Gondwana Research 19 (2011) 321
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Tectonic framework and Phanerozoic evolution of Sundaland
Ian Metcalfe Earth Sciences, Earth Studies Building C02, School of Environmental and Rural Science, University of New England, Armidale NSW 2351, AustraliaNational Key Centre for Geochemical Evolution and Metallogeny of Continents (GEMOC), Department of Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia
Earth Sciences, Earth Studies Building C02, SchooScience, University of New England, Armidale NSW 235
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1342-937X/$ see front matter 2010 International Adoi:10.1016/j.gr.2010.02.016
a b s t r a c ta r t i c l e i n f o
Article history:Received 4 December 2009Received in revised form 23 February 2010Accepted 24 February 2010Available online 21 March 2010
Keywords:SundalandTectonic frameworkPhanerozoic evolutionPalaeogeography
Sundaland comprises a heterogeneous collage of continental blocks derived from the IndiaAustralianmargin of eastern Gondwana and assembled by the closure of multiple Tethyan and back-arc ocean basinsnow represented by suture zones. The continental core of Sundaland comprises a western Sibumasu blockand an eastern IndochinaEast Malaya block with an island arc terrane, the Sukhothai Island Arc System,comprising the Linchang, Sukhothai and Chanthaburi blocks sandwiched between. This island arc formed onthe margin of IndochinaEast Malaya, and then separated by back-arc spreading in the Permian. TheJinghong, NanUttaradit and Sra Kaeo Sutures represent this closed back-arc basin. The Palaeo-Tethys isrepresented to the west by the ChangningMenglian, Chiang Mai/Inthanon and BentongRaub Suture Zones.The West Sumatra block, and possibly the West Burma block, rifted and separated from Gondwana, alongwith Indochina and East Malaya in the Devonian and were accreted to the Sundaland core in the Triassic.West Burma is now considered to be probably Cathaysian in nature and similar to West Sumatra, from whichit was separated by opening of the Andaman Sea basin. South West Borneo and/or East Java-West Sulawesiare now tentatively identified as the missing Argoland which must have separated from NW Australia inthe Jurassic and these were accreted to SE Sundaland in the Cretaceous. Revised palaeogeographicreconstructions illustrating the tectonic and palaeogeographic evolution of Sundaland and adjacent regionsare presented.
2010 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
Geographically, Sundaland comprises the Malay Peninsula, Suma-tra, Java, Borneo and Palawan which are all located on the shallow-water Sunda Shelf that was exposed as land during low sea levelstands in the Pleistocene (Bird et al., 2005). Biogeographically,Sundaland is a globally important hot spot of biodiversity (Sodhiet al., 2004) with its SE boundary marked by the Wallace Line.Geologically, Sundaland forms the SE promontory of the EurasianPlate and includes Burma, Thailand, Indochina (Laos, Cambodia,Vietnam), Peninsular Malaysia, Sumatra, Java, Borneo and the SundaShelf, and is located at the zone of convergence between the IndianAustralian, Philippine and Eurasian Plates (Simons et al., 2007; Fig. 1).
East and SE Asia (including Sundaland) comprises a collage ofcontinental blocks, volcanic arcs, and suture zones that represent theclosed remnants of ocean basins (including back-arc basins). Thecontinental blocks of the region were derived from the margin ofeastern Gondwana and assembled during the Late Palaeozoic toCenozoic (Metcalfe, 2005). This paper provides an overview of thetectonic framework, Phanerozoic evolution, and palaeogeography of
l of Environmental and Rural1, Australia.
ssociation for Gondwana Research.
Sundaland and adjacent regions, focussing on both historic and recentdevelopments, and major ongoing issues.
2. Tectonic framework of Sundaland and adjacent regions
Mainland eastern Asia (with Sundaland at its core) comprises acomplex assembly of continental blocks, arc terranes, suture zonesand accreted continental crust (Figs. 2 and 3).
2.1. Continental blocks of Sundaland
The principal continental blocks that form the core of Sundalandhave been identified and established over the last two decades (e.g.Metcalfe, 1984, 1986, 1988, 1990, 1996a, 1998, 2002, 2006) andinclude the South China block, the IndochinaEast Malaya block(s),the Sibumasu block, West Burma block and SW Borneo block (Fig. 3).More recently, theWest Sumatra block has been established outboardof Sibumasu in SW Sumatra (Barber and Crow 2003, Barber and Crowin press; Barber et al., 2005) and a volcanic arc terrane is nowidentified, sandwiched between Sibumasu and IndochinaEastMalaya (Sone and Metcalfe, 2008).
The continental terranes of Sundaland and adjacent regions can becategorised into six types based on their specific origins and timing ofrifting and separation from Gondwana and amalgamation/accretion
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Fig. 1. Topography and main active faults in East Asia and location of Sundaland at the zone of convergence of the Eurasian, Philippine and IndianAustralian plates. Large arrowsrepresent absolute (International Terrestrial Reference Frame 2000) motions of plates (after Simons et al., 2007).
