The Geology of Indonesia/Papua 1

The Geology of Indonesia/ PapuaIrian Jaya is the eastern-most province of Indonesia and is located on the western half ofthe island of New Guinea. The island of New Guinea is the second largest island in theworld and includes Puncak Jaya (4884 m), the highest peak in Southeast Asia and Australia.Traditionally, the outline of the island of New Guinea has been described as similar to abird flying westward with open mouth (Fig. 1). As a result, the island has beengeographically divided into the Bird’s Head, Neck, Body and Tail regions. The geologic ofthe Irian Jaya is very complex, involving interaction between two plates; the Australian andPacific plates (Fig. 1 ). Most of the Cenozoic tectonic evolution of New Guinea is the resultof oblique convergence between the Indo-Australian and Pacific plates (Hamilton, 1979;Dow et al., 1988). New Guinea and the mountainous Central Range, is commonly cited asthe type locality of an active oceanic island arc - continent collision (Dewey and Bird, 1970).The Central Range is a 1300 km long, 150 km-wide belt with rugged topography andnumerous peaks over 3000 m in elevation. Most of the range is composed of folded andfaulted Mesozoic and Cenozoic strata that was deposited on the Australian passivecontinental margin. The purpose of this paper is to make a general summary of the geologyand tectonics of Irian Jaya from various sources of published information.

14. 1. REGIONAL GEOLOGICAL SETTING In general, from the north to the south, the geology of Irian Jaya can be divided into threebroad geologic provinces: Continental, Oceanic and Transitional provinces. Every geologicprovince has its own characteristic in stratigraphic, magmatic and tectonics history. TheContinental province consists of sediments as apart of Australian craton. The Oceanicprovince consists of ophiolite rocks and island-arc volcanics complex as a part of Pacificplate. The transition province is a zone that consists of highly deformed and regionalmetamorphic rocks as a product of interaction between two plates. However, this relativelysimple zonation doesn’t apply perfectly to the Bird’s Head and Bird’s Neck. Some authorsbelieve that this region consists of widely diverse terrains where their origin is not at thepresent position. Therefore, their geologic history differs and should be separated fromBird’s Body (Pieters et al, 1983; Pigram and Davies, 1987).The central portion of New Guinea (the Bird’s Body) can be divided into four lithotectonicprovinces (Fig. 1.2): the New Guinea Foreland/foreland basin (Arafura Platform), theCentral Range fold-and-thrust belt, a metamorphic (the Ruffaer Metamorphic Belt) andophiolite belt, and a collided Melanesian arc island arc complex (the Meervlaktedepression/north coast basin and the Mamberamo Thrust Belt).The New Guinea Foreland (Arafura Platform) consists of the Arafura Sea and southerncoastal plain of Irian Jaya which lie on Australia continental crust. The stratigraphy of theplatform is composed mostly of unmetamorphosed marine and nonmarine Pliocene andHolocene siliciclastic sedimentary rocks which are underlain by the Cenozoic carbonate andMesozoic siliciclastic strata deposited on the northern passive margin of Australia (Dow andSukamto, 1984a, b). Foreland thrust and the Central Range Fold-and-Thrust Belt aredefined as the New Guinea Mobile Belt (Dow et al., 1988). The Central Range is an orogenicbelt that stretches 1300 km from Irian Jaya to the Papuan Peninsula. The 150 km-wide belthas rugged topography and numerous peaks over 3000 m in elevation. This wide zone is asouth verging fold-and-thrust belt that largely involves Paleozoic to Tertiary rocks of the

