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Bulletin of Geology
Published by Institut Teknologi Bandung
ISSN : 25800752     EISSN : 25800752     DOI : 10.5614/bull.geol.
Core Subject : Science, Engineering,
Earth & Planetary Sciences Energy Engineering
Bulletin of Geology is a research-based periodical scientific open access journal published by Faculty of Earth Sciences and Technology, Institut Teknologi Bandung (ITB). The published article in Bulletin of Geology covers all geoscience and technology fields including Geology, Geophysics, Geodesy, Meteorology, Oceanography, Petroleum, Mining, and Geography. The submitted abstract must be written in English and Bahasa Indonesia, but the article content is English or Bahasa Indonesia.
Arjuna Subject : Ilmu Bumi dan Planet (semua kategori) - Geologi
Articles 100 Documents
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ANALYZING SURFACE ROUGHNESS MODELS DERIVED BY SAR AND DEM DATA AT GEOTHERMAL FIELDS Tahjudil Witra; Asep Saepuloh; Agung Budi Harto; Ketut Wikantika
Bulletin of Geology Vol 1 No 2 (2017): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/bull.geol.2017.1.2.1

Abstract

Surface roughness is a physical property which is used in many applications such as hydrological analyses, erosivity of rocks, and identification of geothermal surface manifestations. In this study, the surface roughness was calculated by a pin-meter. This tool is expected be able to measure the fragmental size at ground surface. However, there is a possibility that the tool still has some errors from the effect of topography undulation. In previous research, detrending method was used to minimise the topographical effect in the measured surface roughness. In this paper, we used Synthetic Aperture Radar (SAR) data from Sentinel-1A, and Digital Elevation Model (DEM) SRTM to evaluate the effectiveness of detrending method of pin-meter. Therefore, the measured surface roughness originated solely from fragmental materials. The selected research areas were Wayang Windu and Patuha geothermal field in Indonesia. Modelling the surface roughness by Sentinel-1A image was conducted by utilising backscattering coefficient and local incidence angle. While surface roughness model from DEM is formed by the Root mean square (RMS) for each grid with the optimum size 19×19 pixels. Both models were compared to pin-meter data which have been detrended. Then, the comparison was analyzed based on determination correlation value (R2). Surface roughness model derived by Sentinel-1A produced R2 about 0.1130 higher than DEM about 0.060. It might indicate that the surface roughness measured by the pin-meter following detrending process is free from the effect of topography undulation. Then, surface roughness model derived by Sentinel-1A data was used to identify surface manifestation. Analysis was performed based on pH measurement at field and scatter plot pattern. According to the selected model, the surface roughness at geothermal surface manifestation zones are inversely proportional to the soil pH.
PENGAYAAN TIMAH (Sn) DAN UNSUR TANAH JARANG (Ce, La, dan Y) ENDAPAN PLASER DI BADAU, KABUPATEN BELITUNG Yan Rizal
Bulletin of Geology Vol 5 No 3 (2021): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