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to form SE Asia. These are discussed below under those six categoriesand the suture zones of the region are briefly described separately.
2.1.1. Continental blocks derived from Gondwana in the DevonianThe South China, Indochina and East Malaya blocks are interpreted
to have formed part of the IndiaAustralian margin of Gondwana inthe Early Palaeozoic and to have rifted and separated from Gondwanaby the opening of the Palaeo-Tethys ocean in the Early Devonian(Metcalfe, 1984, 1988, 1990, 1996a,b, 1998, 2002, 2005, 2006). TheWest Sumatra block (originally proposed by Hutchison, 1994 andBarber and Crow, 2003) and possibly the West Burma block(originally called the Mount Victoria Land Block by Mitchell, 1986,1989) are now also interpreted to have originally formed part of thiscollage of terranes (which also included North China and Tarim) thatseparated from Gondwana in the Devonian (Barber et al., 2005;Metcalfe, 2005; Barber and Crow, in press; Metcalfe, 2009a). For moredetailed description of these blocks and assessment of the evidencefor Gondwana origin see Metcalfe (1988, 1996a, 2006).
The Late Palaeozoic faunas and floras of these continental blocksare warm-water, equatorial Tethyan/Cathaysian Province biotas thatcontrast starkly with coeval cold-water and cold-climate Gondwanabiotas (Metcalfe, 2005). This indicates that these terranes had alreadyseparated from Gondwana by Carboniferous times and migratednorthwards to more equatorial palaeolatitudes. This is supported by
palaeomagnetic data (Zhao et al., 1996; Li and Powell, 2001; Li et al.,2004; see Fig. 4).
2.1.2. Arc terranes derived from South China/Indochina in theCarboniferousPermian
Re-interpretation of the NanUttaradit Suture as a probable back-arc suture which does not represent the main Palaeo-Tethys ocean(Wu et al., 1995; Ueno, 1999; Ueno and Hisada, 1999, 2001; Wanget al., 2000) and correlation of this suture with the Sra Kaeo Suture insouthern Thailand and the Jinghong Suture in southern China led Soneand Metcalfe (2008) to propose the Sukhothai Arc System which wasinterpreted as being derived from the margin of South ChinaIndochinaEast Malaya by back-arc spreading in the Late Carbonifer-ousEarly Permian following the previous suggestion of Ueno andHisada (1999). This arc terrane is represented by the Lincang block inSW China, the Sukhothai block in Central Thailand and theChanthaburi block in SE ThailandCambodia (Fig. 3). The SukhothaiArc terrane is here interpreted to have a thin continental basementthat formed the margin of the South ChinaIndochinaEast Malayasuper-terrane. The arc separated from Indochina by back-arcspreading in the EarlyMiddle Permian and was then accreted toIndochina by back-arc collapse in the Late Permian (Fig. 5). Extensionof this arc terrane into the Malay Peninsula is equivocal and thepreviously recognised East Malaya block may form this continuation,
Fig. 2.Distribution of principal continental blocks, arc terranes and sutures of eastern Asia. WB=West Burma, SWB= SouthWest Borneo block, S= Semitau block, L= Lhasa block,QT=Qiangtang block, QS=QamdoSimao block, SI = Simaoi block, SG= Songpan Ganzi accretionary complex, KL= Kunlun block, QD=Qaidam block, AL=Ala Shan block, LT=Linchang arc Terrane, CT = Chanthaburi arc Terrane.
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but a more likely extension is beneath the Central Belt of the MalayPeninsula (Fig. 3) that forms a gravity high (Ryall, 1982).
2.1.3. Continental blocks derived from Gondwana in the Early PermianAt the end of the Sakmarian stage of the Early Permian the
elongate Cimmerian continental strip (Sengr, 1984) separated fromeastern Gondwana. The eastern portion of this Cimmerian continentincludes the Baoshan and possibly the Tengchong blocks of Yunnan,China (Jin, 1994; Wopfner, 1996), and the Sibumasu block (Metcalfe,1984). These eastern Cimmerian blocks are characterised by LatePalaeozoic Gondwana faunas and floras and by Late CarboniferousEarly Permian glacial-marine diamictites which are interbedded withother marine clastics and turbidites that fill rift grabens (Jin, 1994;Wopfner, 1996; Wang et al., 2001). Metcalfe (1988, 1990) includedthe Qiangtang and Lhasa blocks as part of the separating easternCimmerian continent, but recognised the later docking of the Lhasablock to Eurasia in the Late Jurassic/Early Cretaceous. Metcalfe (1999and subsequent papers) retained the Lhasa block on the margin ofGondwana until the Late Triassic, a scenario supported by Golonka etal. (2006). Other authors (e.g. Baud et al., 1993; Dercourt et al., 1993)
have maintained an Early Permian separation of Lhasa as part of theMega-Lhasa Block. A TriassicJurassic separation is still advocatedhere as proposed and discussed by Metcalfe (1996a).
