Sunday, October 03, 2010

Tectonic setting of Kalimantan, Indonesia

The tectonic features of Kalimantan are divided into two part:
                           1. Tertiary Basins

2. Pre to Early Tertiary Highs

1. Tertiary Basins:


The Barito Basin is situated along the southeastern margin of the Schwaner Shield in South Kalimantan
The Kutei Basin is the largest (165,000 km ) and the deepest (12,000 – 14,000 meters) Tertiary sedimentary basin in Indonesia.
The Tarakan Basin encompasses the basinal areas in NE Kalimantan
The Sandakan Basin, located in the southern portion of the Sulu Sea, with Tertiary deltaic complex in the south of the basin

2. Pre to Early Tertiary Highs :

The oldest fossiliferous rocks of the North- west Kalimantan domain are Late Carboniferous limestone and marble containing diagnostic fusulinids.


Meliat Formation (Middle Miocene)
Description: Interbedded sandstone, claystone and shale with coal intercalation.
Tabul Formation (Late Miocene)
Description: Interbedded claystone, mudstone, sandstone, limestone and coal in the upper part.
Sajao Formation (Plio-Pleistocene)
Description: Quartz sandstone, claystone, siltstone, coal, lignite and conglomerate.
Lengap Formation (Late Miocene)
Description: White tuff, chalky, conglomerate coarse grain sandstone, thick coal seams.
Latih Formation (Miocene)
Description: Quartz sandstone, claystone, siltstone and coal in the upper part, intercalation sandy shale and limestone on the lower part, coal seam 0.2 to 5.5 meter thick.
Labanan Formation (Late Miocene – Early Pliocene)
Description: Alternation of polymict conglomarate, sandstone, siltstone, claystone, intercalation of limestone and coal seam (20 to 150 cms).
Kayan Formation (Upper Oligocene)
Description: Quartz sandstone, shale, siltstone and conglomerate intercalations, silicified wood and minor coal .
Ketungau Formation (Upper Eocene)
Description: Sandstone and mudstone, thin coal seams in upper part.
Selangkai Formation (Upper Cretaceous)
Description: Shale, mudstone, sandstone, conglomarate, fossiliferrous limestone, rare coal genrally carbonaceous or calcareous.
Kuaro Formation (Eocene) 
Description: Shale sandstone, conglomerate, claystone, breccia, marl and limestone intercalated with coal.
Karangan Formation (Eocene)
Description: Conglomerate, sandstone, claystone intercalated with limestone and Lignite.
Kampung baru Formation (Pliocene)
Description: Sandy clay, marl and sand intercalated with coal and tuff .
Tebidah Formation (Lower Oligocene)
Description: Feldspathic lithareanite interbedded with mudstone and siltstone, thin coal seams in places.
Kantu Formation (Upper Eocene)
Description: Sandstone with minor conglomarate, ,mudstone in lower part, interbedded sandstone, siltstone, grey or red mudstone in upper part, locally coal seams.
Silat Shale (Upper Eocene to Lower Oligocene )
Description: Blake carbonaceous mudstone, shale, minor dark siltstone, fine to medium grained sandstone, at places thin coal seams.
Kelinjau Formation (Miocene)
Description: Mudstone, minor sandstone and volcano clastic rock, in places silicified wood and intercalations of coal.
Mentemoi Formation (Eocene to Oligocene)
Description: Lower part is sandstone, upper part is arokosic sandstone, fine to coarse grained reddish. Locally intercalated with quartz conglomerate and claystone with thin coal seams.
Batuayau Formation (Late Eocene)
Description: Sandstone, mudstone, siltstone, commonly carbonaceous, in places intercalation of coal and lignite
Anggota batugambing peanut Formation (Late Oligocene) 
Description: White and ghrey limestone, medium to coarse grained, rich in large forams, algae and coal.
Purukcahu Formation (Late Oligocene to Early Miocene )
Description: Fossiliferrous claystone, dark grey siltstone containing small lenses and thin layered vitrinite coal.
Pulaubalang Formation (Middle Miocene)
Description: Quartz sandstone and grey wacke, claystone with limestone intercalation, tuff and coal.
Balikpapan Formation (Middle to Late Miocene) 
Description: Quartz sandstone and claystone with intercalation of siltstone, shale and limestone with lignite intercalations.
Pamaluan Formation (Late Oligocene to Early Miocene )
Description: Sandstone with intercalation of claystone, shale, marl, siltstone, tuff, coal, Iron oxide and lenses of limestone, claystone with sandstone intercalation, thin coal seams in the lower sequence (25 to 75 Cms), in the upper part of sequence coal seam thickness is 0.5 to 5 Mts.
Montalat Formation (Oligocene)
Description: Cross bedded, white quartz sandstone, locally calcareous interbedded by siltstone, shale and coal.
Warukin Formation (Lower Miocene) 
Description: Sandstone (Tuffaceous and calcareous), siltstone and claystone interbedded with coal beds (0.3 to 2 mts)
Dahor Formation (Middle Pliocene to Pleistocene ) 
Description: Quartz sandstone with coal beds (0.3 to 3 Mts) with in coarse sandstone layers.
Berai Formation (Middle to Late Oligocene ) 
Description: Limestone interbedded by claystone, marl and coal. 


