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INDONESIA
BULLETIN OF THE MARINE GEOLOGY
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.
Arjuna Subject : -
Articles 175 Documents
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Zonation of Marine Geological Environment of Wangi-wangi Island Waters and Adjacent Area Wakatobi Districs Southeast Celebes Province Agus Didit Haryanto; Yudi Darlan; Vijaya Isnaniawardhani; Nisa Nurul Ilmi
BULLETIN OF THE MARINE GEOLOGY Vol 33, No 1 (2018)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (3150.509 KB) | DOI: 10.32693/bomg.33.1.2018.546

Abstract

Wakatobi is one of coastal and marine tourism destination in South–East Celebes Indonesia. Coastal and marine characteristics of this area is composed of diverse biota as the main tourism attraction. Unfortunately, increasing human needs and activities, particularly coral reefs exploitation for construction and other life aspect, endanger the sustainability of marine environment of Wakatobi and the surrounding area. The purpose of this study is to determine marine geology environmental zonation in Wangi–wangi– Kapota Islands, as a consideration for local government in monitoring and regulating the coastal area. The methods that were applied in this study are coastal characteristic mapping, sedimentology, and mineralogy analyses from 34 marine surface sediments. Marine surface sediments have been collected by Marine Geological Institute (MGI) team in 2014. The result indicates that coastal and marine characteristic of Wangi–wangi and Kapota are influenced by geological processes since Middle Miocene. The seafloor morphology is characterized by gentle slopes around coastline that is abruptly changed to very steep slopes seaward. In general, the surficial sediments consisted of biogenic sands that are distributed around coastlines and trapped within coral reefs. Coastal types of this area are generally white coral sand beaches, coral reef platforms, and notches. The area of Wangi–wangi and Kapota can be divided into 4 (four) environmental zone: Flat Plain (Zone I), Sandy Beach (Zone II), Limestone and Coral Reef (Zone III), and Sedimentary Flat (Zone IV). Zone IV in the centre area between Wangi–wangi and Kapota island is considered as the most vulnerable area due to both natural and anthropogenic factor. Keywords: zonation, seafloor morphology, tourism, Wangi–wangi–Wakatobi, Southeast Celebes ProvinceWakatobi adalah salah satu tujuan wisata pantai dan laut yang menarik dikunjungi di Sulawesi Tenggara, Indonesia. Karakteristik pantai dan laut daerah ini disusun oleh keragaman biota laut yang merupakan daya tarik bagi pariwisata. Sayangnya, seiring dengan berkembangnya aktifitas dan kebutuhan manusia, terutama meningkatnya eksploitasi pemanfaatan terumbu karang untuk konstruksi bangunan dan berbagai aspek kehidupan, mengancam kelestarian lingkungan alami Wakatobi dan sekitarnya. Oleh karena itu, penelitian ini dilakukan dengan tujuan untuk membuat zonasi lingkungan pantai dan sekitarnya di Pulau Wangi–wangi dan Kapota, sehingga bisa memberikan pertimbangan bagi pemerintah setempat dalam pengawasan dan regulasi lingkungan kawasan pantai dan sekitarnya. Untuk penelitian ini, metode yang dilakukan adalah pemetaan karakteristik pantai, analisis sedimentologi dan mineralogi yang dilakukan terhadap 34 sedimen permukaan dasar laut. Pengambilan sampel sedimen permukaan dasar laut telah dilakukan oleh Tim Pusat Penelitian dan Pengembangan Geologi Kelautan (P3GL) pada tahun 2014. Hasil penelitian menunjukkan bahwa karakteristik pantai dan laut Wangi–wangi dan Kapota dipengaruhi oleh proses geologi yang telah berlangsung sejak Miosen Tengah. Morfologi dasar laut dicirikan oleh lereng landai di sekitar tepi pantai dan berubah dengan tegas menjadi curam ke arah laut lepas. Pada umumnya tekstur sedimen permukaan dasar laut terdiri atas pasir biogenik tersebar di sekitar garis pantai, dan mengisi di dalam terumbu koral. Jenis pantai sebagian besar berupa pantai pasir koral berwarna putih, pedataran pantai terumbu koral, serta morfologi pantai berupa takik. Kawasan pantai Wangi–wangi dan Kapota bisa dibagi ke dalam 4 (empat) zonasi lingkungan: Flat Plain (Zona I), Sandy Beach (Zona II), Limestone and Coral Reef (Zona III), dan Sedimentary Flat (Zona IV). Zona IV di area tengah antara Pulau Wangi–wangi dan Pulau Kapota merupakan area yang paling rentan mengalami kerusakan lingkungan akibat faktor alami dan aktifitas manusia. Kata kunci: zonasi, morfologi dasar laut, wisata, Wangi–wangi–Wakatobi, Provinsi Sulawesi Tenggara
Characteristics of Boleng Strait Sediments, East Nusa Tenggara, and its Relationship with Current Velocity Hananto Kurnio; Ai Yuningsih; Rina Zuraida
BULLETIN OF THE MARINE GEOLOGY Vol 33, No 1 (2018)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (2984.111 KB) | DOI: 10.32693/bomg.33.1.2018.387