The Geology of Indonesia/Papua 2

Australian continent. The amount of shortening across this belt in Irian Jaya is unknown,but palinspatic reconstruction of cross-section across the thrust belt in Papua New Guineashows approximately 75 km north-south directed shortening (Hobson, 1986).The Ruffaer Metamorphic Belt is a 50 km wide zone of highly-deformed generallylow-temperature (<300°) metamorphic rocks which is bounded on the north by Irian JayaOphiolite Belt and on the south by deformed, but unmetamorphosed, passive margin strata(Dow et al., 1988; Nash et al., 1993; Warren, 1995; Weiland, 1999). The Irian Jaya OphioliteBelt is separated from the Ruffaer Metamorphic Belt by a series of faults and is covered byalluvium of the Meervlakte depression. The suture separating the rocks from two differentplates may be at the boundary between the Ruffaer Metamorphic Belt and the Irian JayaOphiolite Belt. The Derewo fault zone was mapped primarily with aerial photographs andsatellite images as the boundary between the Ruffaer Metamorphic Belt andunmetamorphosed strata in the Irian fold belt by Dow et al. (1986). However, recentmapping shows that the transition from the Ruffaer Metamorphic Belt to unmetamorphosedstrata is gradational from north to south and that from near 137° to 138°E longitude(Warren, 1995). Thus, the mapped DFZ does not correspond to the southern boundary ofthe metamorphic rock as shown on previous maps.The most northern orogenic belt in Irian Jaya is a poorly exposed, complex zone involvingoceanic rock from a collided Melanesian island arc built into the Pacific Plate. This beltconsists of the Meervlakte (lake plain) depression and the Mamberamo Thrust-and-FoldBelt (MTFB). The Meervlakte is an intramontane basin and this basin has been activelysubsiding from Middle Miocene to the present in which the rate of subsidence is greaterthan the rate of sedimentation (Dow et al., 1988). MTFB is a 200-km wide, NW-trendingzone of convergent deformation, largely within the Melanesian arc terrane, that began inthe Pliocene and is still active (Dow and Sukamto, 1984a, b; Dow et al., 1988).

14. 2. TECTONIC SETTING The details of the Cenozoic tectonic evolution of New Guinea are the subject of somedebate. The most commonly published scenario is the subduction polarity reversal (or arcreversal) model which entails movement of the Australian continental crust and mantle intoa northward dipping subduction zone, followed by collision and initiation of southwardsubduction of the Pacific plate at the New Guinea Trench (Dewey and Bird, 1970; Hamilton,1979; Milsom, 1985, Dow et al., 1988; Katili, 1991). A second model proposed to explainrelationships in eastern New Guinea shows the island underlain by a doubly-dipping slab ofoceanic lithosphere (“zippering” model), which is the westward continuation of thesubducted Solomon plate (Ripper and McCue, 1983; Cooper and Taylor, 1987). A thirdmodel is similar to the first, but the subducted Australian plate is simply dipping verticalwithout a reversal in subduction direction (Johnson and Jaques, 1980). Both of these latermodels require significant oblique convergence across most of the island.All of these authors agree that southern New Guinea is underlain by the passive northern margin of the Australian continent which was thickly blanketed from the early Mesozoic by siliciclastics grading into Cenozoic carbonate strata. Most of these authors argue for one major collisional event with an oceanic island arc. Based on the change from carbonate sedimentation to widespread clastic sedimentation derived from orogenic uplifts, the collision apparently began in the late Miocene (Visser and Hermes, 1966; Dow and Sukamto, 1984a; Dow et al., 1988). However, based on the metamorphic age of rocks in

The Geology of Indonesia/Papua 3

Papua New Guinea and the island arc terrane, some workers conclude that the collisionbegan in the early Oligocene (Pigram et al., 1989; Davies, 1990). To account for theserelationships, Dow et al. (1988) propose that New Guinea is the product of two distinctisland arc-continent collisions: one during the Oligocene and a second during the Miocene(Melanesian Orogeny). Quarles van Ufford (1996) proposes that the island is the site of twoorogenic events that are spatially and temporally distinct. The earlier (Eocene-Oligocene)event, termed the “Peninsular orogeny,” was restricted to the Bird's Tail region ofeasternmost New Guinea. The generation and erosion of a significant landmass is recordedin Oligocene and younger clastic sedimentation in the Aure Trough. The “Central Rangeorogeny,” on the other hand, was an event that began in the middle Miocene and generatedthe present width of the island and caused widespread clastic sedimentation. Importantly,Quarles van Ufford (1996) divided the Central Range orogeny into pre-collisional andcollisional stages. The pre-collisional stage is related to the bulldozing and metamorphismof passive margin sediments in a northward-dipping subduction zone. The collisional stageonly occurs when buoyant Australian lithosphere actually jams the subduction zone (Cloos,1993) and crystalline continental basement becomes involved in the deformation.Collisional delamination is proposed as the tectonic process that occurred within thesubducting Australian lithosphere between 7 to 3 Ma. Besides involvement of crystallinebasement, this process causes late-stage igneous activity and a vertical mountain uplift of 1to 2 km. This process culminated with the initiation of the E-W trending, left-lateralstrike-slip that dominates the recent tectonics of western New Guinea.

