bluuebunny/crossref_metadata_2025_split huggingface dataset:
Focal Mechanism and Parameter of Volcano-Tectonic Earthquake Source, in Mount Guntur, West Java
Authors: Hidayati Sri , Suparman Y. , Loeqman A. 
Published: March 2024

DOI: 10.17014/ijog.v6i1.111Guntur Volcano in West Java is one of the most active volcanoes in Indonesia. The last eruption took place in 1847 and the volcanic activity has been dormant since then, however its seismicity is active. During the period of July to October 2009, the hypocenter distribution of VT earthquakes is mostly located at western flank of the volcano, beneath Guntur - Gandapura craters at the depth of less than 5 km. The depth pattern shows deeper to the northwest. The VT earthquakes deeper than 5 km were not found in this period. The focal mechanism of VT earthquakes are oblique normal fault, strike-slip fault and oblique reverse fault types. The mechanism of those earthquakes is not uniquely determined probably due to complicated structures at Guntur volcano complex area, which is aligned in NW-SE direction. T-axis of the oblique normal fault is trending in northwest - southeast direction similar to the structures found in the summit area of Gunung Guntur Volcano. Similarly, one of the strike-slip fault nodal line and P-axis of oblique reverse fault are also trending in northwest - southeast. Ploting of the earthquake source parameters (seismic moment, corner frequency, and stress drop) made to hypocenter distance shows no significant difference on those parameters between earthquakes at close and far distances to Kabuyutan station. It is probably due to the hypocenters are not concentrated in one zone. Meanwhile, the relationship between seismic moment (Mo) and seismic source radius (r) shows that for earthquakes with moment of smaller than 1018 dyne cm, the radius of the hypocenter is constant which is namely 60 m.
Sediment Distribution related to Gold and Silver Placer Deposits in Offshore of Sambas Besar Estuary, Sambas Regency, West Kalimantan
Authors: Usman Ediar , Lugra I. W. 
Published: March 2024

DOI: 10.17014/ijog.v6i1.113Result of grain size analysis of the sea floor sediments from the study area indicates four sediment types, those are silt, sandy silt, silty sand, and sand. The silt unit has the widest distribution that is around 127.2 km2, sandy silt 12.65 km2, sand 1.176 km2, and silty sand 0.44 km2. Result of gold and silver content analysis from some selected samples indicates that the highest gold and silver amount are at PMK-08 location in northern part of the study area with gold content of 0.21 ppm and silver 13.36 ppm; both are silt sediment types. The highest gold and silver content occur within medium - coarse sediments containing subrounded grains of quartz and pyrite, at northern part of the study area. The presence of silver and gold is suggested to be controlled by a north-south longshore current pattern. The source of sediments from Sambas Besar River follows the longshore current, e.g. in northern estuary from south to north, and at southern estuary from north to south direction.
Nannoplankton Assemblage Succession Throughout Cretaceous/ Tertiary Boundary in the “P” Well Section, Santos Basin, Brazil
Authors: Panuju Panuju 
Published: March 2024

DOI: 10.17014/ijog.v6i1.115The massive change in calcareous nannoplankton assemblages throughout Cretaceous/Tertiary (K/T) boundary (65.5 M.a.) has been illustrated by several authors. The diverse and abundant assemblage disappears suddenly above the Cretaceous/Tertiary boundary. This event is related to the most dramatic environmental changes in the Earth's history due to the catastrophic events, those are meteorite impact (Chicxulub) and supervolcano eruption (Deccan) occurring at the end of Cretaceous. The succeeding age was a time of rapid evolution of nannoplankton during Paleocene. A quantitative method analysis of nannoplankton throughout Maastrichtian to Paleocene of “P” well section, Santos Basin, Brazil, indicated that the nannoplankton assemblages abruptly decrease in diversity and abundance and mostly change in species composition. The various complex shapes of species at Maastrichtian also underwent changing to simple plain shapes and small at Paleocene. The sedimentary section ranges from the top of zone CC23 (Coccolith Cretaceous 23) to NP9 (Nannoplankton Paleogen 9). It is bounded by the Last Occurrence (LO) of Tranolithus pachelosus at the base and Fasciculithus tympaniformis at the top. The biostratigraphic discontinuity characterized by the absence of zone CC26 to NP4 is an indicator for the presence of an unconformity at K/T boundary within analyzed section. The Cretaceous nannoplankton assemblages are dominated by Genera Watznaueria, Micula, Arkhangelskiella, Cribrosphaerella, Eiffellithus, Predicosphaera, and Retecapsa, whilst the Paleocene assemblages are dominated by Genera Toweius, Ericsonia, and Coccolithus. Survivor Cretaceous species recovered into Tertiary sediments consist of Braarudosphaera bigelowii, Biscutum melaniae, Neocrepidolithus neocrassus, Placozygus sigmoides, Cyclagelosaphaera reinhardtii, Markalius inversus, and Scapolithus fossilis.
Magma Genesis in Kabanjahe Region Continental Margin Arc of Sumatra
Authors: HaraHap Bhakti H. 
Published: March 2024

