Editorial Board
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: fbahesti@pertamina ep.com 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]
Advisory Board
Prof. Yahdi Zaim—Quarternary Geology—Institute of Technology, Bandung Prof. R. P. Koesoemadinata—Emeritus Professor—Institute of Technology, Bandung
Berita Sedimentologi
• 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.
Volume 20— February 2011 Page 2 Number 20 / February 2011 Berita Sedimentologi Sedimentological journal of the Indonesian Sedimentologists Forum (FOSI), a commission of the Indonesian Association of Geologist (IAGI)
From the editors
Last year, 2010, the Indonesian tologi will be published electroni be geographical. For this edition, Association of Geologist (IAGI) cally in PDF format to reduce for example, we will focus on celebrate the 50th anniversary of cost and give higher flexibility in SUMATRA. the organization. This event give journal editing. Electronic journal As a ‘new’ publication we would a new momentum to the Indone also give more freedom to pub like to hear comments from our sian Sedimentologists Forum lish color figures with different readers, especially FOSI and (FOSI) to reactivate the bulletin. level of resolution. On top of IAGI members. If you like to that, the electronic journal will participate in the editorial team. also reach larger number of read Please let us know. ers as it will be easier to access. We hope the 3000+ members of the Indonesian Geologists Asso Herman Darman ciation (IAGI) who live in differ ent part of the world can get the Editor in Chief benefit of this journal as well. The editorial board will pick a theme for each journal and it will The last ‘Berita Sedimentologi‘ journal was published in 2000 in Inside this issue: paper format. Thereafter many key people in the editorial board left Indonesia and we admitted Bird Foot Print 5 that the hand over was not suc cessful. Talang Akar Formation 7 A new editorial board was set with many new members. We Ombilin Basin 12 hope that the coming publication of Berita Sedimentologi will achieved the following goal: Andaman-Sumatra 18 Forearc • Publish technical journal regularly Langkat structures 22 • Facilitate discussions related to sedimentary geology in University news 285 Indonesia and Southeast Asias region 2 • Provide opportunities for knowledge transfers through generations The coming Berita Sedimen
Volume 20— February 2011 Page 3 About FOSI
he forum was founded in 1995 sia. The forum was accepted as the sedi at least two years relevant experience. as the Indonesian Sedimentolo mentological commission of the Indone FOSI has organized 2 international con gists Forum (FOSI). This or sian Association of Geologists (IAGI) in ferences in 1999 and 2001, attended by ganization is a communication 1996. About 300 members were regis T and discussion forum for geologists, es more than 150 international participants. tered in 1999, including industrial and pecially for those deal with sedimentol academic fellows, as well as students. Most of FOSI administrative work will ogy and sedimentary geology in Indone be handled by the editorial team. IAGI FOSI has close international relations office in Jakarta will help if necessary. with the Society of Sedimentary Geology (SEPM) and the International Associa The official website of FOSI is: http:// tion of Sedimentologists (IAS). www.iagi.or.id/fosi/ Fellowship is open to those holding a recognized degree in geology or a cog nate subject and non graduates who have
FOSI Membership
ny person who has a back the ideal solution, and we may look for ground in geoscience and/or other alternative in the near future. Hav is engaged in the practising ing said that, for the current situation, A or teaching of geoscience or Linked is fit for purpose. its related business may apply for general International members and students are Total registered members: membership. As the organization has just welcome to join the organization. been restarted, we use Linked in 119 (www.linkedin.com ) as the main data February 2011 base platform. We realize that it is not
Volume 20— February 2011 Page 4 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
he islands of oceanic southern Asia (Indonesia, Malaysia, and New Guinea) have played an influential role in the development of evolu tionary T 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 Figure 1: Ombilin Basin located in the Barisan Mountains of central Sumatra. On the left is Sing- wahlunto and Ombilin Coal Mining areas karak Lake (Picture from Google Earth,2009) 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 Figure 2: General Stratigraphy of early part of the Miocene. In the Sawahlunto the bird foot print location 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
Volume 20— February 2011 Page 5 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.
Figure 3 : Outcrop shows the sandstone contains carbonaceous debris Figure 4 : First discovery of avian tracks, the Bird Footprint Fossils and small to medium, parallel ripples. The avian tracks are found at the in Indonesia from Sawahlunto Formation of Early to Middle Mio- base of this outcrop. cene in age.
Figure 6 : Small, circular traces (Skolithos ichnofacies) are proba- Figure 5 : One set of tracks has an angle of 90 degrees between digits bly representing tubes of suspension feeding invertebrates. one and three,probably represents a gruiform (rail), and the second set of tracks has a 120 degree angle between digits.
Volume 20— February 2011 Page 6 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
ABSTRACT of channel plug was deposited in a very low weathered basement granite and quartzite, are energy environment before the channel was effective reservoirs in ten fields in South Tanjung Baru Formation only outcropped in abandoned. Some parts have shaly and coal Sumatra with gas reserves totaling 106 one location so called Tanjung Baru, streaks with mafic and feldspatic minerals. MMBOE ultimate recoverable reserves Palembang, South Sumatra. In total this This formation has an indication to be an (Sardjito, et al, 1991; Petroconsultants, 1996). formation is expossed in an area of about one excellent reservoir. This fact is very important and it is therefore acre. The outcrop is a quartz sandstone absolutely urgent for the goverment of quarry, which has become smaller in size The geology of Tanjung Baru Formation is an Baturaja District, South Sumatra Province to rapidly because of intensive mining activities important object to study because it is the one conserve and to protect the outcrops of the by the local community. The formation is also and only outcrop that needs to be conserved. Lower TAF. The outcrops have very called Gritsand Member (GRM) of the Lower The objective is to save this outcrop from important value to Earth Sciences and Talang Akar Formation/Lemat Formation/ extinction. A socialization to the Governor of exploration in geology, mining and petroleum Lahat Formation. A different name from South Sumatra Province and Head of engineering. The aim of the conservation is to Talang Akar Formation was given to this Palembang Regent needs to be done. The avoid outcrop mining for other purposes. formation because it has an important role in government has to create a regulation to stop the tectonostratigraphy context. Tanjung Baru the mining activities, build a boundary for the An integrated study (fieldtrip and core Formations has different genetic, location and outcrops with plantation and put an analysis) was held by P.T. Medco E&P section type from that of Talang Akar information board to explain that it’s a Indonesia (PT. MEPI) for the Graduate Formation. The formation consists of conservation area. Let all geology students Geoscientists Training 2 2008 at sections conglomeratic sandstone of channel deposit. and also people of all generations to have a Baturaja Muara Dua Palembang and The sections indicate five times of channeling possibility to learn Tanjung Baru Formation Palembang Core Storage. The methodology with each channel has a geometry of 20 m from this outcrop as a geopark. of outcrop description has been conducted for long and 9 m thick. This lag sedimentary the basement rocks to the top formation in deposit consists of fine to very coarse South Sumatra Basin. grained sandstones. The erosional base Introduction The Lemat (Old and Young) Formation has contact has polymictic conglomeratic Hydrocarbon production in the South Sumatra outcropped in the sandstone quarry at sandstone outcrop with gradded bedding and Basin is ranked at the 2nd place after Kutei Tanjung Baru (proposed as locality type and planar crossbedding that indicate high energy Basin in term of total productions. The strato type) and Napalan river in Baturaja deposition like channelized environment in primary reservoirs are within the Talang City, Palembang, South Sumatra Province. shallow marine. The fining upward Akar, Baturaja and Gumai Formations and a The outcrop of Lemat Formation is found in succession was a result of lateral accretion of smaller amount in the fractured basement. Tanjung Baru Sandstone Quarry (TAF channel shifting or a fluvial channel system The uplifted areas and paleohighs, including equivalent the Gritsand Member). The depositional environment. The very fine sand the Mesozoic and Eocene fractured and
Figure 1. Left: South Sumatra Basin configurations. Right: Quarry location of Tanjung Baru sandstone outcrops (See arrow)
Volume 20— February 2011 Page 7 Tanjung Baru Fm.