14. 3. STRATIGRAPHY The details and complete stratigraphic nomenclatures of Irian Jaya are best described inthe geological report and map from Dow et al (1988) published by GRDC Bandung. In thispaper the stratigraphic of the region will be compiled, generalized and simplified fromvarious publications. The stratigraphy of the Australian Craton mainly known from exposedrocks in the deformed northern margin of Australian Craton resulted from regional upliftduring the Central Range Orogeny and drill wells when exploring for oil in the Bird’s Headplatform. The simplified stratigraphic nomenclatures of the rock from Australian Craton aresummarized in Fig.. This diagram shows regional stratigraphic co-relation from the Bird’sHead in the NNW to the Bird’s Body in the ESE.14.3.1. PALEOZOIC BASEMENTThe distribution of Paleozoic rocks in Irian Jaya is poor due to the lack of exposures. Therefore it is difficult to generate regional correlation of this strata throughout the region. In addition, a lot of older strata have been regionally metamorphosed. There are several locations that expose Paleozoic strata in Irian Jaya. The largest block of the rocks exposed In the mountain of the northeastern Bird’s Head is known as Kemum High. On the other hand, the best out crop of unmetamorphosed section of Paleozoic strata is exposed along the Gunung Bijih Mining Access (GBMA) at the southwestern Central Range. The southwestern Central Range forms a simple north-dipping homocline, approximately consisting of 30-km-wide, 18-km-thick sedimentary sequence. The GBMA contains road cuts, which expose the most stratigraphically continuous section in all of Irian Jaya (Sapiie et al, 1999). In the Bird’s Head region, the oldest strata known are the thick Kemoem Formation which consist mostly of slate, phyllitic and minor quartzite. In the Bird’s Head this formation is intruded by Carboniferous biotite granite (Melaiurna Granite). Therefore,

The Geology of Indonesia/Papua 4

the metamorphism is interpreted as occurring in Devonian to early Carbonaceous (Pigramet al, 1982a). However, in the northeast Kemum high, Triassic granitic rocks intrude thelower Paleozoic (i.e. Anggi Granite, Kwatisore, Netoni Intrusive Complex) (Dow et al, 1988).Kemoem Formation is overlain unconformably by the Aifam Group.Aifam Group is used for describing a group of mappable rocks consisting of shallow-watershelf sediments in the lower part and grading upward to fluviodeltaic environment. TheAifam Group is best known from the northern margin of the Bird’s Head Platform and inthis region the group has been subdivided into three formations: Aimau Formation, AifatMudstone and Ainim Formation (Dow et al, 1988). The Aifam Groups occurs widely in theBird’s Head region where it appears to be unmetamorphosed. This group is more stronglydeformed and metamorphosed in the Bird’s Neck area. In the Bintuni area, the TipumaFormation is unconformably overlying the Aifam Group (Biantoro and Luthfi, 1999).In the Central Range (Bird’s Body), Awigatoh Formation is the oldest rock known in IrianJaya. This rock unit was named Awigatoh Formation by Bar et al (1961) and Visser andHermes (1962), and later named as Nerewip Formation on Timika Sheet Map by Parris(1994). This rock is exposed in the Awigatoh Mountain close to the border, the core ofMapenduma and Digul Range anticlines (Paris, 1994; Granath and Argakosoemah, 1989). Inthe Mapenduma anticline, the formation is exposed along Baidu and Nerewip Rivers west ofGBMA (Quarles van Ufford, 1996). The formation consists of metabasalt, metavolcanic withminor limestone, shale and siltstone. Based on limited field observation, this formationappears to be overlain disconformably by Kariem Formation.Kariem Formation along GBMA has been given different names, such as KemoemFormation based on lithologic correlation with the northeastern Bird’s Head Region(Martodjojo et al., 1975), or a new name Otomona Formation on the Timika Map Sheet(Parris, 1994). Originally, Kariem Formation was the description for a group of sedimentaryrock exposed in the Kariem river at Eastern Irian Jaya (Bar et al., 1961; Visser and Hermes,1962). Lithologically this formation consists of fine-grained quartzose turbidite. In thenortheastern Bird’s Head Region, this sediment were metamorphosed, intruded by granite,eroded before late Carboniferous, and overlain unconformably by the Aifam Group (Dow etal, 1988). The age of Kariem Formation is interpreted as Precambrian or Early Paleozoic.This interpretation is based on stratigraphic position that is below the Silurian andDevonian Modio Formation and from the result of reset age of zircon fission-track (ZFT)showing age of 650±63 Ma (Quarles van Ufford, 1996). At the GBMA, the relationshipbetween Kariem Formation with the overlying Tuaba Formation is inferred to bedisconformable (Quarles van Ufford, 1996).Tuaba Formation was named by Pieters et al. (1983) for describing unit exposed in theTuaba river. Tuaba Formation is composed of thick bedded of coarse- to medium-grainedquartz sandstone with interbedded conglomerate and shale. The age of Tuaba Formation isconstrained as Precambrian or early Paleozoic. The formation is stratigraphically below theSilurian to Devonian Modio Formation. However, along the GBMA this formation is in thefault contact (Hannekam Fault) with Modio Formation. Therefore the nature of the contactis unknown (Sapiie et al, 1999). Modio Formation is previously named Modio Dolomite (Pigram and Panggabean, 1983; Dowet al., 1988). Quarles van Ufford (1996) renamed this rock unit from Modio Dolomite toModio Formation to incorporate the siliciclastic member in the upper part. This formation isdivided into two members. The lower A Member is dominated by carbonate specifically

