Journal of Applied Geology
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Paleogeography And Sedimentation Dynamics Of Ujoh Bilang-Batubelah Limestone Member, Upstream Mahakam River, Ujoh Bilang Area, East Kalimantan Province
Get PDFPALEOSTRESS ANALYSIS TO INTERPRET THE LANDSLIDE MECHANISM: A CASE STUDY IN PARANGTRITIS, YOGYAKARTA
Get PDFPaleostress analysis on the landslide boundary faults is able to explain the sliding mechanism. This method is particularly useful to study a paleolandslide. About 30 striated fault planes from the Parangtritis paleo-landslide, located in the Yogyakarta coastline, were analyzed to define their principle stress axes. The eastern boundary fault, named as the Girijati Fault, was the main fault responsible for the mass movement and leaving a considerable steep cliff. It moved normal in a left lateral sense with ENE – WSW extension and dragged the rockmass southward, creating a NNW – SSW extension along the Parangtritis Fault and turn it into the western boundary fault. The rockmass slided along the stratigraphic contact between the underlying Nglanggran Formation and the overlying Wonosari Formation, created a semi-circular crown cliff as the northern boundary and produced some isolated topographic highs of the thrust block near the toe.
Keywords: Paleostress, landslide boundary, fault, paleolandslid
THE IMPACT OF SANITATION ON GROUNDWATER NITRATE LEVEL IN BANTUL DISTRICT, BANTUL REGENCY, YOGYAKARTA SPECIAL PROVINCE, INDONESIA
Get PDFBantul is one district of Yogyakarta Special Province which residents mostly use on-site sanitation. On-site sanitation is well-known for hot-spot system of nitrate groundwater contamination. It is because the wide-practice of failure of on-site sanitation systems. Besides, the failure of on-site sanitation system, it will depend on the age of settlement, population density, sanitation arrangement and sanitation behavior including water use patterns. Because of this, nitrate has leaked to groundwater and polluted many supply wells surrounding the septic systems.
Since the repeated intake of nitrate could cause various acute and chronic effects to human health, especially the infant’s health under 3 months (blue baby syndrome), it is crucial to undertake the study of impact of sanitation on groundwater nitrate level in Bantul district to acquire a better understanding of the effect of settlement age, population density, sanitation arrangement and sanitation behavior on the concentration of nitrate in groundwater. In order to recognize or achieve the understanding of this issue, a methodology is conducted by observation directly to the field, including the measuring of groundwater table and the distance of septic tank to well, and also make the questionnaires for the mentioned parameters.
Finally, the result of each factors (Sanitation arrangement, Settlement age, House density) are shown a low relationship with nitrate concentration, although water use patterns does not. However, the combination of these three factors can show up to find out a better correlation than one factor with this nitrate concentration. Although it has a good relationship with nitrate concentration (average), the variation of nitrate concentration from high to low shows a low relationship. Therefore, the importance of groundwater vulnerability cannot be overlooked in explaining the variation in contaminant concentrations because the nitrate concentration in the groundwater does not only depend on contaminant loading but also groundwater vulnerability.
Keywords: Groundwater, on-site sanitation, nitrate concentration, contaminant loadin
MINERALOGY, GEOCHEMISTRY, AND SEQUENTIAL EXTRACTION EXPERIMENT OF REE IN WEATHERED ANGGI GRANITE, MANOKWARI REGENCY, WEST PAPUA, INDONESIA
Get PDFThis research objective is to identify geochemical andmineralogical characteristics of Rare earth elements(REE) in the weathering products of Anggi Granite, which is located in Manokwari Regency, WestPapua, Indonesia. The research is conducted on 7samples of fresh rocks and 7 samples of weatheredrocks of Anggi Granite. The research analysis consists of petrography, XRD, XRF, and sequential extraction experiment, supported by secondary dataand references. Anggi Granite is S-type and peraluminous granite that contains zircon, monazite andapatite as a rare earth bearing minerals. Weathering products of Anggi Granite do not have a significant enrichment of REE, even some of the samplesare depleted in REE. REE in weathered Anggi Granite are dominantly present in the primary minerals,mostly in zircon and monazite. Extractable formof geochemical fractions include crystalline Fe-oxideoccluded fraction (ilmenite, hematite and goethite),and ion-exchangeable (illite, kaolin and chlorite).Enrichment of REE in the weathered Anggi Granite is influenced by the presence of resistant REEbearing minerals, in the forms of zircon and monazite, degree of weathering related to the presenceof secondary minerals, and other factors such as pHand E
GEOLOGY AND ORE MINERALISATION OF NEOGENE SEDIMENTARY ROCK HOSTED LS EPITHERMAL GOLD DEPOSIT AT PANINGKABAN, BANYUMAS REGENCY, CENTRAL JAVA, INDONESIA