Figure 2. Regional Stratigraphy of South Sumatra Basin (Argakoesoemah and Kamal, 2005). Stratigraphic position of Lemat Formation or Tan- jung Baru outcrops siliciclastic sediments outcropped in this area However, the upper member of the Talang The South Sumatera Basin is one of a series should be named Tanjung Baru sections or Akar Formation called the Transition Member of Tertiary back arc basin located in Sumatera stratotype and it is also the type locality of (TRM) is included the Talang Akar and Java. The basins occupy a geologic Tanjung Baru Formation. The location where Formation. Lithostratigraphically, in position between the stable micro continental the best siliciclastic sediment outcrop exists is accordance with SSI (1996), the complete block, known as the Sunda Platform, and the almost 1 km south of the Baturaja town outcrop of Tanjung Baru Sandstone should be active subduction zone caused by the (Figure 1). determined as Tanjung Baru Formation northward moving Indian Ocean Plate. The because of the lithology, mappable, basin was formed during the Eocene The promotion of GRM into Tanjung Baru stratigraphic contact and either lateral or Oligocene when a series of northerly trending Formation is necessary due to its vertical distribution. grabens developed in response to east west tectonostratigraphy importance. Hutchinson interplate extensional movements. These (1996) concluded that the Eocene to Every year, the outcrops have less volume grabens were filled with locally sourced Oligocene Lahat Formation is composed of due to mining by thelocal community. These volcanoclastics sandstones and shales of the synrift deposits that are as much as 700 highly valuable outcrops of the Tanjung Baru Lemat Formation in depositional 1,070 m thick. The formation was deposited Formation have given stratigraphy and environments ranging from alluvial fan, to in continental, lacustrine, and brackish sedimentation models the Oligo Miocene age fluvial and lacustrine. lacustrine depositional settings. This reservoir has had outcropped. The outcrops have just accounts for nearly 88 MMBOE of ultimate one complete section as type locality and The geology of the studied area, particularly recoverable reserves (Petroconsultants, 1996). strato type. They have excellent porosity and the Musi Platform, is a structural high area The oldest facies of the Young Lemat is permeability and are analogues to the formed during the Eocene Oligocene graben granite wash overlain by coarse clastic reservoir rocks in the South Sumatra Basin. forming period. It appears to behave as a rigid deposits consisting of sandstones and breccias The comparison with tonase economic value structural block through most of the Tertiary. with abundant rock fragments, claystones, for mining, the quartz sandstone remains There is direct evidence to which the area has coals, and tuffs (Hutchinson, 1996). about 1000 m3. The outcrops should be very been subjected to widespread deformation. To rare therefore it is crucial to be conserved and the west, the platform gradually shallows due Firstly, the proposed name of Tanjung Baru protected. to uplift associated with rising volcanic arc. Formation is an increase from a member Baturaja Limestone is exposed at the foothills status of the conglomeratic quartz sandstone of the Gumai Mountains. The northwestern of Lower Talang Akar Formation (Ryacudu, Geology of Baturaja and southwestern margins of Musi Platform 2005) or the Gritsand Member (GRM). are controlled by major faults which bound
Volume 20— February 2011 Page 8
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. the Eocene Oligocene grabens. The north, and in the Saungnaga Area, to the and horst areas. northeastern edge of the block is in the southwest. Generally over the Musi Platform, the Talang present day Lematang Trough, a syncline Akar Formation or Baturaja Limestone lies between the Musi Platform and the Plio unconformably on pre Tertiary basement. Talang Akar Formation Pleistocene Lematang fault which has Talang Akar Formation is interpreted to be a thousands of feet of overthrusting from the As the subsidence associated with graben lacustrine unit deposited on the eroded north. Seismic interpretation of the Lematang formation waned during the Middle to Late basement surface. It is separated from the Trough that forms the northeastern margin of Oligocene, the interbedded sandstones, shales more typically sand prone Talang Akar Musi Platform is limited by its proximity to and coals of Talang Akar Formation were Formation deposited on the eastern side of the the overthrust fault. deposited across the South Sumatra Basin. basin, by the deep water, shaly sediments This unit was derived from the northeast which fill Benakat Gulley. Because of its based on the compositional imprint of its isolation from the coarse clastic sediment Stratigraphy granitic source areas on Sunda Platform. A source to the northeast, the Talang Akar on The Tertiary succession overlying the general depositional environment sequence the Musi Platform represents an environment Mesozoic metamorphic basement consists of from fluvial in the northeast, to deltaic and which is typical for the deposition during this Lemat Formation filling the early half later basinal facies in the southwest can be period. Pre Telisa clastics in the Pigi Trough grabens, unconformably overlain in turn, by reconstructed from sedimentological and are often tuffaceous and usually lack of good Talang Akar Formation, Baturaja Limestone, paleontologic evidences. There are evidences reservoir quality. As the basin continued to Telisa Formation and Palembang Formation of cyclic deposition within Talang Akar subside during the lower Miocene, deposition (Figure 2). Formation providing excellent hydrocarbon of the predominantly non marine Talang Akar reservoirs. The organic rich shales and coals Formation was replaced by widespread of the Talang Akar Formation are considered marine deposition of the Telisa Formation. Lemat Formation to be the major oil source for reservoirs in this Tanjung Baru Formation Outcrops Within the Musi Platform, the Lemat unit and the overlying Baturaja Limestone. 1. Lithology and Stratigraphic Positions Formation consists of volcanoclastic The thicker areas of deposition continued to sandstones and shales, typical of the unit. The be controlled by more rapid subsidence over The outcrop of Tanjung Baru Formation formation is also known from the graben the Oligocene grabens, and as with Lemat consists of fine to very coarse grained areas around the platform and has been Formation, deposition was either thin or non sedimentary rock. It has almost 100 m wide intersected in wells in the Pigi Trough, to the existent on the structurally higher platform and 20 – 25 meters thick (Figure 3) and
Volume 20— February 2011 Page 9 consists of clean quartz conglomerate upward sequence (Figure 4). (Allen, 1988). In the bottom conglomerate, sandstone, quartz sandstone, siltstone and there was an erosional base contact which Quartz sandstone; white, fine – medium sand, intervals of coals without fossils. Their indicates that this sandstone was deposited in grain supported, moderate to poorly sorted, stratigraphic position is determined at the highly erosional processes environment such and subangular to subrounded, quartz lower part of Talang Akar Formation by fault as in channelized environment (Selley, 1970). (abundant), some parts are siltstone of a few and erosional or unconformity contact to the centimeter thick. The light grey siltstone with The conglomerate at the bottom of this Upper Oligocene Lahat Group. The presence silicate cement and without fossils is sequence is predicted as lag deposit which is of paleosoils and basal conglomerates distributed in the upper part of the fining channel floor deposit, while fining upward indicates an unconformity contact. So, the upward sequence. Coals have been found succession is the result of lateral accretion of Tanjung Baru Formation or Lemat Formation occasionally and they are a few centimeter channel shifting (Selley, 1970). Based on all is approximately Lower Miocene in age. thick. of interpretations, it is concluded that the Quartz conglomerate sandstone; grayish white sandstone was deposited in braided channel color, medium sand to granule grain size, which have five, observed channel shifting. moderate to poor sorted, subangular 2. Depositional Environment This sandstone has an excellent reservoir subrounded, matrix supported, polymictic Non calcareous sandstone with planar cross quality. conglomerate with quartz dominant as the bedding structure, and fining upward Genetically, the development of Tanjung fragments, non calcareous, rare basalt and sequences that shows decreasing energy Baru Formation (Gritsand Member) mostly andesites, feldspar, carbon and mafic towards the top can be interpreted as a fluvial differed to the TRM Member: the channel minerals; matrix: quartz, opaque minerals; channel system depositional environment. It sediments that filled in rift basin after syn rift silicates cements, 4 – 6 meter thickness. shows at least four depositional sequences phase. Tectonostratigraphically, the Observed sedimentary structure includes which conglomerate as a lag deposit and very terminology called: immediate post rift graded bedding and in the base there is an fine sand as channel plug which was (Prosser, 1993) or passive rift fill; however erosional base contact. This outcrop has deposited in a very low energy deposition Talang Akar Formation (TRM) as a initial dip oriented to northwest (N230 o before channel was abandoned. transitional deposits to shallow marine. It E/30o). Sediment succession of the upper part characterized an early regional transgressive of the Lag Deposit Sandstone (Figure 3) has Based on the planar cross bedding phase in the South Sumatra Basin. This planar cross bedding structure, channel plug sedimentary structure, the sandstone was formation's development is restricted in the (very fine grain size) and some fractures deposited by traction current mechanism and deep zone, but the Talang Akar Formation is (uncemented, loose) and shows a fining was influenced by highly turbulent current 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.
