guinea. Government Printing Office, TheHague (265pp).
von Rad, U., Exon, N.F., 1983. Mesozoic–Cenozoic sedimentary andvolcanic evolution of the starved passive continental margin off NWAustralia. Studies in Continental Marine Geology, Watkins, J.S., Drake,C.L. (Eds.). AAPG Memoir 34, 253–281.
Wakita, K., Sopaheluwakan, J., Miyazki, K., Munasri, 1996. Tectonicevolution of the Bantimala Complex, South Sulawesi, Indonesia. In:Hall, R., Blundell, D.J. (Eds.). Tectonic Evolution of Southeast Asia,Geological Society Special Publication, 106. Geological Society ofLondon, London, pp. 353–364.
Soeria-Atmadja, R., Suparka, S., Abdullah, C., Noeradi, D., Sutanto, 1998.Magmatism in western Indonesia, the trapping of the Sumba block andthe gateways to the east of Sundaland. Journal of Asian Earth Sciences16, 1–12.
Wensink, H., 1994. Palaeomagnetism of rocks from Sumba: tectonic impli-cations since the late Cretaceous. Journal of Southeast Asian EarthSciences 9, 51–65.
Wensink, H., 1997. Palaeomagnetic data of late Cretaceous rocks fromSumba, Indonesia: the rotation of the Sumba continental fragmentand its relation with eastern Sundaland. Geologie en Mijnbouw 76,55–71.
Wensink, H., Hartosukohardjo, S., Kool, K., 1987. Paleomagnetism of theNakfunu Formation of Early Cretaceous age, western Timor, Indonesia.Geologie en Mijnbouw 66, 89–99.
Wensink, H., Hartosukohardjo, S., Suryana, Y., 1989. Palaeomagnetism ofCretaceous sediments from Misool, northeastern Indonesia. Nether-lands Journal of Sea Research 24, 287–301.
Wilson, M.E.J., Bosence, D.W., 1996. The Tertiary evolution of SouthSulawesi: a record in redeposited carbonates of the Tonasa LimestoneFormation. In: Hall, R., Blundell, D.J. (Eds.). Tectonic Evolution ofSoutheast Asia, Geological Society Special Publication, 106. Geologi-cal Society of London, London, pp. 365–389.
J. Milsom / Journal of Asian Earth Sciences 18 (2000) 761–779 779
