II. SUNDALAND

This chapter of the bibliography combines literature on the relatively stable continental crust region of Western Indonesia, a collage of continental blocks, volcanic arcs and accretionary terranes that amalgamated before Late Cretaceous time, and is now part of the Eurasia continent. It includes the large islands of Sumatra, Java and Borneo (in separate chapters) and a broad shelfal region in-between, named the Sunda Shelf. The geology of this region shares many common elements with the Malay Peninsula and the Malaysian offshore shelfal regions.

It contains 231 pages with about 1970 titles, subdivided in five parts:

  1. II.1. Sumatra - General, onshore geology, volcanism, minerals
  2. II.2. Sumatra - Cenozoic Basins, Stratigraphy, Hydrocarbons, Coal
  3. II.3. Sumatra - Offshore Forearc and islands
  4. II.4. Sunda Shelf (incl. 'Tin islands', Singkep, Karimata)
  5. II.5. Natuna, Anambas

Download pdf - Chapter II. SUNDALAND (2.52 MB)


II.1., II.2., II.3., Sumatra

The geology of Sumatra is ably described in the recent comprehensive compilation by Barber, Crow & Milsom (2005). Additional information may be found in the almost 1100 Sumatra papers listed in this bibliography.

SW-NE cross-section across W part of South Sumatra  (Westerveld 1941)
SW-NE cross-section across W part of South Sumatra (Westerveld 1941)

The 'basement' geology of the large island of Sumatra is composed by complexly deformed Late Paleozoic- Mesozoic sediments and associated volcanic and igneous rocks. The presence of intense compressional deformation and juxtaposition of unrelated stratigraphies was already recognized by Tobler (1917).

The first broad synthesis of the Sumatra basement terranes in modern plate tectonic terms was by Pulunggono and Cameron (1984). They recognized the continuation of the geology of the Malay Peninsula and the principal Gondwana-derived terranes that amalgamated in the Late Triassic and the collision of the 'Woyla' arc/accretionary terrane in the Cretaceous. Additional microcontinental terranes may be present in the present-day fore-arc of North and C Sumatra (Natal, Sikuleh Terranes; Cameron et al. 1980, Wajzer et al. 1991, Barber 2000).

A good overview of Carboniferous- Cretaceous deposits and fossils is the book by Fontaine & Gafoer (1989). Most of the Permian deposits have near-tropical faunas (fusulinid limestones) and floras (the classic 'Cathaysian 'Jambi Flora'), and can be tied to the Indochina- East Malaya group of plates that separated from Gondwana probably in the Devonian. Some areas. Other areas appear to carry an Early Permian near-glacial signature ('Mergui microplate') and can be correlated to the W Thailand- West Malaya 'Sibumasu terrane' that separated from Gondwana in the Permian.

Pre-Tertiary 'basement' is unconformably overlain by sediments of a series of Late Eocene-Oligocene (ages poorly constrained) and younger rift basins, and, in the western half of the present island, by Oligocene- Early Miocene arc volcanics and the Late Miocene-Recent active volcanic arc.

A widespread Plio-Pleistocene compressional event inverted many of the Paleogene rift normal faults, creating most of today's surface anticlines. The oblique subduction of the Indian Ocean plate under Sumatra gave rise to the major Sumatra Fault Zone, a NW-SE trending right-lateral strike slip fault zone across the Barisan Mountains volcanic arc. A similar, parallel fault zone, the Mentawai FZ is present in the offshore and roughly parallels the front of the accretionary prism.

Sumatra has long been an important hydrocarbon province, with all production from the North, Central and South Sumatra 'back-arc' basins. The distribution of oil and gas fields is very 'spotty': fields are found only above, or within less than 50km migration distance from rift basins with Early Oligocene syn-rift lacustrine 'brown shales' and (volumetrically less important) Late Oligocene- earliest Miocene 'early post-rift' coaly source rocks.

The early exploration, in the late 1800's- early 1900's, focused on drilling surface anticlines, many of which had surface oil and gas seeps. Targets were relatively shallow, stacked Middle- Late Miocene fluvial- deltaic sandstone reservoirs. A deeper and volumetrically the most important play is in Late Oligocene- basal Miocene fluvial-deltaic sandstones. It was discovered accidentally over Christmas in 1922 by drilling 'too deep' into the thick Early Miocene marine Telisa shale at Talang Akar-Pendopo in S Sumatra (Talang Akar field in Talang Akar Fm). The first discovery in the Central Sumatra basin was in 1939 in the Lirik field and is also in this play. The largest fields oil fields in Sumatra are the giant 3-5 billion barrels Duri and Minas fields in C Sumatra, discovered in 1941 and 1944.

A third play, which could not be explored in the old days of surface anticline mapping, is in Early-Middle reefal carbonate buildups, and was a main focus of 1970's- 1980's exploration in N and S Sumatra (carbonates are absent in the C Sumatra basin). The Arun field in N Sumatra, discovered in this play in 1971, is one of Indonesia's largest gas fields. A fourth play, in fractured and weathered Pre-Tertiary basement, has generated interest since the mid-1980's, but volumes have been relatively minor.