The Geology of Indonesia/Papua 5

well-bedded stromatolitic dolostone. On the other hand, fine-grained clastic rocksconsisting of bioturbated mudstone and siltstone dominate the upper B Member,fine-grained planar cross-bedded to horizontally laminated sandstone (Quarles van Ufford,1996). Modio formation is interpreted as a transgressive sequence deposited from tidal tomarine self. The age of Modio Formation is constrained as Silurian to Devonian based onLate Devonian (Frasnian) coral found and identified from the limestone in the Modio Bmember (Oliver et al., 1995). The upper contact with Aiduna is not well exposed and isinterpreted to be disconformable (Quarles van Ufford, 1996).Aiduna Formation was first named by Lehner et al. (1955) in the western part of theWaghete sheet as a part of the lower member of the Aifam Formation (Parris, 1994). InGBMA Martodjojo et al. (1975) placed this formation within Aifam Group as Aifam CMember of Visser and Hermes (1962). Pigram and Panggabean (1983) used AidunaFormation in Waghete Sheet area because of difficulty of subdividing the Aifam Group.Parris (1994) on the Timika Sheet area preferred the use of Aiduna Formation replacingAifam C Member, since he had already subdivided the lower Aifam into The Tuaba andModio Formation. Aiduna Formation is characterized by well-bedded coal bearingsilisiclastic rocks. This formation is interpreted to have been deposited in fluvial to deltaicenvironment (Visser and Hermes, 1962; Dow et al., 1988). However, the presence ofBrachiopods indicates that some of the Aiduna Formation was deposited in marineenvironment or perhaps lagoonal area (Martodjojo et al., 1975; Parris, 1994; Quarles vanUfford, 1996). The age of Aiduna Formation is constrained by Brachiopods fossils asPermian (Martodjojo et al., 1975) and by plant flora as Late Permian (Quarles van Ufford,1996). The contact with overlying Tipuma Formation is conformable. 14.3.2. MESOZOIC TO CENOZOIC SEDIMENTATION 14.3.2.1. TIPUMA FORMATIONThe Tipuma Formation is widespread in Irian Jaya, extending from the northwest Bird’sHead to the east near the border. Visser and Hermes (1962) were the first who formallygave the name Tipuma Formation for the rock unit derived from Kembelangan No. 1 well inthe Bird’s neck area. The Tipuma Formation is characterized by a distinctive red color withminor light green mottling. Tipuma Formation was deposited in fluvial environment duringthe period of continental rifting (Pigram and Panggabean, 1983). Field observationindicates that the thickness of the formation changes rapidly along the strike (Quarles vanUfford, 1994). This evidence is interpreted to be representing a horst and grabendepositional topography resulting from active extension. The age of the Tipuma Formationis solely constrained by its stratigraphic position, that is, Triassic to Early Jurassic. Pigramand Panggabean (1983) on Waghete Map Sheet suggested that the contact between theTipuma Formation and the overlying Kembelangan Group is unconformable (post-breakupunconformity).14.3.2.2. KEMBELANGAN GROUP The Kembelangan Group is recognized from the Bird’s Head to the Arafura Platform and is a regionally extensive unit deposited on the northern passive margin of the Australian continent during Mesozoic time (Visser and Hermes, 1962; Dow et al., 1988). Pigram and Panggabean (1983) divided the Kembelangan Group into four formations, the Kopai Formation, the Woniwogi Sandstone, the Piniya Mudstone and the Ekmai Sandstone. In the Bird’s Head region, the Kembelangan Group cannot be subdivided into four formations. The upper part of this group is known as the Jass Formation (Dow et al, 1988). The Jass

