Добірка наукової літератури з теми "Geology of Sumatra"

Lahat is one of the districts within the province of South Sumatra, the site of research, saving many cultural remains, one of them from the paleolithic period, which for so long received no attention from environmental researchers. This is the basis of the main problems that cover geology in general. Therefore, the purpose of this study is to conduct surface geology mapping in general as an effort to present geological information, while the aim is to know the geomorphological aspects, stratigraphy, geological structures associated with existence in paleolithic sites of research area. The research method begins with literature review, survey, analysis, and interpretation of field data. Environmental observations provide information about the landscape consisting of terrestrial morphology units, weak corrugated morphology units, and strong corrugated morphology units. The rivers are in the Old River, the Adult River, and Periodic /Permanent River. The constituent rocks are Gumai Formation, Benakat Air Formation, Muara Enim Formation, Kasai Formation, and alluvial. The geological structure is a strike slip fault that flows northeast-southeast. The study was conducted on the Kikim River, Lingsing River, and Pangi River, which stretches from east to west with direction from south to north. Exploration in the Kikim Basin, Lahat District has managed to find 30 paleolithic sites.Keywords: Geology, Pleistocene, Paleolithic, Open SiteABSTRAKLahat merupakan salah satu kabupaten dalam Provinsi Sumatra Selatan yang menjadi lokasi penelitian, menyimpan banyak tinggalan budaya, salah satunya dari masa paleolitik, yang sekian lama tak mendapat perhatian dari para peneliti lingkungan. Hal inilah yang dijadikan dasar permasalahan utama yang mencakup geologi secara umum. Oleh sebab itu, maksud penelitian ini dalah untuk melakukan pemetaan geologi permukaan secara umum sebagai salah satu upaya untuk menyajikan informasi geologi, sedangkan tujuannya adalah untuk mengetahui aspek-aspek geomorfologi, stratigrafi, struktur geologi yang dikaitkan dengan keberadaan di situs-situs paleolitik wilayah penelitian. Metode penelitian diawali dengan kajian pustaka, survei, analisis, dan interpretasi data lapangan. Pengamatan lingkungan memberikan informasi tentang bentang alamnya yang terdiri dari satuan morfologi dataran, satuan morfologi bergelombang lemah, dan satuan morfologi bergelombang kuat. Sungainya berstadia Sungai Tua, Sungai Dewasa-Tua, dan Sungai Periodik/Permanen. Batuan penyusun adalah Formasi Gumai, Formasi Air Benakat, Formasi Muara Enim, Formasi Kasai, dan aluvial. Struktur geologi berupa patahan geser yang berarah timur laut-tenggara. Penelitian dilaksanakan di Sungai Kikim, Sungai Lingsing, dan Sungai Pangi, yang membentang dari timur ke barat dengan arah aliran dari selatan ke utara. Eksplorasi di DAS Kikim, Kabupaten Lahat telah berhasil menemukan 30 situs paleolitik. Kata kunci: Geologi, Plistosen, Paleolitik, Situs Terbuka

Abstract Prior to the collision of India with Asia, the evolution of island arcs and resultant crustal formation in the now-disrupted easternmost Tethys are poorly constrained. Here, we report for the first time zircon U-Pb and Hf isotopic data from Mesozoic granitoids in Sumatra, Indonesia. Our analyses identified three magmatic episodes at 214–201 Ma, 148–143 Ma, and 102–84 Ma, respectively, with a drastic change in magmatic zircon εHf(t) values from −13.1 to +17.7 in the Late Triassic granitoids, which reveals a fundamental restructuring of the arc system in Sumatra. Subsequently, all Jurassic to Late Cretaceous granitoids have exclusively positive zircon εHf(t) values (+17.7 to +10.2), consistent with juvenile arc development owing to subduction of the easternmost Tethyan lithosphere beneath Sumatra. Such highly positive zircon εHf(t) values of the Sumatran granitoids, in general accordance with those of the Gangdese arc system in South Asia, are markedly higher than those (+13.7 to −14.7) of broadly contemporaneous Cordilleran arcs in Americas and Zealandia. Our findings from the easternmost Tethys provide new insights into not only the tectono-magmatic evolution of eastern Tethys, but also its crucial role in global juvenile crustal growth.

