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Page 2 Volume 20— February 2011
Herman Darman
Chief Editor
Shell International Exploration and Production B.V. P.O. Box 162, 2501 AN, The Hague – The Netherlands Fax: +31-70 377 4978 E-mail: [email protected]
Minarwan
Deputy Chief Editor
Repsol Exploración SA Paseo de la Castellana, 278-280, Madrid 28046 Spain E-mail: [email protected]
Fuad Ahmadin Nasution
PT. Energi Mega Persada Tbk/EMP Tonga Bakrie 24th Floor, Rasuna Epicentrum, Jl. H.R Rasuna Said Jakarta 12960-Indonesia E-mail: [email protected]
Fatrial Bahesti
NAD-North Sumatra Assets Standard Chartered Building 23rd Floor, Jl Prof Dr Satrio No 164 Jakarta 12950 - Indonesia E-mail: [email protected]
Wayan Ismara Heru Young
University Link coordinator
Legian Kaja, Kuta, Bali 80361, Indonesia E-mail: [email protected]
Julianta Panjaitan
Membership coordinator
PT. Schlumberger Geophysics Nusantara, Data & Consulting Services, Jl. Mulawarman Km. 20, P.O.Box 117, Kelurahan Manggar, Balikpapan 76117, Kalimantan Timur, Indonesia, E-mail: [email protected]
Editorial Board
• Published 3 times a year in February, June and October.by the Indonesian Sedimentologists Forum (Forum
Sedimentologiwan Indonesia—FOSI), a commission of the Indonesian Association of Geologists (Ikatan
Ahli Geologi Indonesia—IAGI).
• Cover topics related to sedimentary geology, includes their depositional processes, deformation, minerals,
basin fill, etc.
Advisory Board
Prof. Yahdi Zaim—Quarternary Geology—Institute of Technology, Bandung Prof. R. P. Koesoemadinata—Emeritus Professor—Institute of Technology, Bandung
Berita Sedimentologi
Last year, 2010, the Indonesian
Association of Geologist (IAGI)
celebrate the 50th anniversary of
the organization. This event give
a new momentum to the Indone-
sian Sedimentologists Forum
(FOSI) to reactivate the bulletin.
The last ‘Berita Sedimentologi‘
journal was published in 2000 in
paper format. Thereafter many
key people in the editorial board
left Indonesia and we admitted
that the hand-over was not suc-
cessful.
A new editorial board was set
with many new members. We
hope that the coming publication
of Berita Sedimentologi will
achieved the following goal:
• Publish technical journal
regularly
• Facilitate discussions related
to sedimentary geology in
Indonesia and Southeast
Asias region
• Provide opportunities for
knowledge transfers through
generations
The coming Berita Sedimen-
tologi will be published electroni-
cally in PDF format to reduce
cost and give higher flexibility in
journal editing. Electronic journal
also give more freedom to pub-
lish color figures with different
level of resolution. On top of
that, the electronic journal will
also reach larger number of read-
ers as it will be easier to access.
We hope the 3000+ members of
the Indonesian Geologists Asso-
ciation (IAGI) who live in differ-
ent part of the world can get the
benefit of this journal as well.
The editorial board will pick a
theme for each journal and it will
be geographical. For this edition,
for example, we will focus on
SUMATRA.
As a ‘new’ publication we would
like to hear comments from our
readers, especially FOSI and
IAGI members. If you like to
participate in the editorial team.
Please let us know.
Herman Darman
Editor in Chief
From the editors
Bird Foot Print 5
Talang Akar Formation 7
Ombilin Basin 12
Andaman-Sumatra Forearc
18
Langkat structures 22
University news 285
2
Inside this issue:
Number 20 / February 2011
Sedimentological journal of the Indonesian Sedimentologists Forum (FOSI), a commission of the Indonesian Association of Geologist (IAGI)
Berita Sedimentologi
Page 3 Volume 20— February 2011
T he forum was founded in 1995 as the Indonesian Sedimentolo-gists Forum (FOSI). This or-ganization is a communication
and discussion forum for geologists, es-pecially for those deal with sedimentol-ogy and sedimentary geology in Indone-
sia. The forum was accepted as the sedi-mentological commission of the Indone-sian Association of Geologists (IAGI) in 1996. About 300 members were regis-tered in 1999, including industrial and
academic fellows, as well as students.
FOSI has close international relations with the Society of Sedimentary Geology (SEPM) and the International Associa-
tion of Sedimentologists (IAS).
Fellowship is open to those holding a
recognized degree in geology or a cog-
nate subject and non-graduates who have
at least two years relevant experience.
FOSI has organized 2 international con-
ferences in 1999 and 2001, attended by
more than 150 international participants.
Most of FOSI administrative work will
be handled by the editorial team. IAGI
office in Jakarta will help if necessary.
The official website of FOSI is: http://
www.iagi.or.id/fosi/
About FOSI
the ideal solution, and we may look for
other alternative in the near future. Hav-
ing said that, for the current situation,
Linked is fit for purpose.
International members and students are
welcome to join the organization.
A ny person who has a back-
ground in geoscience and/or
is engaged in the practising
or teaching of geoscience or
its related business may apply for general
membership. As the organization has just
been restarted, we use Linked-in
(www.linkedin.com) as the main data-
base platform. We realize that it is not
FOSI Membership
Page 4 Volume 20— February 2011
Total registered members:
119 February 2011
T he islands of oceanic southern Asia
(Indonesia, Malaysia, and New
Guinea) have played an influential
role in the development of evolu-
tionary thought, initially because of the his-
toric studies by Alfred Russel Wallace and
later by the discovery of Pleistocene human
remains on Java by Eugene Dubois. Unlike
the majority of Sunda Islands, much of the
central core of Sumatra was emergent from
the early Eocene through the early Miocene.
Freshwater lacustrine sediments of the early
Eocene Sangkarewang Formation have
yielded an abundant diversity of fishes and a
single bird skeleton but no other evidence of
terrestrial vertebrates is known until the Pleis-
tocene. In the summer of 2007 a reconnais-
sance survey of Cenozoic sediments were
initiated in the Ombilin Basin located in the
Barisan Mountains of central Sumatra (Figure
1).The outcrop are well exposed in Sa-
wahlunto and Ombilin Coal Mining areas
consists of alternating conglomerates, quartz
sandstones and shale. In addition to exploring
the Sangkarewang Formation we examined
sediments of the Sawahlunto and overlying
Sawahtambang formations which span the
early part of the Miocene. In the Sawahlunto
Formation we discovered two series of avian
tracks representing two different shorebirds
(Figure 2). These tracks were found at the
base of a thinly laminated, coarsening upward
sandstone overlain by a relatively thin layer
(0.5 meter) of coaly shale, followed by a
quartz-sand conglomerate at the top of the
local section (12 meters total thickness). The
sandstone contains carbonaceous debris and
small to medium, parallel ripples are formed
(Figures 3). One set of tracks has an angle of
90 degrees between digits one and three and
is of relatively small size and probably repre-
sents a gruiform (rail). The second set of
tracks has a 120 degree angle between digits
one and three and was likely made by a cha-
radriid (plover) or scolopacid (sandpiper)
shorebird (Figures 4 and 5). In addition to the
bird tracks, small, circular traces (Skolithos
ichnofacies) are present probably representing
First Evidence of Miocene Avian Tracks from Sumatra Short Announcement
Yahdi Zaim*), Rizal Yan*), Gregg F. Gunnell+), Thomas A. Stidham+), Russell L. Ciochon**) and
Aswan*)
* Department of Geology, Institut Teknologi Bandung – Indonesia
+ Laboratory Paleontology, University of Michigan – USA
** Department of Anthropology, University of Iowa – USA
Page 5 Volume 20— February 2011
Figure 1: Ombilin Basin located in the Barisan Mountains of central Sumatra. On the left is Sing-
karak Lake (Picture from Google Earth,2009)
Figure 2: General Stratigraphy of
the bird foot print location
tubes of suspension feeding invertebrates such as clams or worms (Figure 6). The presence of these traces suggests that the bird trcks were formed
on an intertidal beach and the birds may well have been feeding on these invertebrates. The presence of these track ways suggest that further explo-
ration of Tertiary sediments in Sumatra is warranted. The avian tracks from the Sawahlunto Formation are as the first discovery of the Bird Foot-
print Fossils in Indonesia.
Page 6 Volume 20— February 2011
Figure 3: Outcrop shows the sandstone contains carbonaceous debris
and small to medium, parallel ripples. The avian tracks are found at the
base of this outcrop.
Figure 4: First discovery of avian tracks, the Bird Footprint Fossils
in Indonesia from Sawahlunto Formation of Early to Middle Mio-
cene in age.
Figure 5: One set of tracks has an angle of 90 degrees between digits
one and three,probably represents a gruiform (rail), and the second set
of tracks has a 120 degree angle between digits.
Figure 6: Small, circular traces (Skolithos ichnofacies) are proba-
bly representing tubes of suspension feeding invertebrates.
Outcrops Conservation of Tanjung Baru or Lower Talang Akar Formation, Baturaja City of Palembang Area - South Sumatra Basin: How important? Premonowati*),
* Department of Geology, Faculty of Mineral Technology, UPN “Veteran” Yogyakarta
Page 7 Volume 20— February 2011
ABSTRACT
Tanjung Baru Formation only outcropped in
one location so called Tanjung Baru,
Palembang, South Sumatra. In total this
formation is expossed in an area of about one
acre. The outcrop is a quartz sandstone
quarry, which has become smaller in size
rapidly because of intensive mining activities
by the local community. The formation is also
called Gritsand Member (GRM) of the Lower
Talang Akar Formation/Lemat Formation/
Lahat Formation. A different name from
Talang Akar Formation was given to this
formation because it has an important role in
the tectonostratigraphy context. Tanjung Baru
Formations has different genetic, location and
section type from that of Talang Akar
Formation. The formation consists of
conglomeratic sandstone of channel deposit.
The sections indicate five times of channeling
with each channel has a geometry of 20 m
long and 9 m thick. This lag sedimentary
deposit consists of fine- to very coarse-
grained sandstones. The erosional base
contact has polymictic conglomeratic
sandstone outcrop with gradded bedding and
planar crossbedding that indicate high energy
deposition like channelized environment in
shallow marine. The fining upward
succession was a result of lateral accretion of
channel shifting or a fluvial channel system
depositional environment. The very fine sand
of channel plug was deposited in a very low
energy environment before the channel was
abandoned. Some parts have shaly and coal
streaks with mafic and feldspatic minerals.