The Geology of Indonesia/Papua 6

Formation consists of quartz sandstone and calcareous mudstone. The Kembelangan Groupconsists of interlayer carbonaceous siltstone and mudstone in the lower section, andfine-grained glauconitic quartz sandstone and minor shale in the upper section. This groupwas deposited as a passive margin sequence conformably overlying the Triassic riftsequences of the Tipuma Formation (Dow et al., 1988; Parris, 1994). The contact withoverlying Waripi Formation of New Guinea Limestone Group appears to be conformable.14.3.2.3. NEW GUINEA LIMESTONE GROUP (NGLG)During the Cenozoic time, approximately at the Cretaceous and Cenozoic boundary, theisland of New Guinea is characterized by carbonate deposition known as the New GuineaLimestone Group (NGLG). The NGLG overlies the Kembelangan Group as originally definedby Visser and Hermes (1962). In central Irian Jaya, The New Guinea Limestone Group isgenerally divided into four formations. The basal unit is the Paleocene to Eocene Waripi Formation, which is composed offossiliferous dolostone, quartz sandstone and minor limestone. The Waripi Formation wasdeposited in a shallow marine, high energy environment. This formation has gradationalcontact with the Yawee Limestone (undifferentiated NGLG in ) and Late Cretaceous EkmaiSandstone (Pieters et al, 1983). The Eocene Faumai Formation conformably overlies the Waripi Formation. This formationis composed of thick-bedded (up to 15 m) to massive foraminifera-rich limestone, marlylimestone, dolostone and a few quartz-rich sandstone layers up to 5 m thick. The FaumaiFormation was deposited in shallow marine, medium energy environment. The EarlyOligocene Sirga Formation conformably overlies the Faumai Formation. This formation iscomposed of a foraminifera-bearing, coarse- to medium-grained quartz sandstone andsiltstone that is locally pebble-rich. The Sirga Formation was deposited in a fluvial toshallow marine environment after period of non-deposition. This formation is the onlysilisiclastic formation deposited in the Irian Jaya region between the Eocene and MiddleMiocene. Pigram and Panggabean (1983) name this formation as Adi Member. The SirgaFormation deposition is the result of the transgression that followed the Oligocene sea-levelfall as well as Oligocene orogenic activity in eastern New Guinea (Quarles van Ufford,1994). The Imskin Formation is a pelagic limestone which consists of well-beddedcarbonate mudstone, marl, chalk, chert and abundant pelagic foraminifera (Visser andHermes, 1962; Koesoemadinata, 1978; Pieters et al, 1983). This formation representsdeep-marine environment and grades upward into shallow-water carbonate. This formationranges in age from Paleocene to middle Miocene (Pieters et al, 1983). The Oligocene to Middle Miocene Kais Formation conformably overlies the SirgaFormation. This formation is composed primarily of foraminiferal limestone withinterbedded marl, carbonaceous siltstone and coal. The Kais Formation was deposited on amedium- to low-energy carbonate shelf. Biostratigraphic analysis indicates the youngeststrata to be ~ 15 Ma (Quarles van Ufford, 1996). In the Bird’s Head, the Kais Formationrepresents a reef complex comprising platform and patch reef facies. This formation islaterally equivalent to the Klamogun Limestone of Salawati basin. In addition, in theSalawati and Bintuni basins the Kais Formation partly interfingers and is conformablyoverlain by the Klasafet Formation (Dow et al, 1988).14.3.3. LATE CENOZOIC SEDIMENTATIONThe late Cenozoic sedimentation in the Australian continental basement is characterized bythe kilometer-thick siliciclastic sequences overlying middle Miocene carbonate strata