Dr. August Tobler was a well-known Swiss geologist, who, as one of the very first petroleum field geologists in the Netherlands Indies, did more than ten years of geological mapping in the tiger-infested jungles of South Sumatra. He first worked for the Koninklijke/Royal Dutch and Moeara Enim oil companies in South Sumatra from 1900 to 1904. This was followed by six more years of geological mapping in the Jambi basin, as the first non-Dutch geoscientist at the Dienst van het Mijnwezen (Geological Survey). His thoroughly documented monographs and geologic maps of his geological fieldwork in the Palembang and Jambi basins of South Sumatra, as well as the adjacent Barisan Mountains, set new standards for quality and detail.Much of the personal information on Dr. Tobler is from papers by Kugler (1930, 1963), Oppenoorth (1930), Stehlin (1931) and Hottinger (2013). This paper is one of the chapters from a new book that is being prepared by the first author, entitled Pioneers and Milestones of Indonesian Geology (~1820-1960).

Abstract Sumatra is the largest volcanic island of the Indonesian archipelago. The oblique subduction of the Indian Ocean lithosphere below the Sundaland margin is responsible for the development of a NW-SE trending volcanic arc, the location of which coincides approximately with the Great Sumatran Fault Zone (GSFZ). We present in this paper ca. 80 new 40K-40Ar ages measured on Cenozoic calc-alkaline to shoshonitic magmatic rocks sampled all along this arc from Aceh to Lampung. The results show that magmatic activity started during the Paleocene (ca. 63 Ma) all along the arc, and was more or less permanent until Present. However, its spatial distribution increased at ca. 20 Ma, a feature possibly connected to the development of the Great Sumatran Fault. The position of Plio-Quaternary magmatic rocks is shifted away from the trench by a few tens of kilometres with respect to that of Paleocene to Miocene ones, a feature consistent with a significant tectonic erosion of the Sundaland margin during the Cenozoic. The studied samples display typical subduction-related geochemical signatures. However, we have been unable to identify clear geochemical trends, either spatial or temporal. We suggest that the lack of such regular variations reflects a complex igneous petrogenesis during which the contribution of the Sundaland continental crust overprinted those of the mantle wedge and the subducted slab.

AbstractThe occurrence of flash floods in 2017 that hit Tebing Tinggi City in North Sumatra Province caused 33,825 lives to be affected. That shows that the potential for flash floods disasters in the North Sumatra region, including in the Padang River Basin, is classified as very high. The purpose of this study is to determine the location of potential riverbank landslides that cause river flow obstructions (natural dams) in the Padang River Basin. The method used in this study is a qualitative method using geographic information systems. The data analysis technique used is the cone stacking technique of research variable maps. The variables used to analyze the potential of riverbank landslides are the appearance of existing landslides, topography (flow accumulation), and geology (faults). The results of this study indicate that there are 86 locations with potential landslides that can cause natural dams. The most potential location is the Padang sub-watershed with 48 sub-areas.Keywords: Disaster Mitigation, Spatial Modeling, Flash floods, Geographic Information Systems AbstrakKejadian banjir bandang tahun 2017 yang melanda Kota Tebing Tinggi Provinsi Sumatera Utara menyebabkan 33.825 jiwa terdampak. Hal ini menunjukkan bahwa potensi bencana banjir bandang di wilayah Sumatera Utara termasuk di Daerah Aliran Sungai (DAS) Padang tergolong sangat tinggi. Adapun tujuan penelitian ini adalah untuk mengetahui lokasi yang berpotensi terjadi longsor tebing sungai yang mengakibatkan terhambatnya aliran sungai (bendungan alam) di DAS Padang. Metode yang digunakan dalam penelitian ini adalah metode kualitatif dengan menggunakan sistem informasi geografis. Teknik analisis data yang digunakan adalah teknik tumpeng susun peta variabel penelitian. Adapun variabel yang digunakan untuk menganalisis potensi longsor tebing sungai adalah kenampakan longsor eksisting, topografi (akumulasi aliran), dan geologi (patahan). Hasil penelitian ini menunjukkan bahwa terdapat 86 lokasi yang berpotensi longsor yang dapat menyebabkan bendungan alam. Lokasi paling banyak terdapat potensi adalah sub-DAS Padang dengan jumlah sub-area 48 lokasi. Kata Kunci: Mitigasi bencana, Permodelan Spasial, Banjir Bandang, Sistem Informasi Geografis

