Hananto Kurnio
Marine Geological Institute

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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.
Tectonics of Volcanogenic Massive Sulphide (VMS) Deposits at Flores Back Arc Basin: A Review Noor Cahyo Dwi Aryanto; Hananto Kurnio
BULLETIN OF THE MARINE GEOLOGY Vol 35, No 2 (2020)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32693/bomg.35.2.2020.679

Abstract

The bathymetry, petrology, marine magnetic, and seismic-SBP data have identified the northwest-southeast direction submarine ridge that shows hydrothermal activity. This activity occurred through Mount Baruna Komba, Abang Komba, and Ibu Komba. The volcanic rocks are andesite basaltic lava flows, tuff, and pumice. The andesite basaltic lava shows porphyritic, intergranular, intersertal to glomeroporphyritic textures. The rock composes anhedral minerals of k-feldspar, plagioclase, and pyroxene. These minerals present in small-sized, short prismatic dispersed in very fine groundmass minerals or glasses. Most of the volcanic rocks have experienced various degrees of alteration. The k-feldspar and plagioclase are most dominantly transformed into sericite, clay mineral, carbonate, epidote and oxide mineral, opaque mineral, and secondary plagioclase through the albitization process, while pyroxene replaced by chlorite. Other minerals are biotite and quartz, and base metals are present Cu, Zn, Ag, As, Pb, and gold. Mineralization categorizes as the phyllic zone, sub-prophylithic zone, and phyllic-potassic zone that formed at a temperature range of 250-400oC. The submarine hydrothermal alteration in the Komba Ridge is associated with a volcanogenic sulphide deposit controlled by crust thinning due to the crust rifts in the back-arc tectonic setting.Keywords: volcanic rocks, submarine hydrothermal alterations, Komba ridge, volcanogenic massif sulphide (VMS), back-arcData batimetri, petrologi, magnetic laut dan seismic-SBP telah memetakan dan mengidentifikasi suatu punggungan bawahlaut berarah baratlaut-tenggara yang memperlihatkan aktifitas hidrotermal bawah laut. Aktifitas tersebut muncul melalui Gunung Baruna Komba, Abang Komba dan Ibu Komba. Batuan gunungapi penyusun adalah aliran lava andesit basaltic, tuf dan pumis. Lava andesit basaltik memperlihatkan tekstur porfiritik, intergranular, intersertal to glomeroporfiritik. Mineral penyusun berupa k-felspar, plagioklas, dan piroksen dalam bentuk mineral anhedral, prismatik pendek berukuran kecil yang berada dalam masa dasar mineral sangat halus atau gelas. Batuan vulkanik telah mengalami ubahan dalam berbagai tingkat, dimana k-flespar dan plagioklas paling dominan terubah menjadi serisit, lempung, karbonat, epidot dan mineral oksida, opak atau plagioklas sekunder melalui proses albitisasi sedangkan piroksen mengalami proses ubahan digantikan oleh klorit. Mineral ubahan lainnya adalah biotit dan kuarsa dan logam dasar seperti Cu, Zn, Ag, As, Pb, dan emas. Mineralisasi dikategorikan sebagai zona filik, zona sub-profillitik, dan zona filik-potasik yang terbentuk pada kisaran suhu 250-400oC. Alterasi hidrotermal bawah laut di Punggungan Komba berasosiasi dengan suatu endapan sulfida volkanogenik yang dikontrol oleh penipisan kerak akibat peregangan kerak dalam tatan tektonik busur belakang.Keywords: batuan gunungapi, alterasi hidrotermal bawah laut, punggungan Komba, sulfida massif vulkanogenik, busur belakang
Review of Submarine Landslides in the Eastern Indonesia Region Hananto Kurnio; Tommy Naibaho; Catur Purwanto
BULLETIN OF THE MARINE GEOLOGY Vol 34, No 2 (2019)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (6357.203 KB) | DOI: 10.32693/bomg.34.2.2019.618