Volume 20— February 2011 Page 10 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 Sardjito, Fadianto, Eddy, Djumlati, and Exploration and Production Database: Hansen, S., 1991, Hydrocarbon prospect of Petroconsultants, Inc., P.O. Box 740619, the pre Tertiary basement in Kuang area, 6600 Sands Point Drive, Houston TX 77274 South Sumatra: Proceedings Indonesian 0619, USA or Petroconsultants, Inc., P.O. Petroleum Association Twentieth Annual Box 152, 24 Chemin de la Mairie, 1258 Perly, Convention, October, 1991, p. 255 278. Geneva, Switzerland. Selley, R.C., 1970, Ancient Sedimentary Prosser, S., 1993, Rift related linked Environments and their sub surface diagnosis. depositional systems and their seismic Chapman and Hall, London, 287p 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.
Volume 20— February 2011 Page 11 Half-day visit to Solok-Sawahlunto area, Ombilin Basin: A short observation on non-marine depositional sequences RM Iman Argakoesoemah and Didit Ariady Firmansyah
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 Figure 1. Index map of station (STA) of the observations during visit to Solok Sawahlunto area. small intermontane basin began to occur in the Late Eocene by north south tensional displacements followed by dextral strike slip transgression stage is stratigraphically repre age diagnostic fossils are not present, but faulting of the Sumatra Fault System in the sented by a mega sequence ranging from non erosion surface could mark the boundary Oligocene resulted in a pull apart develop marine coarse clastic rift deposits to shales of between both formations as shown by a shift ment of the horst and graben structures in deep open marine with the maximum flooding of Ro value plot in Sinamar 1 well (Koning, northwest southeast trending (Situmorang et occurred in the Mid Miocene. 1985). The Sawahtambang has been described as thick coarse quartz rich sandstones with al, 1991; Howells, 1997). The basin uplift in The Sawahlunto Formation consists of non some overbank coaly claystone suggesting the Mid Miocene or later reduced its extent to marine argillaceous deposits with numerous that the formation was deposited in the flu the present size where the intermontane basin coals and some quartz sandstones. The Ombi vial, braided river setting. is outlined. To the west the basin is presently lin Underground Coalmines situated in Sa bounded by a series of Quaternary to Holo wahlunto city has produced coals since 1891 The geothermal gradient in Sinamar 1 (1984) cene volcanoes while to the east by the pre from this formation. The estimated reserves is only 1.62 degF/100’ (29.6 degC/km) which Tertiary non volcanic sediments. are of about 200 million metric tons. There is cooler than the average gradient of 3.3 The basin began with deposition of the sand are three main coal seams with the most po degF/100’ (60.3 degC/km) in the Central rich, conglomeratic sequence of alluvial fans tential up to 18 m thick and average 9.3 m Sumatra Basin. Several oil shows were re of the basin margins of the Brani Formation thick of black and lustrous bituminous coal ported in the sandstones of the Sawahtambang followed by the Sangkarewang, Sawahlunto, rank (Silkina and Toquero, 2008). It should Formation. One open hole DST recorded Sawahtambang, and Ombilin Formations be noted that large extent of the coals could minor also have potential for coalbed methane (Koesoemadinata and Matasak, 1981; flow of oil (36 deg API gravity) in the upper (CBM) deposits. Koning, 1985; and Noeradi et al, 2005), Fig formation and a gas flow exceeding 13 ure 2. Fresh water lacustrine setting could be The formation is probably conformable over MMCFD (60 deg API gravity) in the middle present in the depocentre of the basin. This lain by the Sawahtambang Formation. The part of the formation (Koning, 1985). The
Volume 20— February 2011 Page 12 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 Figure 2 . General lithostratigraphic column of Ombilin Basin (Noeradi et al, 2005) conducted if continuous measured section is planned since the field condition in some outcrops need special attention for the pur source rocks might be the mature shales tively thin floodplain deposits may help corre pose of safety precaution. (Ro=0.6%) of the Sangkarewang Formation late the sand rich sequence locally. Some of (Avg TOC= 2.6%) while the Sawahlunto them could have been significantly extended (4) The outcrops are useful for the study of coals are still immature with Ro=0.53% laterally and can be used for local correlation non marine Tertiary sequence stratigraphy (Fletcher and Yarmanto, 1993). The hydro marker. Thickness of the individual sand rich though the deposition and tectonic in the re carbon accumulation is considered non sequence could be tens of meters. Individual gion are active. Non marine biostratigraphy commercial (Koning and Karsani, 2000). The coal layer may not be useful for regional cor should be conducted to establish the vertical later well, South Sinamar 1 (1994) drilling relation as the main stratigraphic relationship and lateral regional results is dry. correlation across the basin. swampy, floodplain area may not be very Brief Outcrop Overview extensive in the Sawahlunto Formation at this (5) In addition to the coalmine purposes fur location STA 7, Allied Indo Coal. ther exploration for hydrocarbon occurrence Several large outcrop exposures are present in the basin should remain to be interesting along the coalmines in the Sawahlunto area. Based on the rift basin model, Noeradi et al not only for conventional hydrocarbon but Description for a broad mega sequence over (2005) interpreted that the Brani coarse clas also for unconventional exploration specifi view can be conducted from a distance as the tics of fanglomerate and other related sedi cally coalbed methane. outcrops extend several hundreds of meters ments representing rift basin margin facies laterally. Some of them could have few hun was deposited during the early syn rift phase dreds of meters of repeated vertical se while the Sawahlunto Formation was depos Note: Any content and interpretation appear quences. A closer look will give much better ited during deposition of the late syn rift. The in this paper is solely responsible of the Au impression on sedimentary sequences and Sawahtambang and Ombilin Formations are thors. lithological description and composition. considered to be the post rift phase based on seismically continuous, widespread reflector References Below are a brief description and preliminary package over the whole basin. interpretation of the outcrops based on quick Fletcher, G. and Yarmanto, 1993, Ombilin observation and reading materials. Further geophysical interpretation should be basin field guide book. Indonesian Petroleum taken to ensure that the lithological contrast Association, Post Convention Field Trip, 59 Coaly claystone and coal of the floodplain between the thick sandstone package of the pp. deposits have vertically separated each sand Sawahtambang Formation and the thick, rich sequence as the river channels move Howells, C., 1997, Tertiary response to open marine shale package of the Ombilin laterally and vertically with time. These rela oblique subduction and indentation in Suma
Volume 20— February 2011 Page 13 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.
tra, Indonesia: new ideas for hydrocarbon 1981, Stratigraphy and sedimentation – Om p. 217 249. exploration. Geological Society of London, bilin basin, Central Sumatra (West Sumatra Koning, T., 1985, Petroleum geology of the Special Publications, v.126, p. 365 374. Province). Indonesian Petroleum Association, Ombilin intermontane basin, West Sumatra. Proceedings of the 10th Annual Convention, Koesoemadinata, R.P. and Th. Matasak, Indonesian Petroleum Association, Proceed
Volume 20— February 2011 Page 14 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.
