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BULLETIN OF THE MARINE GEOLOGY

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Published by Marine Geological Institute of Indonesia

ISSN : 14106175 EISSN : 25278843 DOI : -

Core Subject : Science,

Earth & Planetary Sciences

Bulletin of the Marine Geology is a scientific journal of Marine geoscience that is published periodically, twice a year (June and December). The publication identification could be recognized on the ISSN 1410-6175 (print) and e-ISSN: 2527-8843 (on-line) twice a year (June & December) and it has been accredited by Lembaga Ilmu Pengetahuan Indonesia (Indonesian Institute of Sciences) by Decree Number: 818/E/2015. As an open access journal, thus all content are freely available without any charge to the user. Users are allowed to download, and distribute the full texts of the articles without permission from the publisher.

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Articles 173 Documents

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COASTAL CHARACTERISTICS OF SOUTH SINGKEP AREA, RIAU ISLANDS PROVINCE Noor C.D. Aryanto; Setyanto C.D. Pranoto
BULLETIN OF THE MARINE GEOLOGY Vol 29, No 1 (2014)
Publisher : Marine Geological Institute of Indonesia

Observations of coastal characteristics, such as coastal constituent lithology, oceanographic processes and the influence of human activities along the coastal area, are the factors that affect the coastal typology. The typology of coastal area can be divided into 3 types namely: (1) Sandy beaches, dominated by medium size quartz sand, gravelly sand and silt of alluvium deposits ; (2) Rocky beaches that belong to the Tanjung Buku Granite lithologic units and Persing metamorphic complex, its beach slope between 5Â° and 15Â°, and a fault structure encountered. The steep beach slopes (45Â°-50Â°) trends to offshore with the maximum depth of 28 meters below the sea level at the distance of 3.5 km from the its shore line. At the depth of 20 m, there are a foot slope of 1.5 km width interpreted as the fault plane; (3) Muddy beaches is characterized by mangroves, gentle beach slopes until flats. Those sandy and muddy beaches are alluvial deposits of Quarternary sediments. Keywords: Coastal characteristics, relief, oceanographic processes and South Singkep Pengamatan karakteristik pantai, seperti litologi penyusun tubuh pantai, proses-proses oseanografi serta pengaruh aktivitas manusia di sepanjang pantai merupakan faktor-faktor yang mempengaruhi tipologi pantai. Tipe pantai di daerah penelitian, dapat dibagi menjadi 3 jenis pantai, yaitu: (1) Pantai berpasir, disusun oleh dominasi pasir kuarsa, berukuran menengah, pasir kerikilan dan lanau dari alluvium, serta kemiringan pantai rendah; (2) Pantai berbatu merupakan bagian dari satuan batuan Granit Tanjung Buku dan Kompleks metamorfik Persing, kemiringan pantai antara 5Â° hingga 15Â° serta dijumpai sesar. Kearah laut kemiringan lerengnya makin besar (45Â°-50Â°) dengan bagian terdalam mencapai 28 meter pada jarak 3,5 km dari garis pantai. Pada kedalaman laut 20 m, terdapat kaki lereng ( foot of slope) dengan lebar 1,5 km yang diperkirakan sebagai bidang sesar; (3) Pantai berlumpur yang dicirikan oleh tanaman bakau memiliki kemiringan pantai yang relatif datar.Pantai berpasir dan pantai berlumpur merupakan endapan aluvium yang berumur Kuarter. Kata kunci: Karakteristik pantai, relief, proses oseanografi dan Singkep Selatan

ABNORMAL MICROFAUNAL SHELLS AS EARLY WARNING INDICATOR OF ENVIRONMENTAL CHANGES SURROUNDING BERAU DELTA, EAST KALIMANTAN Kresna Tri Dewi; Yusuf Adam Priohandono
BULLETIN OF THE MARINE GEOLOGY Vol 26, No 1 (2011)
Publisher : Marine Geological Institute of Indonesia

