Neogene Structures and Sedimentation History Along the Sunda Forearc Basins Off Southwest Sumatra and Southwest Java
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Marine Geology 219 (2005) 133–154 www.elsevier.com/locate/margeo Neogene structures and sedimentation history along the Sunda forearc basins off southwest Sumatra and southwest Java Susilohadi Susilohadia,b, Christoph Gaedickea,*, Axel Ehrhardta aFederal Institute for Geosciences and Natural Resources, Stilleweg 2, D-30655 Hannover, Germany bMarine Geological Institute, Bandung, Indonesia Received 14 December 2004; received in revised form 27 April 2005; accepted 5 May 2005 Abstract Twenty multi-channel seismic lines in the southwest Sunda arc margin between Manna and west Java have been studied. This study depicts the structures and stratigraphy of the fore-arc basin since Late Paleogene in relation to the regional tectonic events. The paleomorphology of the Cretaceous continental margin persisted until the Oligocene and the paleoshelf margin of the continent extended north-westward off Sumatra. A residual basin filled with turbidite deposits developed just offshore of this margin. Subsequent fore-arc basin evolution was related to the slow down of subduction rate due to the collision of the Indian and Eurasian Plates in the Eocene. The rising Himalayan orogenic zone shed large amounts of sediment to the Indian Ocean and Sunda Trench beginning in the Late Paleogene which led to the growth of the accretionary prisms and the development of the Neogene fore-arc basin. At least two major structural events can be recognized in the fore-arc basin between Late Oligocene and Pliocene. Back thrust-faulting along the southern border of the fore-arc basin and initiation of the Cimandiri Fault Zone occurred in Late Oligocene, whereas the development of the Sumatra and Mentawai Fault Zones was initiated in Pliocene. Four Neogene sedimentary units can be recognized representing three main transgressive–regressive cycles and basin-fill deposits. The cycles resulted from a complex interplay of tectonically induced basin subsidence, eustatic sea level change and sediment supply related to volcanic activity that became abundant since late Middle Miocene. Turbidite deposition was common along and seaward of the basin slope during sea level lows in late Middle Miocene and Late Miocene. Sediment aggradation and progradation occurred during high sea level still stand and fall, respectively. Basin fills occurred mainly during the Pleistocene. D 2005 Elsevier B.V. All rights reserved. Keywords: Fore-arc basin; Sunda arc; Sumatra fault zone; Mentawai fault zone; Java; Sumatra 1. Introduction * Corresponding author. Tel.: +49 511 643 3790; fax: +49 511 643 3663. A joint Indonesian–German project—the Geoscien- E-mail address: [email protected] (C. Gaedicke). tific Investigation of the Active Convergence zone 0025-3227/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.margeo.2005.05.001 134 S. Susilohadi et al. / Marine Geology 219 (2005) 133–154 between the Eurasian and Indo-Australian Plate off ments, gravity profiling, swath bathymetric and Indonesia (GINCO 1)—was undertaken in 1998 to sediment echographic recordings. The main scientific acquire bathymetric and geophysical survey lines off objectives of this project were to study: southeast Sumatra and southwest Java (Figs. 1 and 2). The survey included digital multi-channel seismic re- – The geologic-tectonic development of the plate mar- flection profiles (MCS), gradient magnetic measure- gins and the structure of the subduction zone; and Fig. 1. Generalized tectonic map of western Indonesia and location of study area. Structures on Sumatra are based on Sieh and Natawijaya (2000) and the Mentawai Fault Zone is based on Diament et al. (1992) and the present study. Limit of Cretaceous continental crust is taken from Hamilton (1979). CFZ=Cimandiri Fault Zone. S. Susilohadi et al. / Marine Geology 219 (2005) 133–154 135 102o E 103o E 104o E 105o E 106o E 107o E A-1X A-2X-1 Manna 7-14 13 SUMATRA 5 SO 00 200 1000 1500 SO137-10 Fig.10 SO137-09 o 1000 5 S 1 200 500 2000 Kota Agung SERIBU PLATFORM ENGGANO SO137-12 500 SO137-11 SO137-20 STRAIT 6oS Fig.7 1500 SUNDA SO137-19 6 2000 7-3 13 C-1SX SO PANAITAN SO137-06 JAVA 3 SO137-0 000 Fig.6 1500 UJUNG KULON ACCRETIONARY WEDGE 4 SO137-42 UK-1 C-1 Bayah SO137-27 Pelabuhan 2000 7oS Fig.3 2000 Ratu 1000 3500 SO137-30 SO137-33 Ciletuh 3000 SO137-31 JAMPANG 5000 45 00 400 0 SO137-29 500 200 6000 1500 SO137-34 2500 2500 5500 Fig.4 3000 Fig.5 o 6500 8 S SUNDA TRENCH 2500 5500 6000 2000 SO137-01 SO137-03 Legend Tectonic deformation front 9oS 5000 5500 Bathymetric contour (m) A-2X-1 Drill hole Reflection seismic line, 0 50 SO137-30 Solid line used for Figure 5 10oS 0 500 0 100 km 4 5 00 Fig. 2. Bathymetric map of study area modified from Etopo2 Global 2’ Elevation (Smith and Sandwell, 1997) and the location of the SO137 (GINCO) seismic lines used for this study. Bold lines are used for Figs. 3-7 and Fig. 10. – The facies distribution, stratigraphy and thick- The Sunda Arc is characterized by deep fore-arc nesses of accumulated sediments along the fore- basins, which extend between an outer arc high and arc region. the island arc. The hydrocarbon potential and basin 136 S. Susilohadi et al. / Marine Geology 219 (2005) 133–154 evolution of the basins off northern Sumatra is well 1975; Hamilton, 1979), and became very active during constrained (Izart et al., 1994) while the evolution of the Paleocene when the subduction rate was greater the fore-arc basins off southern Sumatra and south- than 15 cm/yr (Molnar and Tapponnier, 1975; Karig et west Java are poorly understood. The study presented al., 1979). A slow down of the convergence rate to 3 here focuses on the seismic stratigraphy and the de- cm/yr occurred in the Middle Eocene when the Indian velopment of Neogene structures in the fore-arc basin. continent started to collide with Eurasia (Karig et al., The study is based on the interpretation of 20 MCS 1979). The decrease in the convergence rate led to the lines (Fig. 2), which cover an offshore area between development of many extensional basins in Southeast west Manna and southwest Java together with multi- Asia (Daly et al., 1991; Hall, 1996, 1997). In the Late beam bathymetric data off southwest Java. However, Eocene–Early Oligocene a renewed spreading in the this study should be regarded as a preliminary study Indian Ocean led to the change of convergence direc- due to the lack of other controlling data such as well tion to nearly NE and to an increase in the subduction data. In addition, most of the seismic lines are not rate along the Sumatra and Java margins to a steady 5– closely spaced and a lack of tie-lines resulted in 6 cm/yr (Liu et al., 1983; Karig et al., 1979; Daly et al., interpretation uncertainties. 1987; Hall, 1996, 1997). This, in turn, initiated the Neogene fore-arc basin development along the margin of the Sunda arc. The Late Oligocene–Early Miocene 2. Regional geological setting collision of India and Eurasia caused massive amounts of terrigenous sediment to be dumped into the Indian The Sunda Arc comprises the Sunda Trench, outer Ocean and Sunda Trench. These sediments were rap- arc high or fore-arc ridge, the fore-arc basins, the idly accreted, creating the large accretionary prism active volcanic arc and the Cenozoic foreland on (Matson and Moore, 1992). northeast Sumatra and northern Java (Hamilton, Two models are discussed to explain the oblique 1979). Parts of the outer arc high rise above sea subduction along the western Sunda Arc margin: (1) a level and form outer arc islands off western Sumatra, significant counter-clockwise rotation of Sumatra, whereas they lie below sea level south of Java. Karig southern Malaya and Kalimantan in the Middle Mio- et al. (1980) and Moore and Karig (1980) have attrib- cene (Ninkovich, 1976; Hall, 1997) and (2) the re- uted the rapid outgrowth of the fore-arc ridge in the newal of spreading in the Indian Ocean accompanied western part of Sumatra to the accretion of thick by the change of convergence direction of Indian Plate Bengal and Nicobar fan sediments since the Late with respect to the Eurasian Plate to NE (Huchon and Miocene. The fore-arc basins extend from Burma in Le Pichon, 1984; Jarrard, 1986; Malod et al., 1995). the north to eastern Indonesia in the south (Moore et Both models led to increased obliquity that was ac- al., 1980, 1982). They are bordered by the outer arc companied by initiation of strong magmatic activity high and by the margin of the Sunda Island Arc. This (Simanjuntak and Barber, 1996; Hall, 1996, 1997). system resulted from plate convergence along the The oblique subduction beneath Sumatra caused the subducting oceanic Indian–Australian Plate beneath partition of strain into an orthogonal component the continental Eurasian Plate (Hamilton, 1979). resulting in thrust faulting in the accretionary wedge The relative movement between the Indo-Austra- and a right-lateral strike-slip component expressed by lian and Eurasian Plates during the Cenozoic is well the Sumatra Fault (Katili, 1973; Hamilton, 1979; constrained by paleomagnetic data and ocean floor Moore et al., 1980; McCaffrey, 1991, 2000; Malod magnetic anomalies on which various regional plate et al., 1995) and Mentawai Fault (Diament et al., tectonic reconstructions have been proposed (e.g. Daly 1992) systems. The Sunda Strait region represents et al., 1987; Rangin et al., 1999; Longley, 1997; Hall, the transition zone from the oblique convergence 1996, 1997). Since the Early Cenozoic India and Aus- along Sumatra to nearly normal convergence off tralia became a single plate and moved northward southern Java.