Ediar Usman
Marine Geological Institute

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The Mechanism of Sediment Depositional Environment of Core Drilling of Gilimanuk Coast, Bali and Ketapang, East Java, Based on Sediment Textures Ediar Usman
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 (4386.173 KB) | DOI: 10.32693/bomg.31.1.2016.343

Abstract

The analysis result of grains frequency curve and relation between grains size to cumulative have shown medium grains at  Gilimanuk (Core drilling-1) and coarse grains at Ketapang (Core drilling-2). In general both of them are showed by pattern uniformity, which is represented by the similar of curve pattern. On the grain size of -2 phi as medium gravel with percentage between 6.47 to 35.88%, while core drilling -2 on the size of -2 phi between 6.86 to 61.11%.The average grains size of core drilling -1 are gravel about 21.3%, sand 60.2%, silt 5% and clay about 0.4% while core drilling-2 are  characterized by  44.3%, sand 26.8%, silt 24.6% and clay about 0.6%. These result shows that at location of Core drilling -1 is dominated by sand where as at location of Core drilling -2 is dominated by gravel. These situation can be interpreted that the sediment at core drilling -2 location have influenced by strong marine current which can transport the large amount of gravel size compare to the location of Core drilling-1 which is dominated by sand. Based on  the relation shape of grains size curve versus cumulative frequency shows that the sediment of Core drilling-1is interpreted as a beach sand deposits and only one sample which shows as a river sand deposits which was found at depth 0 – 3 m depth. In general, the sample of Core drilling –2 shows that the pattern of sediment tend as a beach sand deposits and only one sample  which shows the combination between coastal deposits and river deposits ( 4 – 5 m depth). From this sample, the coarse to fine grains is deposited by coastal media and fine grains material (about 10%) is deposited by river media. The sample of river deposits is found as lamination  because the only one which is created from combination between coastal and river depos its from all sample of core drilling-2.Keywords: core drilling, grain sediments, media transport, environmental deposition Hasil analisis menggunakan kurva frekuensi butiran serta hubungan antara besar butir terhadap kumulatif menunjukkan dominasi ukuran butiran sedang di daerah Gilimanuk (Bor-1) dan kasar di daerah Ketapang (Bor-2). Pada kedua daerah tersebut, secara umum memperlihatkan pola keseragaman, yang ditunjukkan oleh pola kurva yang sama. Pada ukuran butir -2 phi (kerikil sedang) pada Bor-1 berjumlah antara  6,47 – 35,88%, sedangkan pada Bor-2 pada ukuran -2 phi berjumlah antara 6,86 – 61,11%.Kandungan rata-rata butiran pada Bor-1 adalah: kerikil 21,3%, pasir 60,2%, lanau 5% dan lempung 0,4%, sedangkan Bor-2 adalah: kerikil 44,3%, pasir 26,8%, lanau 24,6% dan lempung 0,6%. Hasil ini menunjukkan bahwa pada Bor-1 didominasi oleh pasir dan pada Bor-2 didominasi oleh kerikil. Hasil ini dapat memberi gambaran bahwa pada Bor-2 berarus lebih kuat karena mampu menstranspor butiran kerikil dalam jumlah yang lebih besar dibandingkan dengan Bor-1 yang didominasi oleh pasir. Berdasarkan beberapa kurva hubungan antara besar butir vs frekuensi komulatif pada Bor-1 menunjukkan endapan pantai (beach sand), hanya satu contoh menunjukkan endapan sungai (river sand), yaitu contoh B1 (0 – 3m). Pada Bor-2, secara umum menunjukkan pola yang lebih mendekati endapan pantai (beach sand), hanya satu contoh menunjukkan kombinasi endapan pantai dan endapan sungai (river sand), yaitu contoh B2 (4 – 5 m). Pada contoh ini, butiran berukuran kasar sampai halus diendapkan oleh media pantai dan ukuran halus dengan persentase sekitar 10% merupakan endapan sungai. Contoh endapan sungai adalah pada B2 (4 – 5 m) ini merupakan endapan sisipan karena satu-satu terbentuk dari kombinasi pantai dan sungai dari seluruh contoh pada Bor-2.Kata kunci:  pemboran inti, butiran sedimen, media transport, lingkungan pengendapan
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.