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Journal Cover Journal of Applied Geology
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  This is an Open Access Journal Open Access journal
   ISSN (Print) 2086-5104
   Published by Universitas Gadjah Mada Homepage  [28 journals]
  • Variation of Slab Component in Ancient and Modern Merapi Products: A
           Detailed Look into Slab Derived Fluid Fluctuation over the Living Span of
           One of the Most Active Volcanoes in Sunda Arc

    • Authors: Esti Handini, Toshiaki Hasenaka, Agung Harijoko, Yasushi Mori
      Pages: 1 - 14
      Abstract: Holocene eruptions of Merapi have produced both medium-K and high-K calc alkaline series which correspond to products older and younger than 1900 years respectively. The change has been attributed to increasing sediment input as the volcano matures. This study presents two Merapi samples which represent Ancient and Modern Merapi. The two samples are analyzed for subduction components including B, Ba, Sr, and Pb using X-ray fluorescence (XRF) spectrometer and prompt gamma ray analysis (PGA). Our finding shows that Ancient Merapi sample from Plawangan Hill lava is close in affinities with younger than 1900 years high-K magma series. On the other hand, Modern Merapi sample from 2006 eruption juvenile is plotted within medium-K magma series which are observed in eruption products older than 1900 years. Ratios of fluid mobile elements to high field strength element (HFSE) (i.e. B/Nb, Ba/Y, Pb/Nb) consistently show that Ancient Merapi sample has higher input of slab derived fluid than Modern Merapi sample. A model using B/Nb and Ba/Nb suggests that Plawangan magma requires 1.5 % of sediment derived fluid, higher than estimated in 2006 eruption magma (1.2 %) and medium-K series magma, and within the range of high-K series magma, to explain its slab component enrichment. This evidence suggests that slab derived component addition to the sub-arc mantle wedge highly fluctuates over short period of evolution of a volcano. One possible explanation is the presence of veined hydrous metasomatized sub-arc mantle as Merapi magma source which allows melting of different mantle area to produce fluctuation of slab components in the course of evolution of Merapi magmas.
      PubDate: 2017-11-13
      DOI: 10.22146/jag.30253
      Issue No: Vol. 2, No. 1 (2017)
       
  • Engineering Geology of Sidosari Area, Magelang, Central Java, Indonesia

    • Authors: Diyaning Ratri, I Gde Budi Indrawan
      Pages: 15 - 24
      Abstract: Development of settlement area in Sidosari area and the surroundings requires complete understanding of the engineering geological conditions, including susceptibility to landslides, to prevent damaged properties and loss of lives. Surface engineering geological mapping at a 1:25000 scale was conducted to develop a detailed landslide susceptibility map for spatial planning and to identify most controlling factor of landslides in the research area based on conditions of geomorphology, rock and soil, geological structure, groundwater seepage, and land use. The engineering geological mapping showed that landslides commonly occurred in the moderate slopes of the denudational hill landform having slope inclination ranging from 9 to 17°, in the areas covered by residual soils of the vitric tuff 2 unit, in the areas of no groundwater seepage, and in the settlement areas, including in Kranjang Lor area where soil creeping occurred. The high susceptibility zone covered 55.5 % of the research area and was characterized by having slope inclinations ranging from 9 to 35°, engineering geological units of vitric tuff 2 and tuff breccia, and land uses of rice and dry fields and settlement. The low cohesion and very high swelling potential of the residual soils of the vitric tuff 2 unit were considered to be the main controlling factor of landslides in the research area.
      PubDate: 2017-11-13
      DOI: 10.22146/jag.30254
      Issue No: Vol. 2, No. 1 (2017)
       
  • Lithostratigraphy of Tabul Formation and Onshore Geology of Nunukan
           Island, North Kalimantan

    • Authors: Salahuddin Husein
      Pages: 25 - 35
      Abstract: Nunukan Island is located in Northeast Kalimantan Basin, one of prolific basin in western Indonesia. However, this island lies in northern verge of the basin and hydrocarbon exploration were limited before the 1940s. No detail geological fieldworks has been published. This paper attempts to share geological information obtained from few accessible outcrops, particularly from the western part of the island where previous oil drilling were carried out. Most of the island have been built by Tabul Formation, which was also the main objective of reservoir for hydrocarbon exploration. It is composed of claystones, siltstones, and sandstones interbeds, deposited in transitional environment during Late Miocene. They exhibit coarsening upward sequence, the lower part composed of heterolitic sandstones deposited in tidal flats, and the upper part composed of arkosic sandstones deposited in distributary channels and mouthbars. The eastern coastal strip was constructed by Tarakan conglomerates, which have been deposited in fluvio-deltaic environment in Pliocene, unconformably over the Tabul clastics. Those Neogene deposition of paleo-Simengaris Delta apparently deformed and inverted in Plio-Pleistocene, contemporaneously with basaltic volcanism which spread widely over northeastern Borneo, which also observed in the northern half of the Nunukan Island
      PubDate: 2017-11-13
      DOI: 10.22146/jag.30255
      Issue No: Vol. 2, No. 1 (2017)
       
  • Assessment of Groundwater Contamination Hazard by Nitrate in Samas Area,
           Bantul District, Yogyakarta, Indonesia

    • Authors: Thilavanh Souvannachith, Doni Prakasa Eka Putra, Heru Hendrayana
      Pages: 36 - 47
      Abstract: Groundwater resource is an essential for various purposes in Bantul district,
      Yogyakarta Special Province, Indonesia, especially on Poncosari village where the water
      supply are depending on shallow groundwater resources. On this village, most of the
      houses using dug wells to provide their water needs and applying inappropriate on-site
      sanitation system, however there are also difference land uses. This condition increase the
      hazard of groundwater contamination by fecal coli bacteria and nitrate. Therefore, this
      research aims in term of three main objectives: firstly, to know the level of nitrate concentration
      in groundwater, secondly, to assess groundwater vulnerability and thirdly, to assess
      the level of groundwater contaminant hazard. Hydrogeology observation was conducted
      and 47 water samples (44 groundwater samples and 3 surface water samples) were collected
      from different land use type and analyze for nitrate (NOô€€€
      3 ) content. Methodology
      used to assess the groundwater vulnerability was Simple Vertical Vulnerability method
      and the groundwater contamination hazard built based on the combination of groundwater
      vulnerability and nitrate loading potential map. Results show that groundwater concentrations
      of nitrate range from 0.09–74.80 mg/L and the highest concentration found in
      the settlement area. Assessment of groundwater vulnerability reveals three areas of moderate,
      moderate high and high classes of vulnerability due to shallow groundwater and
      the sandy dominated overlying material in the study area. Combination of groundwater
      vulnerability and nitrate loading potential map indicated that groundwater contaminant
      hazard of nitrate range from low to high class. High class of hazard located in the settlement
      area, and low hazard of nitrate contamination found in the irrigated rice field area
      PubDate: 2017-11-13
      DOI: 10.22146/jag.30256
      Issue No: Vol. 2, No. 1 (2017)
       
 
 
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