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(Visser and Hermes, 1962; Dow et al, 1988). In the Irian Jaya region, three majorformations are known and all of them are similar in terms of age and lithology (Pieters et al,1983). These are the Klasaman, Steenkool and Buru Formations. They occur respectively inthe Salawati and Bintuni Basins and in the southern part of the Central Range (Akimeugahand Iwur Basins). Locally, they are overlain by younger clastic sediments (i.e. Upa and SeleConglomerates). In northern Irian Jaya, siliciclastic rocks occurred in the North Coast Basin(Meervlakte) in the early middle Miocene (Visser and Hermes, 1962; Dow et al, 1988). Thisrocks unit known as the Makats Formation covers the oceanic basement. 14.3.4. STRATIGRAPHY OF THE PACIFIC PLATEThe detail stratigraphy of the Pacific plate (Oceanic province) is presented by Pieters et al(1983) and Dow et al (1988). In general, the Pacific rocks consist of mantle derived rocks,island-arc volcanis and shalow-marine sediments. The mantle derived rocks are exposedextensively along the Irian Jaya Ophiolite Belt (IOB), the Cyclop Mountain, Waigeo Island,north of Gauttier Mountain and as sliver blocks along the Sorong and Yapen Fault Zone(Dow et al, 1988). The IOB is approximately 400 km long and 50 km wide of east-west beltmade of ultramafic, basic plutonic and high-grade basic metamorphic (Dow et al, 1988).The age of the IOB is unknown, but it is interpreted as Mesozoic based on metamorphicblock. The Auwewa Volcanic Group is the volcanic rocks of the Pacific plate (Dow et al, 1998).Originally, Visser and Hermes named it Auwewa Formation. However, because all thevolcanic rocks have the same ages and is very similar in composition. They are all puttogether within one group. The rocks in the group are mostly the product of island-arcvolcanism which are remarkably uniform (Dow et al, 1988). They are mostly characterizedby basic composition. Throughout Irian Jaya they range in age from Paleogene to EarlyMiocene (Visser and Hermes, 1962). The sediments in Pacific plate are characterized by shallow-marine carbonate withinterbedded terrigenous sediments derived from island-arc and less commonly from themantle rocks. This unit, named as Holandia Formation (Visser and Hermes, 1962) and Dowet al (1988), was raised in status of unit to a group. The group is extensively distributed atWaigeo, Biak, and Yapen islands and on the flank of the Cyclop Mountains. The age of thisgroup ranges from Early Miocene to Pliocene. 14.3.5. STRATIGRAPHY OF THE TRANSITION ZONEThe convergence between Australian and Pacific plates generated rocks of within the zoneof deformation. This group of rocks is classified as transitional zone, which consists mostlyof metamorphic rocks. The metamorphic rocks formed continuous belt (>1000km) fromIrian Jaya to Papua New Guinea.In Irian Jaya low T regionally metamorphosed rocks are exposed along the Weyland Range and the northern flank of the Central Range. Historically, several different name have been proposed for these metamorphic belt such as Derewo Metamorphics (Pieters et al., 1983), Derewo Metamorphic Belt (Nash et al., 1993) and Ruffaer Metamorphic Belt (Dow et al., 1988, Warren, 1995). This belt generally consist of low T ( 300-350C and 5-8 kb) metapelites derived from the Mesozoic passive-margin of the Australian continent. The fact that the metamorphic rocks from Weyland Range recorded higher T (straulite-biotite-garnet; Dow et al., 1988) than in the Central is interpreted as result of the intrusion of the Utawa batholith (Warren, 1995). Isotopic ages from metapelitic rocks in Irian Jaya and Papua New Guinea record a late Oligocene to Earliest Miocene regional

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metamorphic event (Weiland, 1999). The contact seperating this belt and the Irian Fold Beltis gradational (Warren, 1995).