DOI: 10.17014/ijog.v6i2.120Volcanic rocks in Kabanjahe region, Karo Regency, North Sumatra Province, are products of old Toba Caldera, Sibayak Volcano, and Sipiso-piso Volcano. Rhyolitic tuff is the main lithology distributed over a large area in this region. Others are basaltic, basaltic andesitic, andesitic, dacitic, and rhyolitic lavas. Data show that the rock was originated from magma of a continental origin formed at a subduction zone environment. Petrogenetic modelling suggests that the range in composition was mainly controlled by a fractional crystallization of plagioclase, clinopyroxene, hornblende, and biotite. Harker’s variation diagram of major and trace elements show a continuous range that indicates they are cognate. The lava in this area belongs to a high-K, calc-alkaline series, with particular high Nb concentrations. The composition of these high-Nb lavas is more similar to those of intra plate basalts rather than those of calc-alkaline or arc-tholeiitic basalt. The high anomaly of Nb which is accompanied by high Th, Rb, and normative corundum suggests that the source may also be enriched in incompatible elements, a characteristic feature of alkali magmatism. The similarity of the trace element of volcanic rocks to the within-plate basalts indicates that the convecting mantle wedge above subducted slabs contains variable proportions of MORB-source and OIB-source components; fluids added were derived from the subducted slab. Hence, it is interpreted that the high Nb concentration of volcanic rocks from Kabanjahe region were generated from subduction modified OIB source components. Alternatively, a deep seated faulting conduit magma from the lower mantle resulted in the alkaline enrichment of the volcanics. This article performs a petrological aspect, especially based on geochemical analysis including major elements, trace elements, and rare earth elements. The results are plotted into a general and specific classification used in petrology.
Fossilization Type of Elephas hysudrindicus from Blora on the Basis of Petrographic and Scanning Electron Microscopic Analyses
Authors: Herman Danny Z. 
Published: March 2024

DOI: 10.17014/ijog.v6i2.117Either fossils of the hominid or vertebrate have long been known from terraces along the Solo River in Central and East Java. Most terraces consist of andesitic sand to andesitic tuffaceous sand with either gravelpebble or conglomerate and some of them contain vertebrate fossils. It is in this place, an ancient elephant fossil named Elephas hysudrindicus was discovered in 2009. This fossil was discovered at an abandoned sand quarry of Sunggun area, Medalem Village, Kradenan Subregency, Blora Regency which and can be mentioned as a great event for the Geological Museum. It was said as a phenomenal discovery, because the fossil was found within the terrace with condition of nearly complete skeleton of an individual elephant. Some bone fragments of Elephas hysudrindicus fossil is treated as rock specimens because a number of minerals fill in either pore spaces or cavities or cracks within bones, and such infilling minerals can be observed in cut sections of the bones. Main goals of the study are to determine the distribution and type of minerals within the bones, interpret environment of deposition, and identify fossilization type. The methodology used in this study consists of petrographic and Scanning Electron Microscopic (SEM) analyses. Based on the petrographical observation, some bone specimens of Elephas hysudrindicus fossil are characterized by fibrous and porous feature with cracks occuring locally. Whilst, examination with SEM shows that the bone specimens are apparently composed of collophane or massive cryptocrystalline variety of apatite as the principal component of fossil bone, having physical characteristic of spheroidal structure and cavities of 100 to 1500 micron (μ) in diameter. Most cavities and pore spaces are predominantly filled in by either authigenic crystals of rhombohedral calcite and lesser pseudohexagonal kaolinite with either slightly minerals of manganese oxide or iron oxide or ilmenite, including oxidized kaolinite and calcium iron silicate. Impregnation during diagenesis may be the most appropriate expression for fossilization process of the Elephas hysudrindicus. It is indicated by the existing authigenic minerals within the bones cavities, pore spaces, and cracks which are possibly due to precipitation of mineralized fluids originated from groundwater within the terrace.
Mechanism of High Frequency Shallow Earthquake Source in Mount Soputan, North Sulawesi
Authors: Suparman Yasa , Kriswati E. , Pamitro Y. E. 
Published: March 2024