This formation has an indication to be an
excellent reservoir.
The geology of Tanjung Baru Formation is an
important object to study because it is the one
and only outcrop that needs to be conserved.
The objective is to save this outcrop from
extinction. A socialization to the Governor of
South Sumatra Province and Head of
Palembang Regent needs to be done. The
government has to create a regulation to stop
the mining activities, build a boundary for the
outcrops with plantation and put an
information board to explain that it’s a
conservation area. Let all geology students
and also people of all generations to have a
possibility to learn Tanjung Baru Formation
from this outcrop as a geopark.
Introduction
Hydrocarbon production in the South Sumatra
Basin is ranked at the 2nd place after Kutei
Basin in term of total productions. The
primary reservoirs are within the Talang
Akar, Baturaja and Gumai Formations and a
smaller amount in the fractured basement.
The uplifted areas and paleohighs, including
the Mesozoic and Eocene fractured and
weathered basement granite and quartzite, are
effective reservoirs in ten fields in South
Sumatra with gas reserves totaling 106
MMBOE ultimate recoverable reserves
(Sardjito, et al, 1991; Petroconsultants, 1996).
This fact is very important and it is therefore
absolutely urgent for the goverment of
Baturaja District, South Sumatra Province to
conserve and to protect the outcrops of the
Lower TAF. The outcrops have very
important value to Earth Sciences and
exploration in geology, mining and petroleum
engineering. The aim of the conservation is to
avoid outcrop mining for other purposes.
An integrated study (fieldtrip and core
analysis) was held by P.T. Medco E&P
Indonesia (PT. MEPI) for the Graduate
Geoscientists Training 2-2008 at sections
Baturaja-Muara Dua-Palembang and
Palembang Core Storage. The methodology
of outcrop description has been conducted for
the basement rocks to the top formation in
South Sumatra Basin.
The Lemat (Old and Young) Formation has
outcropped in the sandstone quarry at
Tanjung Baru (proposed as locality type and
strato type) and Napalan river in Baturaja
City, Palembang, South Sumatra Province.
The outcrop of Lemat Formation is found in
Tanjung Baru Sandstone Quarry (TAF
equivalent the Gritsand Member). The
Figure 1. Left: South Sumatra Basin configurations. Right: Quarry location of Tanjung Baru sandstone outcrops (See arrow)
Page 8 Volume 20— February 2011
siliciclastic sediments outcropped in this area
should be named Tanjung Baru sections or
stratotype and it is also the type locality of
Tanjung Baru Formation. The location where
the best siliciclastic sediment outcrop exists is
almost 1 km south of the Baturaja town
(Figure 1).
The promotion of GRM into Tanjung Baru
Formation is necessary due to its
tectonostratigraphy importance. Hutchinson
(1996) concluded that the Eocene to
Oligocene Lahat Formation is composed of
synrift deposits that are as much as 700 -
1,070 m thick. The formation was deposited
in continental, lacustrine, and brackish
lacustrine depositional settings. This reservoir
accounts for nearly 88 MMBOE of ultimate
recoverable reserves (Petroconsultants, 1996).
The oldest facies of the Young Lemat is
granite wash overlain by coarse clastic
deposits consisting of sandstones and breccias
with abundant rock fragments, claystones,
coals, and tuffs (Hutchinson, 1996).
Firstly, the proposed name of Tanjung Baru
Formation is an increase from a member
status of the conglomeratic quartz sandstone
of Lower Talang Akar Formation (Ryacudu,
2005) or the Gritsand Member (GRM).
However, the upper member of the Talang
Akar Formation called the Transition Member
(TRM) is included the Talang Akar
Formation. Lithostratigraphically, in
accordance with SSI (1996), the complete
outcrop of Tanjung Baru Sandstone should be
determined as Tanjung Baru Formation
because of the lithology, mappable,
stratigraphic contact and either lateral or
vertical distribution.
Every year, the outcrops have less volume
due to mining by thelocal community. These
highly valuable outcrops of the Tanjung Baru
Formation have given stratigraphy and
sedimentation models the Oligo-Miocene age
has had outcropped. The outcrops have just
one complete section as type locality and
strato type. They have excellent porosity and
permeability and are analogues to the
reservoir rocks in the South Sumatra Basin.
The comparison with tonase economic value
for mining, the quartz sandstone remains
about 1000 m3. The outcrops should be very
rare therefore it is crucial to be conserved and
protected.
Geology of Baturaja
The South Sumatera Basin is one of a series
of Tertiary back arc basin located in Sumatera
and Java. The basins occupy a geologic
position between the stable micro-continental
block, known as the Sunda Platform, and the
active subduction zone caused by the
northward moving Indian Ocean Plate. The
basin was formed during the Eocene-
Oligocene when a series of northerly trending
grabens developed in response to east-west
interplate extensional movements. These
grabens were filled with locally sourced
volcanoclastics sandstones and shales of the
Lemat Formation in deposi tional
environments ranging from alluvial fan, to
fluvial and lacustrine.
The geology of the studied area, particularly
the Musi Platform, is a structural high area
formed during the Eocene-Oligocene graben-
forming period. It appears to behave as a rigid
structural block through most of the Tertiary.
There is direct evidence to which the area has
been subjected to widespread deformation. To
the west, the platform gradually shallows due
to uplift associated with rising volcanic arc.
Baturaja Limestone is exposed at the foothills
of the Gumai Mountains. The northwestern
and southwestern margins of Musi Platform
are controlled by major faults which bound
Figure 2. Regional Stratigraphy of South Sumatra Basin (Argakoesoemah and Kamal, 2005). Stratigraphic position of Lemat Formation or Tan-
jung Baru outcrops
Tanjung Baru Fm.
Page 9 Volume 20— February 2011
the Eocene-Oligocene grabens. The
northeastern edge of the block is in the
present day Lematang Trough, a syncline
between the Musi Platform and the Plio-
Pleistocene Lematang fault which has
thousands of feet of overthrusting from the
north. Seismic interpretation of the Lematang
Trough that forms the northeastern margin of
Musi Platform is limited by its proximity to
the overthrust fault.
Stratigraphy
The Tertiary succession overlying the
Mesozoic metamorphic basement consists of
Lemat Formation filling the early half
grabens, unconformably overlain in turn, by
Talang Akar Formation, Baturaja Limestone,
Telisa Formation and Palembang Formation
(Figure 2).
Lemat Formation
Within the Musi Platform, the Lemat
Formation consists of volcanoclastic
sandstones and shales, typical of the unit. The
formation is also known from the graben
areas around the platform and has been
intersected in wells in the Pigi Trough, to the
north, and in the Saungnaga Area, to the
southwest.
Talang Akar Formation
As the subsidence associated with graben
formation waned during the Middle to Late
Oligocene, the interbedded sandstones, shales
and coals of Talang Akar Formation were
deposited across the South Sumatra Basin.
This unit was derived from the northeast
based on the compositional imprint of its
granitic source areas on Sunda Platform. A
general depositional environment sequence
from fluvial in the northeast, to deltaic and
later basinal facies in the southwest can be
reconstructed from sedimentological and
paleontologic evidences. There are evidences
of cyclic deposition within Talang Akar
Formation providing excellent hydrocarbon
reservoirs. The organic rich shales and coals
of the Talang Akar Formation are considered
to be the major oil source for reservoirs in this
unit and the overlying Baturaja Limestone.
The thicker areas of deposition continued to
be controlled by more rapid subsidence over
the Oligocene grabens, and as with Lemat
Formation, deposition was either thin or non-
existent on the structurally higher platform
and horst areas.
Generally over the Musi Platform, the Talang
Akar Formation or Baturaja Limestone lies
unconformably on pre-Tertiary basement.
Talang Akar Formation is interpreted to be a
lacustrine unit deposited on the eroded
basement surface. It is separated from the
more typically sand-prone Talang Akar
Formation deposited on the eastern side of the
basin, by the deep water, shaly sediments
which fill Benakat Gulley. Because of its
isolation from the coarse clastic sediment
source to the northeast, the Talang Akar on
the Musi Platform represents an environment
which is typical for the deposition during this
period. Pre-Telisa clastics in the Pigi Trough
are often tuffaceous and usually lack of good
reservoir quality. As the basin continued to
subside during the lower Miocene, deposition
of the predominantly non-marine Talang Akar
Formation was replaced by widespread
marine deposition of the Telisa Formation.
Tanjung Baru Formation Outcrops
1. Lithology and Stratigraphic Positions
The outcrop of Tanjung Baru Formation
consists of fine- to very coarse-grained
sedimentary rock. It has almost 100 m wide
and 20 – 25 meters thick (Figure 3) and
Figure 3 (Upper) Outcrops of Tanjung Baru quartz sandstone quarry of Lower Talang Akar (TAF)-Baturaja City of Palembang. (Lower) Left:
The outcrops has been dug and remains mining’s tools track. Right: Planar cross bedding of quartz polimictic conglomeratic sandstone.
Page 10 Volume 20— February 2011
consists of clean quartz conglomerate
sandstone, quartz sandstone, siltstone and
intervals of coals without fossils. Their
stratigraphic position is determined at the
lower part of Talang Akar Formation by fault
and erosional or unconformity contact to the
Upper Oligocene Lahat Group. The presence
of paleosoils and basal conglomerates
indicates an unconformity contact. So, the
Tanjung Baru Formation or Lemat Formation
is approximately Lower Miocene in age.
Quartz conglomerate sandstone; grayish white
color, medium sand to granule grain size,
moderate to poor sorted, subangular -
subrounded, matrix supported, polymictic
conglomerate with quartz dominant as the
fragments, non calcareous, rare basalt and
andesites, feldspar, carbon and mafic
minerals; matrix: quartz, opaque minerals;
silicates cements, 4 – 6 meter thickness.
Observed sedimentary structure includes
graded bedding and in the base there is an
erosional base contact. This outcrop has
initial dip oriented to northwest (N230 o
E/30o). Sediment succession of the upper part
of the Lag Deposit Sandstone (Figure 3) has
planar cross bedding structure, channel plug
(very fine grain size) and some fractures
(uncemented, loose) and shows a fining
upward sequence (Figure 4).