The term Sibumasu block, was proposed by Metcalfe (1984) toreplace previous terms used for the elongate Gondwana-derivedblock in SE Asia characterised by Late Palaeozoic Gondwana biotasand Late CarboniferousEarly Permian glacial-marine diamictites. Theterm was coined so as to explicitly include the elements of SW ChinaSI for Sino, BU for Burma, MA for Malaya and SU for Sumatrawhere unequivocal Early Permian glacial-marine diamictites areknown. Previous terms such as ShanThai, Sinoburmalaya WestMalayawere foundwanting, principally because they did not includethe Sumatran element of the block. Recent usage of the term ShanThai has become so diverse as to become confusing at best andmeaningless at worst. Many authors have in recent times wronglyused Sibumasu and ShanThai interchangeably. In addition, recentinterpretations of the Late Palaeozoic GondwanaCathaysian biogeo-graphic divide in mainland SE Asia have led to erroneous placementsof the eastern margin of Sibumasu and misidentification of thelocation of the PalaeoTethyan Suture Zone by some authors. A
Fig. 3. Distribution of continental blocks, fragments and terranes, and principal sutures of Southeast Asia. Numbered micro-continental blocks, 1. East Java 2. Bawean 3. Paternoster4. Mangkalihat 5. West Sulawesi 6. Semitau 7. Luconia 8. KelabitLongbowan 9. Spratly IslandsDangerous Ground 10. Reed Bank 11. North Palawan 12. Paracel Islands13. Macclesfield Bank 14. East Sulawesi 15. BangaiSula 16. Buton 17. ObiBacan 18. BuruSeram 19. West Irian Jaya. LT = Lincang Terrane, ST = Sukhothai Terrane and CT =Chanthaburi Terrane. CM = ChangningMenglian Suture, C.-Mai = Chiang Mai Suture, and NanUtt. = NanUttaradit Suture.
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discussion of these issues is contained in Metcalfe (2009a,b) and willnot be repeated here. The tectonic framework for the Sundalandregion recently proposed by Ferrari et al. (2008) is here challengedand regarded as both inappropriate and confusing. The use of the termShanThai by Ferrari et al. (2008) for a Cathaysian continental block,which in fact includes both continental crustal and suture zoneelements, and which bears very little resemblance or relationship to
Fig. 4. Palaeolatitude vs. Time for some principal SE Asian continental blocks (After Li et al., 2northern latitudes in the Late SilurianEarly Devonian, Permian, and JurassicCretaceous re
the Gondwanan ShanThai block of Bunopas (1982) see Fig. 6above, is here rejected (see Metcalfe, 2009b for details).
2.1.4. Continental blocks derived from Gondwana in the JurassicMagnetic anomaly data, evidence of rifting, basin formation, and
development of unconformities on the NW Australian margin, andsediment source and palaeocurrent data from Timor, suggest that a
004). Note northwards migration of South China, Sibumasu and Lhasa from southern tospectively.
Fig. 5. Cartoon showing the tectonic evolution of Sundaland (ThailandMalay Peninsula) and evolution of the Sukhothai Arc System during Late CarboniferousEarly Jurassic times(after Ueno and Hisada, 1999; Sone and Metcalfe, 2008).
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piece or pieces of continental crust rifted and separated from AustralianGondwana in the Jurassic. The continental pieces were identified asSouth Tibet, Burma,Malaya, SWBorneo and Sumatra by Audley-Charles(1988)whoproposed their separation fromAustralianGondwana in theJurassic. Veevers et al. (1991) did not identify the continental block thatseparated from the Argo abyssal plain region in the Jurassic but namedthis Argo Land (subsequently Argoland). Metcalfe (1990) suggestedthat the continental block that must have separated from the Argoabyssal plain in the Jurassic might be the Mount Victoria Land block ofMitchell (1989) located in western Burma. Little evidence supportingthis could be presented at that time as the age and nature of the schistbasement of this terranewasnot knownandno rocks older than Triassicwere known. The block was re-named the West Burma block byMetcalfe (1996a,b). Mitchell (1993) re-interpreted the block as part ofan island arc formed by SW directed subduction that was then accretedon to mainland Asia. This interpretation is recently re-proposed by Hallet al. (in press). Other authors have continued to identify Argoland asWest Burma (e.g. Jablonski and Saitta, 2004; Heine and Mller, 2005).TheWest Burma block is bounded to thewest by a belt of ophiolites thatincludes theMountVictoriametamorphics and to the east by theMogokMetamorphic Belt that has recently been correlated with the MedialSumatra Tectonic Zone (Barber and Crow, in press). The recent report ofMiddle Permian...