II.4. Sunda Shelf (incl. 'Tin Islands', Karimata)

Some 240 papers are in the bibliography primarily on the Sunda Shelf, a broad shallow sea, that was exposed land during the Pleistocene glacial lowstands. A pattern of Pleistocene relict river channels draining from Sumatra and Borneo into the South China sea was mapped by Molengraaff (1919), Hanebuth et al. 2000), etc.

  Drowned Pleistocene incised river valleys on Sunda Shelf  
 
Drowned Pleistocene incised river valleys on Sunda Shelf  (Molengraaff, 1920)

The Sunda Shelf forms the relatively stable core of 'Sundaland', an area of relatively old continental terranes (Indochina- E Malaya- SW Borneo?), that amalgamated with Asia before the Permian. Pre-Tertiary rocks outcrop extensively, or are covered by only a thin veneer of fluvial and shelfal relict sediments.

The main economic interest of the region is in the 'tin islands' Lingga, Singkep,Bangka and Belitung, off the NE coast of Sumatra, probably extending to the Karimata islands off SW Kalimantan. They are the S part of the SE Asian tin belt, which extends from N Burma, Thailand and W Malaysia. Mining has taken place since the early 1800's and Indonesia has produced ~15% of all tin mined in the world, mainly from alluvial cassiterite placer deposits eroded from Late Triassic granite intrusives. Today, reserves are largely depleted.

SW-NE cross-sections across Kundur-Batam (top) and Singkep- Lingga (bottom)
SW-NE cross-sections across Kundur-Batam (top) and Singkep- Lingga (bottom), showing imbricated Permo-Carboniferous overlain by less-deformed Triassic clastics, intruded by granite (Bothe, 1928)

The oldest rocks on Bangka and Belitung are Paleozoic mica schists and low-metamorphic, isoclinally folded Carboniferous- Permian flysch-type clastics with basalts,  radiolarian cherts, etc.. Rare limestone blocks with Permian fusulinids (De Roever 1951, Van Overeem 1960) and some poorly preserved Cathaysian flora suggest affinities with the E Malaya block and W Kalimantan.

Cretaceous and Tertiary deposits are absent or very thin.

Suggest Reading Sumatra- Sunda Shelf:
Geology

Verbeek (1897), Molengraaff (1919, 1921), Aernout (1922), Bothe (1928), Westerveld (1936, 1941), Katili (1967, 1968), Ko (1986)

Tin deposits/ mining

Bothe (1925), Wing Easton (1937), Adam (1960), Cissarz & Baum (1960), Hosking (1970), Aleva et al. (1973), Sujitno (1977), Batchelor (1979)

Permian- Triassic fauna/ flora

De Neve & De Roever (1947), Kruizinga (1950), Jongmans (1951), Roever (1951), Van Overeem (1960), Strimple & Yancey (1976), Hosking et al. (1977), Archbold (1983)

Pleistocene Sunda Shelf

Molengraaff & Weber (1921), Van Baren & Keil (1950), Emery (1969), Hehuwat (1972), Hanebuth et al. (2000-2010)


II.5. Natuna

The Natuna area forms the N edge of the Sunda shelf. Geologically it may be viewed as a westerly continuation of the Cretaceous active continental margin of NW Borneo, with a basement of Late Cretaceous granites and metamorphic-accretionary complexes with ophiolitic material.

Natuna island is on the N-S trending Natuna Arch basement high, which is part of the non-extended Sunda Shelf. Its core is composed of intensely folded Jurassic- Cretaceous Bunguran Fm deep water clastics and volcanics with radiolarian cherts and gabbros-serpentinites, and is very similar to the 'Danau Fm' of C Kalimantan (Bothe 1928). It is intruded by Late Cretaceous granites, one of which forms the highest mountain on the island (Mt. Tanai; 1035m). This basement complex is unconformably overlain by thin Oligocene- Miocene fluvial sediments.

The Natuna islands are bordered on three sides by Oligocene rift basins, the Malay- W Natuna basin in the West, The South China Sea in the North and the E Natuna basin in the East.

Most of the publications on the Natuna area are on oil and gas exploration and fields in the West and East Natuna basins. The West Natuna Basin is connected to the larger Malay Basin. Exploration and production focused on Late Oligocene- Miocene fluvial-deltaic clastic reservoirs, mainly in young (~Late Miocene) inversion structures.

The East Natuna basin was not affected by the young inversion tectonics. It contains large E-M Miocene reefal buildups, some of which are gas bearing, typically with high CO2 content.

Suggested Reading Natuna:
Geology

Bothe (1928), Haile (1970, 1971), Pupilli (1973), Franchino (1990), Harahap & Wiryosujono (1994), Hakim & Suryono (1994, 1997), Hakim (2004)

W. Natuna Basin

Wongkosantiko & Wirojudo (1984), Daines (1985), Ginger et al. (1993), Fainstein & Meyer (1997), Phillips et al. (1997), Gunarto et al. (2000), Maynard et al. (2002), Morley et al. (2003), Hakim et al. (2008)

E. Natuna Basin

Sangree (1981), Kraft & Sangree (1982), Franchino & Viotti (1986), Rudolph & Lehmann (1989), Dunn et al. (1996), Bachtel et al. (2004)


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