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IJOG : Indonesian Journal on Geoscience

IJOG
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Published by Geological Agency of Indonesia

ISSN : 23559314 EISSN : 23559306 DOI : -

Core Subject : Science,

Earth & Planetary Sciences

The spirit to improve the journal to be more credible is increasing, and in 2012 it invited earth scientists in East and Southeast Asia as well as some western countries to join the journal for the editor positions in the Indonesia Journal of Geology. This is also to realize our present goal to internationalize the journal, The Indonesian Journal on Geoscience, which is open for papers of geology, geophysics, geochemistry, geodetics, geography, and soil science. This new born journal is expected to be published three times a year. As an international publication, of course it must all be written in an international language, in this case English. This adds difficulties to the effort to obtain good papers in English to publish although the credit points that an author will get are much higher.

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Articles 796 Documents

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Comparative Study among Bivariate Statistical Models in Landslide Susceptibility Map Yukni Arifianti; Pamela Pamela; Fitriani Agustin; Dicky Muslim
Indonesian Journal on Geoscience Vol 7, No 1 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.1.51-63

DOI:10.17014/ijog.7.1.51-63The main purpose of this paper is to compare the performance of bivariate statistical models i.e. Frequency Ratio, Weight of Evidence, and Information Value for landslide susceptibility assessment. These models were applied in Cianjur Regency, West Java Province (Indonesia), in order to map the landslide susceptibility and to rate the importance of landslide causal factors. In the first stage, a landslide inventory map and the input layers of the landslide conditioning factors were prepared in the Geographic Information System (GIS) supported by field investigations and remote sensing data. The 298 landslides were randomly divided into two groups of modeling/training data (70%) and validation/test data sets (30%). The landslide conditioning factors considered for the studied area were slope angle, elevation, slope aspect, lithological unit, and land use. Subsequently, the thematic data layers of conditioning factors were integrated by frequency ratio (FR), weight of evidence (WofeE), and information value (IV). Model performance was tested with receiver operator characteristic analysis. The validation findings revealed that the three models showed promising results since the models gave good accuracy values. The success rates of FR, WofE, and IV models were 0.920, 0.926, and 0.930, while the prediction rates of the three models were 0.913, 0.912, and 0.895, respectively. However, the FR model was proved to be relatively superior in estimating landslide susceptibility throughout the studied area.

Syn-sedimentary Mafic Volcanics in the Eocene Coal-bearing Tanjung Formation, Senakin Peninsula, South Kalimantan (Borneo), Indonesia Tim Allen Moore; Mike C. Friederich; Jessica Trofimovs; Ferian Anggara; D. Hendra Amijaya
Indonesian Journal on Geoscience Vol 7, No 1 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.1.65-85

DOI:10.17014/ijog.7.1.65-85Syn-sedimentary mafic volcanism has been identified within a rift setting (Eocene Tanjung Formation) in the Senakin Peninsula, southeast Kalimantan. Fine-grained, dark-grey basalt lava occurs and has prominent vertically oriented columnar jointing. Petrographically, the basalt is composed of small euhedral pyroxene, olivine, and lath-shaped plagioclase phenocrysts within a very fine-grained dark coloured groundmass. A volcaniclastic unit also occurs and in outcrop has sharp contacts with underlying and overlying sedimentary mudstone. The unit is composed of cm-scale clasts of fine-grained to glassy textured basalt with vesicles of varying size and abundance. Euhedral pyroxene phenocrysts are observed within the clasts, although some with overprinting alteration. Palagonite alteration on the margins of some clasts is noted and is indicative of mafic composition volcanic material that has come into contact with sea water. Presence of bivalve and coral fragments in sandstone and mudstone underlying the volcaniclastic unit indicates emplacement into a marine environment. Core description from 33 locations over an 18 km transect length show that both the basalt and volcaniclastic sediments are extensive throughout the east Senakin area. Lithological relationships and compositional similarities between the basalt and volcaniclastic sediment suggest they are related and were contemporaneous with sedimentation within the Tanjung Formation. It is proposed that the basalt unit is designated the Tanah Rata Basalt Member of the Tanjung Formation. If a wider distribution occurs for the volcaniclastic unit it is proposed that it is termed the Gumbil Volcaniclastic Member of the Tanjung Formation.