Abstract

Islands of Nusa Tenggara are separated by narrow and deep straits resulted from complex tectonic activties. One of the strait is Boleng Strait where tidal current as high as 310 cm/s occurred which might be suitable for an ocean current power plant. Utilization of such resources would need various information of the area, one of them is sediment textures that characterized the seafloor and coastal area and their relationship to current velocity. Grain size analyses were conducted on 12 seafloor sediment samples and 26 coastal sediment samples to identify sediment texture. An additonal 14 seafloor sediment samples with limited volume were observed to determine their sediment types. The result of analysis yielded six types of seafloor sediments: Sand, Gravelly Sand, Sandy Gravel, Silty Sand and Sandy Silt. The sediment grain size is equally influenced by current velocity (r = 0.57) and water depth (r = 0.52) which is reflected by sediment distribution: coarse–grain sediments cover the area near Boleng Strait which has stronger current and fine–grain sediments cover the inner part of the Lewoleba Bay. Plot of six sets of mean grain size and current velocity on Hjulström diagram shows that most of seafloor sediments are on the move and one (SBL. 14) is being eroded. This condition might affect the turbine and thus needs to be taken into consideration when designing the turbine. Grain size analyses on coastal sediment samples show that the mean grain size of coastal sediments ranges between 0.19 mm and 0.62 mm with average value of 0.33 mm that is classified as medium sand. Sand fraction in coastal sediments composes 57% to 100% of the sediments. Observation on mineralogy of the sediments shows abundance of magnetite that concentrates in the fine and medium sand fractions. The presence of magnetite indicate that current–related selective entrainment occurs in the study area. This condition suggests that the coastal area is also strongly affected by ocean current.Key words: current velocity, sediment grain size, Boleng Strait.Aktivitas tektonik di Nusa Tenggara Timur menyebabkan terbentuknya batimetri yang kompleks di sekitar kepulauan tersebut yang dicirikan oleh adanya selat sempit dan dalam yang memisahkan pulau–pulau. Salah satu selat tersebut adalah Selat Boleng yang memiliki kecepatan arus terukur maksimum sebesar 310 cm/s yang dapat digunakan sebagai pembangkit energi listrik. Desain turbin arus akan membutuhkan banyak informasi, salah satunya adalah sedimen dasar laut dan pantai serta hubungannya dengan kecepatan arus. Analisis besar butir dilakukan pada 12 sampel sedimen dasar laut dan 26 sampel sedime pantai untuk menentukan jenis sediment. Sebanyak 14 sampel sedimen dasar laut dengan volume terbatas diamati untuk mengetahui jenis sedimen. Hasil analisis menunjukkan bahwa sedimen dasar laut terdiri atas enam jenis: Pasir, Pasir Kerikilan, Kerikil pasiran, Pasir Lanauan dan Lanau Pasiran. Ukuran butir sedimen dipengaruhi oleh kecepatan arus (r = 0.57) dan kedalaman laut (r = 0.52) yang tercermin pada distribusi sedimen: sedimen berukuran kasar menutupi dasar laut di dekat Selat Boleng yang berarus lebih kuat, dan sedimen berukuran halus menutupi dasar laut di bagian dalam Teluk Lewoleba. Plot enam set ukuran butir rata–rata dan kecepatan arus pada diagram Hjulström menunjukkan bahwa hampir seluruh sampel berada dalam kondisi bergerak dan bahkan satu (SBL. 14) sedang mengalami erosi. Kondisi ini akan mempengaruhi turbin sehingga perlu dijadikan pertimbangan saat mendesain turbin. Hasil analisis besar butir pada sedimen pantai menunjukkan bahwa ukuran butir rata–rata sedimen pantau berkisar 0.19 mm dan 0.62 mm dengan nilai rata–rata 0.33 mm yang termasuk dalam fraksi pasir sedang. Fraksi pasir dalam sedimen pantai menyusun 57%–100% sedimen. Pengamatan mineralogi menunjukkan melimpahnya magnetit yang terkonsentrasi pada fraksi pasir halus–sedang. Keberadaan magnetit menunjukkan adanya proses pemisahan yang berkaitan dengan arus laut. Kondisi ini menunjukkan bahwa daerah pantai Selat Boleng juga dipengaruhi oleh arus laut. Kata Kunci: kecepatan arus, ukuran butir sedimen, Selat Boleng.
Foraminiferal Analysis Related to Paleoceanographic Changes of Arafura Sea and Surrounding During Holocene Luli Gustiantini; Swasty Aninda Piranti; Rina Zuraida; Sangmin Hyun; Duddy A.S. Ranawijaya; F.X. Harkinz Hendro Prabowo
BULLETIN OF THE MARINE GEOLOGY Vol 33, No 2 (2018)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1806.333 KB) | DOI: 10.32693/bomg.33.2.2018.571