The Batang Natal River flows across the Western Barisan Mountains of North Sumatra, exposing a section through the Woyla Group, a major unit of Sumatran island arc basement. Detailed field mapping of the section, followed up by thin section petrology, structural analysis and radiometric dating, was undertaken in order to investigate the geology, structure, origin and tectonic evolution of the Woyla Group. The Woyla Group outcropping in the section is divided into eighteen lithotectonic units, each with distinctive lithological characteristics, including basalts, volcanogenic turbidites and debris flows, and esites, spilites, chert-limest?ne breccias, non-marine volcanogenic sediments, quartz-mica schists, metaturbidites, megabreccias, serpentinite, diorite and massive limestones. Most units are deformed to varying degrees of intensity by tight to isoclinal 'F' folding with an associated 'S1 foliation. A later phase of open 'F2' folding deforms the 'S' foliation, as well as other layered units unaffected by 'D'. All the units are bounded and internally disrupted by strike-slip faults, commonly of NW/SE or WNW/ESE trend. Previous models interpreted the Woyla Group as the remnants of a closed marginal basin. The new model proposed here suggests the Woyla Group is a Mesozoic accretionary complex, built up of pelagic and terrigenous sediments, together with fragments of island arc and oceanic material, that were accreted against the Mesozoic Sumatran continental margin. The complex later subsided, to form part of the basement of the Tertiary forearc basin. The Sumatran Fault System, initiated in the late Mesozoic, or possibly earlier, as a consequence of oblique subduction; transected the Sumatran forearc and the magmatic arc. It resulted in major disruption, translation and reshuffling of fault slivers, thereby assembling the allochthonous and parautochthonous terranes now seen in the Woyla Group. The Woyla Group was subaerially exposed by the late Miocene-early Pliocene uplift of the Barisan Mountains.

On September 12 2007, an Mw 8.4 earthquake occurred within the southern section of the Mentawai segment of the Sumatra subduction zone, where the subduction thrust had previously ruptured in 1833 and 1797. Following the 2007 rupture, a temporary local network was installed in the Mentawai region between December 2007 and October 2008 to record the aftershocks. Additionally, a second network was installed in central Sumatra between April 2008 and February 2009. In this study the data obtained from the Mentawai network were used to determine 2D and 3D Vp and Vp/Vs models, first motion polarity focal mechanisms and accurate hypocentre locations. In addition to this, shear wave splitting (SWS) measurements from both networks were used to determine the type, amount and location of anisotropy. This has enabled us to obtain a detailed image of the structure of the subduction zone, ascertain the down-dip limit of the seismogenic zone and determine the deformation occurring. The forearc islands are characterized by a low Vp (4.5-5.8 km/s) and a high Vp/Vs ratio (>2.0), suggesting that they consist of fluid-saturated sediments. The down-going slab is clearly distinguished by a dipping region of high Vp (8.0 km/s), which can be traced to ~50 km depth, with an increased Vp/Vs ratio (1.75 to 1.90) beneath the forearc islands and the western side of the forearc basin, suggesting hydrated oceanic crust. Beneath the slab, a ~150 km thick layer of sub-slab anisotropy has developed due to the oceanic asthenosphere being entrained by the subducting slab. Two clusters of seismic activity are found within the ~25-30 km thick overriding crust. The location of the first cluster confirms that the Mentawai Fault is active and may accommodate backthrust movement, while the second cluster suggests a backthrust may be present on the eastern side of the forearc basin. Local SWS measurements suggest that in the overriding plate, adjacent to the Sumatran Fault, a layer of anisotropy has formed from fault-parallel aligned fractures and minerals. Beneath the forearc, a shallow continental Moho of < 30 km depth can be inferred. Within the mantle wedge there is no widespread serpentinization; only localized serpentinization is present at the toe. Beneath the backarc, 2D corner flow is occurring in the continental asthenosphere. The co-seismic slip of the 2007 events, as well as the aftershock distribution, suggests that the down-dip limit to rupture propagation is beneath the slab-Moho intersection at ~50 km depth. Consequently, as the Mw 7.7 Mentawai earthquake on 25 October 2010 showed that the updip limit of the seismogenic zone is at the trench, a potential 200 km wide rupture could take place.