A total of 25 sediment samples from surrounding Berau Delta, East Kalimantan have been used for microfaunal study. It is found some abnormal shells of ostracoda, foraminifera and other forms with darkish shells (black, dark green and dark brown). These forms were analyzed using SEM-Energy Dispersive X-ray spectroscopy (EDX or EDS) to know their chemical composition. The result shows that these abnormal forms composed of CaO, SiO2, C, FeO, Al2O3, K2O, and small amount of Na2O and Cl. They may derive from different sources: CaO and MgO from neutralized component during the environmental management to handle the Acid Mine Drainage (AMD). The other components may derive from coal ash during combustion process or other activities. From this result, the small amount (less than 5%) of abnormal shells may be used as early warning indicator of environmental changes in the study area. Keywords: abnormal microfaunal shells, chemical composition, Berau Delta. Sebanyak 25 sampel sedimen dari sekitar Delta Berau, Kalimantan Timur telah digunakan untuk studi mikrofauna. Ditemukan cangkang abnormal dari ostracoda, foraminifera dan spesimen bentuk lain dengan cangkang kegelapan (hitam, hijau tua dan coklat tua) Bentuk-bentuk ini kemudian dianalisa menggunakan SEM-Energy Dispersive X-ray spectroscopy (EDX or EDS) untuk mengetahui komposisi kimiawinya. Hasilnya menunjukkan bahwa cangkang-cangkang mikrofauna yang abnormal ini mengandung CaO, SiO2, C, FeO, Al2O3, K2O, dan sedikit kandungan Na2O dan Cl. Komponen ini kemungkinan mempunyai sumber yang berbeda: CaO dan MgO mungkin berasal dari bahan penetral selama pengelolaan lingkungan untuk mengatasi air asam tambang (AMD). Komponen lain berasal dari abu batubara saat proses pembakaran atau aktivitas lain. Jumlah cangkang abnormal yang sedikit (kurang dari 5%) ini kemungkinan dapat digunakan sebagai indikator peringatan dini adanya perubahan lingkungan di daerah penelitian. Kata kunci: cangkang mikrofauna abnormal, komposisi kimiawi, Delta Berau

THE RATE OF SEDIMENTATION ESTIMATION OF TANJUNG API-API ESTUARY SOUTH SUMATERA BY USING 210Pb PROFILE Purnomo Raharjo
BULLETIN OF THE MARINE GEOLOGY Vol 25, No 1 (2010)
Publisher : Marine Geological Institute of Indonesia

Sedimentary processes occur intensively in Tanjung Api-Api area situated in the estuary of Musi Banyuasin river. A study on 210Pb isotopes of the sediments has been done to understand the rate of sedimentation. For that purpose, the Marine Geological Institute of Indonesia (MGI) has also conducted bathymetry and sediment distribution mappings. Two samples represent depths of 17-30 cm and 190-210 cm below sea floor give age of 11.54 and 22.45 years. The average of sedimentation rate is 2.03 cm/years (from 0 to 0.3 m below seafloor) and 8.9 cm/years (until 2.1 m depth below seafloor). The result shows, decreasing sedimentation rate upward, that indicates the surficial sediment less influenced by wave and surface current nowadays. Keywords : 210Pb isotope, rate sedimentation, Tanjung Api-Api Proses sedimentasi yang intensif terjadi di kawasan Tanjung Api-Api yang terletak di muara Sungai Banyuasin. Penelitian isotop sedimen 210Pb untuk mengetahui kecepatan sedimentasi telah dilakukan oleh Puslitbang Geologi Kelautan, selain itu dilakukan pula pemetaan batimetri dan sebaran sedimen permukaan dasar laut. Dua buah contoh sedimen mewakili kedalaman 17-30 cm dan 190-210 cm di bawah dasar laut memeperlihatkan umur 11,54 dan 22,45 tahun. Kecepatan sedimentasi rata-rata 2,03 cm/tahun (pada kedalaman 0-0,3 meter di bawah permukaan dasar laut) dan 8,9 cm/tahun (hingga kedalaman 2,1 meter di bawah dasar laut). Hasil tersebut menunjukkan penurunan kecepatan sedimentasi ke arah atas, yang mengindikasikan bahwa pada saat ini gelombang dan arus kurang berpengaruh terhadap proses sedimentasi. Kata kunci : isotop 210Pb, kecepatan sedimentasi, Tanjung Api-Api

