Geological Society, London, Special Publications Collision and strike-slip faulting in the northern Molucca Sea (Philippines and Indonesia): preliminary results of a morphotectonic study Claude Rangin, Daharta Dahrin, Ray Quebral and The Modec Scientific Party Geological Society, London, Special Publications 1996; v. 106; p. 29-46 doi:10.1144/GSL.SP.1996.106.01.04 Email alerting click here to receive free email alerts when new articles cite this service article Permission click here to seek permission to re-use all or part of this article request Subscribe click here to subscribe to Geological Society, London, Special Publications or the Lyell Collection Notes Downloaded by Michel Seranne on 31 August 2010 © 1996 Geological Society of London Collision and strike-slip faulting in the northern Molucca Sea (Philippines and Indonesia): preliminary results of a morphotectonic study CLAUDE RANGIN 1, DAHARTA DAHRIN 2, RAY QUEBRAL 3 & THE MODEC SCIENTIFIC PARTY ANNE GAELLE BADER, JEAN PAUL CADET, GLEN CAGLARCAN, BENOIT DEFFONTAINES, CHRISTINE DEPLUS, ERNESTO G. CORPUS, ROBERT HALL, YANN HELLO, JACQUES MALOD, SERGE LALLEMAND, DOMINGO B. LAYUGAN, RI~MY LOUAT, REYNALDO MORALES, KEITH PANKOW, MANUEL PUBELLIER, MICHEL POPOFF, REYNALDO T. RODELAS & TRAMANADI YUDHO 1 URA 1759 CNRS, Ddpartement de Gdotectonique, T 26-0 El, Universitd Pierre et Marie Curie, 4 Place Jussieu, 75252 Paris, France e ITB Bandung, Indonesia 3 Mines and Geosciences Bureau, Manila, Philippines Abstract: A swath mapping, gravity and single channel seismic survey was carried out in the northern Molucca Sea with R.V. L'Atalante. Preliminary interpretation of these data reveals the presence of an almost complete Sangihe arc and forearc. The Miangas-Pujada-Talaud ridge in the central part of the Molucca Sea appears to be a backstop within the Sangihe forearc. East of the ridge very contrasting terranes are separated by a major NW-SE crustal discontinuity interpreted as a left-lateral strike-slip fault. North of 6°N the Philippine Trench inner wall is dissected by NW-SE trending left-lateral strike-slip faults, resulting from the dominantly oblique convergence between colliding arcs. South of 6°N the westward subduction of the buoyant Snellius volcanic plateau, a fragment of the Halmahera arc terrane, has induced the formation of a new plate boundary, the Philippine Trench along what is interpreted as a former strike-slip fault zone. East of the Miangas-Pujada-Talaud ridge there is a wide sedimentary wedge separated from the Snellius Ridge to the south by the major NW-SE crustal discontinuity. The thickness of this wedge cannot be explained by subduction along the very young Philippine Trench. It could be either an accretionary wedge developed at the deformed leading edge of the Sangihe forearc or be part of a former intra-arc basin which was part of the colliding Halmahera arc terrane. There is no clear evidence for accreted oceanic crust belonging to the recently subducted Molucca Sea. The Miangas-Pujada-Talaud ridge is part of the Sangihe forearc, and the ophiolites could represent its basement, uplifted along the outer arc ridge. The dog-leg-shaped Philippine Trench is propagating southward across the fragmented Halmahera arc terrane and its southern segment could reactivate a former strike-slip fault zone. The collision of the Hahnahera arc (a fragment if the Sangihe arc is considered to be built on of the Philippine Sea plate) with the Sangihe arc the thinned margin of Eurasia (Rangin et al. (Fig. 1) has been described by Silver & Moore 1990a). (1978), Hamilton (1979), and Moore & Silver In this paper the geometry of this collision zone (1983). The ophiolites and melanges exposed is documented by a study of the geomorphology of in Talaud, Mayu and Tifore Islands have been the northern Molucca Sea, based on large coverage interpreted as fragments of the almost completely multibeam mapping, with gravity and single subducted Molucca Sea floor formerly separating channel seismic data. This dataset was recorded the two colliding island arcs (Silver & Moore during a cruise of R.V. L'Atalante in April and 1978; McCaffrey et al. 1980). The creation of May 1994 (MODEC cruise), in co-operation with a new plate boundary, the Philippine Trench, the Indonesian Institute of Development and east of the collision zone therefore marks a step in Technological Research, Jakarta (BPPT) and the the incorporation of the intra-oceanic Halmahera Philippines Bureau of Mines and Geosciences, island arc into the Eurasian continental margin, Manila (BMG). From Hall, R. & Blundell, D. (eds), 1996, Tectonic Evolution of Southeast Asia, 29 Geological Society Special Publication No. 106, pp. 29-46. -p+~.qutu.ts qzutu -smeiu 3!a+qusoql!l U.teLU +ql S~aoqs I+SU! +q& "~9S eoonlOlN oq+ jo ~laO~a+tueaj 3!tUeUApO+D "I "~!~I +,wvu ii ~,l un elml. eros P'////A ouoz UOllonPlln S V '"~/ ="''' " o~!i'IOU "q,,,, oAn;~Y 'u!dd.i|!qd V/////~ :)!]ouOow~ uo#low Oluld -- eleld ~ImmW~ )UOJl uo#s#llOO ~ o;nlosqv Ue!lUJlSni ue.lsLln 3 d!Is-Oq!JtS maonlow .... ~+..~,+. ~'" ~ " . • • . • ....,+.~-.+. ~~ .