Abstract

his paper reviews submarine landslide potential in the eastern Indonesia by analyzing published and recently acquired bathymetric data and interpreting seismic reflection data. This review aims to study and invent hazards that might affect seafloor infrastructure construction such as optic cables, especially in the eastern Indonesia Region. The hazards were also recognized as source of tsunamis such as Palu Bay 2018 and Babi Island north of Flores Island in 1992. On the other hand, submarine landslide is a common process of basin fill sedimentation in the region. As blessed with many active volcanoes, it has 130 of total the world 400, Indonesia should aware of tsunami induced by volcanoes especially the ones closed to the sea. There are five active volcanoes frequently produce tsunami in historical times: Anak Krakatau, Sunda Strait; Makian, Maluku Province; Sangihe, Sulawesi; Teon and Nila, Banda Sea; and Iliwerung, Lembata Island, east Lesser Sunda Islands.Key words: submarine landslide, volcanic tsunami, seafloor infrastructure, eastern Indonesia Makalah ini menelaah potensi langsoran dasar laut di wilayah Timur Indonesia melalui analisis publikasi dan data batimetri yang baru diambil serta penafsiran data seismic refleksi. Tinjauan longsoran dasar laut dimaksudkan untuk mempelajari dan menginventarisasi bencana yang mungkin bisa mempengaruhi pembangunan infrastruktur dasar laut seperti halnya kabel optic, terutama di wilayah Timur Indonesia. Bencana tersebut telah dikenal sebagai sumber beberapa tsunami seperti Teluk Palu 2018 dan Pulau Babi utara Lombok di tahun 1992. Sebaliknya, longsoran dasar laut merupakan proses sedimentasi pengisian cekungan yang biasa terjadi di wilayah tersebut. Dikarunia akan gunungapi terbanyak di dunia, sebab memiliki 130 dari 400 dunia, Indonesia harus menyadari bahaya tsunami yang ditimbulkan oleh aktivitas gunungapi terutama yang dekat laut. Terdapat lima gunungapi aktif yang sering menghasilkan tsunami dalam sejarah: Anak Krakatau, Selat Sunda; Makian, Provinsi Maluku; Sangihe, Sulawesi; Teon dan Nila, Laut Banda; dan Iliwerung, Pulau Lembata, Nusa Tenggara Timur.Kata kunci: longsoran dasar laut, tsunami gunungapi, infrastruktur dasar laut, Wilayah Indonesia Timur
Rare Earth Elements Vapor Transport By Fumaroles in the Post Caldera Complex of Weh Island Submarine Volcano, Aceh Province Northern Sumatra Hananto Kurnio; Ediar Usman
BULLETIN OF THE MARINE GEOLOGY Vol 31, No 2 (2016)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (3017.456 KB) | DOI: 10.32693/bomg.31.2.2016.317