14. 4. REGIONAL STRUCTURES Only little structural geologic evidence has been found prior to Late Miocene tectonic event(Melanesian orogeny by Dow et al., 1988) in Irian Jaya. The evidence of the oldeststructures are recorded in the Paleozoic sections. However, the exposure of this group arelimited, therefore the knowledge of the Paleozoic tectonic is also very poor. Most of thestructural features in the island today are product of Late Miocene arc-continent collision.Later tectonic event (<4 Ma) is reactivated some of the older structures becomingdominated left-lateral strike-slip faults (Sapiie et al., 1999). In general, the structuralpattern in Irian Jaya can be divided in three major structural domains: Bird’s Head, Neckand Body. In the Bird’s body, W to NW trending structures is dominant throughout theCentral Range. This W-NW belt known as New Guinea Mobile Belt, a 300-km wide zone ofcontinuos belt from Papua Nugini to Irian Jaya (Dow et al., 1988). The New Guinea MobileBelt is terminated by EW trending continental strike-slip fault, the Tarera-Aiduna FaultZone (TAFZ), at Bird’s neck. The structures in the Bird’s neck are dominated by N-NWtrending fold known as Lenguru Fold Belt (LFB). This fold belt is terminated at the Kemumhigh in the Bird’s head region. In this region, the majority structures are dominated by EWtrending fault system.Sapiie et al. (1999) proposed that the piece of lithosphere north of New Guinea is moving asyet another distinct kinematic entity, the Caroline plate. This microplate is moving nearly,but not exactly, with the Pacific plate. In western New Guinea, the dominant effect of thisinteraction is to cause left-lateral transform motion. This motion starts in the Bismarck Sea,comes on land forming the 250 km long Bewani-Torricelli fault zone, makes a 200 km longright step with convergent deformation along the Mamberamo thrust and fold belt, returnsto left-lateral offset along the Yapen fault zone. Further west, a 300 km long left step formsthe divergent Waipona Trough which links to the Tarera-Aiduna fault zone which in turnextends westward to the Banda Sea. The Tarera-Aiduna fault zone separating the westdirected underthrusting at the Seram Trough from the northward subduction at theTimor/Aru Trench. The restraining bend forming the Mamberamo thrust and fold belt iswell defined from the regional seismicity. As earthquakes occur down to depthsapproaching 150 km, at least 200 km of convergence has occurred in this area and hence asimilar magnitude of strike-slip is indicated along the Bewani-Torricelli and Yapen faultzones. Near Biak Island, convergence probably only recently began as earthquakes areshallow and there is no evidence of significant recent deformation in the nearby NewGuinea Trench (Milson et al. 1992). In western New Guinea, significant west-directedconvergence has been accommodated at the Seram Trough, which has seismicity extendingdown to depths of 100 km. The major releasing bend in the system is the little studied Waipona Trough, a major depocenter since the Pliocene (Dow et al., 1988). Perhaps 50 to 100 km of lithospheric extension could have been centered on this zone. Based upon seismicity, active divergence is concentrated along the east coast of the Bird’s Head, cutting across the Lengguru fold belt. A southern extension of this divergent motion is the Aru Trough, which marks the rifting of the edge of the Australian plate. Total extension in either of these areas is small, perhaps 10 km. Because they do not appear to be long-lived phenomena, it is possible that

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underthrusting in the Biak area and extension along the back of the Bird's Head are veryrecent developments in the area.

Source: http:/ / en. wikibooks. org/ w/ index. php? oldid=1027094Contributors: Herman Darman

LicenseVersion 1.2, November 2002 Copyright (C) 2000,2001,2002 Free Software Foundation, Inc. 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA Everyone is permitted to copyand distribute verbatim copies of this license document, but changing it is not allowed.

0. PREAMBLEThe purpose of this License is to make a manual, textbook, or other functional and useful document "free" in the sense of freedom: to assure everyonethe effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this Licensepreserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others. This License is a kind of "copyleft", which means that derivative works of the document must themselves be free in the same sense. It complements theGNU General Public License, which is a copyleft license designed for free software. We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program shouldcome with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for anytextual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purposeis instruction or reference.

1. APPLICABILITY AND DEFINITIONS This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed underthe terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions statedherein. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you". You accept thelicense if you copy, modify or distribute the work in a way requiring permission under copyright law. A "Modified Version" of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/ortranslated into another language. A "Secondary Section" is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers orauthors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject.(Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matterof historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them. The "Invariant Sections" are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that theDocument is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant.The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none. The "Cover Texts" are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Documentis released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words. A "Transparent" copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public,that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (fordrawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formatssuitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged tothwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount oftext. A copy that is not "Transparent" is called "Opaque". Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML usinga publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent imageformats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGMLor XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by someword processors for output purposes only. The "Title Page" means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this Licenserequires to appear in the title page. For works in formats which do not have any title page as such, "Title Page" means the text near the most prominentappearance of the work's title, preceding the beginning of the body of the text. A section "Entitled XYZ" means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text thattranslates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as "Acknowledgements", "Dedications","Endorsements", or "History".) To "Preserve the Title" of such a section when you modify the Document means that it remains a section "Entitled XYZ"according to this definition. The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimersare considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these WarrantyDisclaimers may have is void and has no effect on the meaning of this License.