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Abstract

Sari Penelitian dilakukan di dalam wilayah Kecamatan Badau, Kabupaten Belitung, Kepulauan Bangka Belitung, dengan tujuan untuk mengetahui daerah sebaran dan pengayaan timah dan unsur tanah jarang pada endapan plaser. Metode yang dilakukan pada penelitian ini antara lain pemetaan geologi, penyontohan batuan, dan penyontohan endapan plaser. Kandungan mineral pada conto endapan plaser diidentifikasi menggunakan metoda Grain Counting Analysis (GCA). Analisis geokimia conto dilakukan dengan menggunakan metoda X-Ray Fluorescence (XRF) untuk menentukan kandungan unsur Sn, Ce, La, dan Y. Untuk mendapatkan nilai anomali kandungan unsur dilakukan analisis univariat. Hasil analisis univariat kemudian dihubungkan dengan kondisi geologi daerah penelitian sehingga dapat ditentukan daerah pengayaan timah dan unsur tanah jarang dominan di bagian tengah daerah penelitian. Kandungan unsur Sn memiliki nilai kandungan dengan rentang yang sangat jauh 9,67 ppm – 82652 ppm, unsur Ce memiliki nilai kandungan dengan rentang 113,33 ppm – 3570 ppm, unsur La memiliki nilai kandungan dengan rentang 72,67 ppm – 1404,33 ppm, dan unsur Y memiliki nilai kandungan dengan rentang 6 ppm – 784,67 ppm. Abstract The research was conducted in the area of ​​Badau District, Belitung Regency, Bangka Belitung Islands, and the aim of the research is to understand the distribution area and enrichment of tin and rare earth elements in placer deposits. The methods used in this research include geological mapping, rock sampling, and placer sediment sampling. Mineral content in placer sediment samples was identified using the Grain Counting Analysis (GCA) method. Geochemical analysis of the samples was carried out using the X-Ray Fluorescence (XRF) method to determine the elemental content of Sn, Ce, La, and Y. Univariate analysis was performed to obtain the anomalous value of the elemental content. The results of the univariate analysis are then linked to the geological conditions of the study area so that the dominant tin and rare earth enrichment areas, in the middle of the study area, can be determined. The Sn has values with a very wide range of 9.67 ppm - 82652 ppm, the Ce values ranging from 113.33 ppm - 3570 ppm, La value ranging from 72.67 ppm - 1404.33 ppm , and Y has values ranging from 6 ppm - 784.67 ppm.
HORIZONTAL STRESS ORIENTATION FROM BOREHOLE BREAKOUT ANALYSIS IN WEST NATUNA BASIN, INDONESIA Gumelar Gumelar; Benyamin Sapiie; Indra Gunawan
Bulletin of Geology Vol 7 No 3 (2023): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

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Abstract

The West Natuna Basin is an intracontinental basin that characterized by number of Eocene – Oligocene half grabens, which inverted during Miocene time. West Natuna Basin formed under transtensional conditions, featuring half grabens trending in a SW-NE direction, accompanied by sinistral (left-lateral) wrench zones striking NW-SE. The inversion reactivates mainly the border fault formed during rifting and resulted in the similar SW-NE structural trend. This research aims to investigate the stress orientation from borehole breakout data that might be responsible for the structural formation in West Natuna area. Borehole breakout data in this research comprise into different types of data, image processed log from one well and caliper log (four arms and six arms) from eight vertical wells. The analysis performed differently for both of the data sets. The image processed log (FMI) data will give the indication of breakout and induced tensile clearly, while the breakout from caliper is interpreted based on some typical shape representing the borehole condition. The analysis from the borehole breakout will implies the minimum horizontal stress (Shmin) orientation that perpendicular to the maximum horizontal stress orientation (SHmax). The analysis resulted in a breakout trend N 36° to 79.5° with standard deviation 4.3-26.1°. The results of breakout analysis are comparable with the existing structure trend in southwestern part of West Natuna Basin that also showing similar trend SW-NE. Implied SHmax orientation at NW-SE trend is coincidence with major strike slip fault that believed the main force for the inversion occurred in West Natuna Basin. As comparison, the regional main fault at neighborhood Malay Basin is relatively parallel with the maximum horizontal stress (SHmax) orientation resulting the basin keep opened and subside until present day time. Key words: West Natuna Basin, borehole breakout, horizontal stress, inversion
KARAKTERISTIK REKAHAN PADA BATUAN DASAR DI BLOK JABUNG, SUB-CEKUNGAN JAMBI, SUMATRA SELATAN Kiddy Nahli Aulia; Benyamin Sapiie
Bulletin of Geology Vol 3 No 1 (2019): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/bull.geol.2019.3.1.3

Abstract

Cekungan Sumatra Selatan merupakan cekungan yang memiliki batuan dasar terekahkan penghasil gas yang cukup berhasil. Batuan dasar di Blok Jabung Sub-Cekungan Jambi memiliki potensi untuk menjadi reservoir pada batuan dasar terekahkan. Saat mengidentifikasi reservoir batuan dasar terekahkan, harus dilakukan identifikasi dari karakteristik rekahan tersebut, karena hidrokarbon pada batuan dasar akan terkonsentrasi pada rekahan yang membuat batuan dasar tersebut memiliki porositas rekahan yang baik. Karakteristik rekahan yang akan dikji adalah tingkat intensitas rekahan, densitas rekahan dan porositas rekahan pada 2 sumur pemboran di daerah penelitian, dengan beberapa rentang kedalaman yang ditentukan. Rentang kedalaman yang berbeda akan memperlihatkan hasil yang berbeda pula. Nilai intensitas, densitas, dan porositas rekahan tidak selamanya memiliki puncak pada kedalaman yang sama, dikarenakan beberapa faktor yang mempengaruhi seperti luas rekahan dan ketebalan rekahan. Porositas rekahan akan menjadi hal yang menarik karena merupakan salah satu syarat untuk menjadi reservoir.
PALEOCURRENT STUDY OF NYALINDUNG FORMATION THROUGH MOLLUSCS PALEONTOLOGICAL ASPECTS IN CI GALASAR TRAVERSE SECTION, SUKABUMI, WEST JAVA Nisrina Bahiyah Kesuma
Bulletin of Geology Vol 6 No 2 (2022): Bulletin of Geology Special Issue: International Seminar on Earth Sciences and Te
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

