ASEM-ASEM BASIN, SOUTH KALIMANTAN

ASEM-ASEM BASIN, SOUTH KALIMANTAN

Asem-asem Basin is one of the Tertiary basins in Indonesia which has considerable energy potential, such as oil and gas and coal. The Asem-Asem Basin is located southeast of the Sundaland Continent Crust and is separated from the Barito Basin by the Meratus Mountains in the West. The Asem-Asem Basin is located in the southeastern part of the Sundaland continental plate boundary. This basin is separated from the Barito Basin by the Meratus Mountain in the west.

 

Map of Location of the Asem-Asem Basin (Rasoul Sorkhobi, 2012)

The Asem-Asem Basin is located in South Kalimantan and to the east of the wing of the Meratus Mountains. The eastern wing whose territory covers offshore areas is estimated to have Upper Oligocene limestones to the Lower Miocene, especially above the basement. To the north, this basin is separated from the Kutai Basin by the existence of Adang Flexure or fault that separates Barito from Kutai. To the south, extends towards the Java Sea to the height of Florence. This basin is asymmetrical with the front in the frontal zone of the Meratus Mountains and exposure to the Sundaland palace.

 

Regional geological map of Kalimantan

 

Physiography

Kalimantan Island is generally a swamp and fluvial region. In addition there are also flat and mountainous regions scattered on this island. The plains are scattered on the edges of the island and most of the mountains are in the center of the island. In the northern part of Kalimantan Island is the Pegungungan Kinibalu zone and in the North-West there are a range of Muller Mountains and the Schwaner Mountains. In the southern part there is the Meratus Mountains.

Physiography of Borneo Island, without scale (Bachtiar, 2005).

Van Bemmelen (1949) divided the western part of Kalimantan Island into two parts, namely:

• Kapuas Atas Mountains, located between the Rejang Valley in the north, Upper Kapuas Basin and Batang Lupar Valley in the south.
• Madi Plateu, located between the Upper Kapuas Basin and Melawi River.

Whereas in the eastern part of Kalimantan, Van Bemmelen (1949) also divided this area into two parts, namely:

• A series of mountains in northern Kalimantan, ending in the Darvel Bay Peninsula.
• Other mountain ranges, ending on the Mangkalihat Peninsula.

On the island of South Kalimantan itself has several large rivers, including the Kapuas River, the Barito River, the Negara River and the Kahayan River. The Barito River is the second largest river on the island of Borneo. The Barito River originates in the Muller Mountains and produces the Barito Basin which is bordered by the Meratus Mountains in the east. The rivers in the area of ​​South Kalimantan originate in the central part of the island of Borneo, namely the Schwaner Mountains and also the Muller Mountains. The Schwaner and Muller Mountains have a height between 200-2000 meters above sea level. While the direction of the rivers is relatively north-south and empties into the Java Sea. These rivers flow at an altitude of 0-200 meters above sea level. These large rivers occupy a large part of the southern part of the island of Borneo. In the eastern part of the Province of South Kalimantan there is the Meratus Complex Mountains which is a trace of subduction activities at the age of Cretaceous (Rotinsulu et al., 2006).

Stratigraphy

The basins in South Kalimantan are the Barito Basin and the Asem-Asem Basin which generally have relatively similar stratigraphic features from the old to the young. The Barito Basin and the Asem-Asem Basin are separated by the Meratus Mountains. In the north it borders the Kutai Basin which is separated by Andang Fault. Whereas the western part is limited by the Sunda Exposure. At first the Barito Basin and the Asem-Asem Basin were the same basin, until the Early Miocene there was the removal of the Meratus Mountains which caused the separation of the two basins (Satyana, 1995).

The stratigraphy of the South Kalimantan area includes several formations, namely basements in the form of Malihan Rock, Tanjung Formation, Berai Formation, Warukin Formation, and Dahor Formation and Alluvial Deposits. These formations are Eocene to Pliocene.

Basement rocks in the form of high levels of metamorphic rocks consisting of low-level amphibolite schist and composed of filite. Sikumbang (1986) introduces this high level metamorphic rock as Sekis Hauran which is composed of green schist containing quartz, muscovite, biotite, hornblende, epidote and low level minerals as Filit Pelaihari which consists of filite containing chlorite and mica minerals on the surface plane shiny and batusabak. This gray rock has a Jura age.

The Tanjung Formation was first introduced by Pertamina (1980; in Supriatna et al., 1981) for the oldest Tertiary rock formations in the Tanjung oil field. The Tanjung Formation is composed of alternating coarse sandstones, conglomerate sandstones and conglomerates at the bottom, gray claystone in the middle and thin siltstone silt and fine sandstone at the top that has a river or fluvial depositional environment and Late Eocene (Martini, 1971). At the top of this formation there is carbonate rock which is the beginning of the formation of the Berai Formation.