Get PDFLow suphidation (LS) epithermal gold deposits were recently found in the Paningkaban area, Central Java province, Indonesia, with more than five hundred artisanal gold miners currently operating in the area. This study is aimed to understand the geological factors controlling the gold mineralization and to characterize the alteration and ore mineralogy of the deposit. Several epithermal veins/veinlets trending N–S, NW–SE, and NE–SW are hosted by Tertiary turbiditic volcanoclastic sedimentary rocks of the Halang formation. This formation is composed of looping gradation of sandstone and siltstone units. Pre- and syn-mineralization structures such as extension joints, normal sinitral fault and sinitral fault control the gold mineralization. Fault movements formed dilational jogs manifested by NW-SE-trending en-echelon tension gash veins. Four main alteration zones are identified: (a) phyllic, (b) argillic, (c) sub propylitic and (d) weak subpropylitic. Ore minerals consist of native gold, electrum, native silver, pyrite, chalcopyrite, sphalerite, galena, arsenopyrite, cubanite, marcasite, covellite and tennantite, which are commonly associated withargillic alteration. Vein structures such as massive, swarm and low angle veins, stockwork and veins dispersed in diatreme breccia are present. Normal banded, cockade, crustiform, bladed carbonates as well as, comb and saccharoidal features are the typical vein textures. It is noteworthy that the veins are basically composed of carbonate with minor quartz at gold grades of up to 83 g/t Au. Based on the vein structures and textures, four stages of ore mineralization were developed consisting of (a) early stage (fluidized breccia and quartz vein), (b) middle stage (carbonate base metal), (c) late stage (late carbonate), and supergene stage. Gold mineralization originated mainly during middle and late stages, particularly in association with cockade, crustiform, bladed carbonate base metal veins. Based on those various features, the LS epithermal deposit in the study area is categorized as carbonate-base metalgold mineralization type
LATE OLIGOCENE THOLEIITIC LAVA FROM KENANGA RIVER, TEGALOMBO PACITAN, EAST JAVA
Get PDFoai:jurnal.ugm.ac.id:article/6671Watupatok Formation in Pacitan area consists of lava with basaltic composition and pillow structure. Kenanga river is only 5 km to southeast Watupatok village as type locality of this formation. Kenanga river’s lava were varying from diabasic with paving surface and columnar joint structure to basaltic composition with pillow structure. Lava were found as effusive flow and dike with sandstone inclusion. In field observation, lava exhibits strong porphiritic to aphyric texture, with vesicular to amygdaloidal structure. Plagioclase as phenocryst has mediumsized (2-4 mm) surrounded by volcanic glass as groundmass. Petrographic analysis shows intersertal to hyalophilitic texture, consist of plagioclase, pyroxene and opaque minerals as phenocryst and also groundmass together with volcanic glass. Seconday minerals are quartz, zeolite and calcite. Geochemichal analysis results indicate a low TiO2 (0.8– 0.9 wt.%), medium to high Al2O3 (14–17 wt.%), high Fe2O3 (10–12 wt.%) and low Mg value (Mg#) (39–42). According to TAS and AFM diagram, the rocks is apparently to be basalt and tholeiitic island arc magma. While spidergram pattern of the trace elements shows relatively flat fo HREE and enriched pattern on LREE. Niobium element displays a depleted anomaly, indicated that the crust influences in parental magma, which is another characteristic of magmatic island arc. Based on regional tectonic, the volcanic rocks from Late Oligocene in the area has relationship with subduction processes between Indo-Australia plate and Eurasian plate.Keywords: Pillow structure, tholeiitic, lava, subductio
Road to earthquake mitigation: Lesson learnt from the Yogyakarta earthquake 2006
Get PDFAt early in the morning of May 27, 2006, people of Yogyakarta was stroke by earthquake and mostly heavily damaged building are in lowland or Yogyakarta depression where is occupied by the Young Merapi sediments. The magnitude of earthquake is Mw = 6.2 and USGS rapid moment tensor shows that this earthquake was due to strike-slip fault movement.Seismic history of Yogyakarta area shows that Yogyakarta was stroke by several earthquakes with different epicenter location. At least two earthquakes stroke the area, that is in 1876 and 1943. The damages are similar to the damages of actual earthquake. Yogyakarta depression is mostly covered by Young Merapi sediments that consist of tuff, volcanic ash, breccias, agglomerate and lava with Quaternary in age. The thickness of this sediment is up to 100 m.Our reactive work was to establish firstly zone of damage. For this purpose, we made aerial photograph along the most damaged area. In the same time one of our teams go to the field to measure the cracks, and the other teams to observe liquefaction, hydro geologic measurement, and observation on landslide induce by earthquake. Secondly, we must understand the soil properties and its thickness, because in seismic history it was a similar damage on the same area due to earthquakes however the earthquake epicenters were different. For this purpose we utilize the method of micro-tremors. We also made some drilling until 60 m each, measuring seismic velocity on bore hole, and magneto telluric measurement. We also have helped by Kyushu University in installing micro seismic net work. The research was followed by either undergraduate and graduate students. Fortunately our research was financed by AUN/Seed Net – JICA. Some of the results were published in a book entitled The Yogyakarta Earthquake of May 27, 2006. Another outcome is the Maps of Microzonation and Earthquake Hazard of Bantul Area that dedicated to Bantul people.Based on aerial photograph observation and field observation on Bantul Regency, especially along the Opak River, and to Wonosari to the East, there was no surface ruptures, so there is no fault on surface. Interpretation of aftershock data was showing the difference cluster. There is still open problem in determining either epicenter or aftershock location. The damage building was interpreted as due to its geologic setting, non engineered building, and close to epicenter of earthquake. This heavily damaged building are located on the Young Merapi sediments at Bantul Regency and lake deposits at Gantiwarno and Bayat area where it can amplify the surface seismic wave. It implies that Peak Ground Acceleration according to Indonesian National Standard should be modified in Yogyakarta area.Keywords: Earthquake, seismic, epicenter, micro-tremor, microzonatio