Geochemical Evolution and Groundwater Flow System in Batujajar Groundwater Basin Area, West Java, Indonesia Rudy Suhendar; M. Sapari Dwi Hadian; Budi Muljana; Taat Setiawan; Hendarmawan Hendarmawan
Indonesian Journal on Geoscience Vol 7, No 1 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.1.87-104

DOI:10.17014/ijog.7.1.87-104Batujajar and its surrounding areas, situated in the west of the Bandung Basin, are geologically composed of various Tertiary rock formations with complex fold and fault systems. Springs and drilled wells in sandstone aquifers, tuffaceous sand, and tuffaceous breccias mark the development of their aquifer systems. This study aimed to determine the characteristics of the hydrogeochemistry by analyzing major ions and stable isotopes (18O and 2H) of thirty-four hydrogeological objects. The groundwater flow pattern in this area is controlled by northwest-southeast lineament, as indicated by the emergence of springs along the transition zone between areas with high and low lineament density. In order of dominance, the groundwater facies are as follows:Ca-Mg-HCO3>Ca-HCO3>Ca-Na-Mg-HCO3>Na-Ca-HCO3. Hydrochemical evolutions were detected from the change of cations from Ca2+ to Mg2+ and then Na+, and this is believed to be the product of cation exchange and dissolution of silicate minerals. However, evolutions toward anion changes were not apparent yet, meaning that HCO3- ions still prevail, or in other words the groundwater flow system is local. Nevertheless, the geological and hydrogeochemical analyses, along with the relative compositions of stable isotopes, revealed that the groundwater had three systems, namely shallow, intermediate, and deep groundwater flows; all of which were segmented in three subgroundwater basins (Sub-GWB). Aquifer systems with shallow to intermediate groundwater flow were found in Sub-GWB-A, Sub-GWB-B, and Sub-GWB-C, while the other ones with deep groundwater flow system were identified in Sub-GWB-B and Sub-GWB-C.Fracture system has an important role as a connector between recharge system in hilly areas and discharge system in plain areas.

Wireline Log Responses, Mudweight, Clay Mineralogy, and Implied Overpressure Condition: Insights from Aru Field, North Sumatra Basin Mohammad Syaiful; Lambok M. Hutasoit; Agus M. Ramdhan; Agus Haris Widayat
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.2.105-119

DOI:10.17014/ijog.7.2.105-119This paper comprehensively discusses overpressuring in the North Sumatra Basin by using wireline log, drilling events and parameters, and clay mineralogical data. It shows an interesting phenomenon related to overpressuring in this basin, i.e. strong log reversals indicating high overpressure, yet the mudweight used during drilling was relatively low, indicating low overpressure with no significant drilling events noted in the final well report.The result of the study shows that wireline log is the best parameter to imply overpressure magnitude. Regarding low mudweight in the strong log reversal zone, it would be elucidated that the drilling in that zone was in underbalance condition with respect to shale pressure, but not to sandstone pressure. The sandstone pressure is interpreted to be lower than shale pressure due to lateral drainage process. By applying the Eaton’s method, the estimated maximum overpressure magnitude in the Baong Formation is in the range of 1,594 - 3,185 psi. or equivalent to the mudweight of 1.61 - 192 g/cm3. The analysis of wireline log in combination with clay mineralogical data shows that there are two compaction lines in the studied area, i.e. smectitic and illitic compaction lines. The cross-plot of density and sonic logs in shale section suggest that the cause of overpressure was loading mechanism. The scanning electron microscope (SEM) image confirms that in overpressure zone, grain to grain contact is still able to be observed fairly well, inferring that loading mechanism is really the cause of overpressure in the studied area.