Volume 20— February 2011 Page 15 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. ings of the 14th Annual Convention, p. 117 Exploration in the Ombilin intermontane AAPG Search and Discovery Article #90913. 137. basin, West Sumatra. AAPG International Noeradi, D., Djuhaeni, and Batara Simanjun Conference and Exhibition, Bali, Indonesia. Koning, T. and Aulia Karsani, 2000, Abstract: tak, 2005, Rift play in Ombilin basin outcrop,
Volume 20— February 2011 Page 16 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.
West Sumatra. Indonesian Petroleum Asso entific and Technical Division, PTBA Ombi Ombilin basin, West Sumatra. Indonesian ciation, Proceedings of the 30th Annual Con lin Coal Project, 14 pp. Petroleum Association, Proceedings of the vention, p. 39 51. 20th Annual Convention, p. 1 15. Situmorang, B., Barlian Yulihanto, Agus Silkina, I. and Napoleon Toquero, 2008, It’s Guntur, Romina Himawan, and T. Gamal About Time. Time Technology Pty Ltd, Sci Jacob, 2005, Structural development of the
Volume 20— February 2011 Page 17 Seismic Expression of Some Geological Features of Andaman-Offshore West Sumatra Subduction zone
Herman Darman—Shell International E&P
subduction zone developed in the south of Myanmar, continue to the Andaman Sea (India), west A 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
Volume 20— February 2011 Page 18 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. Figure 2. Schematic regional cross section of a subduction zone This short section shows a reverse fault which the fore arc basin. East Andaman fault system basin is deeper than 3000 MSec. TWT. bound the west part of the fore arc basin (Figure 5). The fault goes all the way to the developed bathymetric high called ‘invisible A seismic section published in AAPG Ex sea floor at about 3.5 sec. TWT, separating bank’ in the middle of the fore arc basin. Part plorer show a Miocene Limestone unit which the accretionary prism from the fore arc ba of the fore arc is shown on the west of the this towards the deeper water. The interpreta sin. The accretionary prism in the SW of this section. Further west of this section the fore tion also indicates a shelf deposit, shelf edge section is clearly shown as a bathymetric high arc ridge appear to the sea surface as Anda and an isolated shoal (Figure 4). The shelf and the fore arc basin appear as a flat sea man Island (Figure 3). unit is about 3 4 Msec. TWT deep. base. The interpretation suggest Pliocene Recent The Neogene unit is underlain by Pre The fore arc basin was filled with Late Mio stratigraphic interval at the shallowest section. Neogene sediments which is thins towards the cene and younger deposits. Flat reflectors This unit thins in parts due to volcanic activ volcanic arc. In parts the pre Neogene se shows that there were very little tectonic im ity and fault movement. Neogene units are quence has been completely eroded away. pact on this area despite the major earth thicker in the back arc basin compare to the This unit seems thicken to the west of the fore arc basin. The majority of the back arc quakes and tsunami developed in this region.
Figure 3. West to east geoseismic cross section through the northern part of the Andaman fore-arc basin area (after Scaife & Billings, 2010)
Volume 20— February 2011 Page 19 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.
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 References Unfortunately the seismic section is too short Bunting, T, Chapman, C; Christie, P., Singh, Drilling Program (IODP). and too shallow to show the regional picture. S., Sledzik, J., 2007, The Science of Tsuna The complex geology in the accretionary The seismic section is more than 16 sec. TWT mis, Oil Field Review, Autumn 2007 complex result in unclear seismic expression deep and show the oceanic Moho on the SW Caife, S., Billings, A., 2010, Offshore Explo in this area. of the section. An indication of continental ration of the Andaman Sea, GEO ExPro, vol Moho appears in the NE of the section. The 7, no. 5. section also shows the trench and the accre 3. Simeuleu Section tionary wedge of the West Sumatra subduc Durham, L. S., 2010, India Seismic Gets New View, AAPG Explorer, October. In July 2006, Geco acquired 3 deep seismic tion zone (Figure 6). sections in offshore west Aceh. (Bunting et al, Slightly to the south of this line, TGS shot Malod, J. A., Kemal, M., Beslier, M. O., De 2007) to image active faults along the subduc some seismic which was focused on the fore plus, C., Diament, M., Karta, K., Mauffret, tion zone, quantify the volume of water that arc basin. The seismic section clearly shows A., Patirat, Pl., Pubellier, M., Rgnauld, H., penetrated along these faults and provide the fore arc ridge and major regional NW Aritonang, P., Zen, M. T., 1993, Deformation information to optimize the location of future trending fault zone in the SW of the section fo the Fore arc Basin, NW of Sumatra, re borehole location for the Integrated Ocean (Figure 7). In the NE, present day shelf de sponse to oblique subduction, Sumenta Crui ese – Baruna Jaya III – 1991.
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..