2. VERBATIM COPYING You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices,and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever tothose of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute.However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions insection 3. You may also lend copies, under the same conditions stated above, and you may publicly display copies.

3. COPYING IN QUANTITY If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document'slicense notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on thefront cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The frontcover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copyingwith changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying inother respects. If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover,and continue the rest onto adjacent pages. If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copyalong with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public hasaccess to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latteroption, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy willremain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents orretailers) of that edition to the public. It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them achance to provide you with an updated version of the Document.

4. MODIFICATIONS You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the ModifiedVersion under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of theModified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version: A.  Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there

were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that versiongives permission.

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B.  List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, togetherwith at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from thisrequirement.

C.  State on the Title page the name of the publisher of the Modified Version, as the publisher.D.  Preserve all the copyright notices of the Document.E.  Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.F.  Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this

License, in the form shown in the Addendum below.G.  Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.H.  Include an unaltered copy of this License.I.  Preserve the section Entitled "History", Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the

Modified Version as given on the Title Page. If there is no section Entitled "History" in the Document, create one stating the title, year, authors, andpublisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.

J.  Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the networklocations given in the Document for previous versions it was based on. These may be placed in the "History" section. You may omit a networklocation for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to givespermission.

K.  For any section Entitled "Acknowledgements" or "Dedications", Preserve the Title of the section, and preserve in the section all the substance andtone of each of the contributor acknowledgements and/or dedications given therein.

L.  Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not consideredpart of the section titles.

M.  Delete any section Entitled "Endorsements". Such a section may not be included in the Modified Version.N.  Do not retitle any existing section to be Entitled "Endorsements" or to conflict in title with any Invariant Section.O.  Preserve any Warranty Disclaimers.If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from theDocument, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in theModified Version's license notice. These titles must be distinct from any other section titles. You may add a section Entitled "Endorsements", provided it contains nothing but endorsements of your Modified Version by various parties--for example,statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard. You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of CoverTexts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by)any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entityyou are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added theold one. The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or implyendorsement of any Modified Version.

5. COMBINING DOCUMENTS You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions,provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as InvariantSections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers. The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there aremultiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, inparentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the sectiontitles in the list of Invariant Sections in the license notice of the combined work. In the combination, you must combine any sections Entitled "History" in the various original documents, forming one section Entitled "History"; likewisecombine any sections Entitled "Acknowledgements", and any sections Entitled "Dedications". You must delete all sections Entitled "Endorsements."

6. COLLECTIONS OF DOCUMENTS You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of thisLicense in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatimcopying of each of the documents in all other respects. You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License intothe extracted document, and follow this License in all other respects regarding verbatim copying of that document.

7. AGGREGATION WITH INDEPENDENT WORKS A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distributionmedium, is called an "aggregate" if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyondwhat the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate whichare not themselves derivative works of the Document. If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entireaggregate, the Document's Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of coversif the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

8. TRANSLATION Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing InvariantSections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections inaddition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document,and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices anddisclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version willprevail. If a section in the Document is Entitled "Acknowledgements", "Dedications", or "History", the requirement (section 4) to Preserve its Title (section 1) willtypically require changing the actual title.

9. TERMINATION You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify,sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have receivedcopies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

10. FUTURE REVISIONS OF THIS LICENSE The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will besimilar in spirit to the present version, but may differ in detail to address new problems or concerns. See http:/ / www. gnu. org/ copyleft/ .Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "orany later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that hasbeen published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose anyversion ever published (not as a draft) by the Free Software Foundation.

How to use this License for your documents To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license noticesjust after the title page: Copyright (c) YEAR YOUR NAME. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU FreeDocumentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts,and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the "with...Texts." line with this: with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation. If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free softwarelicense, such as the GNU General Public License, to permit their use in free software.