Geochemical Evaluation and Pore Type Characterization of Carbonaceous Rich Facies in Brown Shale Formation, Central Sumatra Basin Asep Kurnia Permana; Yusup Iskandar
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.2.121-133

DOI:10.17014/ijog.7.2.121-133Brown Shale Formation of Pematang Group is a key source rock in the Central Sumatra Basin. The formation consists of three lithofacies: algal rich facies, mixed algal-carbonaceous facies, and carbonaceous rich facies. This paper focuses on evaluating the geochemistry and on characterizing the porosity of the carbonaceous rich facies. Geochemical evaluation of the carbonaceous source rocks was conducted using Rock-Eval pyrolysis, while mineralogy and microtextural characterization were assessed by incident light microscopy and scanning electron microscopy (SEM). The results show that the organic components of the carbonaceous source rocks are predominantly composed of vitrinite with minor inertinite and liptinite. The geochemical characteristics indicate that the carbonaceous rich facies could be ranked as a good to excellent level in terms of source rock potential with high TOC content, mainly containing kerogen type III as a gas prone potential. SEM results show that the pore types in the carbonaceous source rocks can be classified into three main types: porous floccules, organic-porosity, and intraparticle pores. Thus, the carbonaceous rich facies of the Brown Shale Formation contains gas prone source rocks with good generation potential, as well as organic rich shale unconventional reservoirs.

Temporal Variations of Petrological Characteristics of Tangkil and Rajabasa Volcanic Rocks, Indonesia Reza Firmansyah Hasibuan; Tsukasa Ohba; Mirzam Abdurrachman; Takashi Hoshide
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.2.135-159

DOI:10.17014/ijog.7.2.135-159Tangkil and Rajabasa Volcanoes are neighbouring subduction-zone volcanoes located on the southeast tip of Sumatra Island (Sunda Strait, Indonesia). Stratigraphic correlation of lavas in Tangkil-Rajabasa volcanic area was established from field observations, morphological analysis, and K-Ar dating analysis. Detailed petrography and geochemical data of two and eleven lava units from Tangkil and Rajabasa, respectively, were then integrated with the stratigraphy to show the temporal variations. Early stage (> 4.3 Ma) effusives of Tangkil Volcano are dacitic to rhyolitic (67-71 wt. % SiO2; Tklf), whereas the later (c. 4.3 Ma) rocks are basalt to basaltic andesite (c. 52 wt. % SiO2; Tklm). Tangkil shows bimodal magmatism, of which the felsic endmember is > 71 wt. % SiO2 and < 0.1 wt. % MgO. Lavas of Rajabasa Volcano are comparatively younger (c. 0.3 to 0.1 Ma) with compositions ranging from basalt to andesite (51-62 wt. % SiO2; Rbs). Chemical variations of Rajabasa accounts for the interactions of at least three endmembers: Mg-rich medium-K basalt magma, low-Mg medium-K basalt magma, and high-K andesitic magma. During the long evolution of Rbs magma system, the temporal chemistry shows rising-falling variation in SiO2 and MgO indicating the three magmas were active. The felsic endmember magma of Rajabasa is fixed in composition (at ~62 wt. % SiO2; ~2.2 wt. % MgO). The rocks from the last Tklf and Rbs indicate open system processes by containing plagioclase and pyroxene phenocrysts that show resorption of evolved core and overgrowth of less evolved mantle. The multiple zones of dissolution-overgrowth in plagioclase crystals and the fluctuating trend in temporal whole-rock variation suggest that the changes of magmatic condition in temperature, H2O, or chemical composition were repetitive.

Geochemistry of Basaltic Merbabu Volcanic Rocks, Central Java, Indonesia Sri Mulyaningsih; Godang Shaban
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.2.161-178