Volume 20— February 2011 Page 20 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
Volume 20— February 2011 Page 21 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])
Abstract of hydrocarbons. Therefore, understand deformation, minimization of changes in Numerous published studies have shown ing the evolution of basin structure and segment length, or minimization of that cross section balancing and valida physical properties through time should shearing, constant fault slip, fixed faults tion techniques are a powerful method of improve geological models and, in turn, in space, or discontinuous rigid blocks. structural analysis. The construction of significantly reduce exploration risk. Furthermore, these techniques are not seismic cross section is of the greatest based on the fundamental principles of importance to generate regional study of Furthermore, whereas these geophysical the conservation of mass and momentum, basin history. For this reason, palinspatic techniques adequately image the major which govern rock deformation. In addi restoration in time domain of seismic geological structures, this only provides tion, only strain, which is strongly de data have evoked considerable interest, the present day structural geometry of pendent on the geometric restoration in particular in areas of extensional and the subsurface, which commonly has algorithm used, is calculated (Erickson et compressional tectonics regime. The resulted from multiple tectonic events, al., 2000; Hennings et al., 2000; Rouby et basic approaches to restore preserve seis thereby increasing the complexity of the al., 2000; Sanders et al., 2004). There mic section assume plane strain, or con analysis. To more realistically model the fore, physical laws and linear elastic the servation of cross sectional area. Calcula spatial and temporal development of ory replace kinematic and geometric tion of equal areas for a section deformed structural heterogeneities and to address constraints used by the existing methods above a decollement or detachment sur these economical issues, a variety of nu for the restoration of geological struc face can be applied by depositional time. merical techniques have been developed. tures. Strain heterogeneity may be esti It calculates depth to detachment in They fall into three main categories: (1) mated and it is possible effects on bal Langkat area, around 5000 ms in time the geometric and kinematic approaches; ance calculations deduced. The availabil domain to detachment by restoration (2) the stochastic approaches; and (3) the ity of closely spaced seismic lines, cou techniques. In addition to the analysis of physical and geomechanical approaches. pled with well control, however, can give structural traps, cross section validation three dimensional and stratigraphic con can be used in Bampo and Baong Forma The first category includes most of the trol in areas of orogenic contraction. tion as major source rock, especially in restoration techniques used by structural the relative timing of hydrocarbon migra geologists to check the consistency of the 2. Data and Methods tion. The extension and compression subsurface structural interpretations. The geomechanically based restorations factor results 0.20 and 0.63 for Langkat Measures of gaps and overlaps between described in this study were performed area without assuming wrench fault zone the restored parts of a model give qualita manually using constrain length and ar gives additional strain in calculation. The tive values to check the strength of the eas with CorelDraw, a 2 D seismic has result, when compared with several ma geological interpretation. The geometri been interpreted to model complex geo jor oil and gas field in Sumatra, gives cal methods proposed to restore geologi logical structures with a variety of high compression inverted structure clas cal structures are based on a variety of boundary conditions or constraints. In sification that increase confidence for algorithms, which aim at reproducing this study, we only consider the 2 D for finding any giant field. This technique, natural deformation. For instance, the mulation to restore geological cross sec when used with other methodologies, methods include balancing cross sections tions. such as sequence stratigraphy and basin by flexural slip (Dahlstrom, 1969; Hos modelling, allows the interpreter to use sack, 1979; Davison, 1986) to model Detachment fault models of extensional all the available data sets to constrain deformation accommodated by slip along basin development have two end geological models on hydrocarbon an infinite number of bedding interfaces. member geometries (Fig. 1A). The first prospectivity. It is therefore a valuable involves listric normal faults that methodology in both 3D basin analysis More simply, mapview restoration has gradually sole into sub horizontal de and prospect risking/ranking. been done using rigid translation and tachments (Wernicke & Burchfiel 1982; rotation of fault blocks (Dokka and Gibbs 1983). In the second case the 1. Introduction Travis, 1990; Rouby et al., 1993) to fault system has a kinked geometry con Whether paleostructure model are resolv model larger scale deformation. These sisting of two planar fault segments able on seismic reflection surveys, they methods are based on geometrical as (Jackson 1987; Groshong 1989). Under can significantly affect hydrocarbon mi sumptions (Rouby et al., 2000), such as both end member conditions, transla gration and trap location, as well as flow preservation of area, minimization of tion on the sub horizontal detachment
Volume 20— February 2011 Page 22 l1 results in potential voids between the lo hanging wall and footwall blocks, and Sedimentation rates progressively decrease collapse of the hangingwall results in toward the hinge of the basin and precisely the formation of a half graben. The foot mimic the subsidence rates. Since the second increment of displacement is equal to the first, wall block is assumed to remain pas area balance dictates that the newly created sive during extension (Gibbs 1983; d volume of the half graben be equal to that of Groshong 1989). The geometry of the the first increment. Since the volumetric sedi half graben is governed by (1) the rules mentation rate is constant, the basin again of equal area balancing (Gibbs 1983), completely fills with fluvial sediments. Notice Area A= Area B that the younger wedge of sediments pinches (2) the geometry of the fault system, (l 1- l 0)d=A=B and (3) the nature of the deformation in out against the older wedge. This is because l the hanging wall, i.e., collapse along 1 the footwall, the basin bounding fault, and the l l depocenter of the basin remain fixed during zones of vertical shear, collapse along A extension, but the hinge of the basin migrates antithetic faults of variable dip angles, l away from the basin bounding fault. This and the relative amounts of bedding d pattern of fluvial plane shear within the hanging wall sedimentation and pinchout of younger strata block (Gibbs 1983, 1984; White et al. against older strata would continue as long as 1986; Williams & Vann 1987). In gen the displacement rate was uniform. However, eral, half graben become wider and less (l 1- l 0)d=A a doubling of the amount of displacement also doubles the incremental volume of the basin, deep as the dip angle of the antithetic d=A/ (l 1- l 0) which now exceeds the volume of sediments faults along which the hanging wall col Fig. 1. Area Balance for Extension. Above: lo lapses decreases (Crews & McGrew available. Lacustrine deposition occurs. Note is original length of section which compared that (1) the lacustrine wedge of sediment 1990). The dip angle of the border fault with length in deformed state and area. Below pinches against older fluvial strata, (2) the and the depth to detachment also : the regional projected horizontal, to calcu- maximum sedimentation rate in the lacustrine strongly influence the geometry of the late depth to detachment. wedge is higher than the maxima of the two basin: for the same amount of net dis older fluvial wedges, and (3) the depositional placement on the horizontal detachment, ure 1 show the basic approach to section bal surface area of the lacustrine wedge is less basins become narrower and deeper as ance for plane strain, or conservational of than for the fluvial wedges, requiring a higher the dip of the basin bounding fault and cross sectional area. transverse gradient in sedimentation rates. depth to detachment increase (Morley Given initial fluvial sedimentation, lacustrine 1989). In the case of listric faults, a roll The equation expresses the relationship be sedimentation can only occur if there is an tween the undeformed length, the deformed increase in the extension rate and/or if the over geometry results in the hanging length of section and the depth to the decolle volumetric sedimentation rate decreases. The wall because of the increasing size of ment surface (d). This can be expressed in chosen volumetric sedimentation rate results the potential void between the hanging term of average stratigraphic thickness upon in fluvial sedimentation following the first wall and footwall blocks toward the time depth conversion. It is seen to be identi two increments of displacement. After the listric fault. For the ramp flat geome cal to those for orogenic contraction with the third increment, the basin is of such a size that try, a flat bottomed half graben results exception of the change in sign convention lacustrine sedimentation occurs. In general, because the width of the potential void for elongation and is likewise independent of under conditions of accelerated extension, between the hanging wall and footwall the style of deformation. younger units consistently pinch out against blocks is constant over considerable por older units, the maximum sedimentation rate Linear elasticity is used as a tool for restora in younger units is higher than in older units, tion of its length. tion because its fundamental properties are and a transition from fluvial to lacustrine is well suited for such modeling. Therefore, predicted if extension continues long enough The basic approaches to section balance model results can easily be comprehended. and if the effects of accelerated displacement assume plane strain, or conservation of Linear elasticity honors the full complement overcome the effects of any increase in the cross sectional area. Calculation of equal of physical laws that govern geological defor volumetric sedimentation rate. areas for a section deformed above a de mation, including conservation of momentum, collement or detachment surface can be mass, and energy. As a result, physical laws Studies of small normal faults in British coal applied to extension as well as contrac replace kinematic or geometric assumptions fields and larger normal faults in the North tion. Given the equal area balancing commonly used for restoring geological struc Sea imaged on a closely spaced grid of seis tures, such as preservation of segment length, mic lines have shown that the displacement assumption, the cross sectional area of surface area, or volume. on these faults is generally greatest at or near the hanging wall basin is given by: the center of the fault and decreases to zero at This is a feature unique to the detachment its ends (Barnett et al. 1987; Walsh & Watter A = hd (1) fault models. The volume of the basin also son 1987, 1988, 1989; Gibson et al. 1989). where h is the net displacement on the hori changes similarly since uniform plane strain zontal detachment and d is the depth of the conditions prevail (Gibbs 1983). The uni Gibson et al. (1989) used relationships of detachment. The rate of increase in the cross form plane strain condition is most likely to fault growth model I to generate model half sectional area of the basin is constant (dA/dh be satisfied when the basin is bounded graben. Specifically, the along strike dimen = d), and the change in the rate of area in laterally by vertical transfer faults sion of the basin is given by the fault length crease (d2A/dh2) is zero. This is a feature (terminology of Gibbs 1984). (Fig 2). L: unique to the detachment fault models. Fig
Volume 20— February 2011 Page 23 where G is the shear modulus, σ is the stress The preceding equations assumed that the drop after each seismic event, S is the incre normal faults were blind and consequently the ment by which slip increases after each slip displacement of horizons was distributed event (necessary for the fault to grow and for equally in the footwall and hanging wall the growth sequence to match the observa blocks. For non vertical synsedimentary tional data), and D is the maximum displace faults (where the fault intersects the free sur ment. 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.