Abstract

Arafura Sea is located between Papua and Australia as a part of Sahul Shelf. It is strongly influenced by ITF, ITCZ replacement, monsoon, and ENSO circulation that interplay with local mechanism. To understand the paleoceanographic parameter changes during Holocene, we conducted foraminiferal quantitative analysis from a 152 cm length sediment core (Aru–07), in every 10 cm interval. This sediment core was retrieved from 134o00’33.6” E, 5o55’51.59” S, by RV Geomarin 3 belongs to Marine Geological Institute. Geochronology of the sediment was reconstructed based on 2 AMS 14C age dates, analyzed on organic samples. We identified 129 species of benthic and 24 species of planktonic foraminifera that is dominated by planktonic specimens with average of 53.14%. Predominant species are Globigerina bulloides (16.16%), Globigerinoides ruber (11.18%), and Neogloboquadrina dutertrei (5.65%). Benthic type is dominated by genera Bolivina, Bulimina, and Uvigerina by 25.86% (average). This might suggest eutrophic condition associated with carbon-rich or low oxygen level (dysoxic) condition. Single linkage cluster analysis revealed 3 paleoenvironmental zones, are: Zone I: older than 3.9 kyr BP, characterized by depleted oxygen level and nutrient enrichment compared to that of younger zone. Zone II: 3.9 – 2 kyr BP, characterized by oxygen content enrichment and deeper thermocline layer, related to the sea level rise during more neutral or La Niña like condition. Zone III: younger than 2 kyr BP, represent shallower thermocline layer, higher productivity which might be related to upwelling, and dysoxic condition. Sea level might be declined that related to more El Niño like condition.Keywords: Paleoceanographic changes, upwelling, foraminiferal analysis, Arafura SeaLaut Arafura berlokasi di antara Papua dan Australia sebagai bagian dari Paparan Sahul. Kondisi iklim sangat dipengaruhi oleh ITF, perpindahan ITCZ, monsun, dan ENSO yang berinteraksi dengan mekanisme lokal. Untuk memahami perubahan parameter oseanografi selama Holosen, kami melakukan analisis kuantitatif mikrofauna foraminifera, yang dilakukan terhadap sebuah bor sedimen laut sepanjang 152 cm (Aru–07) pada interval setiap 10 cm. Bor sedimen bawah laut ini telah diambil pada posisi 134o00’33.6” BT, 5o55’51.59” LS, menggunakan kapal penelitian Geomarin 3, Pusat Penelitian Geologi Kelautan. Geokronologi sedimen berdasarkan 2 radiocarbon dating, dianalisis dari sampel organik pada sedimen. Teridentifikasi 129 spesies bentik dan 24 spesies plangtonik yang didominasi oleh plangtonik dengan persentase rata-rata 53.14%. Foraminifera Jenis–jenis yang dominan antara lain Globigerina bulloides (16.16%), Globigerinoides ruber (11.18%), dan Neogloboquadrina dutertrei (5.65%). Sedangkan jenis bentik didominasi oleh genus Bolivina, Bulimina, dan Uvigerina, dengan persentase rata–rata 25.86%. Hal tersebut kemungkinan menunjukkan kondisi eutropik yang berasosiasi dengan kondisi kaya karbon dan rendah level oksigen (disoxic). Analisis cluster single linkage menunjukkan tiga zona utama, yaitu: Zona I: lebih tua dari 3.9 kyr BP, dicirikan oleh relatif rendahnya kandungan oksigen dan lebih kaya kandungan nutrien. Zona II: 3.9 – 2 kyr BP, dicirikan oleh meningkatnya kandungan oksigen, dan mendalamnya lapisan termoklin, berkaitan dengan meningkatnya muka air laut ketika kondisi netral atau kondisi seperti La Niña. Zona III: lebih muda dari 2 kyr BP, merupakan zona dengan kondisi lapisan termoklin yang mendangkal, produktifitas meningkat yang kemungkinan berkaitan dengan upwelling, dan kondisi disoxic. Muka air laut kemungkinan turun, berasosiasi dengan kondisi seperti El Niño.Kata kunci: Perubahan paleoseanografi, upwelling, analisis foraminifera, Laut Arafura
Inhibition Effects of Jakarta Bay Sediments to the Growth of Marine Diatom (Chaetoceros Gracilis) Triyoni Purbonegoro; Muhammad Reza Cordova; Rachma Puspitasari; Dwi Hindarti
BULLETIN OF THE MARINE GEOLOGY Vol 33, No 2 (2018)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (572.244 KB) | DOI: 10.32693/bomg.33.2.2018.547