DOI: 10.17014/ijog.7.2.161-178The studied area is located along the hiking track of Kajor - Selo, the south flank of Merbabu Volcano, Central Java, Indonesia. Olivine basalt and augite-rich basalt compose the volcanic rocks. A geochemical study recognizes these basalts which tend to originate from the product of tholeiitic magma, in terms of transitional enriched mantle source. It is interpreted to have been formed as primary magma that mixed later with higher degrees of partial melting with a mantle wedge. Both fl uid and melt were derived from the mixing of lower active continental margin and subducting oceanic slab. This study also shows general trends of increasing incompatible elements, i.e. Rb, Ba, Pb2+, and Sr as LIL trace elements and Th, U, Nb, Ce, Zr, Hf, Nb, and Ta as HFS element comparing to basaltic andesites exposed at Thekelan, they show decreasing compatible of MgO, Fe2O3*, Al2O3, CaO, TiO2, Ni, Sr, and Ba in line with increasing SiO2. It was fractional crystallization process, shown by the slightly wide variation of Rb/Zr and La/Sm that indicates random crustal contamination.

Terrestrial Laser Scanner (TLS) Measurement in A Volcanic Area: Detection of Error Source and Scanned Object Intensity Nia Haerani; Hasanuddin Z. Abidin; Surono Surono; Dudy D. Wijaya
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.2.179-200

DOI:10.17014/ijog.7.2.179-200The purpose of the study of Terrestrial Laser Scanner (TLS) application in an active volcanic crater is to detect the influence of gas emission and local atmospheric change into the accuracy of measurement.The measurement was conducted at Papandayan Volcano crater, along with the local temperature, humidity, and air pressure (thp). The measured target located near a gas emission hole gives a significant fluctuative range due to possible false return by gas particles. The refraction index was calculated using thp data. Two correction models were applied: velocity-geometry and atmospheric delay correction. The atmospheric delay correction gives a more reliable result, however their refraction index calculation does not accomodate specific volcanic gas yet. An intensity map obtained from TLS can also be used for rock segmentation. An experiment from some types of volcanic rocks shows that the intensity value is influenced by a weathering degree of rock outcrops. Rock segmentation using TLS intensity data for fresh outcrops is relatively easier, while for weathered rocks it still needs a field check for validation. The temperature of volcanic rocks also contributes to the intensity value. It is found that the intensity increases along with the temperature of rock.

Terrestrial Laser Scanner (TLS) Measurement in A Volcanic Area: Detection of Error Source and Scanned Object Intensity Haerani, Nia; Abidin, Hasanuddin Z.; Surono, Surono; Wijaya, Dudy D.
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.2.179-200

The Determination of Volcanic Characteristics Based on Deuterium and Oxygen-18 Isotope Compositions: A Case Study at Dieng Plateau, Central Java Priatna Priatna; Nana Sulaksana; Johanes Hutabarat; Iyan Haryanto
Indonesian Journal on Geoscience Vol 7, No 2 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.2.201-213

DOI:10.17014/ijog.7.2.201-213To find out volcanic characteristics, a geochemical approach can be used, one of which is through the measurement of deuterium and oxygen-18 isotopes from condensate and crater water samples. In this study, Dieng Plateau in Central Java was chosen, because it has a wide spread of fumarole fields and crater water. In addition, research in the Dieng Plateau is very useful in the management of geological-based tourism and geopark development in the future. Results of isotope analysis in Candradimuka Crater show the average number of isotope deuterium is δD – 500/00 and isotope oxygen-18 is δ18O –30/00 which produce the value of the mixing fraction of f 18O = 47.11%. This figure is the highest isotope number compared to other craters on the Dieng Plateau. The high value of the isotope-18 mixing fraction is supported by a strong plume from three vents in Candradimuka. Meanwhile, the results of crater water isotope tests obtained the highest results in Sikidang Crater with the value of the deuterium isotope is δD = – 10.300/00 and the isotope oxygen-18 is δ18O = 6.570/00 which are in the metamorphic water area from the mixing of magmatic processes with surface meteoric water. Based on the deuterium isotope approach with oxygen-18 crater water and fumarole condensate supported by subsurface temperature data, most of the Dieng Plateau has magmatic-hydrothermal characteristics, except Candradimuka Crater which belongs to the magmatic group.

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Contact Name
Ivan Ferdian

Contact Email
ivan.ijgbg@gmail.com

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Journal Mail Official
ivan.ijgbg@gmail.com

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Location
Kota bandung,

Jawa barat

INDONESIA