Abstract

Research found out that fumaroles and solfataras are rare earth element (REE) vapor transport agents in Weh Island submarine volcano – Aceh. Shallow high resolution single channel seismic was used to map the distribution of seafloor fumaroles surrounding the submarine volcano. Samples of REE depositions were taken from Jaboi geothermal field, and mineralization zone at Pria Laot coast; as well as seafloor surrounding active fumaroles by divers.  Rare earth elements (REE) were analysed using ICP – MS (inductively coupled plasma – mass spectrometry) with detection limits ranged from 0.05 to 0.1 ppm (part per million).The central part of Weh submarine volcano is the most active REE deposition. This area is build by normal faults and grabens oriented north – south of open character which acted as channel for hydrothermal fluids reaching seafloor surface.Some REE abundances such as La, Ce, Pr, and Nd due to its location in the central of hydrothermal activity. This proximity explains such abundances of this andesitic component sample of agglomerate.  Keywords: REE, vapor transport, fumaroles, Weh Island, Aceh.Penelitian mendapatkan bahwa fumarole dan solfatara adalah sebagai agen transportasi uap Logam Tanah Jarang (LTJ) di gunungapi bawah laut Pulau Weh – Aceh, Provinsi Nanggroe Aceh Darussalam (NAD). Seismik saluran tunggal dangkal resolusi tinggi digunakan untuk memetakan fumarole dasarlaut di sekitar gunungapi bawah laut tersebut.Bagian tengah gunungapi bawah laut Pulau Weh merupakan area paling aktif pengendapan LTJ. Bagian ini dibangun oleh sesar-sesar normal dan graben berorientasi utara – selatan dengan karakter terbuka sebagai saluran untuk fluida hidrotermal mencapai permukaan dasar laut.Kelimpahan unsur tanah jarang La, Ce, Pr dan Nd dikarenakan posisinya pada pusat aktivitas hidrotermal. Kedekatan dengan pusat hidrotermal ini menjelaskan kelimpahan REE dari contoh komponen andesitic yang diambil dari aglomerat ini.Kata kunci: UTJ (Unsur Tanah Jarang), transportasi uap, fumarol, PulauWeh, Aceh.
Nickel in Buli Coastal Area, East Halmahera Hersenanto Catur Widiatmoko; Eddy Mirnanda; Hananto Kurnio
BULLETIN OF THE MARINE GEOLOGY Vol 35, No 1 (2020)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32693/bomg.35.1.2020.598

Abstract

Fragments of ultramafic, metamorphic, basalt and serpentine compose coastal sediments. These fragments derived from outcrops in hinterland as well as the coast. Existence of greywacke sandstone through microscopic observation in coastal sediments indicate deep sea derivation. Marine sediments also show almost the same composition with coastal sediments.Rock fragment abundances of ultramafic (10-47%), serpentine (12-24%) and metamorphic (3-12%) in stream and coastal sediments which have direct relation with the presence of nickel metal in the research area were resulted from petrographic analyses. While mineralographic analyses of heavy mineral concentrate from wooden pan show the existence of ferro nickel (Fe-Ni) and nickeline (Ni-As) in coastal and stream sediments. XRF analyses show nickel contents in seabed sediments 0.0140 to 0.793 %, chromite 0.0179 to 0.1128% and iron 1.2 to 6.85%. Coastal water nickel distribution is controlled by local trapped waves in Buli Bay that excite by equatorial Pacific Ocean waves propagate westward. Nickel occurrences in marine sediments would be an interesting further research.Keywords: nickel, Buli coastal area, East HalmaheraFragmen-fragmen ultramafik, metamorfik, basalt dan serpentin menyusun sedimen pantai. Fragmen-fragmen ini berasal dari singkapan baik di darat maupun di pantai. Dijumpainya fragmen batupasir grewake yang teramati melalui mikroskop dalam sedimen pantai mengindikasikan asal laut dalam. Sedimen dasar laut menunjukkan kecenderungan komposisi yang hampir sama dengan sedimen pantai. Kelimpahan fragmen batuan ultramafik (10-47%), serpentin (12-24%) dan metamofik (3-12%) dalam sedimen sungai dan pantai yang memiliki hubungan langsung dengan keberadaan logam nikel di daerah penelitian dihasilkan dari analisis petrografi. Sedangkan analisis mineralografi pada konsentrat mineral berat hasil dulang mendapatkan fero nikel (Fe-Ni) dan nikelin (Ni-As) dalam sedimen pantai dan sungai.Analisis XRF mendapatkan nikel dalam sedimen dasar laut dengan kandungan 0,0140 hingga 0,793%, kromit 0,0179 hingga 0,1128% dan besi 1,2 hingga 6,85%. Sebaran nikel di perairan pantai dikontrol oleh gelombang lokal yang ditimbulkan oleh gelombang Samudera Pasifik ekuator yang bergerak ke barat. Keterdapatan nikel dalam sedimen dasar laut dapat menjadi riset yang menarik di masa datang.Kata kunci : nikel, pantai Buli, Halmahera Timur.