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INDONESIA
Indonesian Journal on Geoscience
ISSN : 23559314     EISSN : 23559306     DOI : -
Core Subject : Science,
The spirit to improve the journal to be more credible is increasing, and in 2012 it invited earth scientists in East and Southeast Asia as well as some western countries to join the journal for the editor positions in the Indonesia Journal of Geology. This is also to realize our present goal to internationalize the journal, The Indonesian Journal on Geoscience, which is open for papers of geology, geophysics, geochemistry, geodetics, geography, and soil science. This new born journal is expected to be published three times a year. As an international publication, of course it must all be written in an international language, in this case English. This adds difficulties to the effort to obtain good papers in English to publish although the credit points that an author will get are much higher.
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Articles 6 Documents
Search results for , issue " Vol 4, No 2 (2009)" : 6 Documents clear
Evolusi Bentuklahan daerah Manado dan sekitarnya, Sulawesi Utara Poedjoprajitno, S.
Indonesian Journal on Geoscience Vol 4, No 2 (2009)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.2.145-155

Abstract

http://dx.doi.org/10.17014/ijog.vol4no2.20096Landform evolusion in Manado region has been strongly influenced by tectonic activities beside marine and volcanic ones. Based on surface and subsurface (shallow drilling) geological data, landform evolution of the studied areas can be grouped into four morphological environment units consisting of nine environment sets of morphology, these are: ( a). flood basin, ( b). tidal beach, (c).swamp, (d). river channel, (e).volcanic eruption, (f). flood basin influenced by water, (g).coastal/shore, (h). near shore, and (i). offshore. Collumnar analyses on nine drilling data show that the landform evolution history in the Manado region has undergone more than one tectonic event and three eruptions, proved by the presence of discontinuities on morphological environment units and composition, vertically.  
Karakteristik Batubara dan Batuan Sedimen Pembawanya, Formasi Talangakar, di daerah Lampung Tengah Kusnama, Kusnama; Panggabean, Hermes
Indonesian Journal on Geoscience Vol 4, No 2 (2009)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.2.133-144

Abstract

http://dx.doi.org/10.17014/ijog.vol4no2.20095The rock succession of coal bearing formation, situated in Lampung Tengah, occupies the basinal margin or the western part of South Sumatra Basin. Physiographically, the rock succession lies in the Palembang Zone which directly contacts with the southernmost Barisan Mountain Zone. The rock facies consists of conglomerate, and conglomeratic and quartz sandstones in the lower part, whilst the upper part comprises shale, claystone, mudstone, siltstone, and coal with coally shale and shaly coal intercalations. The rock facies of coal bearing unit is strongly believed to be part of the Oligo - Miocene Talangakar Formation deposited in a fluvial – paralic environment which further up section, it turns to be a sub-littoral deposit. The depositional environment strongly affected the coal characteristics and type. Stratigraphically, the rock unit is conformably overlain by the Early - Middle Miocene limestone unit and is intruded by the Middle – Late Miocene granodiorite. The basement of the Tertiary rock succession is metamorphics of the Gunungkasih Complex and the Cretaceous granitic rock. The normal fault controlling the area studied has a northwest - southeast direction and it caused the dip of coal trending north - east direction of 15º - 23º. The coal of the research area was deposited in wet forest swamp environment within a high to medium subsidence level. The coal is grouped to a high to low volatile bituminuous rank, included to a mature category.    
Penentuan Peringkat Bahaya Tsunami dengan Metode Analytical Hierarchy Process (Studi kasus: Wilayah Pesisir Kabupaten Sukabumi) Oktariadi, Oki
Indonesian Journal on Geoscience Vol 4, No 2 (2009)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.2.103-116

Abstract

http://dx.doi.org/10.17014/ijog.vol4no2.20093Hierarchy structure of a tsunami risk encompasses the study of hazard, vulnerability, and capac- ity factors. The focus of this research is hazard factors, with indicators comprise beach slope, beach coarseness (surface material), run up, and earthquake intensity. Computation method used in the deci- sion system is the Analytical Hierarchy Process (AHP). The AHP method is to determine the weight of indicators and matrices of hazard factor hierarchy. The final total score of the hazard factors will be useful for tsunami hazard mapping through a geographic information system (GIS). It consists of four hierarchies of  tsunami hazard that are high, middle, low, and safe levels. The coastal regions in Sukabumi having high tsunami disaster risk are the Gulf of Pelabuhanratu, Ciemas plain (Gulf of Ciletuh), Ujung Genteng Cape, and some parts of coastal plain areas in Sim- penan. Those having middle tsunami disaster risk are coastal area of Surade, Cibitung, Tegalbuleud, whereas those having low tsunami disaster risk are Cisolok cliff, Simpenan, and Ciemas cliff area. The other coastal zones are included into a safe area.  
Geochemical Signature of Mesozoic Volcanic and Granitic Rocks in Madina Regency Area, North Sumatra, Indonesia, and its Tectonic Implication Zulkarnain, Iskandar
Indonesian Journal on Geoscience Vol 4, No 2 (2009)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.2.117-131