Pematang Formation (Oligocene to early Miocene ) 
Description: Carboneceous and red shale, Coal, siltstone, sandstone and breccio conglomerate
Lakat Formation (Oligocene to early Miocene ) 
Description: Lower part: polymict conglomerate, quartz sandstone and intercalated claystone, siltstone and tuff, with coal lenses. Upper part: alternating bands of quartz sandstone and silty carboneceous claystone with siderite nodules
Kelese Formation (Eocene)
Description: Light grey, brown and greenish, strongly lithified polymict conglomerate and conglomeratic sandstone with intercalation of siltstone ,claystone and coal
Lower member of Ombilin Formation (Mio-Pliocene ) 
Description: Micaceous quartz sandstone,arkose,clayey shale Quartz conglomerate and coal
Upper member of Ombilin Formation (Miocene)
Description: Sandy claystone ,Tuffaceous sandstone, quartz sandstone, glauconite sandstone, marly sandstone, coal seams and conglomerate with andesitic components
Muaraenim Formation (Mio-Pliocene )
Description: Sandstone,sandy claystone,and Lignite which reaches upto 10% of the formation thickness
Sinamar Formation (Oligocene) 
Description: Conglomerate coarse grained quartz sandstone, Miceceous quartz sandstone, Arkosic sandstone. claystone, marl, sandy claystone, coal seams and coral limestone
Talangakar Formation (Oligocene)
Description: Brownish dark grey sandstone, Sandy tuff and tuffecious sandstone with uniformly distributed, lignite locally and intercalated clay stone. Yellowish white limestone lenses in the lower part of the formation.
Papanbeteopang Formation (Oligocene)
Description: Polymict conglomarate, sandstone, claystone, siltstone and breccia with intercalation of tuffaceous sandstone and claystone, coal
Airbenakat Formation (Miocene)
Description: Clay stone alternating with sandstone incalation of calcareous conglomarate, siltstone, marl and coal. In the upper part dominantly sandstone
Simpangaur Formation (Pliocene)
Description: Claystone, breccia, tuffaceous sandstone, sandstone contains mollusas with coal intercalations
Kasai Formation (Late Pliocene)
Description: Conglomarate and Quartz sandstone, tuffaceous claystone containing silicified wood with pumice tuff and lignite intercalations
Bintunan Formation (Late Pliocene)
Description: Polymict conglomarate sandstone, claystone, pumice tuff with lignite intercalations, claystone contains mollusus
Sihapas Formation (Miocene) 
Description: Clean quartz sandstones, carbanaceous shales, siltstones, conlomarates 
Telukkido Formation (Jurassic to Cretaceous)
Description: Pyritic feldspathic meta quartzos Arenites and Argillites, thin coal and plant remains
Kumun Formation (Mio-Pliocene)
Description: Sandstone, Conglomarate, breccia, Lignite and tuff intercalation
Lemau Formation (Miocene)
Description: Breccia, dacaoitic tuff, sandstone with lignite intercalation, claystone containing mollusus and calcareous sandstone
Ranggam Formation (Mio-Pliocene)
Description: Alternate sandstone, claystone and conglomarate with lenses of coal

Tuesday, August 17, 2010

Biological Sulfate Reduction (BSR)

Organic matter decomposition can be a consequence of sulfate reduction in the sediments of coastal waterways (and other aquatic systems) [1]. The process is performed by anerobic sulfate-reducing bacteria. The bacteria require: metabolisable organic matter; an anoxic environment (or microenvironment); and dissolved sulfate. Hydrogen sulfide gas (H2S) and alkalinity are generated in the process (see simplified reaction 1).