Quartz sandstone; white, fine – medium sand,
grain-supported, moderate to poorly sorted,
and subangular to subrounded, quartz
(abundant), some parts are siltstone of a few
centimeter thick. The light grey siltstone with
silicate cement and without fossils is
distributed in the upper part of the fining
upward sequence. Coals have been found
occasionally and they are a few centimeter
thick.
2. Depositional Environment
Non calcareous sandstone with planar cross
bedding structure, and fining upward
sequences that shows decreasing energy
towards the top can be interpreted as a fluvial
channel system depositional environment. It
shows at least four depositional sequences
which conglomerate as a lag deposit and very
fine sand as channel plug which was
deposited in a very low energy deposition
before channel was abandoned.
Based on the planar cross bedding
sedimentary structure, the sandstone was
deposited by traction current mechanism and
was influenced by highly turbulent current
(Allen, 1988). In the bottom conglomerate,
there was an erosional base-contact which
indicates that this sandstone was deposited in
highly erosional processes environment such
as in channelized environment (Selley, 1970).
The conglomerate at the bottom of this
sequence is predicted as lag deposit which is
channel floor deposit, while fining upward
succession is the result of lateral accretion of
channel shifting (Selley, 1970). Based on all
of interpretations, it is concluded that the
sandstone was deposited in braided channel
which have five, observed channel shifting.
This sandstone has an excellent reservoir
quality.
Genetically, the development of Tanjung
Baru Formation (Gritsand Member) mostly
differed to the TRM Member: the channel
sediments that filled in rift basin after syn-rift
phase. Tectonostratigraphically, the
terminology called: immediate post-rift
(Prosser, 1993) or passive rift fill; however
Talang Akar Formation (TRM) as a
transitional deposits to shallow marine. It
characterized an early regional transgressive
phase in the South Sumatra Basin. This
formation's development is restricted in the
deep zone, but the Talang Akar Formation is
in the platform or basin margin.
Figure 4. (Upper) Left: Tanjung Baru Formation is found at least four (fining upward) sequence of sandstone. Right: Conglomeratic sandstone of
channel deposit in Tanjung Baru sandstone quarry. (Lower) Left: Siltstone of channel deposits, about 10 cm thick in between the massive quartz
sandstone. Right: Lag deposits of channel, with thin orientation of quartz pebble in between the massive quartz sandstone.
Page 11 Volume 20— February 2011
3. Outcrop Conservations
The outcrop of Tanjung Baru Formation
(Early Miocene) has been characterized as
lithology of excellent reservoir. It is very
ideal and urgent to be conserved. The aims of
the conservation are as follow: a). a very rare
of ideal reservoir characterization for HC
production in the basin; b. Tanjung Baru
Formation has ideal channel system
sedimentation; c). as a learning object for old
reservoirs in the South Sumatra Basin. In
contrast, the sandstone mining will extinguish
the formation records.
Particularly for learning object, the local
government is as follow: Governor, Head of
Baturaja Region (Bupati) have to stop the
sandstone quarry. It is very urgent to protect
and create regulations to stop the mining. The
outcrop should be proposed as a Geopark.
Actually, it is necessary to have plantation
surrounding the outcrops.
Acknowledgment
My thanks to the Management of (PT.
MEPI), Mr. Edi Bambang Setyobudi, Mr.
Asril Kamal, Mr. Dindot Subandrio and
Graduates Geoscientist Training (GGT 2008)
for their valuable suggestions, supports and
discussions.
References
Argakoesoemah, R. M. I. and Kamal, A.,
2005, Ancient Talang Akar deepwater
sediments in South Sumatra Basin: A new
exploration play. Proceedings of the 31st
Indonesian Petroleum Association Annual
Convention,
Hutchison, C. S., 1996, South-East Asian Oil,
Gas, Coal and Mineral Deposits: Clarendon
Press Oxford.
Petroconsultants, 1996, Petroleum
Exploration and Production Database:
Petroconsultants, Inc., P.O. Box 740619,
6600 Sands Point Drive, Houston TX 77274-
0619, USA or Petroconsultants, Inc., P.O.
Box 152, 24 Chemin de la Mairie, 1258 Perly,
Geneva, Switzerland.
Prosser, S., 1993, Rift-related linked
depositional systems and their seismic
expression. Geological Society of London,
Special Publications, 71, 35-66
Komisi Sandi Stratigrafi Indonesia (SSI),
1996, Sandi Stratigrafi Indonesia. Ikatan Ahli
Geologi Indonesia (IAGI), 96 p.
Sardjito, Fadianto, Eddy, Djumlati, and
Hansen, S., 1991, Hydrocarbon prospect of
the pre-Tertiary basement in Kuang area,
South Sumatra: Proceedings Indonesian
Petroleum Association Twentieth Annual
Convention, October, 1991, p. 255-278.
Selley, R.C., 1970, Ancient Sedimentary
Environments and their sub-surface diagnosis.
Chapman and Hall, London, 287p
Half-day visit to Solok-Sawahlunto area, Ombilin Basin: A short observation on non-marine depositional sequences RM Iman Argakoesoemah and Didit Ariady Firmansyah
Page 12 Volume 20— February 2011
Introduction
This is a brief note of our visit to Solok, Sa-
wahlunto area, Ombilin Basin on November
8, 2008 for the purpose of our efforts to
broaden our knowledge on non-marine depo-
sitional sequence and its relationship to the
development of hydrocarbon petroleum sys-
tem in the region. Exposure of the outcrops is
excellent in the form of accessibility and ver-
tical extent of the stack of the sequences.
Unfortunately, as the time was limited, there
was no opportunity to conduct sufficient de-
tailed description of the outcrops. However,
several notes of the broad observation of the
whole large view of the outcrops were made.
Part of them is discussed in this paper.
A total of eight (8) locations (=STA) were
visited during this half-day reconnaissance
trip. The traverse began from Solok using a
car towards northeast to the locations 1 to 8
following the existing main road to Sa-
wahlunto, Figure 1. The outcrops are easily
accessed and visible from the main road.
Some of the outcrops are located immediately
on the edge of the road.
General Overview
The Ombilin Basin has been interpreted as a
small intermontane basin began to occur in
the Late Eocene by north-south tensional
displacements followed by dextral strike-slip
faulting of the Sumatra Fault System in the
Oligocene resulted in a pull-apart develop-
ment of the horst and graben structures in
northwest-southeast trending (Situmorang et
al, 1991; Howells, 1997). The basin uplift in
the Mid-Miocene or later reduced its extent to
the present size where the intermontane basin
is outlined. To the west the basin is presently
bounded by a series of Quaternary to Holo-
cene volcanoes while to the east by the pre-
Tertiary non-volcanic sediments.
The basin began with deposition of the sand-
rich, conglomeratic sequence of alluvial fans
of the basin margins of the Brani Formation
followed by the Sangkarewang, Sawahlunto,
Sawahtambang, and Ombilin Formations
(Koesoemadinata and Matasak, 1981;
Koning, 1985; and Noeradi et al, 2005), Fig-
ure 2. Fresh water lacustrine setting could be
present in the depocentre of the basin. This
transgression stage is stratigraphically repre-
sented by a mega-sequence ranging from non-
marine coarse clastic rift deposits to shales of
deep open marine with the maximum flooding
occurred in the Mid-Miocene.
The Sawahlunto Formation consists of non-
marine argillaceous deposits with numerous
coals and some quartz sandstones. The Ombi-
lin Underground Coalmines situated in Sa-
wahlunto city has produced coals since 1891
from this formation. The estimated reserves
are of about 200 million metric tons. There
are three main coal seams with the most po-
tential up to 18 m thick and average 9.3 m
thick of black and lustrous bituminous coal
rank (Silkina and Toquero, 2008). It should
be noted that large extent of the coals could
also have potential for coalbed methane
(CBM) deposits.
The formation is probably conformable over-
lain by the Sawahtambang Formation. The
age-diagnostic fossils are not present, but
erosion surface could mark the boundary
between both formations as shown by a shift
of Ro value plot in Sinamar-1 well (Koning,
1985). The Sawahtambang has been described
as thick coarse quartz-rich sandstones with
some overbank coaly claystone suggesting
that the formation was deposited in the flu-
vial, braided river setting.
The geothermal gradient in Sinamar-1 (1984)
is only 1.62 degF/100’ (29.6 degC/km) which
is cooler than the average gradient of 3.3
degF/100’ (60.3 degC/km) in the Central
Sumatra Basin. Several oil shows were re-
ported in the sandstones of the Sawahtambang
Formation. One open-hole DST recorded
minor
flow of oil (36 deg API gravity) in the upper
formation and a gas flow exceeding 13
MMCFD (60 deg API gravity) in the middle
part of the formation (Koning, 1985). The
Figure 1. Index map of station (STA) of the observations during visit to Solok-Sawahlunto area.
Page 13 Volume 20— February 2011
source rocks might be the mature shales
(Ro=0.6%) of the Sangkarewang Formation
(Avg TOC= 2.6%) while the Sawahlunto
coals are still immature with Ro=0.53%
(Fletcher and Yarmanto, 1993). The hydro-
carbon accumulation is considered non-
commercial (Koning and Karsani, 2000). The
later well, South Sinamar-1 (1994) drilling
results is dry.
Brief Outcrop Overview
Several large outcrop exposures are present
along the coalmines in the Sawahlunto area.
Description for a broad mega-sequence over-
view can be conducted from a distance as the
outcrops extend several hundreds of meters
laterally. Some of them could have few hun-
dreds of meters of repeated vertical se-
quences. A closer look will give much better
impression on sedimentary sequences and
lithological description and composition.
Below are a brief description and preliminary
interpretation of the outcrops based on quick
observation and reading materials.
Coaly claystone and coal of the floodplain
deposits have vertically separated each sand-
rich sequence as the river channels move
laterally and vertically with time. These rela-
tively thin floodplain deposits may help corre-
late the sand-rich sequence locally. Some of
them could have been significantly extended
laterally and can be used for local correlation
marker. Thickness of the individual sand-rich
sequence could be tens of meters. Individual
coal layer may not be useful for regional cor-
relation as the main
swampy, floodplain area may not be very
extensive in the Sawahlunto Formation at this
location STA 7, Allied Indo Coal.
