Asri Sunda Basin

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					                                      Asri Sunda Basin

Asri Basin is one of the Sunda ideogeosynclines Tertiary Sundaland stable borders.
Twenty-one prospects have been drilled since offshore exploration began in late 1968
with the oil and / or gas is found in 52% of the business. A north-south Horst and graben
framework on rough surfaces set the Late Cretaceous erosion, deposition, and growth
throughout the Tertiary tectonic in all but the northeastern extremity basin.
Volcanic and sedimentary rocks are fluvial deposits early. The amount of sediment
influx is mainly responsible for the sinking graben block differential during the early
development of the basin and produce thick sediment delta during the early Miocene.
Downwarp backdeep followed by the invasion of the sea through the parts of the island
in the next selatant geanticline. High tectonic blocks prevented the attack segments of
the basin during the early development of the basin. With continued deforestation and
downwarp, violation of the expanded Miocene basin Sunda .. Local high areas persist,
but violations continue to dominate.

        As the basin filled segment, flat surface precipitation developed nearby. Slight.
Slight decrease in sea level produces regional regression, followed by a large breach in
the post-mid-Miocene .. The end of this period the second transgressive, most
disconnected ideogeosynclines be one geosyncline area around Sundaland. Final
regional regression occurred in late Miocene, culminating in the emergence of a
complete during the Pleistocene. Worldwide Pleistocene ice melted hollows caused
resubmergence to present sea conditions. Production has been established at intervals of
goods manufactured in Sumatra. Major new pay has been established in the Oligocene
volcanic tuffs and Oligocene-Miocene sandstones of the Gutters Root. Possible
commercial shows have been found in Miocene limestone Batu Radja transgressive and
weathered bedrock. Major oil production indicated Air Benakat sandstone body. Gas
production has been established in Limestone Parigi.

By:Gumirlang Sucahyo                                                              Page 1
                                                             Sunda Basin is an extension
                                                     of Java northern basin or subbasin
                                                     called beautiful. Sunda Basin is
                                                     relatively small basins formed during
                                                     the Cenozoic. Sunda Basin is derived
                                                     from the back-arc deposentrum or
                                                     referred to the back of the bow
                                                     deposentrum      Java.    From the
                                                     perspective of exploration results,
                                                     sunda mature basin is a particularly
                                                     hollow. From the results of
                                                     exploration in areas thistle and other
similar field in the northern sub-basin beautiful (1980's to 1990's) shows that in the
reservoir in the northern part of the sub Asri (reservoir Gutters Roots) will be able to re-
found the potential presence of petroleum . The eastern part of the sub basin Asri rare to
do exploration pengebaoran widely. Because since the beginning of the syn-rift in the
area. And to know the potential that exists in that region will require further evaluation
in the field of exploration.

       Asri Basin which is located approximately 180 km to the north off the northern
coast of Java and about 140 km to the east off the southeastern coast of Sumatra, with
water depths of about 20 to 25 meters. Asri Basin is shaped half graben structures
trending north-south that is part of a series of structures with the main orientation

By:Gumirlang Sucahyo                                                                 Page 2
direction northwest-southeast  composed of Asri Basin area to the southeast into the
area until the direction of Arjuna Basin in Central Java. Boundary faults of the basin
half-graben is visible as an arc until hurul L which can be explained as a result of the
movement of a motion transtensional shear fracture (wrenching). This sliding movement
is probably the main movement in the early Tertiary before the compression due to
movement of the time after Oligocene subduction. As a result of the sliding motion that
they form a north-south trending faults that control the deposition of synrift rocks in the
basin half-graben.

        Sectional shape of simple Asri Basin often makes people think that the formation
of these basins has a rift forming process is simple, but detailed analysis of the structures
that form Asri Basin produces a thought that the development of structures that form the
Asri Basin is not as simple shape. Asri Basin is not a result of a motion to open a modest
but        is       the        result       of        a        transtensional        motion.
Asri Basin formation is divided into two main phases, namely phase of Paleogene Rift
which is divided into the pre-rift (infra-rift) and phase and phase Neogene synrift Post
Pre-rift phase began with penelusupan (subduction) of the Indian Ocean plate under the
Sunda plate on the Continent until the Late Cretaceous Paleocene. Furthermore, the
Early Eocene when continental plates are interested because the sliding motion
stretching and bending (sagging) occurs puddles. Bending forming sedimentary basin
filled by the river (fluvial) keeps going up then the surrounding area was covered by
water and lake basins and settling into fine sediments such as shale-lempungan
(Banuwati Formation).

        Synrift stage begins with terpatahkannya lithosphere and form the northwest-
trending fracture southeast which then forms the arch or form sharp angles like the letter
L. Cracks are forming limit for the formation of half-graben basins and alluvial fan
sediments can be found along the fracture. This phase begins with the removal and
erosion resulting in some lack of harmony a local angle, further sedimentation is more
influenced by movements in the major rift faults and produces thick sedimentation and
not symmetrical. Once the fault movement stopped, then began the sedimentation of
rocks in an environment influenced by tidal sea water because sea level continues to rise
from the Oligocene to Early Miocene.