According to the Ade observation (Ade, W., pers. Comm.) “95% of all commercial oil fields in the Sumatra region occur within 17 km of seismically mappable structural grabens in the producing basins”. The Ade observation proposes a link between the subsidence of the source rocks (the Talang Akar Formation) in the grabens and the maturity of the organic material. To test the validity of the Ade observation, subsurface mapping of the region was carried out using geophysical logs. Using the well log information, the basement and the formation tops have been mapped with a special emphasis on Talang Akar and Air Benakat Formations. The isopach maps of these formations show that most of the producing wells on the Sunda shelf are in fact located in and around the major structural basins. Trends in the occurrence of the oil fields have also been observed which are analogous to the orientation of the grabens. Structural mapping of the basins have identified several wrench faults. These are of particular interest as wrench faults provide good structural traps for oil in the Los Angeles and the North Sumatra Basins and may prove to be very important for future exploration in southern Sumatra and northwest Java. In South Sumatra Basin, 77.78% of the potential oil fields are located in the 17 km margin from the grabens. For Sunda/Asri Basins and the Ardjuna Basin, it is 100 and 92 respectively. Identifying the source rocks in this 17 km window will enhance the success rate of oil exploration in the Sundaland Basins.
Department of Geological Sciences

The research involves mapping of subsurface at a scale of 1:25,000 the top of three geological formations in the Southern Part of Sumatra – the Airbenakat Formation, the top of the Talangakar Formation, and the top of structural basement in the Jambi Trough. Isopach maps of the formations will be constructed. These maps will form the basis of a basin analysis and hydrocarbon source rock assessment of the Jambi Trough using Basin Mod basin modeling software (Rockworks Software). The studies utilize the L. Bogue Hunt Southeast Asia database housed in the Department of Geological Sciences at Ball State University. Seismic record sections, geophysical logs, cutting descriptions, and paleontological reports will provide basic geological data to enable mapping of the three horizons. Although hydrocarbon accumulations are abundant in Central and Southern Sumatra, the nature of the source rocks is only partially understood. The proposed research will map the Airbenakat and Talangakar Formations while identifying the areas of thermally mature source rock is the main goal of the research. This study will identify characteristics which will enable the identification of thermally mature rocks in other regions of Sumatra. The area of the project is located at the Southeastern part of Asia in Indonesia and mainly the Jambi trough located in Southern Sumatra. Generally, the geology and tectonics of this area (Sumatra) is controlled by the subduction of the Indian plate towards the east and beneath the Eurasia plate.
Department of Geological Sciences

The main objective of this research is to understand the seismic structure beneath Sumatra and its surrounding regions by using seismic tomography. The structure is interpreted as P wavespeed velocity anomalies relative to the ak135 model. The main data source is P wave traveltimes up to 2006 obtained from the International Seismological Centre with relocation using the EHB scheme. Summary rays are constructed for these ISC data to decrease the number of data and to give a more even rays distribution so that we obtain 1,750,070 ISC residuals. We also include arrivals reported to Geoscience Australia, data from RSES-ANU and the Indonesian Meteorological and Geophysical Bureau (BMG). The data recorded by the RSES arrays are analysed by using an adaptive stacking method and the BMG arrivals are picked by hand with an STA/LTA procedure used to speed up the analysis. The tomographic model using a 1{u00B0}x1{u00B0} degree grid parameterization extended from 70{u00B0}E to 193{u00B0}E and 45{u00B0}N to 45{u00B0}S which covers Himalaya to Tonga and Japan to Australia, is embedded inside a 2{u00B0}x2{u00B0} global model. Pseudo bending technique for 1D forward calculation is firstly performed and the conjugate least square is then applied to invert the residuals and obtain the velocity perturbation of the region. Subsequently, the 3D ray tracing and inversion scheme are reiterated to improve the 3D seismic structure of the region. This 1{u00B0}x1{u00B0} regional model is validated by resolution tests: with checkerboard and synthetic slab models. Within the region with sufficient ray coverage the checkerboard is resolved well. The 3D ray tracing and inversion reproduce the synthetic slabs well; even in complicated cases. This new regional model is very consistent with those produced by Widiyantoro et al., 1999 and Replumaz et al., 2004. In order to emphasize the understanding of the seismic structure beneath Sumatra and its surrounding regions a 0.5{u00B0}x0.5{u00B0} grid parameterization is embedded inside the 1{u00B0}x1{u00B0} regional model within the 2{u00B0}x2{u00B0} global model. The finer resolution model is chosen as the region from 80{u00B0}-125{u00B0}Eand 15{u00B0}S-l5{u00B0}N which covers Andaman, Sumatra, and eastern Indonesia. The 3D forward calculation and inversion are reiterated to obtain the smaller regional model with higher resolution. The higher resolution model offers better definition of the nature of the slabs and low velocity zones. Beneath the Aceh-Andaman region the old incoming lithosphere subducts steeply and terminates abruptly at ~500 km depth. A slab tear is found beneath this section that connects the Sumatran to the Himalayan subduction zone indicating a unified subduction zone a few million years ago. The Northern and Central Sumatran slabs dip shallowly with little deflection at ~500 km depth associated with younger, warmer incoming lithosphere. The slab-pull forces beneath Aceh-Andaman section may be less significant because the slabs terminate much shallower than beneath Sumatra. This behaviour may influence the frequency of large earthquakes. In the Java region with older lithosphere the slabs dip more steeply deflect backward and forward in the mantle transition zone.