Based on the rift basin model, Noeradi et al
(2005) interpreted that the Brani coarse clas-
tics of fanglomerate and other related sedi-
ments representing rift basin margin facies
was deposited during the early syn-rift phase
while the Sawahlunto Formation was depos-
ited during deposition of the late syn-rift. The
Sawahtambang and Ombilin Formations are
considered to be the post-rift phase based on
seismically continuous, widespread reflector
package over the whole basin.
Further geophysical interpretation should be
taken to ensure that the lithological contrast
between the thick sandstone package of the
Sawahtambang Formation and the thick,
open-marine shale package of the Ombilin
Formation shall not lead to the improper in-
terpretation. The impedance or velocity con-
trast between both formations shall be con-
tinuous laterally along the presence of both
formations in the basin unless the lithological
contrast diminishes near the basin margin.
Conclusion and Recomendation
Below are some brief conclusions and recom-
mendations:
(1) Quality of the outcrops is extremely excel-
lent. They are continuous and some of them
are extent to be several hundreds of meters
both in vertical and lateral views. Any de-
tailed geological observations could be made
continuously.
(2) Any outcrops in the Solok-Sawahlunto
region specifically in the area where coal-
mines are present and active should have to
be properly documented. Regular field visit
and detailed geological study should be per-
formed to ensure that the geological informa-
tion is continuously recorded otherwise the
outcrops will disappear shortly due to coal-
mine activity.
(3) Sufficient safety preparation should be
conducted if continuous measured section is
planned since the field condition in some
outcrops need special attention for the pur-
pose of safety precaution.
(4) The outcrops are useful for the study of
non-marine Tertiary sequence stratigraphy
though the deposition and tectonic in the re-
gion are active. Non-marine biostratigraphy
should be conducted to establish the vertical
stratigraphic relationship and lateral regional
correlation across the basin.
(5) In addition to the coalmine purposes fur-
ther exploration for hydrocarbon occurrence
in the basin should remain to be interesting
not only for conventional hydrocarbon but
also for unconventional exploration specifi-
cally coalbed methane.
Note: Any content and interpretation appear
in this paper is solely responsible of the Au-
thors.
References
Fletcher, G. and Yarmanto, 1993, Ombilin
basin field guide book. Indonesian Petroleum
Association, Post Convention Field Trip, 59
pp.
Howells, C., 1997, Tertiary response to
oblique subduction and indentation in Suma-
Figure 2. General lithostratigraphic column of Ombilin Basin (Noeradi et al, 2005)
Page 14 Volume 20— February 2011
tra, Indonesia: new ideas for hydrocarbon
exploration. Geological Society of London,
Special Publications, v.126, p. 365-374.
Koesoemadinata, R.P. and Th. Matasak,
1981, Stratigraphy and sedimentation – Om-
bilin basin, Central Sumatra (West Sumatra
Province). Indonesian Petroleum Association,
Proceedings of the 10th Annual Convention,
p. 217-249.
Koning, T., 1985, Petroleum geology of the
Ombilin intermontane basin, West Sumatra.
Indonesian Petroleum Association, Proceed-
Figure 3. Repeated stacked sand-rich se-
quences with several lenses of large fluvial
channels. Thickness and width of some chan-
nels should be measurable. The thick, coarser
grain of sediments (dirty white) encased by
light grey argillaceous flood-plain deposits
could be interpreted as part of the main chan-
nel fill, but the thin and discontinuous one of
much smaller channel fills could be inter-
preted as the crevasse splays. However, de-
tailed observation should be made, as the
alluvial fan sequence is present and could be
inter-fingering laterally with the fluvial de-
posits, see Figure 2. The information is im-
portant for interpretation of the variation of
fluvial system (and alluvial fan) depositional
outline and development including non-
marine sequence stratigraphy interpretation
of the region
Figures 4a (above) and 4b (below). This
picture shows several erosion surfaces indi-
cated by irregular sharp-based contact be-
tween fluvial channel (dirty white) and flood
plain (light grey) deposits of the Sawahlunto
Formation at STA 2 location, Korean coal-
mine. The width of some channels is possible
to be measured in the outcrops. It should be
noted that the channels at this location may
not be the main river channels as their sizes
are relatively smaller than those observed in
the basin. The thin, discontinuous, silty sand-
sheets within the swamp are possible deposit
of the crevasse splays. Note: This outcrop
extends laterally several hundred meters.
Page 15 Volume 20— February 2011
Figure 5. Detailed view of erosion surface
shown by irregular sharp-based contact be-
tween fluvial channel and the underlying
flood plain sediments. The outcrop is very
fresh showing excellent view of micro-
sedimentary structure. Ripple lamination and
others in carbonaceous siltstones with finer
grain of sandstones are present, see the in-
serted photograph. Note: It is Sawahlunto
Formation at STA 3 location, Korean coal-
mine.
Figure 6. Detailed view of erosion surface of
thick sand-rich channels eroded fine-grained
sandstones of the underlying earlier channel.
These thick, stacked sandstone deposits are
interpreted to have been deposited as multi-
story river system channel of the Sawahlunto
Formation at STA 4 location as opposed to
the interpretation of possible proximal allu-
vial fan sediments. Detailed sedimentary
structure of the sandstones and biostratigra-
phy analysis of the intercalated shale be-
tween the channels are crucial just to confirm
the possibility of fresh water lake deposits
present in the depocentre of the basin at this
location. That possibility could enrich alter-
native interpretation of other non-marine
depositions present in the basin. The basin
geometry should be properly mapped, if pos-
sible.
Figures 7a (above) and 7b (below). Possible
inter-fingering contact between the overlying
alluvial fan deposits and underlying mean-
dering swampy sediments of the Sawahlunto
Formation. It should be noted here that the
possibility to have freshwater lacustrine delta
during Sawahlunto deposition should not be
ignored. Therefore, further detailed strati-
graphical and sedimentological observations
are obviously required for this outcrop at this
location and others in the surrounding areas.
Note: The outcrop is located at STA 5.
Page 16 Volume 20— February 2011
ings of the 14th Annual Convention, p. 117-
137.
Koning, T. and Aulia Karsani, 2000, Abstract:
Exploration in the Ombilin intermontane
basin, West Sumatra. AAPG International
Conference and Exhibition, Bali, Indonesia.
AAPG Search and Discovery Article #90913.
Noeradi, D., Djuhaeni, and Batara Simanjun-
tak, 2005, Rift play in Ombilin basin outcrop,
Figure 8. Close-up of the sedimentary struc-
tures of stacked channels developed in the
Sawahlunto Formation located at STA 5.
Parallel lamination and others with top and
bottom sets of cross-bedding structures can be
recognized along the outcrop. Paleo-current
could be measured accordingly. Any possible
broad direction of the major fluvial shift is
interesting to be exercised.
Figure 9. Large scale of outcrop showing the
presence of thick and large channel sand-
stones that seems to be encased by thick
floodplain deposits (light grey) of the Sa-
wahlunto Formation at STA 6, Allied Indo
Coal mining. Since the lateral extent of the
channel sandstone package is significantly
thick, wide and gentle it could be interpreted
that the equilibrium profile (=base level) of
the fluvial system at the time in this location
rose above the alluvial profile resulted in the
river aggraded the floodplain. This is an
indication of positive fluvial accommodation
took place during deposition of the Sa-
wahlunto.
Figure 10. Development of thin, scattered
crevasse splays within the large and thick
overbank swampy deposits (light grey) of the
Sawahlunto Formation at location STA 7,
Allied Indo Coal mining. The tectonic contri-
bution to the fluvial accommodation in the
basin centre at the time seems to be signifi-
cant resulted in thick fluvial system accumu-
lation as indicated by anomalously thick
floodplain deposits. This is a typical of the
presence of local tectonic sag where the ac-
celerated subsidence took place in the pull-
apart tectonic setting, ie. the Sawahlunto
deposition.
Page 17 Volume 20— February 2011
West Sumatra. Indonesian Petroleum Asso-
ciation, Proceedings of the 30th Annual Con-
vention, p. 39-51.
Silkina, I. and Napoleon Toquero, 2008, It’s
About Time. Time Technology Pty Ltd, Sci-
entific and Technical Division, PTBA Ombi-
lin Coal Project, 14 pp.
Situmorang, B., Barlian Yulihanto, Agus
Guntur, Romina Himawan, and T. Gamal
Jacob, 2005, Structural development of the
Ombilin basin, West Sumatra. Indonesian
Petroleum Association, Proceedings of the
20th Annual Convention, p. 1-15.
Figure 11. Outcrop of the Sawahtambang
Formation in location STA 8 (Sawahtambang
gorge) showing multi-story, stacked thick
sandstones of the braided river deposits
where some appear to have been amalga-
mated. The formation is well-cropped out in
the basin margin. Towards the basin depocen-
tre, part of the formation has been eroded
following the Mid-Miocene to Pliocene basin
uplift.
Figure 12. Part of the close-up of the outcrop
in Figure 11 above showing detailed sedi-
mentary structures. Cross-bedded sandstones
with composition of mostly quartz are com-
mon in the Sawahlunto Formation.
Figure 13. Outcrop of the Sawahtambang
Formation at the same location (STA 8) as
shown in Figures 11 and 12 above, but it is
located across the main road. Good layered,
multi-story quartz-rich sandstones with ir-
regular shape of the base of the channels can
be observed from a distance.
Seismic Expression of Some Geological Features of Andaman-Offshore West Sumatra Subduction zone Herman Darman—Shell International E&P
Page 18 Volume 20— February 2011
A subduction zone developed in
the south of Myanmar, continue
to the Andaman Sea (India), west
of Sumatra and south of Java
(Indonesia). Two major fault system devel-
oped parallel to the subduction zone, so called
the Mentawai Fault System and Sumatra Fault
system. To the north, where the subduction
zone changes its orientation from NNW-SSE
to NS, a spreading zone developed towards
the east of Andaman Sea (Figure 1). This
zone is a complex and active geological sys-
tem. The 2004 Aceh Tsunami was a major
disaster which was triggered in this subduc-
tion zone.