Tsunami Potential Due To Strike-Slip Earthquake Affected by Submarine Landslide Wiko Setyonegoro
BULLETIN OF THE MARINE GEOLOGY Vol 31, No 2 (2016)
Publisher : Marine Geological Institute of Indonesia

The most of earthquakes in the western part of North of Sumatra, Indonesia have tsunami potential. This paper discuss about tsunami height which was triggered by large energy of earthquake along strike-slip fault and submarine landslide. Beyond of a view historical tsunamis in the western part Sumatra in Aceh, which was occured on April 11, 2012 have given several questions for the majority of earth scientist in relation with the potential for tsunami. The 8.6 M earthquake might have no tsunami potential significantly, with the hypothesis that mechanism of the earthquake source is strike-slip. However BMKG, in accordance with standard operating procedures stated that this earthquake "potential tsunami". But here we will give other parameters that affect a potential tsunami by performing the calculation of the effects of landslides. This paper describes how potential and kinetic energy spread during landslide and analysis of mechanism and underwater structures named as guyot as the cause of the earthquake along strike-slip fault. This paper discuss about scoup study on landslide which give the hypothesis that the type of submarine landslide or landslide of near shore cliff also will have influence to tsunami height or run-up. The key is, how strongly the all of disturbance above will increasing or decreasing ofÂ sea water volume. The result for the first case, strike-slip earthquake without the submarine landslide obtain maximum run-up in Meulaboh is 1.5864 m, with E~Mo (seafloor deformation). For the second case is strike-slip earthquake influenced by submarine landslide obtained ETotal ~1020 ~ Mo (seafloor deformation) which obtained tsunami run-up in Meulaboh 1.7726 m. So in this case, the landslide under the sea it also affected to the maximum tsunami height, but not significantly influence. For the last case, strike-slip earthquake influenced by landslide of near shore cliff: ETotal is estimated Ekfall ~ 1022 ~ Mw ~ 8 SR, equivalent with vertical of seafloor deformation and obtain tsunami run-up in Meulaboh 16.9372 m.Keywords: tsunami run-up, fault, strike-slip, submarine landslide, uppper the sea landslide, potential energy, kinetic energySebagian besar gempabumi yang terjadi pada area barat Sumatera Indonesia berpotensi tsunami. Tulisan ini memodelkan kemungkinan ketinggian tsunami yang dipicu oleh gempabumi dengan energi besar sepanjang sesar geser yang dipengaruhi oleh longsoran bawah laut. Gempabumi dengan kekuatan 8,6 Mw pada 11 April 2012 yang terjadi di bagian barat Sumatera telah menimbulkan kepanikan akan tetapi tidak menimbulkan bencana tsunami besar karena terjadi di sepanjang sesar geser kerak Samudera Hindia. Berdasarkan pemodelan, gempabumi sepanjang sesar geser dapat memicu tsunami besar bilamana diikuti oleh longsoran bawah laut. Tujuan dari penelitian ini adalah untuk memodelkan propagasi gelombang tsunami dengan proses mekanisme gempabumi strike-slip yang dipengaruhi oleh kondisi batimetri, volume struktur, jumlah dan jenis tanah longsor bawah laut yang dapat memicu ketinggian gelombang tsunami. Perhitungan dan pemodelan ini melibatkan simulasi energi potensial dan energi kinetik yang mempengaruhi ketinggian gelombang tsunami pada garis pantai. Hasil pemodelan pertama, dengan anggapan gempabumi sesar geser yang tidak dipengaruhi oleh proses longsor bawah laut menghasilkan ketinggian tsunami di Meulaboh 1,5864 m, dengan E ~ Mo (deformasi dasar laut). Untuk kasus pemodelan kedua dengan anggapan gempabumi sesar geser disertai oleh longsoran di bawah permukaan laut diperoleh Etotal ~ 1020 ~ Mo (deformasi dasar laut) yang menghasilkan ketinggian tsunami di Meulaboh 1,7726 m. Untuk pemodelan ketiga, gempabumi sesar geser yang diikuti oleh longsoran di tebing dekat pantai dengan Etotal diperkirakan Ekfall ~ 1022 ~ Mw ~ 8 SR setara dengan jenis mekanisme deformasi vertikal yang dapat menghasilkan ketinggian gelombang tsunami di Meulaboh sampai dengan 16,9372 m. Kata Kunci: run-up tsunami, sesar geser, longsoran bawah laut, longsoran diatas permukaan laut, energi potensial, energi kinetik

