Lithostratigraphy of Tabul Formation and Onshore Geology of Nunukan Island, North Kalimantan

Nunukan Island is located in Northeast Kalimantan Basin, one of prolific basin in western Indonesia. However, this island lies in northern verge of the basin and hydrocarbon exploration were limited before the 1940s. No detail geological fieldworks has been published. This paper attempts to share geological information obtained from few accessible outcrops, particularly from the western part of the island where previous oil drilling were carried out. Most of the island have been built by Tabul Formation, which was also the main objective of reservoir for hydrocarbon exploration. It is composed of claystones, siltstones, and sandstones interbeds, deposited in transitional environment during Late Miocene. They exhibit coarsening upward sequence, the lower part composed of heterolitic sandstones deposited in tidal flats, and the upper part composed of arkosic sandstones deposited in distributary channels and mouthbars. The eastern coastal strip was constructed by Tarakan conglomerates, which have been deposited in fluvio-deltaic environment in Pliocene, unconformably over the Tabul clastics. Those Neogene deposition of paleo-Simengaris Delta apparently deformed and inverted in Plio-Pleistocene, contemporaneously with basaltic volcanism which spread widely over northeastern Borneo, which also observed in the northern half of the Nunukan Islan

Basin Evolution Palispatic Model of Bonaparte Basin, Australia Northwest Shelf

This research area is located on the Australian NW Shelf close to the westernedge of the Sahul Platform. This research is aimed to generate the palispatic basin model of Bonaparte Basin, Australian Northwest Shelf. It is to predict the impact of Neogene collision on the petroleum system distribution on Australian Northwest Shelf. The main data used in this research are seismic data using qualitative method analysis. The well data is used to well-seismic tied. After data acquisition, the seismic data are interpreted based on the horizon and structure interpretation. These interpretation are to reconstruct the basin evolution thorough geologic time. According to data analysis, the basin evolution palispatic model are divided into Paleo-proterozoic, Paleozoic, Triassic, Early Jurassic, Middle Jurassic, Late Jurassic, Early Cretaceous, Late Cretaceous, Early Eocene, Late Miocene and Recent condition. Regional tectonically there are at least three important events in NW Shelf: Middle Triassic-Jurassic NNE–SSW extension phase, Late Jurassic NE–SW extension phase and the Neogen collision phase; the Neogen collision effects on Northwest Shelf Australia. These three events contributed in forming and disturbing the Paleozoic and Mesozoic petroleum system in Bonaparte basin especially

Regional Depositional Model Of South Makassar Basin Depocenter, Makassar Strait, Based On Seismic Facies

South Makassar Basin Depocenter (SMBD) is located in Southern Makassar Strait which has petroleum potential by the presence of oil and gas indications within the area based on Airborne Laser Fluorescence survey. However, detail studies within this area are not developed well. One of the studies which can be utilized for further discoveries of oil and gas field in SMBD is a study of depositional model using seismic facies method to maximize limited seismic and well data. Interpretation of depositional model in Eocene (syn-rift phase) was varied from alluvial plain and alluvial fan complex, continued gradually to platform. In Oligocene time (post-rift phase), massive transgression caused a major deepening in entire SMBD where the depositional environment changed to basinal plain. In early Miocene – recent interval (syn-orogenic phase), SMBD was relatively in stable condition at basinal plain environment. Lower Tanjung Sequence will be the most prolific petroleum play in SMBD due to its adequate source rock, reservoir rock and seal rock as well. Keywords: South Makassar basin, depositional model, seismic facie

Identification of Permeable Structures and Heat Source in the Geothermal Working Area of Galunggung Volcano and the Heat Source Connectivity to the Karaha-Cakrabuana Area Using Gravity Data

Galunggung volcano area is a geothermal concession area that adjacent with Karaha-Cakrabuana concession area with a distance around 1 km. Indonesian Government planning to build power plant in 2025 so additional research needed to support the plan. Gravity survey could help in identifying permeable structure (fault) as well as heat source to a certain depth. The results of data processing showed the presence of faults seen on the FHD, SVD, and ABL residual maps, while for heat sources it was shown from the closed contour patterns on the ABL, residual, and regional maps. Derivative analysis in strengthens the position and type of fault from the match between the maximum FHD value and zero SVD value. From these results, identified the existence of three faults in the study area and were all identified as normal faults. 3D modelling gave a picture of density contrast in research area. From the section profile that pass through Galunggung and Telaga Bodas crater, heat source was interpreted as density with value 2.8 – 3.0 gr/cm3 and marked by orange to red color that coincide below Galunggung crater and continoued to Talaga Bodas crater at depths below -3000 masl. This indicate that both concession area was connected

PALEOSTRESS ANALYSIS TO INTERPRET THE LANDSLIDE MECHANISM: A CASE STUDY IN PARANGTRITIS, YOGYAKARTA

Paleostress analysis on the landslide boundary faults is able to explain the sliding mechanism. This method is particularly useful to study a paleolandslide. About 30 striated fault planes from the Parangtritis paleo-landslide, located in the Yogyakarta coastline, were analyzed to define their principle stress axes. The eastern boundary fault, named as the Girijati Fault, was the main fault responsible for the mass movement and leaving a considerable steep cliff. It moved normal in a left lateral sense with ENE – WSW extension and dragged the rockmass southward, creating a NNW – SSW extension along the Parangtritis Fault and turn it into the western boundary fault. The rockmass slided along the stratigraphic contact between the underlying Nglanggran Formation and the overlying Wonosari Formation, created a semi-circular crown cliff as the northern boundary and produced some isolated topographic highs of the thrust block near the toe. Keywords: Paleostress, landslide boundary, fault, paleolandslid