Abstract

Jakarta Bay coastal ecosystem is known suffered from water pollution and habitat degradation. Solid and fluid waste from households and several industrial areas flow and ended up in the bay. Ecotoxicological studies are needed to assess the effects of pollutant on marine organism, including phytoplankton as the primary producer. Therefore chemical analysis and toxicity test were performed to investigate the impact of Jakarta Bay Sediments to marine diatoms Chaetoceros gracilis. Heavy metals concentration especially Cu, Pb, Cd, and Hg in the sediments were lower than in previous studies. It could be related to the stricter environmental regulations which started enforced at the end of 1990s. Meanwhile, PAH and pesticide were higher than in previous studies. Increasing activities and maritime traffic in surrounding area of Tanjung Priok Port area and most likely comes from other adjacent harbors (Muara Baru, Muara Angke, and Marina Ancol harbor) and the massive usage of the pesticide compound in the households of the Jakarta City area were suspected to be the reasons. Estuaries area and locations <10 km were identified and predicted would produce harmful effects since the concentration of Zn and Hg in those area exceeded Probable Effects Level (PEL) of Sediment Quality Guidelines (SQG). The growth responses of Chaetoceros gracilis were varied greatly. Most of the sites (24 from 31 sites) showed inhibition effects on the growth of diatoms, ranged from 1.75-35.33 % (17.75±9.59 %) relative to control, with the highest inhibition value was at Cengkareng Drain estuary (M2). The relationship between the concentration of contaminants and the inhibition response could not be clearly explained, however, there is an assumption that low concentrations of some heavy metals were suspected to give adverse effects on diatom’s growth.Keywords: sediment, toxicity, marine diatoms, Chaetoceros gracilis, Jakarta BayEkosistem Teluk Jakarta dikenal mengalami pencemaran air dan degradasi habitat. Limbah cair dan padat berasal dari perumahan dan industri mengalir dan berakhir di teluk tersebut. Kajian ekotoksikologi diperlukan untuk mengetahui pengaruh pencemar terhadap organisme laut termasuk fitoplankton sebagai produsen primer. Analisis kimia dan uji toksisitas dilakukan untuk mengetahui dampak sedimen Teluk Jakarta terhadap diatom laut Chaetoceros gracilis. Konsentrasi logam berat terutama Cu, Pb, Cd, dan Hg dalam sedimen lebih rendah dari penelitian sebelumnya. Hal tersebut berkaitan dengan peraturan lingkungan ketat yang mulai diberlakukan pada akhir 1990-an. Namun demikian, konsentrasi PAH dan pestisida lebih tinggi dari penelitian sebelumnya. Hal tersebut diduga kuat akibat dari peningkatan aktivitas dan lalu lintas maritim di daerah sekitar Pelabuhan Tanjung Priok, juga kemungkinan besar berasal dari pelabuhan lain yang berdekatan (Muara Baru, Muara Angke, dan pelabuhan Marina Ancol) serta akibat penggunaan besar-besaran senyawa pestisida kegiatan rumah tangga di wilayah Kota Jakarta. Daerah dan lokasi estuaria <10 km diidentifikasi dan diprediksi akan menghasilkan efek berbahaya karena konsentrasi Zn dan Hg di area tersebut melebihi Probable Effects Level (PEL) dari Pedoman Kualitas Sedimen (SQG). Respon pertumbuhan diatom laut Chaetoceros gracilis sangat bervariasi. Sebagian besar stasiun (24 dari 31 stasiun) menunjukkan efek penghambatan pada pertumbuhan diatom, berkisar antara 1,75-35,33% (17,75 ± 9,59%) relatif terhadap kontrol, dengan nilai penghambatan tertinggi di muara Sungai Cengkareng (M2). Hubungan antara konsentrasi kontaminan dan respon penghambatan tidak dapat dijelaskan dengan lebih pasti namun terdapat asumsi konsentrasi rendah dari beberapa logam berat diduga memberikan efek buruk pada pertumbuhan diatom.Kata Kunci: sedimen, toksisitas, diatom laut, Chaetoceros gracilis, Teluk Jakarta
Spectral Decomposition with Continuous Wavelet Transform for Hydrocarbon Zone Detection of North Bali Waters Tumpal Bernhard Nainggolan; Muh. Nur Iqlal Manai; Subarsyah Subarsyah
BULLETIN OF THE MARINE GEOLOGY Vol 33, No 2 (2018)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (8653.339 KB) | DOI: 10.32693/bomg.33.2.2018.556