STUDY OF GAS POTENCY BASED ON GRAVITY ANOMALY MODELING AND SEISMIC PROFILE ANALYSIS AT BANGGAI-SULA BASIN Ediar Usman; Panuju Panuju
BULLETIN OF THE MARINE GEOLOGY Vol 28, No 2 (2013)
Publisher : Marine Geological Institute of Indonesia

Banggai-Sula Basin is one of the basins with character of the micro-continent derived from northern part of Australia. Some traces the migration in the central part of Papua are slate, schist, and gneiss, current movement is facilitated by the Sorong Fault, which runs from the northern part of Papua to eastern part of Sulawesi. Results of gravity anomaly model (2D and 3D), seepage distribution, seismic and fields existing of oil and gas production in the western part of the Banggai-Sula Basin obtained a new prospect area in the northern part of Peleng Island, western part of Banggai Island, southern part of Banggai-Taliabu Islands, western and eastern part of Sulabesi Island. The new prospect area is reflected in the centre with form of the low morphology on gravity model and prospect trap on seismic data in the western part of Tolo Bay. Results of chemical analysis on the source rock of Buya Formation on Tmax vs Hydrogen Index (Tmax vs HI) Diagram shows the type III kerogen quality and the Oxygen Index vs Hydrogen Index (OI vs HI) Diagram shows the gas prone Type II, so that giving the impression that this area has the potential to containing the gas. The quality of the gas is included in the category of immature to mature type. Key word : marine geology, gravity anomaly model, trap, source rock, hydrocarbon quality, Banggai-Sula Basin Cekungan Banggai-Sula merupakan salah satu cekungan dengan karakter mikro-kontinen yang berasal dari pecahan Australia bagian utara. Beberapa jejak migrasi terdapat di bagian tengah Papua berupa batuan slate, schist, dan gneiss, pergerakannya saat ini difasilitasi oleh Sesar Sorong yang membujur dari Papua bagian utara hingga bagian timur Sulawesi. Hasil pemodelan gaya berat (2D dan 3D), daerah rembesan, seismik dan keberadaan lapangan produksi migas di bagian barat Cekungan Banggai-Sula diperoleh hasil daerah prospek baru di bagian utara P. Peleng, bagian barat P. Banggai, selatan P. Banggai-Taliabu, barat dan timur P. Sulabesi. Daerah prospek tersebut tercermin dari daerah pusat cekungan dengan bentuk morfologi rendahan pada data gaya berat dan prospek perangkap (leads) pada data seismik di bagian barat sekitar Teluk Tolo. Hasil analisis kimia batuan sumber pada Diagram Tmax vs Indeks Hidrogen menunjukkan kualitas kerogen tipe III dan pada Diagram Indeks Oksigen vs Indeks Hidrogen menunjukkan tipe II gas prone, sehingga memberikan gambaran bahwa daerah ini berpotensi mengandung gas. Kualitas gas tersebut termasuk dalam kategori belum matang sampai matang. Kata kunci : geology kelautan, model anomali graviti, perangkap, batuan induk, kualitas hidrokarbon, Cekungan Banggai-Sula

SUBMARINE VOLCANO CHARACTERISTICS IN SABANG WATERS Hananto Kurnio; Subaktian Lubis; Hersenanto Catur Widi
BULLETIN OF THE MARINE GEOLOGY Vol 30, No 2 (2015)
Publisher : Marine Geological Institute of Indonesia

