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INDONESIA
Indonesian Journal on Geoscience
ISSN : 23559314     EISSN : 23559306     DOI : -
Core Subject : Science,
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 6 Documents
Search results for , issue " Vol 4, No 3 (2009)" : 6 Documents clear
Pendolomitan Batugamping Formasi Rajamandala di Lintasan Gua Pawon, Bandung Barat Maryanto, Sigit
Indonesian Journal on Geoscience Vol 4, No 3 (2009)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.3.203-213

Abstract

http://dx.doi.org/10.17014/ijog.vol4no3.20095Diagenetic process records could be observed based on the petrography and XRD mineralogy labo- ratory analyses from thirty-two samples of limestone taken from the Rajamandala Formation at Pawon Cave Section, West Bandung. These laboratory analyses show that the rocks have partially been affected by a dolomitization. The dolomitization recorded at the limestone is a fabric selective dolomitization of the rock matrix, continued to the whole components of the limestone. The dolomite crystals are generally idiotopic to xenotopic mosaic rhombohedral in shapes with fine to moderate crystal sizes. Dolomite mainly consists of magnesium ion initiated from water formation trapped soon after the rock deposited. The middle part of the Rajamandala Formation, which is commonly affected by dolomitization is generally associated with meteoric water dissolution and creates several caves.  
Organic petrology and Rock-Eval characteristics in selected surficial samples of the Tertiary Formation, South Sumatra Basin Hermiyanto, M. H.; Ningrum, N. Sudini
Indonesian Journal on Geoscience Vol 4, No 3 (2009)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.3.215-227

Abstract

http://dx.doi.org/10.17014/ijog.vol4no3.20096Organic petrologic data of the DOM of Talangakar and Muaraenim Formations show that the organic matter consisting mainly of vitrinite group is essentially composed of telocollinite (1.0 – 70.8 %) and desmocollinite (0.8 – 66.6 %) with minor telinite (0.6 – 9.4 %), detrovitrinite (0.6 – 6.0 %), and cor- pocollinite (0.6 – 2.0 %). Minor exinite (0.4 – 7.8 %) and inertinite (0.4 – 8.0 %) are also determined. However, mineral matter varies from 0.6 – 99.44 %. Downwards, the increase in vitrinite reflectance (0.33 – 0.48 %) is concomitant with the depth of each formation. Furthermore, based on Rock-eval pyrolysis, TOC value of the Talangakar Formation ranges from 0.09 – 15.38 %, Gumai 0.34 – 0.39 %, Airbenakat 0.32 – 4.82 %, and Muaraenim between 0.08 – 15.22 %. Moreover the PY (Potential Yield) value variation of the Talangakar, Gumai, Airbenakat, and Muaraenim Formations are between 0.04 – 36.61 mg HC/g rock, 0.53 – 0.81 mg HC/g rock, 0.1 – 4.37 mg HC/g rock, and 0.07 – 129.8 mg HC/g rock respectively. Therefore, on the basis of those two parameters, the four formations are included into a gas - oil prone source rock potential. However, the Talangakar and Muaraenim Formations are poor to excellent category, whereas the Air Benakat tends to indicate a poor – fair category and Gumai Formation are only within a poor category. Tmax value of the Talangakar ranges from 237 – 4380 C, Gumai 316 – 3590 C, Airbenakat 398 – 4340 C with exceptions of 4970 C and 5180 C, and Muaraenim Forma- tions 264 – 4250 C. The Talangakar Formation contains kerogen Type II dan III, with the HI (Hydrogen Index) value varies from 45.16 – 365.43. However two samples show value of 0. The organic content of the Gumai and Air Benakat Formations are included into kerogen type III, with HI value ranges from11.87 – 40.82, and 19 – 114 respectively. Moreover the Muaraenim Formation has two category of kerogen type and HI value, those are type III with the HI value of 1 and kerogen type I with HI value of 821.29. The diagram of Tmax vs HI shows that the organic thermal maturation of the four formations are included into an immature to mature level.  
Ignimbrite Analyses of Batur Caldera, Bali, based on 14C Dating Sutawidjaja, Igan S.
Indonesian Journal on Geoscience Vol 4, No 3 (2009)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.3.189-202

Abstract

http://dx.doi.org/10.17014/ijog.vol4no3.20094The Batur Caldera, in the northeastern part of Bali Island, is an elliptical collapse structure 13.8 by 10 km in size and another circular composite collapse structure with a diameter of 7.5 km in its centre. Two stages of the collapse were interrupted by silicic andesite lavas and domes. The first collapse was initiated by the eruption of about 84 km3 of the dacitic "Ubud Ignimbrite", about 29,300 years B.P., which caused a steep-walled depression about 1 km deep. The second ignimbrite was erupted from a large crater about the present lake, and it  produced about 19 km3 of a similar voluminous dacitic ignimbrite, called the "Gunungkawi Ignimbrite" about 20,150 years B.P. This second eruption trig- gered a second collapse, which created the central circular caldera, and formed a basin structure. Both the Ubud and Gunungkawi Ignimbrites consist of a similar dacitic composition, white to red (the most abundant nearly 90 %) and dark grey to black dacitic pumice clasts. The large clasts, up to 20 cm in diameter, are in the non-welded ignimbrite, particularly in the upper part of the Gunungkawi Ignimbrite. The intracaldera ignimbrite, called the "Batur Ignimbrite" about 5 km3  in volume is a densely welded ignimbrite and generally shows typical welded features. The ignimbrite comprises at least five different flow units, separated by thin (15 - 40 cm) welded pumiceous airfall deposits, with flattened pumice clasts. Another large eruption occurred about 5,500 years B.P., producing around 0.09 km3  andesitic ignimbrite. This was initiated by phreatomagmatic eruptions, indicated by thick phreatomagmatic and surge deposits, underlying the ignimbrite. The caldera and its vicinity are partly filled, and variably mantled by later eruptive products of dacitic and andesitic phreatomagmatic and airfall deposits.  
Kondisi Permukaan Air Tanah dengan dan tanpa peresapan buatan di daerah Bandung: Hasil Simulasi Numerik Hutasoit, Lambok M.
Indonesian Journal on Geoscience Vol 4, No 3 (2009)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.3.177-188