Tsunami hazards were greatly underestimated along the coasts of countries bordering the northeastern Indian Ocean until the occurrence of the 26 December 2004, Mw 9.2 earthquake and its ensuing tsunami. Sourced off the coast of northern Sumatra, on the plate boundary between the Indo-Australian and Eurasian plates, the rupture of the 2004 earthquake propagated ~1300 km northward. The magnitude of this earthquake and the reach of its tsunami exceeded all known precedents, based on instrumental and historic records. The coseismic deformational and post-tsunami depositional features facilitated opportunities to conduct tsunami geology studies along the coasts of countries bordering the Indian Ocean. Several questions are being posed, the answers of which have implications for tsunami hazard assessment. How did this plate boundary behave prior to and after the great earthquake? Was the 2004 earthquake the first of its kind on the Sumatra-Andaman plate boundary? If it had a predecessor, when did it occur and was it a true predecessor in terms of its rupture dimensions and tsunamigenic potential? What types of depositional evidence are preserved and how can we use them to develop the history of past tsunamigenic earthquakes? Researchers are exploring the affected regions and using the imprints left by the 2004 event, to address these questions. There are two components to this study: one, a seismotectonic analysis of the region from the perspective of plate driving forces and their relative roles in the interseismic and post-seismic phases. This study uses global data catalogs like the NEIC PDE (National Earthquake Information Centre Preliminary Determination of Epicenters) and the Global Centroid Moment Tensor (CMT) solutions for earthquake source parameters to understand the along-strike variations in seismicity patterns before and after the 2004 earthquake. The 2004 experience was unprecedented in South Asia. Unaffected by tsunami hazards in the past, tsunami geology is a nascent field for most South Asian researchers. Very little background field data is available on the deformational features of great earthquakes along this plate boundary and the depositional characteristics of extreme coastal surges, such as tsunamis and storms. Where do we begin our search for evidence of past tsunamigenic earthquakes? How best can we use the 2004 tsunami and its deposits as a proxy? What problems are encountered in the interpretations? This thesis addresses these questions in part and presents observations from the Andaman Islands (the ~400 km, northern segment of the Sumatra-Andaman subduction zone) and the southeast coast of India, towards developing a reliable database of tsunami geology for 2004-type events. The premise is that regions affected by the 2004 earthquake are more likely to conserve signatures from older events. Based on the stratigraphic context of the proxy and quality of age estimates, this work presents evidence for past earthquake related deformation and tsunami deposition. In this work we use deformational and depositional features from the Andaman Islands, falling within the 2004 rupture zone and from one location on the Tamil Nadu coast of India (Kaveripattinam). From a perceptive understanding of the features related to tectonic deformation of the Sumatra-Andaman subduction zone, we have selected the Andaman segment that demonstrates explicit evidence for deformation and tsunami deposition through geomorphological and stratigraphic features, which are key to our exploration. A gist of each chapter is given below. The introduction (chapter 1) presents the background, motivation and scope of this work and the organization of this thesis, also summarizing the contents of each chapter. Chapter 2 provides a review of literature on subduction zone earthquakes and updates on tsunami geology, to place this study in the global context. The next two chapters discuss the seismotectonics of the Sumatra-Andaman plate boundary, the important earthquakes and their source processes. In chapter 3 we discuss the Andaman segment (from 10–15° N), characterized by relatively lower level seismicity, but distinctive, as it falls within the northern limit of the 2004 rupture. The deformational and depositional features here are better exposed due to availability of land straddling the hinge line separating the areas of 2004 uplift and subsidence. Here, the pre-2004 earthquakes used to occur along a gently dipping subducting slab, up to a depth of about 40 km. Post-2004, the earthquakes moved up-dip, extending also to the outer-rise and outer-ridge regions, expressing post-earthquake relaxation [Andrade and Rajendran, 2011]. The southern Nicobar segment (5–10° N) differs from the Andaman segment in its style of deformation and seismic productivity. The decreasing obliquity of convergence, the likely influence of a subducting ocean ridge on the subducting plate and the character of the subducting oceanic plate make this segment distinctly different. In chapter 4 we present an analysis of its seismotectonic environment based on the well-constrained focal mechanisms of historic and recent earthquakes. We report that left-lateral strike-slip faulting on near N-S oriented faults control the deformation and the style of faulting is consistent to ~80 km within the subducting slab [Rajendran, K. et al., 2011]. The 11 April 2012 sequence of earthquakes on the subducting oceanic plate, between the Sumatra Trench and the Ninety East Ridge are the more recent among the oceanic intraplate earthquakes that demonstrate the reactivation of N-S oriented fossil fractures. The limited availability of land and the 2004 coseismic deformation dominated by subsidence, followed by prolonged waterlogging makes exploration difficult in the Nicobar segment. Thus, we focus on the Andaman Islands for deformational and depositional evidence, using observations that can be corroborated through multiple proxies and depositional environments that are not prone to other coastal surges, such as cyclones and storms. The criteria for selection of sites, evaluation of deposits and determination of limiting ages are discussed in chapters 5 through 9. In chapter 5 we discuss different types of coastal environments and their response to high-energy sea surges. We also give a brief review of the comparative analyses of storm and tsunami deposits, a highly debated issue and then discuss important characteristics of these two deposits, using examples from the 2004 tsunami and the 2011 Thane cyclone that affected parts of the Tamil Nadu coast. An important component of tsunami geology is the ability to identify and select datable material from tsunami deposits and chose an appropriate method for dating (chapter 6). The types of material used vary from peat layers, peat-rich soil, gastropod shells, wood, charcoal, organic remains such as bones, coral fragments, pottery sherds and buried soil. Techniques such as AMS Carbon-14 and Thermoluminescence are commonly used with appropriate calibrations and corrections. In addition to the dates generated in this study (based on wood and shell dates) we use some previous dates from the entire stretch of the rupture within the Indian Territory and assign a relative grading to these ages, based on the quality criterion evolved in this study. We believe that this is the first attempt to segregate age data obtained from coastal deposits, and assign them a specific quality grading based on their environment of deposition and the type of material dated. Chapter 7 presents results of our investigations in the Andaman Islands, which cover ~30% of the rupture area. A coseismically subsided mangrove from Rangachanga (Port Blair, east coast of South Andaman) led us to a former subsidence during AD 770–1040, which we believe is the most convincing evidence for a previous tectonic event. Data based on inland deposits of coral and organic debris yielded a younger age in the range of AD 1480–1660. Both these dates fall in the age brackets reported from other regions of this plate boundary (mainly Sumatra) as well as distant shores of Sri Lanka, Thailand and mainland India. To understand the nature of distant deposits, we present observations from Kaveripattinam, an ancient port city on the east coast of India, where a high-energy sea surge deposit, found 1 km inland is attributed to a paleotsunami. The inland location of this archeological site at an elevation of 2 m and characteristics of the deposit that help discriminate it from typical storm deposition provide clinching evidence in favor of a 1000-year old regional tsunami (chapter 8). In chapter 9 we discuss the results of our study. We evaluate the nature of deformation/deposition and the calibrated age data in the context of their environments. Ages based on the organic material associated with coral debris (at Hut Bay and Interview Island) and the remains of mangrove roots, 1 m below the present ground level (at Port Blair) are considered as reliable estimates, due to their sheltered inland location and the in situ root horizon used for dating. Age data from Kaveripattinam is also considered reliable, based on its inland location beyond the reach of storm surges, sediment characteristics typical of tsunami deposition and ages based on multiple methods and samples. The age data based on the sites presented in this thesis are more conclusive about the 800 to 1100 AD and 1250 to 1450 AD tsunamis, and the former is represented from regions closer to the 2004 source as well as distant shores reached by its tsunami. Chapter 10 presents our conclusions and the scope for future studies. We present this as the first study of its kind in the northeastern Bay of Bengal, wherein the coseismic vertical coastal deformation features along an interplate subduction boundary and a variety of tsunami deposits are used to categorize depositional environments and ages of paleoearthquakes and tsunamis. To our knowledge, this is the first study of its kind where the effects of a recent tsunami have been used to evaluate paleodeposits based on their respective environments of occurrence. Our results have implications for tsunami geology studies in coastal regions prone to tsunami hazard.