The Andaman - Offshore West Sumatra sub-
duction system is where part of the Indo-
Australian oceanic plate moving northwards
and going beneath the southern tip of Eura-
sian continental plate. Sumatra Island, which
is part of Indonesian volcanic island arc, oc-
curs parallel to and inland from the boundary
between these two plates. An accretionary
prism or wedge has formed from sediments
that accreted onto the non-subducting plate.
Most of the material in this wedge consists of
marine sediments scraped off from the down-
going slab of Indian oceanic plate with some
erosional products of Sumatra volcanics.
Fore-arc ridge in this system is a chain of
islands (e.g. Andaman, Simeulue, Nias,
Mentawai, and Enggano), formed by the ac-
cretionary wedge. A series of fore-arc basins
developed between the accretionary ridge and
the volcanic arc (Figure 2).
This region is also an active petroleum explo-
ration area. Recently, there are a number of
companies (e.g. Spectrum, TGS and Geco)
provide new and reprocessed seismic lines to
the market. These seismic lines show the
geological features in this subduction system.
1. Andaman Section
2010 articles in Geo-ExPro and AAPG Ex-
plorer displayed seismic sections of Andaman
Sea. These sections were recently reprocessed
by Spectrum in 2010 to support exploration
licenses by the Indian authority. The regional
seismic section shows a submarine volcanic
arc, which separates the back-arc basin from Figure 1: Regional tectonic setting of Andaman—Offshore West Sumatra subduction zone. Sec-
tion 1: Andaman section; Section 2: West Aceh section; Section 3: Simeuleu Section
Page 19 Volume 20— February 2011
the fore-arc basin. East Andaman fault system
developed bathymetric high called ‘invisible
bank’ in the middle of the fore arc basin. Part
of the fore-arc is shown on the west of the
section. Further west of this section the fore
arc ridge appear to the sea surface as Anda-
man Island (Figure 3).
The interpretation suggest Pliocene-Recent
stratigraphic interval at the shallowest section.
This unit thins in parts due to volcanic activ-
ity and fault movement. Neogene units are
thicker in the back arc basin compare to the
fore-arc basin. The majority of the back-arc
basin is deeper than 3000 MSec. TWT.
A seismic section published in AAPG Ex-
plorer show a Miocene Limestone unit which
this towards the deeper water. The interpreta-
tion also indicates a shelf deposit, shelf edge
and an isolated shoal (Figure 4). The shelf
unit is about 3-4 Msec. TWT deep.
The Neogene unit is underlain by Pre-
Neogene sediments which is thins towards the
volcanic arc. In parts the pre-Neogene se-
quence has been completely eroded away.
This unit seems thicken to the west of the
section in the fore-arc ridge zone. It is be-
lieved that the deeper stratigraphic unit has
limited data control.
2. West Aceh Section (Profile Sumenta 32)
A seismic section published by Malod et al is
a result of Baruna Jaya shallow seismic sur-
vey in 1991. The survey is part of collabora-
tion between Indonesian and France govern-
ment.
This short section shows a reverse fault which
bound the west part of the fore-arc basin
(Figure 5). The fault goes all the way to the
sea floor at about 3.5 sec. TWT, separating
the accretionary prism from the fore-arc ba-
sin. The accretionary prism in the SW of this
section is clearly shown as a bathymetric high
and the fore-arc basin appear as a flat sea
base.
The fore-arc basin was filled with Late Mio-
cene and younger deposits. Flat reflectors
shows that there were very little tectonic im-
pact on this area despite the major earth
quakes and tsunami developed in this region.
Figure 2. Schematic regional cross section of a subduction zone
Figure 3. West to east geoseismic cross section through the northern part of the Andaman fore-arc basin area (after Scaife & Billings, 2010)
Page 20 Volume 20— February 2011
Unfortunately the seismic section is too short
and too shallow to show the regional picture.
The complex geology in the accretionary
complex result in unclear seismic expression
in this area.
3. Simeuleu Section
In July 2006, Geco acquired 3 deep seismic
sections in offshore west Aceh. (Bunting et al,
2007) to image active faults along the subduc-
tion zone, quantify the volume of water that
penetrated along these faults and provide
information to optimize the location of future
borehole location for the Integrated Ocean
Drilling Program (IODP).
The seismic section is more than 16 sec. TWT
deep and show the oceanic Moho on the SW
of the section. An indication of continental
Moho appears in the NE of the section. The
section also shows the trench and the accre-
tionary wedge of the West Sumatra subduc-
tion zone (Figure 6).
Slightly to the south of this line, TGS shot
some seismic which was focused on the fore-
arc basin. The seismic section clearly shows
the fore-arc ridge and major regional NW
trending fault zone in the SW of the section
(Figure 7). In the NE, present day shelf de-
posit is well imaged. Meulaboh fore-arc basin
has thick post late Miocene deposit adjacent
to the NW trending fault zone as this fault
generate an accommodation space fore about
2 sec. TWT deep.
Conclusion
Recent seismic sections published by Spec-
trum, Geco and TGS, shows different element
of the Andaman-Offshore West Sumatra.
Indonesian BPPT Baruna Jaya shallow seis-
mic, acquired in 1991, shows sea bottom
profiles which are controlled by tectonic fea-
tures. These seismic lines clearly show the
subsea volcanic arc, accretionary wedge, fore-
arc basin, the trench, and boundaries of each
element.
Both carbonate and clastic deposits are shown
on the seismic sections with indication of
potential hydrocarbon.
References
Bunting, T, Chapman, C; Christie, P., Singh,
S., Sledzik, J., 2007, The Science of Tsuna-
mis, Oil Field Review, Autumn 2007
Caife, S., Billings, A., 2010, Offshore Explo-
ration of the Andaman Sea, GEO ExPro, vol
7, no. 5.
Durham, L. S., 2010, India Seismic Gets New
View, AAPG Explorer, October.
Malod, J. A., Kemal, M., Beslier, M. O., De-
plus, C., Diament, M., Karta, K., Mauffret,
A., Patirat, Pl., Pubellier, M., Rgnauld, H.,
Aritonang, P., Zen, M. T., 1993, Deformation
fo the Fore-arc Basin, NW of Sumatra, re-
sponse to oblique subduction, Sumenta Crui-
ese – Baruna Jaya III – 1991.
Figure 4. An example of limestone build-up—the basins’s cap rock. The section length is 28 km.
Data courtesy of Spectum ASA, published in AAPG Explorer—October 2010
Figure 5. Profile SUMENTA 32, west Aceh section showing reverse fault bounding the Aceh
Basin to the west and interpreted as possible strike-slip fault zone. Location of the profile is in
Figure 1..
Page 21 Volume 20— February 2011
Figure 6. Simeulue Section. A) Preliminary results from the Geco WG1 seismic line with interpretation revewals faulting and deep boundaries. The
main thrust fault can be seen on this image, as well as other reflectors. The Moho, short for the Mohorovicic discontinuity, is the boundary between
the Earth’s crust and the mantle, and can be identified here. B) A seismic section acquired by TGS showing the northwest-southeast trending fault
system as the primary tectonic feature in the west of Meulaboh—Sibolga Basin
Palinspatic 2D Seismic Restoration: Simple Method for Reconstructing Inverted Structure and Basin History, A Case Study in Langkat Area, North Sumatra Basin Fatrial Bahesti—PT Pertamina EP ([email protected])
Page 22 Volume 20— February 2011
Abstract
Numerous published studies have shown that cross-section balancing and valida-tion techniques are a powerful method of structural analysis. The construction of seismic cross-section is of the greatest importance to generate regional study of basin history. For this reason, palinspatic restoration in time domain of seismic data have evoked considerable interest, in particular in areas of extensional and compressional tectonics regime. The basic approaches to restore preserve seis-mic section assume plane strain, or con-servation of cross sectional area. Calcula-tion of equal areas for a section deformed above a decollement or detachment sur-face can be applied by depositional time. It calculates depth to detachment in Langkat area, around 5000 ms in time domain to detachment by restoration techniques. In addition to the analysis of structural traps, cross-section validation can be used in Bampo and Baong Forma-tion as major source rock, especially in the relative timing of hydrocarbon migra-tion. The extension and compression factor results 0.20 and 0.63 for Langkat area without assuming wrench fault zone gives additional strain in calculation. The result, when compared with several ma-jor oil and gas field in Sumatra, gives high compression inverted structure clas-sification that increase confidence for finding any giant field. This technique, when used with other methodologies, such as sequence stratigraphy and basin modelling, allows the interpreter to use all the available data sets to constrain geological models on hydrocarbon prospectivity. It is therefore a valuable methodology in both 3D basin analysis and prospect risking/ranking.
1. Introduction
Whether paleostructure model are resolv-able on seismic reflection surveys, they can significantly affect hydrocarbon mi-gration and trap location, as well as flow
of hydrocarbons. Therefore, understand-ing the evolution of basin structure and physical properties through time should improve geological models and, in turn, significantly reduce exploration risk. Furthermore, whereas these geophysical techniques adequately image the major geological structures, this only provides the present-day structural geometry of the subsurface, which commonly has resulted from multiple tectonic events, thereby increasing the complexity of the analysis. To more realistically model the spatial and temporal development of structural heterogeneities and to address these economical issues, a variety of nu-merical techniques have been developed. They fall into three main categories: (1) the geometric and kinematic approaches; (2) the stochastic approaches; and (3) the physical and geomechanical approaches. The first category includes most of the restoration techniques used by structural geologists to check the consistency of the subsurface structural interpretations. Measures of gaps and overlaps between the restored parts of a model give qualita-tive values to check the strength of the geological interpretation. The geometri-cal methods proposed to restore geologi-cal structures are based on a variety of algorithms, which aim at reproducing natural deformation. For instance, the methods include balancing cross sections by flexural slip (Dahlstrom, 1969; Hos-sack, 1979; Davison, 1986) to model deformation accommodated by slip along an infinite number of bedding interfaces. More simply, mapview restoration has been done using rigid translation and rotation of fault blocks (Dokka and Travis, 1990; Rouby et al., 1993) to model larger scale deformation. These methods are based on geometrical as-sumptions (Rouby et al., 2000), such as preservation of area, minimization of
deformation, minimization of changes in segment length, or minimization of shearing, constant fault slip, fixed faults in space, or discontinuous rigid blocks. Furthermore, these techniques are not based on the fundamental principles of the conservation of mass and momentum, which govern rock deformation. In addi-tion, only strain, which is strongly de-pendent on the geometric restoration algorithm used, is calculated (Erickson et al., 2000; Hennings et al., 2000; Rouby et al., 2000; Sanders et al., 2004). There-fore, physical laws and linear elastic the-ory replace kinematic and geometric constraints used by the existing methods for the restoration of geological struc-tures. Strain heterogeneity may be esti-mated and it is possible effects on bal-ance calculations deduced. The availabil-ity of closely spaced seismic lines, cou-pled with well control, however, can give three-dimensional and stratigraphic con-trol in areas of orogenic contraction.