Abstract

The East Java Basin is developed from an oceanic basin in front of Late Cretaceous Java Trench subduction zone to presently back-arc basin behind the Java-Lombok volcanic arc to the south. Many studies conclude hydrocarbon discovery in deep carbonate Ngimbang Formation. However, as a result of the active tectonic history of the region, there are fractures from Ngimbang Formation upward to the Oligo-Miocene Kujung Formation. It developes enhanced permeability medium for a good hydrocarbon migration. This paper presents shallow gas detection zone in the Mundu Formation by applying the spectral decomposition method with continous wavelet transform. Spectral decomposition can be effectively used to identify hydrocarbon reservoirs by analyzing seismic data in the frequency domain. Spectral decomposition with frequency 20 Hz shows the potential zone at time 779 - 832 ms which is suitable with depth 2237.5 - 2355.6 feet in well TRG-1. This method is supported with quantitative calculation of petrophysical analysis that determines 5 pay flag zones range from 2208.5 feet until 2347.5 feet.Keywords : East Java Basin, spectral decomposition, continuous wavelet transform, petrophysical analysisCekungan Jawa Timur terbentuk dari cekungan samudera di tepi zona subduksi pulau Jawa pada masa Cretaseous/Kapur Akhir hingga cekungan busur belakang sistem vulkanik Jawa-Lombok di selatan. Banyak penelitian menyimpulkan penemuan hidrokarbon pada lapisan karbonat Formasi Ngimbang yang dalam. Namun, sebagai akibat dari sejarah tektonik aktif dari wilayah tersebut, terdapat rekahan dari Formasi Ngimbang sampai ke atas hingga Formasi Kujung pada masa Oligo-Miosen. Kejadian tersebut menyebabkan timbulnya peningkatan permeabilitas medium yang baik untuk migrasi hidrokarbon. Makalah ini menyajikan deteksi zona gas dangkal pada Formasi Mundu dengan menerapkan metode dekomposisi spektral dengan transformasi wavelet kontinyu. Dekomposisi spektral dapat secara efektif digunakan untuk mengidentifikasi reservoir hidrokarbon dengan menganalisa data seismik dalam domain frekuensi. Dekomposisi spektral dengan frekuensi 20 Hz menunjukkan zona potensial pada kedalaman domain waktu 779 - 832 ms yang sesuai dengan 2237.5 - 2355.6 kaki pada sumur TRG-1. Metode ini didukung dengan perhitungan kuantitatif analisa petrofisika yang menentukan 5 zona gas mulai dari 2208.5 kaki hingga 2.347.5 kaki.Kata kunci : Cekungan Jawa Timur, dekomposisi spektral, transformasi wavelet kontinyu, analisa petrofisika
Channel Controlled Foraminiferal Distribution off Bakkhali, West Bengal, India Sachin Kumar Tripathi; Resmi S.; Satyendra Baraik; Debasis Sengupta; Amitava Lahiri
BULLETIN OF THE MARINE GEOLOGY Vol 33, No 2 (2018)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (4941.68 KB) | DOI: 10.32693/bomg.33.2.2018.557

Abstract

Study area is situated 8 km south of the Bakkhali Island, West Bengal of India and its subaqueous environment influenced by the fluvial processes such as Hooghly River in west and its distributary like Muri Ganga in the centre and Saptamukhi River in the east. To understand the submarine behavior of these channels and associated meiobenthos, total of 28 sediment samples have been studied in detail. The study reveal that a total of fifteen species of recent benthic foraminifera belonging to 13 genera under 11 families were present and their distribution mainly controlled by channel morphology and sediment character. Based on the distribution of these benthic foraminiferal species, two assemblages have been identified. First assemblage, observed within the Hooghly and Muri Ganga channel, where salinity is comparatively low and sediment is mainly dominated by silt and clay. The most dominating benthic foraminifers of this assemblage are Ammobaculites agglutinans, Cribrostomoides jeffreysii and Asterorotalia trispinosa. Whereas, second assemblage mainly comprise of A. trispinosa, Ammonia beccarii, Asterorotalia spp., Elphidium excavatum, Elphidium crispum and Ammonia tepida noticed over the sand bars and adjoining shallow area. Keywords: channel morphology, Muri Ganga, Hooghly, sand bar
Late Holocene Heavy Metals Record of Jakarta Bay Sediments Rina Zuraida; Riza Rahardiawan; Yani Permanawati; Indra Adhirana; Andrian Ibrahim; Nazar Nurdin; Haryadi Permana
BULLETIN OF THE MARINE GEOLOGY Vol 33, No 2 (2018)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1209.764 KB) | DOI: 10.32693/bomg.33.2.2018.569