Abstract

http://dx.doi.org/10.17014/ijog.vol4no3.20093Significant groundwater level drawdown caused by groundwater abstractions has been reported to occur in Bandung and its surrounding area. One potential method to recover the groundwater condi- tion is artifical recharge, considering high quantity of rainfall in this area. In this research, numerical simulation has been performed in order to predict groundwater condition in the next five years, if: 1) no recovery action is taken (do-nothing) (Scenario 1), and 2) artificial recharge is performed (Scenario 2). Hydrogeological condition reconstruction  required for physical model development  reveals that the main aquifer in the researched area is Cibeureum Formation, which comprises volcanic fans; the main aquitard is Kosambi  Formation, crasisting of lake deposit, whilst the hydrogeologic basement in the research area is the Cikapundung Formation, other Quaternary volcanic rocks, except the Cibeureum Formation, and Tertiary rock units. The recharge area is the areas where the Cibeureum Formation crops out. The result of numerical simulation of Scenario 1 shows that if there is no recovery action taken on the groundwater condition, then in year 2013 the Critical Zone will increase about 116 % and the Damage Zone will increase about 570 %. The result of this scenario also shows that there will be groundwater mining in several areas in the Damage Zone with the total area of 244 km2 or 41 % of the total  confined aquifer area. Result of the numerical simulation of Scenario 2 shows that  the artificial recharge in the above Critical and Damage Zones will effectively recover groundwater condition in year 2013 which means is, the whole area becomes Safe Zone. The amount of the artificial recharge is about 164 million m3/year and it started from year 2009. The artificial recharge means recharge well, surface reservoir, or recharge ditch where the Cibeureum Formation crops out, or injection well where this formation does not crop out.  
Karakteristik Batuan Sumber (Source Rock) Hidrokarbon pada Formasi Batuasih di daerah Sukabumi, Jawa Barat Praptisih, Praptisih; Kamtono, Kamtono; Putra, P. S.; Hendrizan, M.
Indonesian Journal on Geoscience Vol 4, No 3 (2009)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.3.167-175

Abstract

http://dx.doi.org/10.17014/ijog.vol4no3.20092The purpose of the study carried out on the claystone of Batuasih Formation in Sukabumi area is to find out the hidrocarbon potential and its characteristics. The Batuasih Formation, overlying conform- ably the Walat Formation, consists  of claystone, dark gray, shaly, brittle, containing clay ball, calcite veins, with carbonate intercalations. The geochemical analysis conducted on twelve samples shows the TOC values vary between 0.49 – 1.14 % and Tmax of 431 – 434o C. Four samples are categorized to be immature, while the rests are mature. HI values of the Batuasih Formation varying from 77-191 mg HC/ TOC indicate that the samples are of C and CD organic facies. Based on those analyses, the source rock is favourably potential to generate a small quantity of hydrocarbon and gas. The hydrocarbon source rock potential level in the investigation area shows a poor to fair organic richness, and its kerogen is included into types II and III. The source rock quality based on the Hydrogen Index (HI) value tends to be a gas prone. 
Analisis stratigrafi awal kegiatan Gunung Api Gajahdangak di daerah Bulu, Sukoharjo; Implikasinya terhadap stratigrafi batuan gunung api di Pegunungan Selatan, Jawa Tengah Hartono, Hill Gendoet; Bronto, Sutikno
Indonesian Journal on Geoscience Vol 4, No 3 (2009)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.3.157-165

Abstract

http://dx.doi.org/10.17014/ijog.vol4no3.20091Generally, Tertiary volcanisms in the Southern Mountains, Central Jawa were started with the formation of pillow lavas having basalt to basaltic andesite in composition. This initial stage volcanism developed into a  construction period of composite volcanoes that consist of alternating basaltic to andesitic lava flows, breccias, and tuffs. The construction period could be followed by a destructive phase, producing pumice-rich pyroclastic breccias, lapillistones, and tuffs of high silica andesite to dacite, or even rhyolite in composition. A stratigraphic measuring section at Bulu area, Sukoharjo Regency, presents an alternat- ing fine-grained andesitic volcaniclastic material and some limestones, with the total thickness is 143.33 m. The thickness of bedded volcaniclastic material tends to be thickening upward from 35 m until 90 m. The grain size of the volcaniclastic material also tends to be coarsening upward from clay size through silt and fine sand to coarse sand and granules. Paleontological analysis on fossils contained in the lime- stone gives an age of Early Miocene (N7 - N9). The volcaniclastic rocks is conformably overlain by the Mandalika Formation, comprising alternating andesitic breccias, lavas, and tuffs. These data imply that the fine-grained volcaniclastic material is an initial product of the construction period of Gajahdangak Volcano in the area, that formed the Mandalika Formation. This Formation is overlain by the Semilir Formation, composed of pumice-rich pyroclastic breccias and tuffs with dacitic composition. This as- sociated volcanic rock reflects a product of a caldera explosion or a destructive phase. Based on the characteristics of lithology of volcanic products from the initial stage, to a construction and destruction period, and compiled age data, the Southern Mountains represent formal volcanic rock units that are able to be divided into many formations.  

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