GEORADAR INVESTIGATION AT THE KEDULAN TEMPLE EXCAVATION SITE, KALASAN, YOGYAKARTA

Kedulan Site is the buried and ruined 9th century Mataram Hindu Kingdom temple, located in Tirtomartani Village, Kalasan District, Sleman Regency, Yogyakarta Special Province. This temple was incidentally discovered by sand diggers on 24 November 1993 under several meter thick of fluvio-volcanic deposit of the modern Merapi. Several technical studies were needed to carefully excavate the temple, including geology and geophysical approaches. One of the geophysical method have been applied was ground penetration radar (georadar). This method uses radar technology to obtain a continuous profile of the shallow sub-surface and thus allows scientists to image soil substratums based on differing dielectric constants. Georadar investigation by Department of Geological Engineering, Faculty of Engineering, Universitas Gadjah Mada, was conducted on 4 December 2007. The main purpose was to identify the location of the outer stone fence as an estimation to define the temple site area to be excavated. About one line was chosen to cross the site in north-south direction in a distance of 328 m. Two runs were completed on the same line but different courses, i.e. forward and backward, where one was checked with another. The result indicates the presence of the outer stone fence was possibly buried in a depth of 7 m. It was located about 40 m distance outside the inner stone fence. Assuming the fences were quadrangle relative to the main temple, hence it is estimated that the site area to be excavated is about 13.830 m² and total 96.808 m³ gravels and sands to be removed

Carbonate Facies and Depositional Environment of Pre-Parigi Carbonate in Ardjuna Sub-basin: Application of Core-facies Coding and Electro-facies

The Pre-Parigi Formation is one of the formations in the West Java Basin North as a potential reservoir. However, the carbonate rocks of the Pre-Parigi Formation are considered to have high heterogeneity due to rock and depositional processes its diagenesis, so an appropriate approach is needed to understand its reservoir distribution. Therefore, in this study, interpretation of the facies distribution of the Pre-Parigi Formation was carried out using the integration of core data and well logs. On the core data, facies coding and clustering is performed to interpret the facies association. Then, the identified facies associations are integrated with the characters so that facies interpretation can be carried out for all intervals and all wells. The end result is an interpretation of the distribution of the facies of Pre-Parigi Carbonate. Based on the analysis results, the Pre-Parigi Carbonate in the study area is composed of five facies associations, such as deep shelf (FA 1), fore-slope (FA 2), near-reef lagoon (FA 3), lagoon (FA 4), and restricted circulation shelf – tidal flat (FA 5). FA 1 is characterized by a very high value, slightly serrated gamma-ray character. FA 2 is characterized by a high gamma-ray, serrated, intercalated with a fining-upward low gamma-ray layer, FA 3 is characterized by a low value and blocky gamma-ray, FA 4 is also characterized by a gamma-ray with a fairly low value, but has a pattern that tends to be serrated, and then FA 5 is characterized by a serrated gamma-ray character with a slightly higher value than FA 4. Based on the integration of all interpretations, the Pre-Parigi Carbonate in the study area can be divided into three depositional sequences (DS), where DS-1 develops in all area as a reef-initiation, DS-2 developed in the MVA-1 and MVA-3 wells, and did not develop in the MVA-6 well (had a give-up phase), and then DS-3 only developed in the MVA-3 well. In general, facies interpretation using the core-facies coding and electro-facies characterizing methods tends to be effective and provides more confidence interpretation. Keywords: Pre-Parigi Carbonate, Carbonate facies, Core-facies coding, Arjuna Sub-basi

GROUND MOTION IN YOGYAKARTA CITY, YOGYAKARTA SPECIAL PROVINCE, INDONESIA ON DENSELY MICROTREMOR OBSERVATIONS AND SHEAR WAVE VELOCITY

Microtremor is currently considered the foremost tool in site effect studies. The ground motion is estimated with microtremor observations, meaning that subsoil mechanical properties and geometry are evaluated and from them an estimate of local amplification is computed. Here, the ground motion is studied by the site effects of seismic hazard zonation of urban areas in Yogyakarta City. The main purpose of this paper is zoning the geological engineering features and assessing seismic of the research urban area. In this regard, the microtremors are measured at 274 sites by single station sampling method and Nakamura technique. The microtremors of all over the city are processed by a model of Mitutoyo-GPL-6A3P. The amplification factor generally ranges between 0.70 and 5.56 and the natural frequency normally varies between 0.40 and 3.30 Hz. The information layers are prepared in GMT used for detecting the zonation of potential seismic hazard. The shear wave velocity is calculated in 12 existing drilling sites based on the geotechnical approach of SPT for soil condition. To study the ground motion, geological engineering condition is investigated using amplification factor, natural frequency, shear wave velocity maps which are analyzed using densely single microtremor observation and SPT from existing drilling sites. Keywords: Ground motion, amplification factors, natural frequency; H/V spectral ratio, microtremor observations, Yogyakarta Urba

Reconstruction of Early Holocene Paleogeography of Graal-Muritz Southern Baltic Sea, Germany

This paper presents an example of shallow marine single channel seismic survey for coastal area. The working area was Graal-Miiritz, located in southern Baltic Sea of Germany. This area was covered by extenJive glacial deposits of late ice age of Late Pleistocene. Determined purpose is to extract a figure of paleogeography of Early Holocene based on hydroacoustic measurements (boomer). The knowledge of paleogeography is important in field of coastal dynamics, in order to predict future coastal changes in response to various natural factors. Another important value of the study of paleogeography in this area is its data as a basic to calculate amount of glacial deposits that has economical meaning, regarding such deposits are being today exploited, especially for sand and gravel. Key Words: paleogeography - Graal-Miiritz - coastal - Baltic Sea German