South Sumatra is considered a mature exploration area, with over 2500MMbbls of oil and 9.5TCF of gas produced. However a recent large gas discovery in the Kali Berau Dalam-2 well in this basin, highlights that significant new reserve additions can still be made in these areas by the re-evaluation of the regional petroleum systems, both by identification of new plays or extension of plays to unexplored areas. In many mature areas the exploration and concession award history often results in successively more focused exploration programmes in smaller areas. This can lead to an increased emphasis on reservoir and trap delineation without further evaluation of the regional petroleum systems and, in particular, the hydrocarbon charge component. The Tungkal PSC area is a good example of an area that has undergone a long exploration history involving numerous operators with successive focus on block scale petroleum geology at the expense of the more regional controls on hydrocarbon prospectivity. An improved understanding of hydrocarbon accumulation in the Tungkal PSC required both using regional petroleum systems analysis and hydrocarbon charge modelling. While the Tungkal PSC operators had acquired high quality seismic data and drilled a number of wells, these were mainly focused on improving production from the existing field (Mengoepeh). More recent exploration-driven work highlighted the need for a new look at the hydrocarbon charge history but it was clear that little work had been done in the past few year to better understand exploration risk. This paper summarises the methodology employed and the results obtained, from a study, carried out in 2014-15, to better understand hydrocarbon accumulation within the current Tungkal PSC area. It has involved integration of available well and seismic data from the current and historical PSC area with published regional paleogeographic models, regional surface geology and structure maps, together with a regional oil generation model. This approach has allowed a better understanding of the genesis of the discovered hydrocarbons and identification of areas for future exploration interest.