~'o~ : • • Nisvb :oTvJ.N" • • • • , ° . • . • • • " • ~ . +/: +:..,,---, • ~'. ":, ", .'..'.s • " A ~. " . ra:mtq Ills i~O L ~.i-...' • o . .;.. .... ,.'......'.'........:~.:,..:::... I~401 " " • qr~ • .": ~. .i.. .: ~. ' "~.;~."..: ". ) " • • .~.- ~:'~,~,8"" "..'.. ....,<. i ~''......... • ,g~(~)m.. :.......~..-...:~',~..• • -. m."X\+"'',,~-~" .. " " I%10 ~" ]].... • '~.+~/.+,,+,.... o" ",,~ ~(+)si' " " • . " • • • ~ • . N.O I~ Qd~, O;eld oU!Oed ='-~2 • e 0 • • o ~ I.I. o 5(.,I, oL;~L COLLISION AND FAULTING IN THE N MOLUCCA SEA 31 The preliminary interpretations of these data tration of 2 s twt). Gravity, magnetic, seismic and attempts to answer some basic questions are reflection and swath mapping surveys were con- presented here. How does the collision zone ducted to map geological structures and the thick- between the Molucca Sea basin margins change ness of sediments between the Halmahera and from frontal to oblique collision, after oceanic crust Sangihe arcs and the Philippine and Cotabato of the Molucca Sea has been entirely subducted Trenches. The position, speed and direction of the between the two colliding arcs? What is the ship were given by the GPS (Global Positioning morphotectonic signature of a newly created plate System) navigation system. The preliminary boundary, the Philippine Trench? interpretation of the structures in the survey area Gravity and seismological data from the is based on the morphological and geophysical data Molucca Sea were published by Silver & Moore gathered on board in real time. A total of 3725 (1978) and McCaffrey et al. (1980) but the only nautical miles were surveyed during the cruise detailed bathymetric map available before the providing a detailed bathymetric map (Fig. 2). cruise was that of Krause (1966). Seabed mapping L'Atalante is equipped with a SIMRAD EM-12 should allow a better understanding of the dual multibeam echo sounder which provides geometry of this diachronous collision and the bathymetry and reflectivity imagery of the sea rapid structural variations expected in the transition floor. Only the bathymetric data are discussed here. zone between collision and oblique subduction. The MODEC cruise also involved continuous Here, the focus is on the interpretation of newly gravity and magnetic measurements and six acquired seabed surface data (bathymetry and channel seismic recording. The few seismic data reflectivity, 3.5 kHz echo sounder and single presented here are single channel records acquired channel seismic reflection with a maximum pene- on board and are not yet reprocessed. 123 ° E ~23"3o 124°E 124°3(~ 125°E msO3OE 126"E ms*3OE 127°E 127o30E 128°E 128°3<~ 129"E r r i I i l + 7oh 7*N +°" - 6ON +'+'_- _- 5"30N 5°N ]-+/ t 1 \: ,++,,,., - [ +.-', + - 4o30N 4*N 3°3ON +' i 3°N • " Morotai ~3ON 2=30N -- ~ Tagulandang _ ~ -- _ Halmahera~'i~ 2°N 2ON 123°E 123°30E 124°E 124°~E 125°E 12S°30E 126°E 1~°3OE 1 27°E +27*3oE 128°E t2B*~E 1290E Fig. 2. MODEC cruise tracks. 32 C. RANGIN ET AL. Geodynamic framework presence of a slab more than 700 km below the Celebes Sea (Cardwell et al. 1980) provides an The Molucca Sea is located at the junction of three indication of the extent of the subducted oceanic convergent major lithospheric plates (Fig. 1). The basin. Eurasian plate is bounded by active volcanic arcs The Philippine archipelago is the site of the (west Mindanao, Sangihe, and north Sulawesi) and active collision between the Philippine Sea plate includes the marginal basins of the Celebes Sea and carrying an extinct volcanic arc and continental South China Sea which opened in Palaeogene fragments rifted away from the Eurasian margin times. The northern margin of the Australian plate (Holloway 1982; Rangin et al. 1990a). The present extends from New Guinea in the east to central tectonic setting of the Philippines shows an elon- Sulawesi in the west. The Philippine Sea plate has gated Philippine Mobile Belt, fringed by two recent a western part formed largely of Palaeogene and subduction zones (Lewis & Hayes 1983), and older oceanic crust (the West Philippine Basin) traversed axially by the 2000 km long left-lateral which probably formed in a backarc environment. Philippine fault (Willis 1937; Allen 1962; Aurelio The associated arc currently comprises a major part et al. 1991). The volcanic arc of Oligocene age, of the Philippine archipelago, now orientated which forms the basement to the eastern part of the approximately north-south between Luzon and mobile belt, is in tectonic contact with the Eurasian Mindanao, and extending southwards into the margin represented by continental fragments Halmahera arc. exposed in the western part of this belt, and rifted Kinematically, the Australian plate is moving away from the Eurasian mainland in south China northward with respect to Eurasia at a rate of 7- (Holloway 1982; Rangin et al. 1990a). 8 cm a -1. The Philippine Sea plate is moving west- Southeast of Mindanao, the collision between the wards with respect to Eurasia about a pole of Halmahera arc and the along-strike equivalent of rotation located at approximately 48°N and 157°E the western part of Mindanao occurred during the (Seno et al.