(Eq. 1) SO42- + 2(CH2O) = H2S + 2HCO32-

Sulfate reduction is often a dominant process in eutrophic systems, occurring after the oxygen-consuming bacteria have removed dissolved oxygen. If dissolved oxygen is present in the water column, organic matter is preferentially decomposed by oxygen-consuming bacteria (follow link to Decomposition of Organic Matter).

Figure 1. A conceptual model of sulfate reduction and hydrogen sulfide and iron sulfide production in a coastal lake. SRB - Sulfate reducing bacteria.

The Fate of Hydrogen Sulfide
Some hydrogen sulfide from sulfate reduction can be released to the atmosphere (Figure 1). Hydrogen sulfide can be oxidised to sulfate or sulfur (So), or can react with iron sulfide minerals in the sediment (Figure 1 and 2). Iron monosulphides (FeS) form first, but are readily converted to pyrite (FeS2; Figure 2). The overall reaction is shown in Equation 2 [7].

(Eq. 2) Fe2O3 + 4S2-(mostly from H2S) + 6H+ = 2FeS2 + 3H2O + 2e

Figure 2. Diagramatic representation of the process of pyrite formation. (From Berner, 1983 [8]).

Consequences of Sulfate Reduction
  • H2S smells like rotton eggs, and can detract from the aesthetic amenity of coastal waterways when it is released to the atmosphere [2,5].
  • H2S is toxic to a wide range of aquatic organisms [3];
  • H2S can inhibit nitrification [4]. When nitrification is inhibited, coupled nitrification-denitrification is also inhibited.
  • Ammonium (NH4+) is released from organic matter during degradation by sulfate reduction (Equation 3) [6]. Ammonium is a bioavailable and is readily taken up by plants.
(Eq. 3) 106(CH2O)16(NH3)(H3PO4) + 53SO42- ® 106 CO2 + 16 NH3 + H3PO4 + 106 H2O + 53 S2-

  • Iron sulfides (e.g. pyrite), formed during sulfate reduction, are an active component of acid sulfate soils (ASS), and problems with acid production and drainage can arise if the pyrite is oxidised.
  • Iron sulfides cannot bind phosphate. Therefore, when iron oxyhydroxides are converted to iron sulfides during sulfate reduction, phosphate can be released to the water column [9].

1. Skyring, G.W. 1987. Sulfate Reduction in Coastal Ecosystems. Geomicrobiology Journal 5, 3/4, 295-374.

2. Murray, E. 2002. GA nose about smelly lake. AusGEO News 65, 7-9.

3. Connell, D.W., and Miller, G.J. 1984. Chemistry and Ecotoxicology of Pollution. John Wiley & Sons, N.Y.

4. Joye, S.B. and Hollibaugh, J.T. 1995. Influence of sulfide inhibition of nitrification on nitrogen regeneration in sediments. Science 270, 623-625.

5. Murray, E.J. and Heggie, D.T. 2002. Factors influencing extensive sulphate reduction in Lake Wollumboola, and intermittently closed/open lake (ICOLL) on the NSW south coast, Proceedings of the annual conference of the Australian Marine Sciences Association, 10-12 July 2002, Fremantle WA.

6. Froelich, P. N., Klinkhammer, G. P., Bender, M. L., Luedtke, N., Heath, G. R., Cullen, D., Dauphin, P., Hammond, D., Hartman, B., and Maynard, V. (1979). Early oxidation of organic matter in pelagic sediments of the eastern equatorial Atlantic; suboxic diagenesis. Geochimica et Cosmochimica Acta Pergamon, Oxford. 43, 1075-1090.

7. Berner, R.A. 1971. Principles of Chemical Sedimentology. McGraw Hill, Inc, U.S.A, 192-209

8. Berner, R.A. 1983. Sedimentary pyrite formation: An update Geochemica et Cosmochimica Acta 48, 605-615

9. Roden, E.E. and Edmonds, J.W. 1997. Phosphate mobilization in iron-rich anaerobic sediments: microbial Fe(iii) oxide reduction versus iron-sulphide formation. Arch. Hydrobiol. 139, 347-378.