The aim of the study is to understand the characteristics of a volcano occurred in marine environment, as Weh Island where Sabang City located is still demonstrated its volcanic cone morphology either through satellite imagery or bathymetric map. Methods used were marine geology, marine geophysics and oceanography. Results show that surface volcanism (sea depth less than 50 m) take place as fumaroles, solfataras, hot ground, hot spring, hot mud pool and alteration in the vicinities of seafloor and coastal area vents. Seismic records also showed acoustic turbidity in the sea water column due to gas bubblings produced by seafloor fumaroles. Geochemical analyses show that seafloor samples in the vicinities of active and non-active fumarole vent are abundances with rare earth elements (REE). These were interpreted that the fumarole bring along REE through its gases and deposited on the surrounding seafloor surface. Co-existence between active fault of Sumatra and current volcanism produce hydrothermal mineralization in fault zone as observed in Serui and Pria Laot-middle of Weh Island which both are controlled by normal faults and graben.Keywords: submarine volcano, hydrothermal mineralization, Sabang-Weh-Aceh. Tujuan kajian adalah memahami karakteristik suatu gunungapi yang berada dalam lingkungan marin, sebagaimana Pulau Weh dimana Kota Sabang terletak masih menunjukkan morfologi kerucut volkaniknya baik melalui citra satelit maupun batimetri. Metoda yang digunakan adalah geologi kelautan, geofisika kelautan dan oseanografi. Hasil menunjukkan bahwa volkanisma permukaan (kedalaman laut kurang dari 50 m) terdapat dalam bentuk fumarola, solfatara, lahan panas, mata air panas, kolam lumpur panas dan alterasi sekitar lobang kepundan dasar laut dan pantai. Rekaman seismik juga menunjukkan turbiditas akustik dalam kolom air laut akibat gelembung gas yang dihasilkan oleh fumarola dasar laut. Analisis geokimia menunjukkan bahwa contoh-contoh dasar laut sekitar lobang kepundan fumarola yang aktif maupun tidak aktif kaya akan logam tanah jarang. Ini ditafsirkan bahwa proses fumarola tersebut membawa REE melalui gas-gasnya dan mengendapkannya pada permukaan dasar laut di sekitar. Ko-eksistensi antara Sesar Sumatera aktif dan volkanisma Resen menghasilkan mineralisasi hidrotermal dalam zona sesar seperti teramati di Serui dan Pria Laot - bagian tengah Pulau Weh yang keduanya dikontrol oleh sesar normal dan graben. Kata kunci: gunungapi bawah laut, mineralisasi hidrotermal, Sabang-Weh-Aceh.

THE FORMATION OF SUBMARINE BARUNA KOMBA RIDGE ON NORTHEAST FLORES WATERS IN RELATION TO LOW ANOMALY OF MARINE MAGNETISM Lili Sarmili; Mustaba Ari Suyoko
BULLETIN OF THE MARINE GEOLOGY Vol 27, No 2 (2012)
Publisher : Marine Geological Institute of Indonesia

There are three submarine ridges found on northeast of Flores waters. One of them is Baruna Komba submarine ridge found on south of Komba (Batutara) Volcano. Two others are Abang and Ibu Komba volcanoes located more to the southeast of the Baruna Komba. The position of the Baruna Komba situated more closely to the active Komba volcano and it is considered that the formation of Baruna Komba ridge is younger than the Abang and Ibu Komba volcanoes. The Baruna Komba also interpreted before as a magmatic volcano. Data from marine magnetism shows that there is a low or negative anomaly on Baruna Komba ridge whereas on Abang and Ibu Komba ridges, they are high and positive anomalies. These data indicate that the Baruna Komba ridge is not a volcanic ridge but it is a submarine ridge formed by a volcanic detritus or non magnetized sedimentation. The low anomaly around these submarine ridges gives northwest to southeast lineation and we interpreted also as a big fault on the west side of these ridges. On the other hand, the Abang and the Ibu Komba ridges are closely related to submarine magmatic volcanoes. Keywords : The Baruna Komba, magmatic volcano, volcanic detritus, Northeast Flores Waters. Di perairan sebelah timur laut pulau Flores ditemukan tiga bukit bawah laut. Salah satunya adalah Baruna Komba sebagai bukit bawah laut yang ditemukan di selatan gunung api Komba. Dua bukit lainnya adalah Abang dan Ibu Komba di sebelah tenggara Baruna Komba. Posisi Baruna Komba terletak lebih dekat dengan gunung api Komba yang masih aktif sehingga ditafsirkan sebagai bukit bawah laut termuda dibandingkan gunung api bawah laut Abang dan Ibu Komba. Baruna Komba ditafsirkan sebelumnya sebagai gunung api juga. Dari data magnetik kelautan menunjukkan bahwa adanya anomali negatif atau rendah di atas Baruna Komba, sedangkan di atas Abang dan Ibu Komba menunjukkan anomali positif atau tinggi. Data magnetik ini menandakan bahwa bukit bawah laut Baruna Komba bukan sebagai gunung api tetapi terbentuk oleh material seperti lava, breksi gunung api dan lahar yang terendapkan sewaktu letusan gunung api Komba. Sebaliknya, bukit bawah laut Abang dan Ibu Komba dapat ditafsirkan sebagai gunung api bawah laut yang bersifat magmatik. Kata Kunci : Baruna Komba, gunung api bersifat magmatik, endapan vulkanik, perairan timur laut Flores.