2. Data and Methods
The geomechanically based restorations described in this study were performed manually using constrain length and ar-eas with CorelDraw, a 2-D seismic has been interpreted to model complex geo-logical structures with a variety of boundary conditions or constraints. In this study, we only consider the 2-D for-mulation to restore geological cross sec-tions. Detachment fault models of extensional basin development have two end-member geometries (Fig. 1A). The first involves listric normal faults that gradually sole into sub-horizontal de-tachments (Wernicke & Burchfiel 1982; Gibbs 1983). In the second case the fault system has a kinked geometry con-sisting of two planar fault segments (Jackson 1987; Groshong 1989). Under both end-member conditions, transla-tion on the sub-horizontal detachment
Page 23 Volume 20— February 2011
results in potential voids between the hanging wall and footwall blocks, and collapse of the hangingwall results in the formation of a half-graben. The foot-wall block is assumed to remain pas-sive during extension (Gibbs 1983; Groshong 1989). The geometry of the half-graben is governed by (1) the rules of equal-area balancing (Gibbs 1983), (2) the geometry of the fault system, and (3) the nature of the deformation in the hanging wall, i.e., collapse along zones of vertical shear, collapse along antithetic faults of variable dip angles, and the relative amounts of bedding-plane shear within the hanging wall block (Gibbs 1983, 1984; White et al. 1986; Williams & Vann 1987). In gen-eral, half-graben become wider and less deep as the dip angle of the antithetic faults along which the hanging wall col-lapses decreases (Crews & McGrew 1990). The dip angle of the border fault and the depth to detachment also strongly influence the geometry of the basin: for the same amount of net dis-placement on the horizontal detachment, basins become narrower and deeper as the dip of the basin-bounding fault and depth to detachment increase (Morley 1989). In the case of listric faults, a roll-over geometry results in the hanging wall because of the increasing size of the potential void between the hanging wall and footwall blocks toward the listric fault. For the ramp-flat geome-try, a flat-bottomed half-graben results because the width of the potential void between the hanging wall and footwall blocks is constant over considerable por-tion of its length. The basic approaches to section balance assume plane strain, or conservation of cross-sectional area. Calculation of equal areas for a section deformed above a de-collement or detachment surface can be applied to extension as well as contrac-tion. Given the equal-area balancing assumption, the cross-sectional area of the hanging wall basin is given by:
A = hd (1) where h is the net displacement on the hori-zontal detachment and d is the depth of the detachment. The rate of increase in the cross-sectional area of the basin is constant (dA/dh = d), and the change in the rate of area in-crease (d2A/dh2) is zero. This is a feature unique to the detachment fault models. Fig-
ure 1 show the basic approach to section bal-ance for plane strain, or conservational of cross-sectional area. The equation expresses the relationship be-tween the undeformed length, the deformed length of section and the depth to the decolle-ment surface (d). This can be expressed in term of average stratigraphic thickness upon time-depth conversion. It is seen to be identi-cal to those for orogenic contraction with the exception of the change in sign convention for elongation and is likewise independent of the style of deformation. Linear elasticity is used as a tool for restora-tion because its fundamental properties are well suited for such modeling. Therefore, model results can easily be comprehended. Linear elasticity honors the full complement of physical laws that govern geological defor-mation, including conservation of momentum, mass, and energy. As a result, physical laws replace kinematic or geometric assumptions commonly used for restoring geological struc-tures, such as preservation of segment length, surface area, or volume. This is a feature unique to the detachment fault models. The volume of the basin also changes similarly since uniform plane strain conditions prevail (Gibbs 1983). The uni-form plane-strain condition is most likely to be satisfied when the basin is bounded laterally by vertical transfer faults (terminology of Gibbs 1984). (Fig 2).
Sedimentation rates progressively decrease toward the hinge of the basin and precisely mimic the subsidence rates. Since the second increment of displacement is equal to the first, area balance dictates that the newly created volume of the half-graben be equal to that of the first increment. Since the volumetric sedi-mentation rate is constant, the basin again completely fills with fluvial sediments. Notice that the younger wedge of sediments pinches out against the older wedge. This is because the footwall, the basin-bounding fault, and the depocenter of the basin remain fixed during extension, but the hinge of the basin migrates away from the basin-bounding fault. This pattern of fluvial sedimentation and pinchout of younger strata against older strata would continue as long as the displacement rate was uniform. However, a doubling of the amount of displacement also doubles the incremental volume of the basin, which now exceeds the volume of sediments available. Lacustrine deposition occurs. Note that (1) the lacustrine wedge of sediment pinches against older fluvial strata, (2) the maximum sedimentation rate in the lacustrine wedge is higher than the maxima of the two older fluvial wedges, and (3) the depositional surface area of the lacustrine wedge is less than for the fluvial wedges, requiring a higher transverse gradient in sedimentation rates. Given initial fluvial sedimentation, lacustrine sedimentation can only occur if there is an increase in the extension rate and/or if the volumetric sedimentation rate decreases. The chosen volumetric sedimentation rate results in fluvial sedimentation following the first two increments of displacement. After the third increment, the basin is of such a size that lacustrine sedimentation occurs. In general, under conditions of accelerated extension, younger units consistently pinch out against older units, the maximum sedimentation rate in younger units is higher than in older units, and a transition from fluvial to lacustrine is predicted if extension continues long enough and if the effects of accelerated displacement overcome the effects of any increase in the volumetric sedimentation rate. Studies of small normal faults in British coal fields and larger normal faults in the North Sea imaged on a closely-spaced grid of seis-mic lines have shown that the displacement on these faults is generally greatest at or near the center of the fault and decreases to zero at its ends (Barnett et al. 1987; Walsh & Watter-son 1987, 1988, 1989; Gibson et al. 1989). Gibson et al. (1989) used relationships of fault growth model I to generate model half-graben. Specifically, the along-strike dimen-sion of the basin is given by the fault length L:
Fig. 1. Area Balance for Extension. Above: lo
is original length of section which compared
with length in deformed state and area. Below
: the regional projected horizontal, to calcu-
late depth to detachment.
Area A= Area B
l1
lo
( 1- 0)d=A=Bl l
d
Al
l
l
l1
d
( 1- 0)d=A
d=A/
l l
( 1- 0)l l
Page 24 Volume 20— February 2011
where G is the shear modulus, ∆σ is the stress drop after each seismic event, S is the incre-ment by which slip increases after each slip event (necessary for the fault to grow and for the growth sequence to match the observa-tional data), and D is the maximum displace-ment.
The preceding equations assumed that the normal faults were blind and consequently the displacement of horizons was distributed equally in the footwall and hanging wall blocks. For non-vertical synsedimentary faults (where the fault intersects the free sur-face of the earth), there is an asymmetry be-tween hanging wall and footwall displace-
Fig. 2. Three models of extensional basin development. (A) Linked fault system model involves two end members: (1) listric fault-subhorizontal
detachment and (2) planar kink fault geometry. In both instances horizontal displacement (h) on the detachment fault creates a potential void be-
tween the hanging wall and footwall, which is erased by the collapse of the hanging wall along vertical faults in (1) and antithetic faults dipping at
45° in (2). The deformation is area balanced. Adapted from Gibbs (1983) and Groshong (1989). (B) Domino fault block model in which both the
faults and the intervening fault blocks rotate during extension. i is the initial dip angle of the faults; is the dip after extension; is the dip of a horizon
that was horizontal before extension; F' is the initial fault spacing; F is the fault spacing after extension. Adapted from Wernicke & Burchfiel
(1982). (C) Essential elements of the fault growth model (modified from Gibson et al. 1989). The ruled "ellipse" is the map view of a normal fault in
which displacement is greatest at the fault center and decreases to zero at the ends. Contours represent the elevation change (positive for dotted
contours, negative for solid contours) of the originally horizontal free surface. Note that the footwall uplift is smaller than the hanging wall subsi-
dence. L is the length of the fault, R is the radius of the fault (L/2), T is fault motion toward the reader, A is away. (D) Graph of cumulative basin
volume vs. horizontal component of fault displacement for the models presented in this paper. The change in the rate of increase in basin volume is
zero for the detachment fault model, negative for the domino model, and positive for the two fault growth models.
Page 25 Volume 20— February 2011
ment of horizons, with the asymmetry in-creasing as the fault dip decreases.
3. Result and Discussion
The picture of the completed seismic line restored onto solid rock deformation using a texture drawing tool. This allows one to fol-low the deformation of the formation layers at each stage of the restoration. The results of the restoration are shown in Figure 2. The changes in fault crosscutting relationships through time. When analyzing the evolution of the sand layers, one observes that they roll back along the fault to their original horizontal position, whereas the free right border of the model translates without any rotation. Dip changes seen across faults on geoseismic lines demon-strate that most faults are listric faults. In the final restored state (stage 6 of Figure 6), the pre-rift beds are tilting as Malacca Platform. In the extensional regimes, it is important to calculate depth to detachment for the base-ment faulting. The brittle-ductile transition occurs at depth of 10-15 km. The depth of detachment estimates with simple equation (Fig.2) and given in time domain around 5000 ms. It gives geometric information, in particu-lar of deep target formation may be in seismic data acquisition in order to optimizing the structural model. Where subsidence and extensional values are required, regionally balance section is critical in providing a structural check on extension and compression factor. Total extension strain gives 0.2 from pre-rift to Mid-Miocene while in plio-pleistocene tectonic gives up to 0.6 compressed. These in turn may be important for hydrocarbon maturation and regional sub-sidence history studies. In the two fluvial wedges, the sedimentation rates (thickness/time) are everywhere equal to the incremental subsidence rates. Sedimenta-tion rates decrease toward the lateral edges and toward the hanging wall hinge of the basin. The maximum sedimentation rate in each fluvial wedge increases in progressively younger strata. In progressively younger syn-rift lacustrine strata, the maximum sedimenta-tion rate is constant or decreases slightly at the center of the basin and increases slightly in those cross sections located closer to the lateral edge of the basin. Within a given lacustrine wedge, sedimentation rates gener-ally increase toward the fault a t the center of the fault trace. The post-rift lacustrine units deposited after fault displacement ceased record a decrease in maximum sedimentation rate because their depositional surface areas increase through time, and thus the thickness of sediment deposited per unit time decreases.