Abstract

This paper reports copper, zinc, lead, cadmium, and chromium records of Jakarta Bay sediment since 600 AD and reonstruct environmental changes since that time. Jakarta Bay This study uses samples from a 150 cm long gravity core (TJ-17, 106.902488°E, 5.99381°S) that was acquired from the eastern part of Jakarta Bay in 2010 onboard RV Geomarin I by the Marine Geological Institute. Heavy metal content in Jakarta Bay sediments is used to track environmental changes onland from this site. Heavy metal concentration was analyzed using atomic absorption spectrometry on bulk samples that were taken in 5 cm interval. The results yield background level of Cu at 16 ppm, Zn at 75 ppm, Pb at 20 ppm, Cd at 0.01 – 0.15 ppm, and at Cr 80 ppm. Vertical record of heavy metals show two stages of environmental changes in the region: from 600 AD to 1600 AD and 1800 AD onward. These changes are interpeted as related to land use changes caused by human activity in the West Java region.
The Content of Placer Heavy Mineral and Characteristics of REE at Toboali Coast and Its Surrounding Area, Bangka Belitung Province Noor CD Aryanto; Udaya Kamiludin
BULLETIN OF THE MARINE GEOLOGY Vol 31, No 1 (2016)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (3256.08 KB) | DOI: 10.32693/bomg.31.1.2016.318

Abstract

Bangka Island and surrounding areas (including coast and seabed sediments) is known as main tin producer (cassiterite) in the world as these part of the Southeast Asia Granitic belt, but in fact, other than as a producer of tin, Bangka Belitung is also as heavy mineral placer (as accessories mineral) and REE potential producer which one based on the geological conditions.The potential of accessories minerals on sediment coast, other than cassiterite that occurs around Betumpak Cape, i.e: magnetite (7.86 %), ilmenite (4.9%), zircon (2.51%) and apatite (1.07%) respectively with content. While the content of monazite by using a hand drill has the potential content of up to 67.8 g/m3, while the content of monazite hypothetical resources off the coast of Bangka approximately 471,087,689 m3. As for the content of monazite hypothetical resources off the coast of South Bangka are approximately 23,995,820 m3.At Toboali coast, South Bangka the presence of REE in sediments are above the Earth's crust generally. They’re concentrations, such as La (5.07 to 199 ppm), Ce (106-394 ppm), Pr (5.11-59.7 ppm), Nd (16.5-201 ppm), Sm (9.97-52.3 ppm), Eu (0.18-1.55 ppm), Gd (9.11-39.3 ppm), Tb (1.35-8.14 ppm), Dy (9.01-56.3 ppm), Ho (1.89-12.3 ppm), Er (5.19-33.9 ppm), Tm (0.77-5.62 ppm), Yb (3.3-37.5 ppm) and Lu (0.71-5.41 ppm). LREE (La-Eu) highest content is generally found in the location of the tailings sludge (TBL-13C), not so in HREE (Gd-Lu), the highest content is widely available on the sandy beach sediments (TBL-13B). Tectonic environment of Toboali granitoid rocks by plotting a spider diagram refers to the chondrite normalization is continental magmatic arc.Keywords: Placer heavy mineral, REE, Granitic Belt, Bangka Belitung Province. Pulau Bangka dan daerah sekitarnya (termasuk di pantai dan sedimen dasarlaut) telah lama dikenal sebagai penghasil timah (kasiterit) utama di dunia sebagai dari bagian Jalur Granit AsiaTenggara, selainmineral berat sebagai pembawa unsur tanah jarang (UTJ) sangat dimungkinkan mengingat kondisi geologinya.Potensi mineral ikutan di sedimen pantai selain kasiterit, seperti di pantai Muntok antara lain, seperti magnetit (7,86%), ilmenit (4,9%), zirkon (1,32%) dan apatit (1,07%). Adapun kandungan monasit berdasarkan hasil pemboran tangan memperlihatkan kandungan hingga 67,8 g/m3 dengan kandungan potensi sumber daya di seluruh Pantai Bangka sekitar 471.087.689 m3 dengan potensi sumberdaya hipotetik di Pantai Bangka Selatan mendekati 23.995.820 m3. Di Pantai Toboali, Bangka Selatan kehadiran Unsur Tanah Jarang (UTJ) dalam sedimen, umumnya di atas konsentrasi kerak bumi. Kandungan unsur tanah jarang tersebut, seperti La (5,07 - 199 ppm), Ce (106-394 ppm), Pr (5,11-59.7 ppm), Nd (16,5-201 ppm), Sm (9,97-52,3 ppm), Eu (0,18-1,55 ppm), Gd (9,11-39,3ppm), Tb (1,35-8,14 ppm), Dy (9,01-56,3 ppm), Ho (1,89-12,3 ppm), Er (5,19-33,9 ppm), Tm (0,77-5,62 ppm), Yb (3,3-37,5 ppm) dan Lu (0,71-5,41 ppm). Kandungan tertinggi unsur tanah jarang ringan (UTJ-R) seperti La hingga Eu umumnya dijumpai pada lokasi tailing (TBL-13C) berbeda halnya dengan unsur tanah jarang berat (UTJ-B), kandungan tertingginya dijumpai pada sedimen pantai pasiran (TBL-13B). Berdasarkan hasil perajahan pada diagram laba-labanya, memperlihatkan bahwa lingkungan tektonik granit Toboali merupakan busur benua magmatik. Kata kunci: Mineral berat letakan, Unsur Tanah Jarang (UTJ), Jalur Granit, Provinsi Bangka Belitung
Coastal Protection of Southern Part of The Bintuni Bay From Oil Spill: An Environmental Sensitivity Index Approach Undang Hernawan; Rahayu Kusumah Risdianto
BULLETIN OF THE MARINE GEOLOGY Vol 32, No 2 (2017)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (2753.708 KB) | DOI: 10.32693/bomg.32.2.2017.395