DETERMINING A SUFFICIENT DEPTH OF PILE FOUNDATION ON THE PERTAMINA GRAVING DOCK DESIGN SORONG PAPUA Franto Novico
BULLETIN OF THE MARINE GEOLOGY Vol 24, No 1 (2009)
Publisher : Marine Geological Institute of Indonesia

Engineering geological aspect and bearing capacity of pile foundation are significant for safety of upper structure, especially for substantial constructions such as a docking ship. Moreover, it provides effectiveness and cost efficiency when applies in rural areas of Indonesia. This is due to lack of docking ship appropriately built at rural areas particularly in eastern areas of Indonesia. Karim island of Papua even though is a small island yet is very strategic as Pertamina place its transitory function on that island connecting its oil supply route to Sorong. Appropriate docking ship construction is required to aim the effective and efficient port management. Choosing the most suitable structure for a docking is also the key. Graving dock structure has been chosen by Pertamina as the most appropriate type of structure for the docking ship in Karim Island. The structure of graving dock planned to be built in Karim island Papua, is projected to be able to serve the maximum 7500 DWT ship capacity, with approximately dimension is 125 x 25 x 8 meters. Therefore, to support the plan, type and design of the best foundation is the key. There are two methods could be done in determining the type and bearing capacity foundation. Field and laboratory test applied ASTM, field observation result by applying Meyerhoff theory and laboratorial analysis derived from Tarzaghi theory. Those observation and analysis has confirmed that the soil layer at the graving dock design consists of three layers, those are; cover layer, silt-clay layer and clay rock unit. Therefore, the most suitable foundation to be constructed in that area is a pile massive foundation, with depth of pile foundation approximately -20 m below the land surface, and the ultimate point load pile massive for 30x30 cm â€“ 75x75 cm dimension approximately 79.76 â€“ 406.25 ton, and frictional resistance value approximately 24.59 â€“ 61.48 ton. Keyword : Pile Pondation, bearing capacity, Graving dock Aspek geologi teknik dan besarnya nilai kapasitas suatu pondasi tiang pancang merupakan suatu hal yang sangat penting demi keamanan pembangunan struktur bagian atas, khususnya untuk bangunan yang besar dan tinggi. Pembuatan dok kapal menjadi tuntutan yang tak bisa dielakkan demi terlengkapinya manajemen pelabuhan yang efektif dan efisiensi pada daerah yang terpencil. Bangunan graving dock kapal yang direncanakan pada Pulau Karim Papua, diproyeksikan untuk dapat melayani kapal dengan kapasitas maksimal 7500 DWT, dengan dimensi berkisar 125 x 25 x 8 meter. Jenis dan perencanaan pondasi yang tepat sangat penting guna menunjang keamanan bangunan graving dock itu sendiri. Metoda yang digunakan untuk mengetahui jenis pondasi dan daya dukung pondasi didapat dari hasil uji lapangan dan laboratorium. Pengujian lapangan dan laboratorium berdasarkan ASTM, analisis data lapangan mempergunakan metoda Mayerhoff sedangkan analisis data laboratorium mempergunakan metoda Terzaghi. Lapisan tanah pada rencana graving dock terdiri dari tiga bagian yaitu; lapisan penutup, lempung lanauan dan satuan batuan lempung. Untuk itu jenis pondasi yang dipilih adalah pondasi tiang pancang massif. Kedalaman pemancangan pondasi berkisar -20m dari muka tanah. Hasil analisis menunjukkan kuat tekan tiang pancang massif untuk diameter 30x30 cm hingga 75x75 cm berkisar 79.76 â€“ 406.25 ton, sedangkan untuk nilai tarik berkisar dari 24.59 hingga 61.48 ton. Kata Kunci : Tiang pancang, nilai kapasitas, Graving dock