The next stage of Neogene-Post Rift started with diendapkannya rocks in the marine
environment (marine) from the melampar Gantar Formation to the basin in the northwest
Java, so it stratigraphy of these areas will have the same stratigraphic arrangement.
Performed structural analysis produces an understanding of the interior structure of the
Asri Basin showing the development of a pattern of segmented shear fault structures that
affect the formation Banuwati which is pre-rift sediments Palaeogene age. The
development of the structure is then covered by a transtensional motion seen in seismic

By:Gumirlang Sucahyo                                                                  Page 3
section shows a sliding motion at an early age (Plio-Pleistocene), which forms the
southern boundary of the Basin Asri.


Stratigraphy Bandung area is the result of volcanic activity from early Tertiary to
Quaternary, other than that revealed non-volcanic sedimentary rocks.

• Formation Rajamandala

In geology, the only non-volcanic sedimentary rocks exposed in the west of Bandung
Basin is Rajamandala Formation (Sudjatmiko, 1972), which is composed of limestone,
mudstone,        marl,       sandstone        and       quartz-old       Oligocene.
• Formation and Formation Jampang Citarum

In geokronologi, volcanic rock identified since the age of about 59 million years ago
(58.999 ± 1.94 Mya., Middle Paleocene) and 36.9 Mya. (36.881 ± 3.96 Mya., Upper
Eocene), which is found in the Cupunagara, east of Mount Tangkubanparahu (Bronto
DRR., 2004a, b). Volcanic rocks Middle Miocene (12.0 ± 0.10 Mya.) Were found from
the data geothermal drilling, seen as the bedrock of Mount Wayang (Pertamina, 1988).
This volcanic rocks from Early Neogene (Sudjatmiko, 1972).

• Formation Beser

                              Further volcanic rocks of Pliocene age (4.36 ± 0.04
                              Mya. - 2.62 ± 0.03 Mya.) Complexes found in Mount
                              Malabar - Papandayan (Katili & Sudradjat, 1984), and
                              Paseban Selacau south Cimahi, Cipicung and kromong
                              in Banjaran - Ciparay, South London (Sunardi &
                              Koesoemadinata, 1999). According Alzwar DRR.
                              (1992) volcanic rocks at Mount Kromong and Soreang
                              include Beser Formation.

By:Gumirlang Sucahyo                                                          Page 4
        Dam (1994) found that deposition in the Bandung Basin itself that began around
126,000 years ago, a rock klastika volcano and lake sediments. Analysis of absolute age
paleosol beneath the bedrock is estimated as the Bandung Basin gives an average age of
135 000 years ago. In between paleosol and Bandung Basin sedimentary rock bottom
there are many layers of volcanic ash tefra or. It indicated that the activities of volcanism
that began forming Bandung lake.

Furthermore, researchers said that the lake was formed by four stages Bandung. Lake
Bandung four phases formed about 20,000 years ago, but the remnants of the basin there
are up to 16,000 years ago. At this time the area was the lowest part of Bandung Basin
and is often flooded in the rainy season.

In the area of North London, aged Quaternary volcanic rocks are divided into the Old
Quaternary volcanic rocks, volcaniclastic rocks irreducibly young and young volcanic
rocks Tangkubanparahu (Silitonga, 1973). Deposition pyroclastic flows expected as a
result of Sunda caldera eruptions and known generically as mineral tras Lembang have
age 38,300 years (Hadisantono, 1988).

In South London, Quaternary volcanic rocks are divided into many units, such as
volcanic rock Guntur, base and Kendang, Mandalawangi volcanic rock and volcanic
rock Malabar (DRR Alzwar., 1992).

Eastern Bandung, ranging from the Sumedang, Nagreg to Garut, entirely composed of
Quaternary volcanic rocks (Silitonga, 1973; Alzwar DRR., 1992). Cone shape volcano

By:Gumirlang Sucahyo                                                                  Page 5
that is still quite unclear include Mount Tampomas, Jarian Hill, Mount Kareumbi
(Karenceng Mountains), and Mount Mandalawangi, while the volcano is tereosi
information including altitude volcanic rocks to the east of Mount Kareumbi to Nagreg
put into Volcano rock units irreducibly.

Volcanic Stratigraphy

From the analysis of Landsat imagery, research trips and Radiometric dating can be
identifi ed volcanic cones that reflect the oldest to the youngest volcano stratigraphy.
Refers to the distribution of rock units within the volcanic stratigraphy Stratigraphy
Password Indonesia (Martodjojo and Djuheni, 1996) explores the source of the eruption
of the volcano. Lithological composition parameters are not strong enough to be
dividing lithologies, because in the activity of a source volcanism volcanic eruptions can
produce different compositions. Instead, the eruption and age of different sources can
produce similar rock composition. According to sources eruption, volcanic rock in the
South London area can be divided into nine lithologies plus pyroclastic lithologies
Pangalengan (PP) and Alluvium deposits.

By:Gumirlang Sucahyo                                                               Page 6

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