L Field is a brownfield located in the South Sumatra Basin with numerous producing wells. Adjacent to this field, there is a large carbonate reservoir with a significant recovery factor. Carbonate is found in L Field but it was deposited in distal environment with different characters. In attempt to prolong the life of L Field, its carbonate reservoir is evaluated. An integration between geology, petrophysics, reservoir and production engineering works has been done to get comprehensive results. The evaluation was put into 2 categories, qualitative and quantitative methods. The qualitative method is done by geologist whom deals with well-by-well review, reservoir correlations, depositional environment interpretation according to regional context, and qualitative candidates scoring. The quantitative method is divided into petrophysical and production data analyses as well as well integrity. The final screening candidates are the result of both methods. Based on the core description from adjacent field, carbonate in L Field has 2 different zones, zone A and B. From the qualitative perception only, zone A can be categorized as non-reservoir, due to high gamma-ray reading. However, the solubility test confirms that the zone has high calcareous content. After final scoring, L-14 well has the highest score for zone A and L-15 for zone B. This Poster highlighted the importance of a cohesive approach among multi-disciplines works which can successfully identify missed pay potential to proving up reserves. As a result, a significant amount of volumetric has been calculated for carbonate in L Field. Due to the good solubility result of the formation with HCl, matrix acidizing stimulation is also prepared. To prove-up reserves in L Field initially, it is recommended to open zone A of L-14 and zone B of L-15. The workover will continue with the remaining wells which have lower scores contingent on both wells' results