Volume 20— February 2011 Page 24 ment of horizons, with the asymmetry in These post rift strata may be recognized by restoration should be constructed iteratively creasing as the fault dip decreases. the large map region over which the sedimen in order to derive chronologic model. Finally, tation rate is constant within a stratal wedge. care should be taken in interpreting very spe 3. Result and Discussion This is because these units were deposited cific results of the basin filling models pre The picture of the completed seismic line over much of their extent on a flat surface sented here because: (1) the effects of com restored onto solid rock deformation using a (the undeformed upper surface of the last paction and erosion of previously deposited texture drawing tool. This allows one to fol synrift unit). sediments were not considered, (2) fluvial low the deformation of the formation layers at deposits were not allowed to aggrade above each stage of the restoration. The results of Several giant oil and gas field have been cal the outlet level of the basin, (3) the displace the restoration are shown in Figure 2. The culated their extensional and compressional ment and filling increments in all models changes in fault crosscutting relationships factor. Langkat area plotted as challenging were unrealistically large, and (4) the isostatic through time. area for future exploration based on field consequences of sediment loading were not classification. However, compressional and considered. The advance analysis using When analyzing the evolution of the sand extensional factor reveals that inverted tec sophicticated restoration software than manu layers, one observes that they roll back along tonic occur intensively during basin filling ally can reduces interpretational error inherent the fault to their original horizontal position, history as following table and graphic : in seismic data. whereas the free right border of the model translates without any rotation. Dip changes OIL/GAS FIELD Extensional Compressional Acknowledgements seen across faults on geoseismic lines demon RANTAU 0.35 0.43 This paper is an outgrowth of a chapter of the KUALA SIMPANG BARAT 0.28 0.69 strate that most faults are listric faults. In the LIRIK 0.25 0.7 regional study of North Sumatra Basin. I final restored state (stage 6 of Figure 6), the BAJUBANG 0.36 0.62 thank to Dirjen Migas and Pertamina EP that pre rift beds are tilting as Malacca Platform. TEMPINO 0.28 0.72 has gave authority for publishing this paper as KENALI ASAM 0.57 0.63 a poster at The HAGI 34th Annual Meeting SUBAN 0.22 0.36 In the extensional regimes, it is important to MUSI 0.15 0.26 2009 in Yogyakarta. calculate depth to detachment for the base PENDOPO 0.5 0.4 ment faulting. The brittle ductile transition TANJUNG MIRING 0.27 0.43 References occurs at depth of 10 15 km. The depth of SUNGAI HITAM 0.3 0.8 Dahlstrom, C. D. A., 1969, Balanced cross LANGKAT AREA 0.2 0.63 detachment estimates with simple equation section: Canadian Journal of Earth Sciences, (Fig.2) and given in time domain around 5000 v. 6, p. 743– 757. ms. It gives geometric information, in particu Davison, I., 1986, Listric normal fault pro lar of deep target formation may be in seismic files: Calculation using bed length balance data acquisition in order to optimizing the and fault displacement: Journal of Structural structural model. Geology, v. 8, p. 209– 210. Dokka, R. K., and C. J. Travis, 1990, Late Where subsidence and extensional values are Cenozoic strike slip faulting in the Mojave required, regionally balance section is critical Desert, California: Tectonics, v. 9, p. 311– in providing a structural check on extension 340. and compression factor. Total extension strain Erickson, S. G., S. Hardy, and J. Suppe, 2000, gives 0.2 from pre rift to Mid Miocene while Sequential restoration and unstraining of in plio pleistocene tectonic gives up to 0.6 structural cross sections: Application to ex compressed. These in turn may be important tensional terranes: AAPG Bulletin, v. 84, p. for hydrocarbon maturation and regional sub 234– 249. sidence history studies. Gibbs, A. D., 1983, Balanced cross section Future basin filling models should seek to construction from seismic sections in areas of In the two fluvial wedges, the sedimentation remedy the deficiencies and should be tested extensional tectonics: Journal of Structural rates (thickness/time) are everywhere equal to against a growing body of fine scale strati Geology, v. 5, p. 153–160. the incremental subsidence rates. Sedimenta graphic data for extensional rift basins (e.g., Hennings, P. H., J. E. Olson, and L. B. tion rates decrease toward the lateral edges Olsen & Kent 1990). Nonetheless, the simpli Thompson, 2000, Combining outcrop data and toward the hanging wall hinge of the fying assumptions used in the models pre and three dimensional structural models to basin. The maximum sedimentation rate in sented here should not detract from the main characterize fractured reservoirs: An example each fluvial wedge increases in progressively thrust of this paper—that there are inherent from Wyoming: AAPG Bulletin, v. 84, p. younger strata. In progressively younger syn tectonic differences among the three end 830–849. rift lacustrine strata, the maximum sedimenta member models, which yield different stratal Hossack, J. R., 1979, The use of balanced tion rate is constant or decreases slightly at geometries and successions in modeling cross section in the calculation of orogenic the center of the basin and increases slightly Langkat sub basin. contraction: A review: Journal of the Geologi in those cross sections located closer to the cal Society (London), v. 136, p. 705– 711. lateral edge of the basin. Within a given 4. Conclusions Laurent, M., Frantz, M., 2006, Chronologic lacustrine wedge, sedimentation rates gener Improving structural interpretation gains modeling of faulted and fractured reservoirs ally increase toward the fault a t the center of benefit by use of palinspatic restoration with using geomechanically based restoration: the fault trace. The post rift lacustrine units area balancing. In particular, well understand Technique and industry applications: AAPG deposited after fault displacement ceased of the structural pattern and tectonic evolution Bulletin, v. 90, p. 1201–1226. record a decrease in maximum sedimentation of such areas can result if such techniques are Rouby, D., P. R. Cobbold, P. Szatmari, S. rate because their depositional surface areas integrated into seismic interpretation. While Demerican, D. Coelho, and J. A. Rici, 1993, increase through time, and thus the thickness seismic section data rarely permit a unique Least squares palinspastic restoration of re of sediment deposited per unit time decreases. interpretation of structure, balance geoseismic gion of normal faulting— Application to the
Volume 20— February 2011 Page 25 Preserved Amplitude Seismic Section Fig.3. Result of Palinspatic Restoration from Pre-rift to Compression Stage of a regional Horizon Interpretation seismic line in Langkat-Medan Area. PalinspaticRestoration (Area Balancing)
Structural Model (Extension/ Compressing and Depth to Detachment Calculating) Campos Basin (Brasil): Tectonophysics, v. 22 KM Depth to detachment calculating : 221, p. 439–452. A1=A2 22 KM* 3600 ms = 36 KM*D Rouby, D., H. Xiao, and J. Suppe, 2000, 3 D D = 2200 ms restoration of complexly folded and faulted Depth to Detachment due to isostacy surfaces using multiple unfolding mecha
3600 ms 3600 = 3600 + (3600-2200) = 5000 ms nisms: AAPG Bulletin, v. 84, p. 805– 829. CompressionalStrain = 0.6 Sanders, C., M. Bonora, D. Richards, E. Total Extensional Strain = 0.2 Kozlowski, C. Sylwan, and M. Cohen, 2004, Kinematic structural restorations and discrete 36 KM fracture modeling of a thrust trap: A case study from the Tarija Basin, Argentina: Ma D rine and Petroleum Geology, v. 21, p. 845– 855.