INDICATION OF HYDROTHERMAL ALTERATION ACTIVITIES BASED ON PETROGRAPHY OF VOLCANIC ROCKS IN ABANG KOMBA SUBMARINE VOLCANO, EAST FLORES SEA Lili Sarmili; Johanes Hutabarat
BULLETIN OF THE MARINE GEOLOGY Vol 29, No 2 (2014)
Publisher : Marine Geological Institute of Indonesia

The presence of mineral alteration or secondary processes to rocks on submarine volcano of Abang Komba was caused by an introduction of hydrothermal solutions. Those are indicated by the presence of a resembly of minerals alteration seen in their petrographic analyses. They are characterized by replacement partially surrounding of plagioclase phenocrysts, partially replacing plagioclase by sericite, carbonate and clay minerals. The replacement of pyroxene partly by chlorite, and the presence of albitisation (secondary albite) contained in fine rectangular plagioclase sized. Other fitures occasionally observed by the presence of partial oxidation of ore minerals and the presence of quartz, and epidote as an alteration from plagioclase and pyroxene. Keywords : alteration, resembly of minerals alteration, oxidation, submarine vulcano of Abang Komba. Gejala alterasi atau proses-proses sekunder yang terjadi pada batuan di gunung bawah laut Abang Komba adalah disebabkan oleh introduksi larutan hidrotermal. Semua ini ditunjukkan dengan kehadiran kumpulan mineral ubahan yang terlihat dalam sayatan batuan. Kumpulan mineral ini dicirikan dengan adanya penggantian sebagian yang mengelilingi fenokris plagioklas, penggantian sebagian plagioklas oleh serisit, karbonat dan mineral lempung. Penggantian sebagian piroksen oleh klorit, dan adanya gejala albitisasi (albit sekunder) yang terdapat pada plagioklas berbentuk balokan yang berukuran halus. Gejala lainnya yang kadang-kadang teramati adanya oksidasi sebagian dari mineral bijih dan hadirnya kuarsa, serta epidot sebagai hasil ubahan plagioklas dan piroksen. Kata kunci : alterasi, kumpulan mineral ubahan, oksidasi, gunung bawahlaut Abang Komba.

DIAGENETIC FEATURES OF PALEO LAGOONAL REEF OF TACIPI AREA, SOUTH CELEBES Andri Slamet Subandrio; Ediar Usman
BULLETIN OF THE MARINE GEOLOGY Vol 26, No 2 (2011)
Publisher : Marine Geological Institute of Indonesia

Limestone outcrops of the Tacipi area is an ideal carbonate platform part of Neogene East and West Sengkang Basin that are located in the south part of Sulawesi, precisely in western of Bone city. The limestones of this area, outcropping mainly on the north-south oriented hills such as Temapole, Anadara, Tamping, Lappa, etc., are the best reef example in the Tacipi area, as the reef itself, its debris and detritus can be distinguished in the field. Throughout the ridges and pinnacle in Tacipi field the limestones are predominantly homogenous boundstones on the top and detrital bioclastic packstones with local grainstones, and wackestones at the bottom. There are four major reef zonation indentified pacth reef, barrier reef, fore reef and lagoon. The extensive freshwater leaching of fossil fragments and calcareous cement give the preservation of biomouldic and vug pore spaces. Abstract Limestone outcrops of the Tacipi area is an ideal carbonate platform part of Neogene East and West Sengkang Basin that are located in the south part of Sulawesi, precisely in western of Bone city. The limestones of this area, outcropping mainly on the north-south oriented hills such as Temapole, Anadara, Tamping, Lappa, etc., are the best reef example in the Tacipi area, as the reef itself, its debris and detritus can be distinguished in the field. Throughout the ridges and pinnacle in Tacipi field the limestones are predominantly homogenous boundstones on the top and detrital bioclastic packstones with local grainstones, and wackestones at the bottom. There are four major reef zonation indentified pacth reef, barrier reef, fore reef and lagoon. The extensive freshwater leaching of fossil fragments and calcareous cement give the preservation of biomouldic and vug pore spaces.

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