Journal of Applied Geology
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Assessment of Groundwater Contamination Hazard by Nitrate in Samas Area, Bantul District, Yogyakarta, Indonesia
Get PDFGroundwater 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 (NO 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 are
Groundwater Level Changes in Shallow Aquifer of Yogyakarta City, Indonesia: Distribution and Causes
Get PDFThe population in Yogyakarta City, Indonesia has increased since 1970, resulting in high groundwater utilization. This normally results in a decline of groundwater level in shallow aquifer beneath the city. However, expansion of the city and urbanization effects can also have the opposite effect and lead to a rise of groundwater levels due to urban recharge. This study investigates groundwater level changes in Yogyakarta City during a time period of 30 years between 1985 and 2015. Collected data in this research are groundwater level, rainfall, population density, sewer system, and land use. Overlaying various spatial information reveals a pattern of groundwater level rise in some areas of the city by 0–12 m, whilst in other areas a decline of 0–9 m is discovered. Rising groundwater levels are mainly found in areas moderate to high population density where sewer system networks have been installed. The rising of groundwater levels is this expected to be caused by urban recharge and sewers leakage
Engineering Geology of Sidosari Area, Magelang, Central Java, Indonesia
Get PDFDevelopment 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
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
Get PDFHolocene 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
Lithostratigraphy of Tabul Formation and Onshore Geology of Nunukan Island, North Kalimantan
Get PDFNunukan 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 Islan
Geology, Geochemistry and Hydrothermal Fluid Characteristics of Low Sulfidation Epithermal Deposit in the Sangon Area, Kokap, Special Region of Yogyakarta
Get PDFOn the basis of the previous studies and reconnaissance survey in the studyarea covering Sangon, Kalirejo, Kokap Sub-district, Kulon Progo Regency, Special Region of Yogyakarta, it reveals some facts of the occurrence of quartz veins with massive, crustiform, comb, drusy cavity, saccharoidal, granular, and reniform/mammillated textures, the appearance of lattice bladed barite and hydrothermal breccia veins. Referring to those characteristics, the deposit type in the study area is interpreted to be low sulfidation epithermal type. This study is aimed to understand and characterize the geological condition, rock and ore geochemistry and the mineralizing fluids. The alteration and ore mineralization are almost observed in entire rock units particularly the intrusive andesite 1. Their formation is controlled by the tension fractures (NW–SE and NE–SW) which associate with sinistral strike slip faults (NE–SW), dilational jog (NNW–SSE), oblique normal fault (WNW–ESE), and predictable normal fault at the NE of study area (NW–SE). The alteration zones are developed to be silica-clay (quartz-illite-kaolinite-kaolinite/smectite), argillic (smectite-illite/smectite), and propylitic (chlorite-calcite±epidote). The precipitationof ore minerals is controlled by boiling, mixing, and wall-rock alteration, and canbe found in the quartz veins (quartz-adularia-sericite) and disseminated in the alteration zones, which their high variability is only can be found in the quartz veins, including pyrite, sphalerite, chalcopyrite, galena, marcasite, and arsenopyrite. Based on the ICPAES measurement of 5 quartz vein samples, the Cu, Zn, Pb, and As grade reach about 5,171 ppm, 8,995 ppm, 6,398 ppm, 34.1 ppm, and 1,010.5 ppm, respectively. Gold is not detected. Fluid inclusion microthermometric analysis shows Th of 242.1–257.6 °C and salinity of 1.57–3.87 wt.% NaCl equiv., which indicate a depth below the paleosurface of 384–516 m, and pressure of 101.7–136.6 bar. The ore deposit in the study area is interpreted to be a deep basemetal low sulfidation epithermal type. Gold might be depleted in this epithermal type
Petrophysics Analysis for Reservoir Characterization of Upper Plover Formation in the Field “A”, Bonaparte Basin, Offshore Timor, Maluku, Indonesia
Get PDFHydrocarbon potential within Upper Plover Formation in the Field “A” has not been produced due to unclear in understanding of reservoir problem. This formation consists of heterogeneous reservoir rock with their own physical characteristics. Reservoir characterization has been done by applying rock typing (RT) method utilizing wireline logs data to obtain reservoir properties including clay volume, porosity, water saturation, and permeability. Rock types are classified on the basis of porosity and permeability distribution from routines core analysis (RCAL) data. Meanwhile, conventional core data is utilized to depositional environment interpretations. This study also applied neural network methods to rock types analyze for intervals reservoir without core data. The Upper Plover Formation in the study area indicates potential reservoir distributes into 7 parasequences. Their were deposited during transgressive systems in coastal environments (foreshore - offshore) with coarsening upward pattern during Middle to Late Jurassic. The porosity of reservoir ranges from 1–19 % and permeability varies from 0.01 mD to 1300 mD. Based on the facies association and its physical properties from rock typing analysis, the reservoir within Upper Plover Formation can be grouped into 4 reservoir class: Class A (Excellent), Class B (Good), Class C (Poor), and Class D (Very Poor). For further analysis, only class A-C are considered as potential reservoir, and the remain is neglected
Geochemistry, Hydrothermal alteration and Ore mineralogy of Skarn Mineralization at Wethey-Pheshey area, Thabeikkyin Township, Mandalay Region, Myanmar
Get PDFWethey-Pheshy area is located 80 km north of Mandalay at Thabeikkyin Township, Mandalay Region. X-ray Diffraction (XRD) Analysis and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) were applied in this study. Geochemical studies on the host rocks indicate that major and minor oxides compositions of metamorphicrocks show some degree of variation. CaO, MgO, FeO, TiO2 and P2O5 concentration of the metamorphic rock samples show a coherent negative correlation with SiO2 whereas Na2O is positively correlated with SiO2. The metamorphic rocks are strongly enriched in light rare earth elements (LREE) and relatively depleted in heavy rare earth element (HREE). The depleted Eu-nomalies in the chondrite-normalized REE diagrams indicate a plagioclase-depleted Eu crustal source or fractionation during magmatic differentiation. Intrusion of granitic rocks in the diopside marble caused the base metal ore mineralization and associated skarn alterations. Granite shows the sub-alkaline nature and peraluminous character. It is identified as I-type granite (magnetite series) developed in the volcanic arc setting. Hydrothermal alteration types associated with gold and skarn mineralization in the study area include calc-silicate alteration, propylitization, sericitization (argillitization) and hematization. Based on the nature and characteristics of host rocks, mineralization and alteration style and geochemical characteristics in the study area is identified as intrusion-related skarn mineralization. Common ore minerals include chalcopyrite, galena, sphalerite, pyrite, gold and Fe-oxides.