33.5 KM
COMPRE PLIO- PLEISTOSEN : Barisan Orogenic SSION Fault reactivation, right lateral faulting PHASE Swampy depositional system.
QUIESE MID-MIOCENE : Basin stability(subsidence NCE slowly; small uplift) followed by global rising sea TECTONI level, Lower Baong Fm. C PHASE LATE MID-MIOCENE : Diendapakanbatupasir turbitid Duyung, Gebang dengan sumber dari utara. Dan Sembilan sand dari barat 32 KM (Pegunungan Bukit Barisan sebagai sumber sedimen dari barat) EARLY MIOCENE : Upper Baong shale, filling accomodation space. Progradational of Keutapang Fm, continued with Seurula&Julu Rayeu Fm.
POST EARLY MIOCENE: Cont. sea level rise, Belumai RIFTING and Peutu Fm deposition as carbonate and PHASE clastic carbonate lithology.
RIFTING EARLY –LATE OLIGOCENE BAWAH : PHASE Horst-graben filled by Bampo Shale with 30 KM lacustrine envirinment. LATE OLIGOCENE : Sea level rise, Bampo shale.
FASA MID-EOCENE : NSB setting in edge of Sundaland PRE LATE-EOCENE – EARLY OLIGOCENE : Sea level RIFTING fall, alluvial fan, conglomeratic sandstone of Parapat&Tampur Formation.
Volume 20— February 2011 Page 26 BOOK REVIEW Sumatra. Geology, Resources and Tectonic Evolution Fatrial Bahesti (Pertamina)
ARBER, A. J., CROW, M. J. & There is much more to the geology of Suma doubt that this volume will replace Van MILSOM, J. S. 2005. Sumatra. tra than its present day position above an Bemmelen as the standard reference for any Geology, Resources and Tectonic active subduction zone. It also contains one of one working in Sumatra and will no doubt be Evolution. Geological Society the world’s most prominent strike slip faults the focus of much more work in the years to B Memoir no. 31. ix + 290 pp. London, Bath: (the Sumatra Fault), an active volcanic arc, a come. Additionally, it guides the reader Geological Society of London. ISBN 1 partially emergent forearc, and an extensive through further information sources such as 86239 180 7. doi:10.1017/ back arc region. It contains a globally signifi other geological, geophysical, geochemical, S0016756806212974. cant petroleum province, some coal reserves and mineral maps covering the area. It also and more limited mineral resources. The points the reader towards the nationally im geological evolution of the island can be portant archive of resources. This book provides collaborative approach of traced back to the Carboniferous or older. Overall, this is an excellent book and cer geology of Sumatra since previous publica A review of Granites and Pre Tertiary vol tainly represents compulsory reading for tion of van Bemmelen, the Dutch geologist canic rocks of Sumatra gives a valuable undergraduate and postgraduate students who published a ‘comprehensive and mas history of the exploration and development who wish to carry out research and revisiting terly summary’ of the Geology of Indonesia, of recently oil and gas discovery in fracture of Sumatra’s resources exploration. The initially in 1949. Much of the geological re basement system in Sumatra, which played an booklet is well referenced. With over 200 search conducted in Sumatra in the latter part important role in establishing the concept, and pages, and packed with illustrations and of the twentieth century has been carried out provides a general introduction to the geology photographs (all black and white), it repre by the British Geological Survey and the of the Northern and Southern Provinces. sents excellent value for money. It also University of London SE Asia Research There are a few papers in Indonesia con serves its intended purpose as an excellent Group. The whole island has been mapped cerned with Pre Tertiary fracture basement reference guide for more experienced re geologically at the reconnaissance level and play and magmatism Paleozoic island arc searchers who may need reminding of the completed in the mid 1990s, together with development on the active margin of Sumatra. exploration opportunity. supplementary data obtained by academic Palaeozoic orogeny in the Sumatra consider institution and petroleum and mineral explo the subduction history of the Sundaland mar ration companies, has resulted in a vast in gin and its implication to describe crease in geological information, which is pre tertiary basin present in Suma summarized in this volume. The editors and tra. most of the contributors are associated with these organizations and are thus able to draw More specifically, a gap in the cur on considerable personal experience. In addi rent treatment is the limited cover tion they have incorporated references to age of the basins containing hydro pretty much every single paper or book to carbon reserves. Oil company data have dealt with the geology of the island. It is always subject to the constraint thus follows in the tradition of Van Bem and confidentially, particularly in melen. Indonesia given the involvement of Directorate of Oil&Gas in all li The opening part of this book presents a con cences, but it would have been cise introduction to the topic of Seismology interesting to see some of the com and Neotectonics that contains some late ad prehensive datasets that must exist ditions which provide a comprehensive sum in these areas and would help to mary of the information that became available address the thorny question of the immediately after the 2004 Sumatra’s earth extent to which strike slip deforma quake and tsunami and has a note added in tion is associated with the formation proof to include data from other after and subsequent inversion of the shocks up to the end of April 2005. It might Sumatra basins. In addition, the therefore seem prescient to have planned the BGS and University of London publication of a memoir describing the geol projects were models of construc ogy of Sumatra for 2005. In comparison to tive collaboration with Indonesian other publications that have followed the organizations and it is perhaps a earthquake, this volume can fairly claim to pity that none of their Indonesian provide a comprehensive context in which to counterparts are represented place these momentous geological events. amongst the authors. There is no
Volume 20— February 2011 Page 27 University
As Berita Sedimentologi journal aimed to bridge communications, the editor has pre pared a special column for the academia, both lecturer and students.