Abstract

http://dx.doi.org/10.17014/ijog.vol4no2.20094Five samples consisting of two Permian-Triassic basalts, two Triassic-Jurassic granitic rocks, and a Miocene andesite were collected from the Madina Regency area in North Sumatra that is regionally situated on the West Sumatra Block. Previous authors have proposed three different scenarios for the geological setting of West Sumatra Permian Plutonic-Volcanic Belt, namely an island-arc, subduction related continental margin arc, and continental break-up. Petrographic analysis of the Mesozoic basaltic samples indicates that they are island-arcs in origin; however their trace element spider diagram patterns (Rock/MORB ratio) also show the character of back-arc marginal basin, besides the island-arc. Furthermore, their REE spider diagram patterns (Rock/ Chondrite ratio) clearly reveal that they were actually generated in a back-arc marginal basin tectonic setting. Meanwhile, the two Mesozoic granitic rocks and the Miocene andesite reflect the character of an active continental margin. Their spider diagram patterns show a significant enrichment on incompat- ible elements, usually derived from fluids of the subducted slab beneath the subduction zone. The high enrichment on Th makes their plots on Ta/Yb versus Th/Yb diagram are shifted to outside the active continental margin field. Although the volcanic-plutonic products represent different ages, their La/Ce ratio leads to a probability that they have been derived from the same magma sources. This study offers another different scenario for the geological setting of West Sumatra Permian Plutonic-Volcanic Belt, where the magmatic activities started in a back-arc marginal basin tectonic setting during the Permian-Triassic time and changed to an active continental margin during Triassic to Miocene. The data are collected through petrographic and chemical analyses for major, trace, and REE includ- ing literature studies.  
Indikasi munculnya Kubah Lava berdasarkan Rekaman Seismik Wittiri, S. R.
Indonesian Journal on Geoscience Vol 4, No 2 (2009)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.2.93-101

Abstract

http://dx.doi.org/10.17014/ijog.vol4no2.20092In the last two decades, there are six volcanoes erupting and are ended up with the growth of lava dome at the crater. Among them, formerly there are three volcanoes that have crater lakes. For the intermediate magma, like most Indonesian volcanoes, the lava dome formation is a usual phenomenon. The interesting symptom is indicated by the seismic waves. They are supposed to relate to the magma breakthrough into the surface. The seismic phenomena of those volcanoes have a similarity, which can be estimated that the  mechanism of rock fracturing is relatively similar.  
Waduk Parangjoho dan Songputri: Alternatif Sumber Erupsi Formasi Semilir di daerah Eromoko, Kabupaten Wonogiri, Jawa Tengah Bronto, Sutikno; Mulyaningsih, Sri; Hartono, G.; Astuti, B.
Indonesian Journal on Geoscience Vol 4, No 2 (2009)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.2.77-92

Abstract

http://dx.doi.org/10.17014/ijog.vol4no2.20091The Semilir Formation was typically originated from products of a very explosive volcanic activity, i.e. breccias, lapillistones, and tuffs containing abundant pumice. It has a light grey to white colour and high silica andesite to dacite in composition, mainly rich in volcanic glass and quartz. Sedimentary structures of these volcanic rocks are massive, grading, planar bedding, and cross-bedding to antidunes, with grain size varies from ash (≤ 2 mm) to lapilli (2 – 64 mm) to bomb and block (> 64 mm). The formation is widely distributed from the west side (Pleret and Piyungan areas, Bantul Regency, Special Province of Yogyakarta) until Eromoko area in the east (Wonogiri Regency, Jawa Tengah Province). Stratigraphically, the Semilir Formation underlies the Nglanggeran Formation, and overlies the Mandalika Formation in the eastern part and Kebo-Butak Formation in the western part. Geomorphological- and lithological analyses of the Semilir Formation in areas of Parangjoho and Song- putri Dams, Eromoko Sub-regency, Wonogiri Regency indicate that the two depressions were alternatively volcanic sources of the Semilir Formation in the Eromoko area. This is proved by the presence of co-ignimbrite breccias(co-ignimbrite lag fall deposits), that descriptively they are polymict breccias. This rock is characterized by a mixing of pumice and various hard rock fragments that primarily are juvenile materials (volcanic blocks, bombs), accessory-, and accidental rock fragments set in pumice-rich volcanic ash and lapilli sizes. The accessory materials came from older volcanic rocks, whereas the accidental ones were originated from basement rocks. During a caldera forming event or a destruction period of an older composite volcanic cone(s), all older rocks resting above the magma chamber were ejected to the surface by a very high magmatic pressure. Since they were heavier than the juvenile material, most accessory and accidental rock fragments were left (lag fall) in caldera rim behind the ash and pumice flow. In the dam areas of Parangjoho and Songputri, the lag fall fragments consisting of andesite, pyroxene andesite, dacite, and pumice, being 10 – 150 cm in diameter are set in pumice-rich lapilli tuffs. Some of the rock fragments are volcanic blocks and bombs, while the older rocks are angular to very angular shape, having prismatic jointing or jigsaw-crack structures. The eruptions in the Parangjoho and Songputri craters were controlled by north-south trending fractures, and they resemble to the Katmaian caldera explosion type.  

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