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Abstract

Nyalindung Formation contains mollusc fossils in the Classes of Gastropoda and Bivalvia which can be used as environmental proxy for paleocurrent study, although this study has not been carried out in this rock unit. Located in Ci Galasar River, Nyalindung District, Sukabumi Regency, the research traverse section showed beds of mollusc fossils with several stratigraphic unit and locality fossils of Middle Miocene. Paleocurrent analysis was conducted in four location distributed in three different stratigraphic unit. Based on molluscs shells’ orientation, Nyalindung Formation in research area was deposited in different current direction. Measured in four locations, the current showed changes in the ancient currents from bimodal, complex, unimodal within direction N 291 ° -300 ° E, and unimodal in N 281 ° -290 ° E direction. These changes are combined with fossils association and later interpreted as changes in depositional environment setting. The bimodal current alongside the presence of Turritella terebra talahabensis and Cypraea sp. indicates litoral environment. Meanwhile, complex shells’ orientation with the presence of Gemmula (Gemmula) granosa woodwardii, Dientomochilus javanus, and Terebra talahabensis indicates litoral to neritic environment that is strongly affected by waves. The unimodal current in N 291 ° -300 ° E showing similar fossil association with complex current indicates similar environment setting, which is litoral to neritic, but with lower influenced of waves and more on faster unidirectional current. Lastly, N 281 ° -290 ° E current direction showed large bivalves fossil association such as Chione tjikoraiensis and Cavatodens jonkeri which indicates inner neritic environment influenced by unidirectional current. Based on tectonic setting in Middle Miocene, the unidirectional current affecting the deposition of Nyalindung Formation is suspected as long shore current.
PARAGENESIS MINERAL DAN INKLUSI FLUIDA PADA ENDAPAN EPITERMAL, AREA MAIN RIDGE DAN OSELA, DISTRIK BAKAN, SULAWESI UTARA Rizqi Faishal Sipatriot; Andri Slamet Subandrio
Bulletin of Geology Vol 4 No 1 (2020): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

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Abstract

This research was conducted to determine mineral paragenesis and the characteristics of hydrothermal fluids which form high sulfidation epithermal deposits. The research was conducted in the Main Ridge and Osela areas, Bakan Distict, Motandoi Village, East Pinolosian District, Bolaang Mongondow Regency, North Sulawesi Province. Research methods include megascopic petrology, petrographic, mineragraphic, geochemical and fluid inclusion analysis. The association of minerals, intensive silicification process and vuggy textures indicate the presence of high sulfidation epithermal mineralization. In the Main Ridge area the range content of Au 0.4-1 g/t, Ag 1-3 g/t, Cu 5-63 g/t, Pb 5-55 g/t, Zn 4-5 g/t, whereas in the Osela area the range content of Au 1-89.4 g/t, Ag 4-33 g/t, Cu 306-403 g/t, Pb 30-120 g/t, Zn 14-41 g/t, the pattern corresponds to the presence of euhedral pyrite, chalcopyrite and enargite-luzonite in the Osela area and not present in the Main Ridge area. Main Ridge area has homogeneity temperature (Th) 212 oC, salinity 2.5 wt. % NaCl eq., and mineralization depth 210 m, in the Osela area it has Th 267 oC, salinity 2.9 wt. % NaCl eq., and mineralization depth 620 m. Fluid inclusion data indicate the mixing of hydrothermal fluids that develop in the Main Ridge area, while the Osela area shows the dilution of hydrothermal fluids during the process of fluid evolution.
GEOLOGI BATUBARA DAERAH TANJUNG ENIM, KABUPATEN MUARA ENIM, PROVINSI SUMATERA SELATAN Yan Rizal
Bulletin of Geology Vol 5 No 2 (2021): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