These post-rift strata may be recognized by the large map region over which the sedimen-tation rate is constant within a stratal wedge. This is because these units were deposited over much of their extent on a flat-surface (the undeformed upper surface of the last synrift unit). Several giant oil and gas field have been cal-culated their extensional and compressional factor. Langkat area plotted as challenging area for future exploration based on field classification. However, compressional and extensional factor reveals that inverted tec-tonic occur intensively during basin filling history as following table and graphic :
Future basin filling models should seek to remedy the deficiencies and should be tested against a growing body of fine-scale strati-graphic data for extensional rift-basins (e.g., Olsen & Kent 1990). Nonetheless, the simpli-fying assumptions used in the models pre-sented here should not detract from the main thrust of this paper—that there are inherent tectonic differences among the three end-member models, which yield different stratal geometries and successions in modeling Langkat sub-basin.
4. Conclusions
Improving structural interpretation gains benefit by use of palinspatic restoration with area balancing. In particular, well-understand of the structural pattern and tectonic evolution of such areas can result if such techniques are integrated into seismic interpretation. While seismic section data rarely permit a unique interpretation of structure, balance geoseismic
restoration should be constructed iteratively in order to derive chronologic model. Finally, care should be taken in interpreting very spe-cific results of the basin filling models pre-sented here because: (1) the effects of com-paction and erosion of previously deposited sediments were not considered, (2) fluvial deposits were not allowed to aggrade above the outlet level of the basin, (3) the displace-ment and filling increments in all models were unrealistically large, and (4) the isostatic consequences of sediment loading were not considered. The advance analysis using sophicticated restoration software than manu-ally can reduces interpretational error inherent in seismic data.
Acknowledgements
This paper is an outgrowth of a chapter of the regional study of North Sumatra Basin. I thank to Dirjen Migas and Pertamina EP that has gave authority for publishing this paper as a poster at The HAGI 34th Annual Meeting 2009 in Yogyakarta.
References
Dahlstrom, C. D. A., 1969, Balanced cross section: Canadian Journal of Earth Sciences, v. 6, p. 743– 757. Davison, I., 1986, Listric normal fault pro-files: Calculation using bed-length balance and fault displacement: Journal of Structural Geology, v. 8, p. 209– 210. Dokka, R. K., and C. J. Travis, 1990, Late Cenozoic strike-slip faulting in the Mojave Desert, California: Tectonics, v. 9, p. 311– 340. Erickson, S. G., S. Hardy, and J. Suppe, 2000, Sequential restoration and unstraining of structural cross sections: Application to ex-tensional terranes: AAPG Bulletin, v. 84, p. 234– 249. Gibbs, A. D., 1983, Balanced cross-section construction from seismic sections in areas of extensional tectonics: Journal of Structural Geology, v. 5, p. 153–160. Hennings, P. H., J. E. Olson, and L. B. Thompson, 2000, Combining outcrop data and three-dimensional structural models to characterize fractured reservoirs: An example from Wyoming: AAPG Bulletin, v. 84, p. 830–849. Hossack, J. R., 1979, The use of balanced cross section in the calculation of orogenic contraction: A review: Journal of the Geologi-cal Society (London), v. 136, p. 705– 711. Laurent, M., Frantz, M., 2006, Chronologic modeling of faulted and fractured reservoirs using geomechanically based restoration: Technique and industry applications: AAPG Bulletin, v. 90, p. 1201–1226. Rouby, D., P. R. Cobbold, P. Szatmari, S. Demerican, D. Coelho, and J. A. Rici, 1993, Least-squares palinspastic restoration of re-gion of normal faulting— Application to the
OIL/GAS FIELD Extensional Compressional
RANTAU 0.35 0.43
KUALA SIMPANG BARAT 0.28 0.69
LIRIK 0.25 0.7
BAJUBANG 0.36 0.62
TEMPINO 0.28 0.72
KENALI ASAM 0.57 0.63
SUBAN 0.22 0.36
MUSI 0.15 0.26
PENDOPO 0.5 0.4
TANJUNG MIRING 0.27 0.43
SUNGAI HITAM 0.3 0.8
LANGKAT AREA 0.2 0.63
Page 26 Volume 20— February 2011
Campos Basin (Brasil): Tectonophysics, v. 221, p. 439–452. Rouby, D., H. Xiao, and J. Suppe, 2000, 3-D restoration of complexly folded and faulted surfaces using multiple unfolding mecha-nisms: AAPG Bulletin, v. 84, p. 805– 829. Sanders, C., M. Bonora, D. Richards, E. Kozlowski, C. Sylwan, and M. Cohen, 2004, Kinematic structural restorations and discrete fracture modeling of a thrust trap: A case study from the Tarija Basin, Argentina: Ma-rine and Petroleum Geology, v. 21, p. 845– 855.
Depth to detachment calculating :
A1=A2
22 KM* 3600 ms = 36 KM*DD = 2200 ms
Depth to Detachment due to isostacy
= 3600 + (3600-2200) = 5000 ms
CompressionalStrain = 0.6
Total Extensional Strain = 0.2
D
36 KM
22 KM
3600 ms
Preserved Amplitude Seismic Section
Horizon Interpretation
PalinspaticRestoration (Area Balancing)
Structural Model (Extension/Compressing and
Depth to Detachment Calculating)
33.5 KM
32 KM
30 KM
POST RIFTING PHASE
EARLY MIOCENE: Cont. sea level rise, Belumaiand Peutu Fm deposition as carbonate and clastic carbonate lithology.
RIFTING PHASE
EARLY –LATE OLIGOCENE BAWAH :
Horst-graben filled by Bampo Shale with lacustrine envirinment.
LATE OLIGOCENE : Sea level rise, Bampo shale.
FASA
PRE RIFTING
MID-EOCENE : NSB setting in edge of Sundaland
LATE-EOCENE – EARLY OLIGOCENE : Sea level fall, alluvial fan, conglomeratic sandstone of Parapat&Tampur Formation.
COMPRESSION PHASE
PLIO- PLEISTOSEN : Barisan Orogenic
Fault reactivation, right lateral faulting
Swampy depositional system.
QUIESENCE
TECTONIC PHASE
MID-MIOCENE: Basin stability(subsidence slowly; small uplift) followed by global rising sea level, Lower Baong Fm.
LATE MID-MIOCENE: Diendapakanbatupasirturbitid Duyung, Gebang dengan sumber dariutara. Dan Sembilan sand dari barat(Pegunungan Bukit Barisan sebagai sumbersedimen dari barat)
EARLY MIOCENE : Upper Baong shale, filling accomodation space. Progradational of Keutapang Fm, continued with Seurula&JuluRayeu Fm.
Fig.3. Result of Palinspatic Restoration from
Pre-rift to Compression Stage of a regional
seismic line in Langkat-Medan Area.
BOOK REVIEW
Sumatra. Geology, Resources and Tectonic Evolution
Fatrial Bahesti (Pertamina)
Page 27 Volume 20— February 2011
B ARBER, A. J., CROW, M. J. &
MILSOM, J. S. 2005. Sumatra.
Geology, Resources and Tectonic
Evolution. Geological Society
Memoir no. 31. ix + 290 pp. London, Bath:
Geological Society of London. ISBN 1
8 6 2 3 9 1 8 0 7 . d o i : 1 0 . 1 0 1 7 /
S0016756806212974.
This book provides collaborative approach of
geology of Sumatra since previous publica-
tion of van Bemmelen, the Dutch geologist
who published a ‘comprehensive and mas-
terly summary’ of the Geology of Indonesia,
initially in 1949. Much of the geological re-
search conducted in Sumatra in the latter part
of the twentieth century has been carried out
by the British Geological Survey and the
University of London SE Asia Research
Group. The whole island has been mapped
geologically at the reconnaissance level and
completed in the mid-1990s, together with
supplementary data obtained by academic
institution and petroleum and mineral explo-
ration companies, has resulted in a vast in-
crease in geological information, which is
summarized in this volume. The editors and
most of the contributors are associated with
these organizations and are thus able to draw
on considerable personal experience. In addi-
tion they have incorporated references to
pretty much every single paper or book to
have dealt with the geology of the island. It
thus follows in the tradition of Van Bem-
melen.
The opening part of this book presents a con-
cise introduction to the topic of Seismology
and Neotectonics that contains some late ad-
ditions which provide a comprehensive sum-
mary of the information that became available
immediately after the 2004 Sumatra’s earth-
quake and tsunami and has a note added in
proof to include data from other after-
shocks up to the end of April 2005. It might
therefore seem prescient to have planned the
publication of a memoir describing the geol-
ogy of Sumatra for 2005. In comparison to
other publications that have followed the
earthquake, this volume can fairly claim to
provide a comprehensive context in which to
place these momentous geological events.
There is much more to the geology of Suma-
tra than its present-day position above an
active subduction zone. It also contains one of
the world’s most prominent strike-slip faults
(the Sumatra Fault), an active volcanic arc, a
partially emergent forearc, and an extensive
back-arc region. It contains a globally signifi-
cant petroleum province, some coal reserves
and more limited mineral resources. The
geological evolution of the island can be
traced back to the Carboniferous or older.
A review of Granites and Pre-Tertiary vol-
canic rocks of Sumatra gives a valuable
history of the exploration and development
of recently oil and gas discovery in fracture
basement system in Sumatra, which played an
important role in establishing the concept, and
provides a general introduction to the geology
of the Northern and Southern Provinces.
There are a few papers in Indonesia con-
cerned with Pre-Tertiary fracture basement
play and magmatism Paleozoic island arc
development on the active margin of Sumatra.
Palaeozoic orogeny in the Sumatra consider
the subduction history of the Sundaland mar-
gin and its implication to describe
pre-tertiary basin present in Suma-
tra.