Volume 20— February 2011 Page 28 SEPM NEWS
Special Publication #95 systems are products of the factors that Cenozoic Carbonate Sys- these varying influences. controlled their tems of Australasia The studies reported in formation, and to Edited by: William A. Morgan, this volume range from those wanting to Annette D. George, Paul M. syntheses of tectonic and understand the (Mitch) Harris, Julie A. Kupecz, depositional factors influ range of potential and J.F. (Rick) Sarg encing carbonate hydrocarbon The Cenozoic carbonate systems deposition and controls reservoirs discovered in these carbonates and of Australasia are the product of on reservoir formation the events that led to favorable reservoir and a diverse assortment of deposi and petroleum system trap development. tional and postdepositional proc development, to local esses, reflecting the interplay of studies from the South SEPM Membership for potential members eustasy, tectonics (both plate and China Sea, Indonesia, in Indonesia local scale), climate, and Kalimantan, Malaysia, Interested on sedimentological international evolutionary trends that influ the Marion Plateau, the publications? You can now join SEPM for enced their initiation and development. These Philippines, Western Australia, and New US$20/year. For easy access registration systems, which comprise both landattached Caledonia that incorporate outcrop and sub form, go to the following link: and isolated platforms, were initiated in a surface data, including 3 D seismic imaging https://www.sepm.org/Forms.aspx? wide variety of tectonic settings (including of carbonate platforms and pageID=224 rift, passive margin, facies, to understand the interplay of factors and arc related) and under warm and cool affecting the development of these systems water conditions where, locally, siliciclastic under widely differing input affected their circumstances. development. The lithofacies, biofacies, This volume will be of importance to geo growth morphology, diagenesis, and hydro scientists interested in the variability of Ceno carbon reservoir potential of these zoic carbonate systems and
IAS NEWS
Up to 10 grants of about 1000€ twice a year capability of the researcher, and reasonable origin of ooids; ness of the budget. coastal sedi The IAS has established a grant scheme de ments; forma signed to help PhD students with their studies tion of stromato by offering to support postgraduates in their SP41 - Perspectives in Carbonate Geology lites; impact of fieldwork, data acquisition and analysis, visits storms on sedi to other institutes to use specialised facilities, Swart, P., Eberli, G., McKenzie, J. (Wiley ments; and the or participation in field excursions directly Blackwell, 2009 ISBN 978 1 4051 9380 1) formation of related to the PhD research subject. Up This special publication Perspectives in Car dolomite. The remainder of the papers apply to 10 grants, each of about1000€ are awarded bonate Geology is a collection of papers most the study of modern environments and sedi twice a year. These grants are available for of which were presented at a symposium to mentary processes to ancient sediments. IAS members only, and only for PhD stu honor the 80th birthday of Bob Ginsburg at dents. Students enrolled in MSc programs are the meeting of Geological Society of America Other details about IAS is available in: NOT eligible for grants. Research grants are in Salt Lake City in 2005. The majority of the http://www.sedimentologists.org/ NOT given for travel to attend a scientific papers in this publication are connected with conference, NOR for acquisition of equip the study of modern carbonate sediments. ment. Student travel grants for conferences Bob Ginsburg pioneered the concept of com can be usually obtained directly from organiz parative sedimentology that is using the ers of the meeting. modern to compare to and relate to and under The Postgraduate Grant Scheme Guide stand the ancient. These studies are concerned lines provide a summary of required informa with Bob's areas of passion: coral reefs and tion needed for a successful Grant Applica sea level; submarine cementation and forma tion. Applications are evaluated on the basis tion of beach rock; surface sediments on of the scientific merits of the problems, the Great Bahama Bank and other platforms;
Volume 20— February 2011 Page 29 IAGI NEWS
Call For Paper Makassar 2011. & Geophysics In repeating the previous similar successful 36th HAGI and 40th IAGI Joint Convention Mix Energy Sce events, joint convention between HAGI and Makassar 2011 nario and Policy IAGI: Joint Convention Jakarta in 2003, Joint Convention Surabaya in 2005, and Joint Con Date Abstracts vention Bali in 2007, this Joint Convention 26 – 29 September 2011, Clarion Hotel Authors are invited Makassar is delivering a theme of Exploring Makassar, South Sulawesi to submit the abstracts related to the topics. Eastern Indonesia to represent the spirit of Acceptance of paper would be selected on current exploration and research of geology Theme condition of maximum 300 words, covering and geophysics in Indonesia. Its challenge, “Exploring Eastern Indonesia” objectives, methods, results, and conclusions, opportunities, process, concept, technology, preferably written in English. Abstract should remarkable research, and experiences, in ex Topics not contain figures. Author should indicate ploring energy (petroleum, mineral, coal, Natural Resources of Indonesia his/her preference in presenting the paper as nuclear, etc.) and understanding the earth Mineral and Energy Resources Management oral or poster presentations. should be discovered on Joint Convention Environmental Issues Submit abstract to: [email protected] Hazard Mitigation Geodynamics, Seismol Submission deadline: 11 February 2011 ogy, Volcanology Announcement: 15 March 2011 Atmospheric Science, Extended Abstract deadline: 30 April 2011 Oceanography, Marine Geology JCM 2011 Secretariat Sedimentology and Strati Patra Office Tower 20th Floor. Suite 2045 graphy Jl. Gatot Subroto Kav. 32 34 G&G Methods, Technol South Jakarta 12950 ogy and Application Tel / Fax:. +62 21 5250040 Engineering Geology Unconventional Geology
AAPG NEWS
10 Teams to participate in the Asia Pacific •University of Pembangunan Nasional GTW – IBA competition “Veteran” Yogyakarta (Indonesia) October 2010 In order to represent the Asia Pacific at the •University of Indonesia (Indonesia) The Asia Pa AAPG 2011 Imperial Barrel Award competi cific Region tion at the AAPG ACE2011 in April, 10 In this global competition, university teams saw a success teams are vying for this honour : analyze a dataset (geology, geophysics, land, ful conclusion economics, production infrastructure, and to its inaugural •Indian Institute of tech other relevant materials) in the eight (8) Geosciences Technology Workshop (GTW) nology, Bombay (India) weeks prior to their local competition. Each which took place on the 28 29 October 2010 team delivers their results in a 25 minute pres in Singapore. The GTW theme of “Pore Pres •Indian Institute of entation to a panel of industry experts. Stu sure and Related Issues – Special Focus: Asia Technology Kharagpur dents have the chance to use real technology Pacific” was particularly pertinent as the (India) on a real dataset, receive the feedback from Asia Pacific region contains numerous rap •Indian Institute of an industry panel, have the opportunity to idly formed and highly overpressured basins Technology Roorkee impress potential employers in the audience, and is an area in which pore pressure predic (India) and the chance to win cash awards for their tion is particularly challenging. The GTW schools. The industry panel of judges will was attended by 88 delegates and contained •Pandit Deendayal Petroleum University select the winning team on the basis of the 23 presentations from industry experts, (India) technical quality, clarity and originality of its among whom were Keynote Presenters Rich presentation. The judging will take place over •Khon Kaen University (Thailand) ard Swarbrick of GeoPressure Technology 1 3 March 2011. We wish the Teams all the UK and Nader Dutta of Schlumberger USA. •Chulalongkorn University (Thailand) best! Running alongside the GTW were two short courses on Pore Pressure and Petroleum Ge •China University of Petroleum (China) More information can be obtained from www.aapg.org/iba omechanics, taught by Richard Swarbrick and •Institute of Technology Bandung (Indonesia) Mark Tingay (University of Adelaide) respec tively.
Volume 20— February 2011 Page 30 Sponsorship for FOSI
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Guidance for contributors
The editorial board welcome articles related of 200 DPI resolution, submitted in JPG or sedimentary rocks in Indonesia, Southeast TIFF format. Asia and vicinity. The topic and deadline of The whole article, text and figures, should not the coming Berita Sedimentologi bulletin are Berita Sedimentologi is exceed 5 pages of A4. stated below. voluntarily prepared by For the setting of the article, contributors can Contributors are expected to submit their And for the benefit of follow one of the existing article from this or article in Microsoft Word, ASCII / Text or previous bulletin. FOSI MEMBERS PDF format. Pictures need to be annotated with minimum
Future Berita Sedimentologi
The editorial board will prepare 2011 2012 publications with the following schedule and 2012 topics February 2012: Papua 2011 • Title deadline: 10 December 2011
February 2011 (this edition): Sumatra • Article deadline: 10 January 2012
June 2011: Borneo / Kalimantan June 2012: Timor • Title deadline: 10 April 2011 • Title deadline: 10 April 2011 • Article deadline: 10 May 2011 • Article deadline: 10 May 2011
October 2011: Java October 2012: Halmahera • Title deadline: 10 August 2011 • Title deadline: 10 August 2012 • Article deadline: 10 September 2011 • Article deadline: 10 Septeber 2012
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Volume 20— February 2011 Page 31