Abstract

The southern part of Bintuni Bay with highly sensitive ecosystem conditions has evolved into an oil and gas industry where potential impacts on coastal and offshore environments need to be anticipated and planned comprehensively for environmental protection from oil spills. The main problem is the determination of areas that are sensitive and vulnerable to oil spills. This study is to analyze the factors and components that affect the level of environmental sensitivity and mapping Environment Sensitivity Index (ESI) to the oil spill.  The study was carried out by identifying and assessing each land units of its and use. Land use and land cover are interpreted through the use of satellite imagery with classification methods of guided satellite imagery. Field survey was also conducted in order to improve the accuracy of land use interpretation. Data analysis was performed by spatially by GIS method. The result indicated that ESI can be divided into five categories, are very sensitive (2,395.98 hectares or 2.38%), sensitive (13,133.53 hectares or 13.07%), moderately sensitive (17,902.78 hectares or 17.81%), low sensitive (52,409.14 hectares or 52.14%) and not sensitive (14,681.48 hectares or 14.61%). Although the study area is dominated by low sensitivity category, however the coastal protection from oil spill still should be prioritized.Keywords:  coastal protection, Environmental Sensitivity Index, Oil Spill, Bintuni Bay Wilayah bagian selatan Teluk Bintuni dengan kondisi ekosistem yang sangat sensitif telah berkembang menjadi industri minyak dan gas dimana potensi dampaknya terhadap lingkungan pesisir dan lepas pantai  perlu diantisipasi dan terencana secara komprehensif untuk perlindungan lingkungan dari kemungkinan tumpahan minyak. Masalah utamanya adalah penentuan daerah yang sensitif dan rentan terhadap tumpahan minyak. Penelitian ini menganalisis faktor dan komponen yang berpengaruh terhadap tingkat sensitivitas lingkungan dan pemetaan Indeks Sensitivitas Lingkungan (ISL) terhadap tumpahan minyak. Studi ini dilakukan dengan cara identifikasi dan penilaian unit lahan pada setiap penggunaan lahan. Penggunaan dan penutup lahan diinterpretasikan melalui penggunaan citra satelit dengan metode klasifikasi citra satelit terbimbing. Guna meningkatkan akurasi interpretasi penggunaan lahan juga dilaksanakan survei lapangan. Analisis data hasil penilaian unit identifikasi dilakukan secara spasial dengan metode SIG. Hasil penelitian menunjukkan bahwa ESI dapat dibagi menjadi lima kategori, yaitu sangat sensitif (2.395,98 hektar atau 2,38%), sensitif (13.133,53 hektar atau 13,07%), cukup sensitif (17.902,78 hektar atau 17,81%), sensitif rendah (52,409.14 hektar atau 52,14% dan tidak sensitif (14.681,48 hektar atau 14,61. Meskipun sebagian besar daerah daerah penelitian termasuk dalam kategori sensitif rendah, namun demikian perlindungan dari tumpahan minyak harus tetap diprioritaskan.Kata Kunci: perlindungan pantai, Indeks Sensitivits Lingkungan, tumpahan minyak, Teluk Bintuni 
Seabed Characterization through Image Processing of Side Scan Sonar Case Study: Bontang and Batam Subarsyah Subarsyah; Lukman Arifin
BULLETIN OF THE MARINE GEOLOGY Vol 34, No 1 (2019)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (10200.514 KB) | DOI: 10.32693/bomg.34.1.2019.590

