TARAKAN BASIN - BORNEO

TARAKAN BASIN - BORNEO

Tarakan Basin, as the name implies, is around Tarakan Island. The island is geographically located in the Tarakan area, and its surrounding area, East Kalimantan Province, about 240 km north - northeast of Balikpapan. Geologically this island is located in the middle of the Tarakan Basin which is part of the NE Kalimantan Basin. Basically, the NE Kalimantan Basin is divided into 4 groups Sub basins: Tidung Sub Basin, Berau Sub Basin, Muara Sub-Basin, and Tarakan Sub-Basin.

Tarakan Basin is located in the northern part of Kalimantan Island. The area reaches 68,000 km2. In general, the northern part of this basin is limited by Mangkaliat exposure, in the East it is bordered by the Sulawesi Sea and in the West it is limited by the Central Range Complex.

 

Map of Location of the Tarakan Basin

Tarakan Basin can be divided into several sub-basins namely:

1. Tidung Sub-Basin

This sub-basin is located in the north and is on land extending to Sabah and developing during the Late Eocene to the Middle Miocene. Separated from the Berau Basin children to the south by the Latong Punggungan. Apart from Tarakan by the Sebuku Exposure, the anticline and fault rise northwestward along the coast and are bordered by a flat shear fault in northern Sempoa.

2. Tarakan Sub-Basin

This sub basin developed mainly in offshore areas filled with thick Plio-Pleistocene clastic deposits with deposition centers around Bunyu Island and Tarakan and have experienced pinchout and onlap to the west

and south.

3. Estuary Sub Basin

This sub basin is located off the coast of Tinggian Mangkalihat. It has the southernmost deposition center, developing off the coast. It is bounded by parallel parallel faults, the Mangkalihat and Maratua faults, cracked and passive margin sediments, and Oligocene carbonate structuring - Recent in the postrift section, which is the host rock at Eocene age.

4. Sub-Berau Basin

The Berau sub-basin is located in the southernmost part of the Tarakan Basin which developed from Eocene to Miocene and has a similar deposition history with the Tidung Sub-Basin. The dominant structure found on Tarakan Island is a normal fault trending Northwest to North with a fractured plane tilted to the East. Some of these faults are growth faults with roll over.

Tarakan Sub-Basin (Tossin and Kodir, 1996)

TEKTONIK

Tarakan Basin has a variety of faults, structural elements and trends. The tectonic history of the Tarakan basin begins with the extension phase from the Middle Eocene which forms a NW-SE direction wrench and influences the process of fracturing the Makassar strait which stops at the Early Miocene. This initial tectonic phase is the opening phase of the basin to the east which is indicated by the presence of enechelon block faulting which has a slope to the east.

From the Middle Miocene to the Pliocene is a more stable condition where sediment is deposited with a delta environment that spreads from several systems of distribution patterns from west to east. Examples of rivers that have a downstream in this area are the Proto-Kayan, Sesayap, Sembakung and several others. In this phase, the basin experiences subsidence due to the gravity of the load from the increasingly deltaic deposits, resulting in an electrical fault. The growth of the fault structure here indicates that the process of deployment of delta deposits to the west has taken place which has become less and begins to be deposited with carbonates. In the basin that leads to the east is composed of thick delta deposits, which are associated with normal syngenetic faults (normal faults that form together with precipitation).

The final tectonic phase in this basin is the compression process that occurs in Plio - Late Pleistocene due to the collision of the Philippine plate with the Borneo / East Kalimantan plate. This reactivates the existing structure and reverses the direction of some gravitational faults. However, a stronger force is in the northern part of the basin where the Miocene and Plosen deposits become folded and broken with NW - SE direction to WNE - ESE. In the eastern part of the basin, this compression phase forms a high structure because the sediment material is plastic so it forms the Bunyu and Tarakan anticlines.

From the tectonic phase it is believed that the deformation formed from the beginning of the tectonic process is the main controller of the formation of hydrocarbon deposits in the Tarakan basin.

Tectonic Order of the Tarakan Basin (Modified BEICIP, 1985)

REGIONAL GEOLOGY OF STRATIGRAPHY AND SEDIMENTATION

The Tarakan Basin is composed of Tertiary-aged rocks deposited on the Pre-Tierier bedrock. The dynamics of sedimentation in the Tarakan basin began at the Eocene age, initially the Tarakan Basin was a land area that deposited the Sembakung Formation - Green Formation. In the Oligocene a precipitation pattern of transgression is formed which is dominated by coarse clastic and carbonate rocks (Seilor Formation). The development of the transgression system continues until fine sediment is deposited (Nainputo Formation) and in some places reef limestone (Tabular Formation) is deposited. Then a regression occurs until the basin is lifted, and then coarse clastic sediments are deposited which the source is referred to as the Central Range Complex (LEMIGAS, 2006).

The depositional environment is a complex delta and stretches from West to East (Trained / Stretch Formation). The Tabul Formation is in the east which is a part of the Production Department which is composed of claystone facies. In the late Miocene, the elevation of Kuching took place, thus lifting the northern part of the Tarakan Basin. And in the Pliocene a delta environment was formed and deposited the Tarakan Formation.

The stratigraphy of the tarakan basin, from old to young is as follows:

Stratigraphy of the tarakan basin

Sembakung Formation

Early Tertiary rocks consist of the Sembakung Formation, which overlaps unaligned Late Cretaceous rocks, consisting of carbonic siliciclastic rocks from the litoral marine environment to the shallow sea at the time of the Eocene.

Green Formation

The Sujau Formation consists of clastic (conglomerates and sandstones), shale, and volcanic sediments. The clusters of the Sujau Formation represent the first stage of filling a "graben like" basin which may have been formed as a result of the burning of Makassar in the Early Eocene. The lithology of the composition of 1000 meters of volcanic acid, sandstone, volcaniclastic. The geological structure that develops is very complex and results in this area being strongly folded.

Seilor Formation

Micritic limestones from the Seilor Formation are deposited in harmony above the Sujau Formation and the Mangkabua Formation which consists of sea and marrow shales which are Oligocene to be a sign of succession change to basin.

Mangkabua Formation

In this formation there was a progradational change from the Seilor (micrite limestone) formation to a thick and massive batunapal. There are Nummulites fichteli (Marks, 1957) which are Oligocene. This formation eroded intensively at the end of the Oligocene because of the tectonic process in the form of lifting caused by volcanic activity.

Reference:

• Google.com
• Yahoo.com
• Wikipedia.com
• GDA Consultant, 2006, PRELIMINARY STUDY OF POTENTIAL HYDROCARBON IN Sangatta Block, Onshore, East Kalimantan, Pertamina UEP IV (Unpublished)
• http://nicoandreasnainggolan.blogspot.com/2014/04/tarakan-basin.html