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Abstract

This paper is based on research results to obtain an overview of the geology of the Tanjung Enim area and its coal potential. Data processing was performed using Minescape 5.7 software. The research was conducted in an area of ​​52.8 km2. The rock units found can be divided into six rock units, namely the Sandstone Unit, the Claystone Unit including the seven main coal seams in it (coal seams A1, A2, B, B1, B2, C, D), Sandstone Unit - Siltstone including four hanging coal seams. . Sandstone Unit - Tuff, Andesite Intrusion Unit, and Alluvial Deposits Unit. The Claystone Unit and Sandstone Unit - Batulanau are equivalent to the Muaraenim Formation, which is a coal-bearing formation in the study area. The results of the calculation of coal resources are based on surface mapping data and supported by 27 drill well data belonging to PT. Bukit Asam, Tbk., It was found that the hanging coal seam resource content was 25,570,170 tons and the main coal seam was 1,275,631,640 tons.The coal quality rating in the hanging coal seam is Subbituminous B Coal, A1 coal seam is Subbituminous A Coal while the A2, B, B1, B2, and C coal seam ratings are High volatile C Bitumious.
ANALISIS KUALITAS AIR TANAH PADA AKIFER DANGKAL UNTUK KEBUTUHAN HIGIENE SANITASI DI DESA BUMI HARAPAN, KABUPATEN PENAJAM PASER UTARA, PROVINSI KALIMANTAN TIMUR Imam Priyono; Yohanes Stefanus Samuel Wowiling
Bulletin of Geology Vol 7 No 2 (2023): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

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Abstract

Desa Bumi Harapan merupakan desa terdekat dari pusat pengembangan Kawasan Ibu Kota Nusantara (K-IKN). Dalam prosesnya, akan semakin banyak terjadi perpindahan penduduk ke daerah ini. Semakin tinggi jumlah penduduk menyebabkan semakin tinggi juga jumlah pemakaian air. Oleh karena itu, tujuan dilakukannya penelitian ini adalah untuk membahas mengenai kualitas air tanah untuk kebutuhan higiene sanitasi sebagai aspek penunjang kehidupan warga ibu kota yang baru. Metode yang digunakan adalah studi literatur serta pengambilan data primer yaitu pengukuran sampel air tanah pada 40 titik sumur gali milik warga dan pengambilan sampel air tanah pada perwakilan 4 titik sumur gali. Sampel air tanah dianalisis di Laboratorium Kesehatan Daerah (Labkesda) Kota Balikpapan sesuai dengan baku mutu air higiene sanitasi pada PERMENKES No. 32 Tahun 2017 dan hasil analisis parameter tersebut akan ditentukan kualitasnya melalui metode Indeks Pencemaran (IP) pada KEPMEN LH No. 115 Tahun 2003. Terdapat beberapa parameter yang nilainya tidak sesuai dengan baku mutu meliputi kekeruhan, pH (kondisi asam), besi (Fe2+), mangan (Mn2+), zat organik (KMnO4), total coliform, dan E. coli. Analisis Indeks Pencemaran (IP) menunjukan kualitas air tanah untuk kebutuhan higiene sanitasi pada daerah penelitian tergolong dalam cemar ringan. Litologi daerah penelitian dominan tersusun oleh satuan batu lempung yang merupakan bagian dari Formasi Pamaluan. Batu lempung tersebut membentuk sistem hidrogeologi tertutup sehingga membuat air tanah menjadi asam. Selain itu, batu lempung berkontribusi pada sedikit peningkatan kadar besi terlarut dalam air tanah serta membuat air tanah menjadi keruh pada musim penghujan. Lapisan tanah pada daerah penelitian mempunyai ciri keberadaan mineral Hematit (Fe2O3) dan Goetit (FeO(OH)) yang berkontribusi pada peningkatan kandungan besi terlarut di dalam air tanah. Pengolahan air tanah yang disarankan pada daerah penelitian meliputi penyaringan air sederhana kombinasi dengan kapur dan kaporit, penyaringan keramik, Water treatment plant, dan pembuatan saluran buangan.
BASIN GEOMETRY ANALYSIS OF “NOKEN” AREA, MESOZOIC INTERVAL, AKIMEUGAH BASIN, PAPUA David Ontosari; Benyamin Sapiie; Hermes Panggabean; Edy Slameto
Bulletin of Geology Vol 2 No 2 (2018): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/bull.geol.2018.2.2.3