Abstract

Acoustic waves propagate through a medium meet the Snell’s Law, its energy is reflected and some are scattered back at certain angle. The Side Scan Sonar (SSS) methods use this principle to identify seabed character. The intensity of the backscatter greatly depends on the morphology and sediments texture or rocks distributed on seabed.The intensity of backscatter waves is a representation of the morphology, sediments texture, and types of rock that distributed on the seabed, therefore it is possible to estimate sedimentary texture and identify the presence of rocks or coral reefs based on this information. In this publication authors estimate sediments texture, rocks or coral reefs based on backscatter intensity through the image processing on the Side Scan Sonar (SSS) image. Intensity will be converted into pixel values on the image with range value 1-255 (gray scale image) and entropy values which are statistical measures of randomness. Entropy value is maximum when most of pixel value image is in the middle of the colour spectrum range (between very dark to very bright), in contrast, it is minimum when pixel value is in the spectrum of very dark or very bright. Based on both parameters, classification is conducted. The classification is carried out on the SSS image at Bontang and Batam that have very different seabed characters.The classification results using an image processing shows that the distribution of sediment textures consist of 4 (four) classes for either Batam or Bontang. In the Bontang area, very fine sediments were identified which are associated with low value of both intensity and entropy - dark zones in gray scale images, and coarse sediments associated with high value of both intensity and entropy - bright zone in the gray scale image. Similar characteristic is observed in Batam area, which are identified fine sediment (associated to low intensity) - coarse sediments (high intensity). In contrast to Bontang, in Batam the entropy exhibit the opposite value, high value are correlated to fine sediment and vice versa. This might be due to the presence of rocks and sedimentary structures.Keywords: Side Scan Sonar, Intensity, Backscatter and entropy.Gelombang akustik sebagian besar energinya dipantulkan memenuhi prinsip snellius dan sebagian kecil dihamburkan balik dengan sudut. Metode Side Scan Sonar (SSS) memanfaatkan prinsip hambur-balik gelombang untuk mengidentifikasi permukaan dasar laut. Intensitas gelombang dari karakter hambur-balik akan sangat tergantung morfologi dan tekstur sedimen atau batuan dari permukaan dasar lautnya. Intensitas gelombang hambur-balik merupakan representasi dari morfologi, tekstur sedimen, dan jenis batuan yang tersebar di permukaan dasar laut, sehingga sangat memungkinkan untuk melakukan estimasi tekstur sedimen dan identifikasi keberadaan batuan maupun terumbu karang berdasarkan informasi tersebut. Pada publikasi ini akan dilakukan estimasi tekstur sedimen atau batuan berdasarkan intensitas hambur-balik melalui image yang dihasilkan oleh Metode Side Scan Sonar (SSS). Intensitas akan dikonversi ke dalam nilai pixel dalam image dengan rentang nilai 1-255 (gray scale image) dan nilai entropi yang merupakan ukuran statistik ketidakteraturan dari image. Entropi akan maksimum ketika nilai pixel kebanyakan di tengah dari rentang spektrum warna dan sebaliknya akan minimum ketika nilai pixelnya berada di spektrum warna sangat gelap atau sangat terang. Berdasarkan kedua parameter tersebut, kemudian dilakukan klasifikasi. Klasifikasi dilakukan pada data SSS Bontang dan Batam yang memiliki karakter permukaan dasar laut yang sangat berbeda.Hasil klasifikasi dengan image processing memperlihatkan pola sebaran tekstur sedimen masing-masing terdiri dari 4 (empat) kelas baik untuk Batam atau Bontang. Pada area Bontang teridentifikasi sedimen sangat halus yang berasosiasi dengan intensitas dan entropy rendah - zona gelap pada gray scale image dan sedimen kasar yang berasosiasi dengan intensitas dan entropy tinggi - zona terang pada gray scale image. Karakter yang sama juga teramati pada area Batam, yaitu teridentifikasi sedimen halus (berasosiasi dengan intensitas rendah) - sedimen kasar (intensitas tinggi). Namun, berbeda dengan di Bontang, di Batam nilai entropi menunjukkan nilai yang sebaliknya, yaitu nilai tinggi berkorelasi dengan sedimen halus, dan sebaliknya. Hal ini diperkirakan akibat keberadaan batuan dan struktur sedimen.Kata Kunci: Side Scan Sonar, Intensitas, Hambur balik dan Entropi.

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