More specifically, a gap in the cur-
rent treatment is the limited cover-
age of the basins containing hydro-
carbon reserves. Oil company data
is always subject to the constraint
and confidentially, particularly in
Indonesia given the involvement of
Directorate of Oil&Gas in all li-
cences, but it would have been
interesting to see some of the com-
prehensive datasets that must exist
in these areas and would help to
address the thorny question of the
extent to which strike-slip deforma-
tion is associated with the formation
and subsequent inversion of the
Sumatra basins. In addition, the
BGS and University of London
projects were models of construc-
tive collaboration with Indonesian
organizations and it is perhaps a
pity that none of their Indonesian
counterparts are represented
amongst the authors. There is no
doubt that this volume will replace Van
Bemmelen as the standard reference for any-
one working in Sumatra and will no doubt be
the focus of much more work in the years to
come. Additionally, it guides the reader
through further information sources such as
other geological, geophysical, geochemical,
and mineral maps covering the area. It also
points the reader towards the nationally im-
portant archive of resources.
Overall, this is an excellent book and cer-
tainly represents compulsory reading for
undergraduate and postgraduate students
who wish to carry out research and revisiting
of Sumatra’s resources exploration. The
booklet is well referenced. With over 200
pages, and packed with illustrations and
photographs (all black-and-white), it repre-
sents excellent value for money. It also
serves its intended purpose as an excellent
reference guide for more experienced re-
searchers who may need reminding of the
exploration opportunity.
As Berita Sedimentologi journal aimed to
bridge communications, the editor has pre-
pared a special column for the academia, both
lecturer and students.
University
Page 28 Volume 20— February 2011
Special Publication #95
Cenozoic Carbonate Sys-
tems of Australasia
Edited by: William A. Morgan,
Annette D. George, Paul M.
(Mitch) Harris, Julie A. Kupecz,
and J.F. (Rick) Sarg
The Cenozoic carbonate systems
of Australasia are the product of
a diverse assortment of deposi-
tional and postdepositional proc-
esses, reflecting the interplay of
eustasy, tectonics (both plate and
local scale), climate, and
evolutionary trends that influ-
enced their initiation and development. These
systems, which comprise both landattached
and isolated platforms, were initiated in a
wide variety of tectonic settings (including
rift, passive margin,
and arc-related) and under warm and cool-
water conditions where, locally, siliciclastic
input affected their
development. The lithofacies, biofacies,
growth morphology, diagenesis, and hydro-
carbon reservoir potential of these
systems are products of
these varying influences.
The studies reported in
this volume range from
syntheses of tectonic and
depositional factors influ-
encing carbonate
deposition and controls
on reservoir formation
and petroleum system
development, to local
studies from the South
China Sea, Indonesia,
Kalimantan, Malaysia,
the Marion Plateau, the
Philippines, Western Australia, and New
Caledonia that incorporate outcrop and sub-
surface data, including 3-D seismic imaging
of carbonate platforms and
facies, to understand the interplay of factors
affecting the development of these systems
under widely differing
circumstances.
This volume will be of importance to geo-
scientists interested in the variability of Ceno-
zoic carbonate systems and
the factors that
controlled their
formation, and to
those wanting to
understand the
range of potential
hydrocarbon
reservoirs discovered in these carbonates and
the events that led to favorable reservoir and
trap development.
SEPM Membership for potential members
in Indonesia
Interested on sedimentological international
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origin of ooids;
coastal sedi-
ments; forma-
tion of stromato-
lites; impact of
storms on sedi-
ments; and the
formation of
dolomite. The remainder of the papers apply
the study of modern environments and sedi-
mentary processes to ancient sediments.
Other details about IAS is available in:
http://www.sedimentologists.org/
capability of the researcher, and reasonable-
ness of the budget.
SP41 - Perspectives in Carbonate Geology
Swart, P., Eberli, G., McKenzie, J. (Wiley-
Blackwell, 2009 - ISBN 978-1-4051-9380-1)
This special publication Perspectives in Car-
bonate Geology is a collection of papers most
of which were presented at a symposium to
honor the 80th birthday of Bob Ginsburg at
the meeting of Geological Society of America
in Salt Lake City in 2005. The majority of the
papers in this publication are connected with
the study of modern carbonate sediments.
Bob Ginsburg pioneered the concept of com-
parative sedimentology - that is using the
modern to compare to and relate to and under-
stand the ancient. These studies are concerned
with Bob's areas of passion: coral reefs and
sea-level; submarine cementation and forma-
tion of beach rock; surface sediments on
Great Bahama Bank and other platforms;
Up to 10 grants of about 1000€ twice a year
The IAS has established a grant scheme de-
signed to help PhD students with their studies
by offering to support postgraduates in their
fieldwork, data acquisition and analysis, visits
to other institutes to use specialised facilities,
or participation in field excursions directly
related to the PhD research subject. Up
to 10 grants, each of about1000€ are awarded
twice a year. These grants are available for
IAS members only, and only for PhD stu-
dents. Students enrolled in MSc programs are
NOT eligible for grants. Research grants are
NOT given for travel to attend a scientific
conference, NOR for acquisition of equip-
ment. Student travel grants for conferences
can be usually obtained directly from organiz-
ers of the meeting.
The Postgraduate Grant Scheme Guide-
lines provide a summary of required informa-
tion needed for a successful Grant Applica-
tion. Applications are evaluated on the basis
of the scientific merits of the problems, the
IAS NEWS
Page 29 Volume 20— February 2011
Call For Paper
In repeating the previous similar successful
events, joint convention between HAGI and
IAGI: Joint Convention Jakarta in 2003, Joint
Convention Surabaya in 2005, and Joint Con-
vention Bali in 2007, this Joint Convention
Makassar is delivering a theme of Exploring
Eastern Indonesia to represent the spirit of
current exploration and research of geology
and geophysics in Indonesia. Its challenge,
opportunities, process, concept, technology,
remarkable research, and experiences, in ex-
ploring energy (petroleum, mineral, coal,
nuclear, etc.) and understanding the earth
should be discovered on Joint Convention
Makassar 2011.
36th HAGI and 40th IAGI Joint Convention
Makassar 2011
Date
26 – 29 September 2011, Clarion Hotel
Makassar, South Sulawesi
Theme
“Exploring Eastern Indonesia”
Topics
Natural Resources of Indonesia
Mineral and Energy Resources Management
Environmental Issues
Hazard Mitigation
Geodynamics, Seismol-
ogy, Volcanology
Atmospheric Science,
Oceanography, Marine
Geology
Sedimentology and Strati-
graphy
G&G Methods, Technol-
ogy and Application
Engineering Geology
Unconventional Geology
& Geophysics
Mix Energy Sce-
nario and Policy
Abstracts
Authors are invited
to submit the abstracts related to the topics.
Acceptance of paper would be selected on
condition of maximum 300 words, covering
objectives, methods, results, and conclusions,
preferably written in English. Abstract should
not contain figures. Author should indicate
his/her preference in presenting the paper as
oral or poster presentations.
Submit abstract to: [email protected]
Submission deadline: 11 February 2011
Announcement: 15 March 2011
Extended Abstract deadline: 30 April 2011
JCM 2011 Secretariat
Patra Office Tower 20th Floor. Suite 2045
Jl. Gatot Subroto Kav. 32-34
South Jakarta 12950
Tel / Fax:. +62-21-5250040
IAGI NEWS
GTW –
October 2010
The Asia Pa-cific Region saw a success-ful conclusion to its inaugural Geosciences Technology Workshop (GTW) which took place on the 28-29 October 2010 in Singapore. The GTW theme of “Pore Pres-sure and Related Issues – Special Focus: Asia Pacific” was particularly pertinent as the Asia-Pacific region contains numerous rap-idly formed and highly overpressured basins and is an area in which pore pressure predic-tion is particularly challenging. The GTW was attended by 88 delegates and contained 23 presentations from industry experts, among whom were Keynote Presenters Rich-ard Swarbrick of GeoPressure Technology UK and Nader Dutta of Schlumberger USA. Running alongside the GTW were two short courses on Pore Pressure and Petroleum Ge-omechanics, taught by Richard Swarbrick and Mark Tingay (University of Adelaide) respec-
tively.
•University of Pembangunan Nasional
“Veteran” Yogyakarta (Indonesia)
•University of Indonesia (Indonesia)
In this global competition, university teams analyze a dataset (geology, geophysics, land, economics, production infrastructure, and other relevant materials) in the eight (8) weeks prior to their local competition. Each team delivers their results in a 25 minute pres-entation to a panel of industry experts. Stu-dents have the chance to use real technology on a real dataset, receive the feedback from an industry panel, have the opportunity to impress potential employers in the audience, and the chance to win cash awards for their schools. The industry panel of judges will select the winning team on the basis of the technical quality, clarity and originality of its presentation. The judging will take place over 1-3 March 2011. We wish the Teams all the
best!
More information can be obtained
from www.aapg.org/iba
10 Teams to participate in the Asia Pacific
IBA competition
In order to represent the Asia Pacific at the AAPG 2011 Imperial Barrel Award competi-tion at the AAPG ACE2011 in April, 10
teams are vying for this honour :
•Indian Institute of tech-
nology, Bombay (India)
•Indian Institute of Technology Kharagpur
(India)
•Indian Institute of
Technology Roorkee
(India)
•Pandit Deendayal Petroleum University
(India)
•Khon Kaen University (Thailand)
•Chulalongkorn University (Thailand)
•China University of Petroleum (China)
•Institute of Technology Bandung (Indonesia)
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FOSI MEMBERS
Page 31 Volume 20— February 2011
The editorial board will prepare 2011-2012
publications with the following schedule and
topics
2011
February 2011 (this edition): Sumatra
June 2011: Borneo / Kalimantan
• Title deadline: 10 April 2011
• Article deadline: 10 May 2011
October 2011: Java
• Title deadline: 10 August 2011
• Article deadline: 10 September 2011
2012
February 2012: Papua
• Title deadline: 10 December 2011
• Article deadline: 10 January 2012
June 2012: Timor
• Title deadline: 10 April 2011
• Article deadline: 10 May 2011
October 2012: Halmahera
• Title deadline: 10 August 2012
• Article deadline: 10 Septeber 2012
Future Berita Sedimentologi
Note: Depends on the number of articles, editors may change the topic