Comparison of Grain-Size Profile and Depositional Process in Mandeh and Nyalo Bar, Mandeh Bay, West Sumatera, Indonesia
Get PDFShipwreck of MV Boelongan Nederland situated in offshore of Mandeh Bay of West Sumatera is announced as potential area for tourism destination. Many studies were produced in term of its archeological and historical side but there is no significant work in sedimentological aspect. It is critical to understand depositional process of study area regarding the design of construction to minimize the impact of dynamic activity of waves within the area. Moreover, some areas along Mandeh Bay are covered by Cubadak Island as a protection for wave action derived from Indian Ocean that can produce more complexity in depositional process and will reflect to its characteristic of grain-size profiles. Utilizing thirteen sediment samples in two areas that correspond to inside (Mandeh Bar) and outside (Nyalo Bar) coverage of Cubadak Island, this study attempted to compare and contrast both grain-size profiles as well as interpretation of depositional process based on well-known analysis such as bivariate scatter plots, Linear Discriminant Function plot (LDF), Log probability curves and C-M diagram. Result of this study can be integrated by other researches to gain better policy in maintaining the shipwreck conservation. High energy of Indian Ocean wave supported by strong current clearly dominated depositional process in Nyalo Bar with coarser grain-size; good sortation, lower Y2 of LDF plot; extremely high population of traction materials and lower range of C-M. By contrast, presence of Cubadak Island disrupted the wave effectively and created lower and fluctuated energy in Mandeh Bar. This phenomenon was clearly depicted in its characteristic of finer grain-size with higher Y2 value; high abundance of saltation materials and greater ratio of C-M value
The Effect of Differences Leachate Concentration and Material Properties on Electrical Conductivity of Volcanic Deposits – Case Studies Piyungan Landfill Bantul Yogyakarta
Get PDFMonitoring at the contaminated subsurface soil, have been conducted by using the geophysical surface method, especially for geoelectrical resistivity method. Monitoring is commonly conducted by using geoelectrical resistivity through measuring the value of Electrical Resistivity (ER) or Electrical Conductivity (EC) of leachate contaminated soil layer. EC measurement value of soil is affected by many factors, among others, particle conduction of soil materials, surface conduction, fluid conduction in the pores as well as the effect of particle shape and soil materials. Piyungan landfill is the main disposal site of Yogyakarta municipal solid waste. This landfill located mainly on the tertiary rocks of volcanic rocks and its weathering products. In order to improve the accuracy of geoelectrical measurements on resistivity in monitoring soil layers from contaminated leachate on this area, this research conducted several measurements on physical properties of soil sample and electrical properties of leachate in the saturated soil samples. The measurement of physical properties includes: porosity, clay content, particle content, and cation exchange capacity (CEC) value. The soil samples were collected from 3 locations around Piyungan Landfill. Type of soils are taken from the alluvial deposits (Sample B), weathered tuffaceous sandstone-claystone (Sample D), and weathered andesitic breccia (Sample F). Samples were made in containers, saturated with aquades-leachate solution with 12 different concentration levels. Electrical conductivity (EC) was measured by using Soil Box Miller and Geoelectric Resistivity Oyo McOhm. According to results of physical properties analysis, the grain size of soils are dominantly sandy clayey silt in grain size distribution, with clay content ranging from 33.0--38.4 %, the CEC values ranging from 26.8--52.7 meq/100 gr, and the porosity of samples B, D and F is 58.85 %, 55.30 %, 59.24 %, respectively. Based on the experiments with 12 different leachate concentrations, there is a linear increase in EC of 0.718mS/cm for every increase in electrical conductivity pore fluid (ECf ) 1 mg/l in samples B, while in samples D and F are 0.492 mS/cm and 0.284 mS/cm respectively. Plotting the data of EC vs ECf for each samples and ER vs ECf , it can be concluded the slope ofDEC/DECf differ for each samples and the electrical conductivity value of different concentration of leachate is very sensitive for alluvial deposits compare to the weathered tuffaceous sandstone-claystone and weathered volcanic breccia deposits