Thursday, April 15, 2010

Geology of Indonesia - by separate regions

Geological map of Asia and far east

Geology of Kalimantan

Geology of Indonesia sedimentary basins

Geology of Java

Geology of Halmahera

Geology of Banda Arc

Geology of Arafura sea

Geology of Lesser Sunda Island

Geology of Makassar

Geology of Natuna

Geology of Papua

Geology of Sulawesi Sea

Geology of Sulawesi

Geology of Sumatera

Geology of Timor

Source: Wikibooks

Geology of Indonesia- At a glance

The Geology of Indonesia

This is the embryo of the online book about the geology of Indonesia. This wiki books means to be collaborated approach to acquire maximum knowledge available about the subject. This book is a collaborative approach of Indonesia geologists. Intended to compile the current technical knowledge on the geology of Indonesia. The subject is ranging from tectonics, structural geology, and stratigraphy. Because Indonesia is a vast region, the general geology for each region is described separately under the Regional Geology chapter.
The book also covers the geological application for the petroleum, natural resources and geological hazards. The geological hazard will also cover the recent development of earthquake, tsunami, and other hazards in Indonesia. Indonesia is located on the Pacific Ring of Fire with extensive volcanic network which give rise to the recent earthquake.
Indonesia is the largest archipleagic state in the world comprising five major islands and about 300 smaller island groups. Altogether there are 13,667 islands and islets of which about 6,000 inhabited. The archipelago is situated on a crossroad between two oceans, the Pacific and Indian oceans, and bridges two continents, the Asian and Australian. Indonesia has a total area of 9,8 million sq km, of which more than 7,9 million sq km under water. Physiographically, the islands of Sumatra, Java and Kalimantan are attached to the Sunda Shelf of the Asian continent. On this landmass the water depth does not exceed 200 meters. To the east, Irian Jaya and the Aru islands lie on the Sahul Shelf, which are parts of the Australian continent. Located between these two shelfal is the island grop of Nusa Tenggara, Sulawesi, Maluku and Halmahera. These islands are encircled by deep seas which in many places reach 5,000 meters. About 60 Tertiary sedimentary basins, spread out from Sumatra in the west to Irian Jaya in the east, are identified in Indonesia. So far only 38 basins have been explored and drilled for petroleum and 14 of the are now producing oil and gas. Seventy three percent of these basins are located offshore, about one third of them in the deeper sea, with water depth exceeding 200 m.
Indonesia is a meeting place of two tectonic plates, Australia and Asia. The Australian plate was moved northward and subducted under the Eurasian plate. The subduction zone can be traced from northern tip of Sumatra until the Lesser Islands, that creates deep submarine trench. Most of the earthquake also concentrate in this subduction zone. This subduction also trigger the formation of volcanic range from Sumatra, Java to Lesser Islands.
The Eastern Indonesia also experienced another subduction of Pacific plate that move southwesterly under the Eurasian plate. This subduction create the formation of volcanoes in the North Sulawesi, Sangihe and Halmahera.
The Indonesian archipelago includes some of the world's largest islands and the smallest coral islets. The main islands of Sumatra and Java contain high mountain ranges and active volcanoes. Mountainous terrain also persists into West Irian, the Indonesian portion of the island of New Guinea in the east, and in the central parts of Kalimantan on the island of Borneo and in Sulawesi. Elsewhere the land is low, lying either with forest cover much of which has been subsequently cleared for agriculture, or comprises swamps and marshes associated with the deltaic mouths of rivers or on coastal islands. About half of the territories is covered by sea with large areas of relatively shallow water in the South China, Java, and Arafura Seas and the Straits of Malacca. There are deep waters in the south of the archipelago, the north in the Celebes Sea and the western Pacific Ocean. Indonesian geology is very complex, dominated by several large tectonic plates. Seismic and volcanic activity indicates that these plates are still in motion to some extent. The deep Timor Trench, in the Timor Sea, is earthquake active. Indonesia and Australia in 1994 agreed on a joint exploitation of a hydrocarbon-rich area in the Timor Sea, as a follow up on an accord reached in 1989. In December 1995, they signed an Agreement on Maintaining Security. Although Australia was one of the few