The Berai Formation is deposited in harmony above the Tanjung Formation, but in some parts there is a relationship that indicates an inconsistency. But in general this formation is deposited in harmony above the Tanjung Formation. The Berai Formation, which is dominated by limestones, has a deposition environment of the front reef, perhaps between the back, sublitoral, relatively shallow reefs, perhaps less than 30 meters, in the form of shallow sea or lagoon which is late Oligocene - Early Miocene (Te1-5 Adams, 1970).

The Warukin Formation was first used by Pertamina (1980; in Supriatna et al., 1981) and the location of its type is in the Kambilin area, Balikpapan, East Kalimantan. In harmony the Warukin Formation is deposited on the Berai Formation which is composed of gray-colored claystone, sandstone and coal inserts. The lower part of this rock sequence consists of the dominance of gray to blackish claystone with the insertion of medium-sandstone sandstones with parallel laminated sedimentary structures from carbon material, flaser and burrow. This formation is deposited in the marsh and tidal depositional environments of the Early Miocene-Late Miocene age.

The Dahor Formation is deposited incongruously above the Warukin Formation. The Dahor Formation is composed of claystone to sandstone clay, coarse sandstones - conglomerates that have gradual bedding structures, reddish sandstone with parallel laminated sedimentary structures and crossings and conglomerates that have components of granite, malihan, sediment and volcanic size 5-15 cm.

The Dahor Formation has a delta deposition environment and is Plio-Plistocene. Alluvial deposits in the Asem-Asem Basin are the result of a river (fluviatil) process which consists of deposits of mud, sand, gravel, greasy and lumps that are of the Quaternary age.

 

Regional regional stratigraphy of Asem-asem

Geological Structure

The geological structure found in South Kalimantan is anticline, syncline, upward fault, horizontal fault, and fault fault. The fold axis is generally northeast-southwest direction and is generally parallel to the normal direction of fault. In South Kalimantan there are two large basins, namely the Barito Basin and the Asem-Asem Basin. These two basins are bordered by the Meratus Mountains which cross from the north-southwest. The Barito Basin and the Kutai Basin are separated by an east-west fault in the northern part of South Kalimantan Province, this fault is known as Adang Fault (Mudjiono and Pireno, 2006).

 

Regional geological structure of the Asem-asem Basin

The structural regime that occurs in the Barito Basin is the transpression and transmission regime. The structure found is a fold that traverses northeast-south southwest (NNE-SSW) in the northern part of the basin. While in the Meratus Mountains there are faults carrying basements. These faults are marked by the presence of drag or fault bend fold and fault fault. Whereas the folds in the Meratus Mountains, which are in the northern part of the mountain, are trending north-south-southwest (NNE-SSW) and those in the south are north-south. Many folds are found in the form of anticlines and some synclines. There are many upward faults in the Meratus Mountains region with a general north-east-southwest direction (NNE-SSW). Horizontal faults are also found in the Meratus Mountains, generally not too long, in contrast to the rise faults that have a continuous continuity. Horizontal faults are generally in the form of faults trending and trending northwest-southeast (Satyana, 2000).

The study of geophysical data shows that the Meratus - Samarinda anticlinorium is estimated to have a general north-directed axis slope and is indicated regionally based on rock moves that the fault zone can generally be divided into three blocks, namely north, middle and south blocks. The northern block has been lifted on the western wing of the anticlinorium along the northern fault zone and is called the Tanjung fault zone. The middle block is located between the Tanjung fault zone and the Klumpang fault zone which is characterized by the emergence of granitic and ultrabasic breakthrough rocks along the fault zone. While the southern block is characterized by the extent of the development of the northeast trending fault which is closely related to the breakthrough diorite and ultramafic rock complex. A number of faults are southeast-northwest trending which are associated with magnetite deposits in the Pleihari region and can be observed from the emergence of a fault system intersection of all the blocks above.

Reference:

• Heryanto, R., 2010. Geologi Cekungan Barito. Bandung: Badan Geologi Kementrian Energi Sumber Daya Mineral.
• Muhammad Hidayat  Et Al, 2015,  Kondisi Dan Sumber Daya Geologi Pada Cekungan Asem-Asem, Provinsi Kalimantan Selatan, Jurusan Teknik Geologi,Sekolah Tinggi Teknologi Nasional, Yogyakarta
• http://suarageologi.blogspot.co.id/2012/06/stratigrafi-cekungan-asem-asem_14.html
• http://rorygeobumi.blogspot.co.id/2012/04/fisiografi-kalimantan.html
• http://rorygeobumi.blogspot.co.id/2012/04/kerangka-tektonik-regional-kalimantan.html