Abstract

Area "Noken" is located in the Akimeugah Basin, southern of Papua, covering onshore and offshore areas. In previous research, this area is still defined as laterally uniform passive margin basin during Mesozoic Era. A number of data include airborne-gravity anomaly, satellite gravity (TOPEX-Sandwell), land gravity, the total intensity of magnetism, oil and gas wells, seismic, and data retrieval surface sample obtained from the Center for Geological Survey, Geological Agency (PSG) and the Center for Data and Information (Pusdatin) Ministry energy and Mineral Resources (ESDM). Data processed by the method of forward-inversion modeling on Geosoft software and mapped by the method of minimum curvature in the Petrel software. The results of the analysis are fault and stratigraphic horizons in the Mesozoic Era. Their density recorded properly using distribution data from three wells (Well A, Well B, and Well C). Based on interpretation of gravity maps, total magnetic intensity maps, and subsurface geological model at the top of the Mesozoic, could be concluded that the geometry of the basin in "Noken" area during Mesozoic was dominated by the graben and half-graben, with the longitudinal axis of the fault trending relative northeast - southwest (NW- SW). Isopach map of the Mesozoic interval is supporting data to prove this basin geometry. In particular, during Triassic syn-rifts were formed and the post-rift sediments were formed during Jurassic - Cretaceous. The longitudinal axis of the basin is relatively parallel to the fault constituent. Based on the analysis of the structure of the subsurface geological structure map of the Mesozoic and Cenozoic, gravity sections and models can be interpreted that tectonic evolution during Cenozoic changes the geometry of the basin became trending northwest-southeast.
POTENSI PENGAYAAN TIMAH DAN UNSUR TANAH JARANG PADA ENDAPAN PLASER DI DAERAH AIR BELO, KABUPATEN BANGKA BARAT Firdaus El Afghani
Bulletin of Geology Vol 6 No 1 (2022): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

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Abstract

Daerah penelitian terletak di Air Belo, Kabupaten Bangka Barat. Penelitian bertujuan untuk menentukan daerah potensi timah dan unsur tanah jarang serta menentukan arah eksplorasi lanjut di daerah penelitian. Studi ini berfokus pada endapan aluvial yang tergolong sebagai endapan plaser. Endapan plaser di daerah penelitian terdiri atas dua jenis yaitu endapan aluvial purba dan endapan sungai aktif. Metode penelitian yang dilakukan antara lain pemetaan geologi, analisis geokimia, dan Grain Counting Analysis (GCA). Analisis geokimia dengan metode X-ray Fluorescence (XRF) Portable dilakukan terhadap sampel endapan aluvial dan granit untuk mengetahui kandungan timah dan unsur tanah jarang. Mineral berat yang terkandung dalam endapan aluvial diidentifikasi menggunakan GCA. Berdasarkan analisis geokimia, daerah pengayaan timah terletak di area tenggara daerah penelitian sedangkan daerah pengayaan unsur tanah jarang terbagi menjadi tiga area yaitu area baratlaut, baratdaya, dan utara daerah penelitian. Oleh karena itu, arah eksplorasi lanjut untuk timah yaitu pada arah tenggara daerah penelitian sedangkan arah eksplorasi lanjut untuk unsur tanah jarang yaitu arah baratlaut, baratdaya, dan utara daerah penelitian. Disisi lain, GCA menunjukkan bahwa mineral berat yang diduga membawa timah dan unsur tanah jarang adalah kasiterit, zirkon, dan turmalin. Densitas mineral menjadi faktor pengontrol penyebaran timah dan unsur tanah jarang di daerah penelitian. Sebagai contoh, unsur tanah jarang lebih tersebar dibandingkan timah dikarenakan mineral pembawa unsur tanah jarang seperti turmalin (ρ=2,9-3,1 g/cm3) dan zirkon (ρ=4,6-5,8 g/cm3) memiliki densitas yang lebih rendah sehingga lebih mudah tertransport dibandingkan kasiterit (ρ=6,98-7,01 g/cm3).

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