states in the world to recognise Indonesian rule over East Timor, until then Canberra considered Indonesia a military danger. Foreign oil firms are operating in the Timor Sea, where they have developed large gas and oil discoveries. Indonesia is located at the meeting point of the Australian, Pacific and South-East Asian plates. The Indian Plate passed close to Sumatra before colliding with Eurasia. As a result, the Indonesian archipelago comprises a number of Middle to Late Tertiary-aged back arc basins strung out parallel to the main chain of mountains which has been thrown up by the collision of the tectonic plates. The back arc basins have been filled with deltaic clastics mostly shed off adjacent shield areas. Invasion later by the sea resulted in deposition of platform carbonates and the build up of reefal limestones. Source rocks for these basins are frequently anoxic shales deposited in restricted lagoonal conditions in Early Tertiary grabens under the back arcs. Until recently all the major discoveries in Indonesia were associated with Tertiary sediments or, locally, with either basement or Tertiary volcanics. The oil and gas in the latter two are said to be sourced from Tertiary sediments. The Pre-Miocene rocks of South-East Asia and the potential for new oil and gas discoveries in these rocks are now the subject of wide interest in the industry. A number of major Pre-Miocene discoveries have been made during the past decade, including the Bach Ho (White Tiger) off south-eastern Vietnam. The field has about 200m barrels of oil in fractured and altered granitic basement. But the Pre-Miocene section is still relatively under-explored in much of South-East Asia. Discoveries in this section during the past six years have served to stimulate interest in it. In Pre-Miocene reservoirs on the Chinese side, for example, there are "buried hills" of prime importance to geologists. In Indonesia, where the western regions are mature while the east is largely unexplored, Eocene sandstones serving as a main reservoir have proved to contain large reserves of natural gas. A case in point is the Arco-operated Pagerungan field in the East Java Sea, which has major gas deposits in Eocene sandstones. Indonesia has 60 sedimentary basins, of which 36 in the mature west have been fully explored and 14 of them are now producing oil and gas. In the under- explored east, 39 Tertiary and Pre-Tertiary basins could be rich in hydrocarbons. But the eastern regions are remote, mountainous and jungle-clad, and lack infrastructure. A wildcat in Irian Jaya, a frontier region, can cost up to $40m, and in many cases helicopters are required to transport equipment and supplies. About 75% of exploration is located in producing concessions in western Indonesia. There are four oil producing regions: Sumatra, the Java Sea, East Kalimantan and Natuna. There are three main gas regions: East Kalimantan, Arun and Natuna. The main hydrocarbon provinces in Indonesia are the following: Sumatra, the biggest and longest island in Indonesia to the west, accounts for more than 60% of Indonesia's oil production. There, Caltex produces over 55% of Indonesia's oil. This is part of Riau province which also oversees the administration of Natuna islands. North Sumatra, in Aceh province, is an oil and gas producing region, with oil primarily in Tertiary clastics and mostly in small sized fields. Arun, however, with reserves in place of 10 TCF of gas and 750m barrels of condensate, is one of the world's largest suppliers of LNG and is reservoired in a pinnacle limestone reef. But Arun's proven reserves are depleting rapidly. Most of the hydrocarbons in this region are located onshore. Some potentially large gas deposits are in reefs offshore. Central Sumatra, mainly Riau province where Caltex operates, is primarily an oil zone with a small number of gas fields. Most of the hydrocarbons there are reservoired in deltaic sandstones contained in anticlinal structures. The province has Indonesia's two largest oilfields, both operated by Caltex: Minas, with oil reserves in place in excess of 4 bn barrels; and Duri, a shallow oil accumulation whose reserves of primary recovery were estimated in the early 1990s to be about 600m barrels. Duri is the site of one of the world's largest steam flood projects and ultimate recovery could exceed 3 bn barrels. South Sumatra is primarily an oil province, with hydrocarbons reservoired in both clastic and carbonate rocks. Field sizes are generally small. West Java and the adjacent Java Sea form an oil and gas province. Oilfields are reservoired in clastic and carbonate rocks and in fractured volcanics. Numerous oil and gas fields have been located offshore.
Source: Wikibooks