DOI: 10.17014/ijog.v6i3.122Moment tensor analysis had been conducted to understand the source mechanism of earthquakes in Soputan Volcano during October - November 2010 period. The record shows shallow earthquakes with frequency about 5 - 9 Hz. Polarity distribution of P-wave first onset indicates that the recorded earthquakes are predominated by earthquakes where almost at all stations have the same direction of P-wave first motions, and earthquakes with upward first motions.In this article, the source mechanism is described as the second derivative of moment tensor, approached with first motion amplitude inversion of P-wave at some seismic stations. The result of moment tensor decomposition are predominated by earthquakes with big percentage in ISO and CLVD component. Focal mechanism shows that the recorded earthquakes have the same strike in northeast-southwest direction with dip about 400 - 600. The sources of the high frequency shallow earthquakes are in the form of tensile-shear cracks or a combination between crack and tensile faulting.
Simulation of Groundwater Flow, Denpasar-Tabanan Groundwater Basin, Bali Province
Authors: Tirtomihardjo Heryadi , Setiawan T. 
Published: March 2024

DOI: 10.17014/ijog.v6i3.123Due to the complex structure of the aquifer systems and its hydrogeological units related with the space in which groundwater occurs, groundwater flows were calculated in three-dimensional method (3D Calculation). The geometrical descritization and iteration procedures were based on an integrated finite difference method. In this paper, all figures and graphs represent the results of the calibrated model. Hence, the model results were simulated by using the actual input data which were calibrated during the simulation runs. Groundwater flow simulation of the model area of the Denpasar-Tabanan Groundwater Basin (Denpasar-Tabanan GB) comprises steady state run, transient runs using groundwater abstraction in the period of 1989 (Qabs-1989) and period of 2009 (Qabs-2009), and prognosis run as well. Simulation results show, in general, the differences of calculated groundwater heads and observed groundwater heads at steady and transient states (Qabs-1989 and Qabs-2009) are relatively small. So, the groundwater heads situation simulated by the prognosis run (scenario Qabs-2012) are considerably valid and can properly be used for controlling the plan of groundwater utilization in Denpasar-Tabanan GB.
Engineering Geological Characteristics of the Residual Soil, Lower Quaternary Sediments in Kertajati Region, Majalengka, West Java
Authors: Sudarsono Untung , Hasibuan G. 
Published: March 2024

DOI: 10.17014/ijog.v6i3.125Only few engineering geological researches on residual soil have been conducted in Indonesia, whereas many infrastructure projects take place on undulating area and mountainous area which are composed of residual soils. The paper discusses residual soil characteristics of the Lower Quaternary sediment (Qos) in Kertajati area, Majalengka. The methodology of the research consists of engineering geological mapping, in situ test using 2.5 ton penetrometer, sampling and laboratory test for index properties, Atterberg limits, grain size analysis, and strength tests. Field test analysis data show that the thickness of residual soil resting on the basement rock in the study area varies from 2.40 - 14.20 m. Upwards, it comprises sands, silts, and clays, respectively. Laboratory analysis data indicate that the residual soil is dominated by fine-grained fraction, composed of high plastic clay (CH). Relationship among engineering geological parameters was analysed using linear regression and tested using statistic method t-test to find real correlation among variables within 95 - 90% significance level.. Based on the test, there are real positive correlation with 19 degree of freedom and 5% and 10% level of significance are found in between plasticity indexes (IP) and liquid limits (LL), between plasticity indexes (IP) and clay contents (C), between specific gravities (G ) and clay contents (C). The real negative correlation with nine degree of freedom and 5% and 10% level of significance occurs in between cohesion (c) dengan friction angle (φ). Corelation between degree of saturation (G ) and clay contents (C) with 19 degree of freedom is found in 10% level of significance.
Experiment of Industrial Waste Absorption using Activated Carbon from Coal of Tanjung Tabalong, South Kalimantan
Authors: Gani M. Ulum , Widodo Widodo 
Published: March 2024

DOI: 10.17014/ijog.v6i4.130Activated carbon made from Tanjung Tabalong coal was investigated its absorption capability to organic and inorganic elements in industrial waste. Coal was carbonized at low temperature of 600C to produce semicoke, and then was activated at temperature of 700C with activation time of 120 minutes with water steam flow. The absorption capability of activated carbon to chemical oxygen demand (COD) was performed using 2.5 and 9.0 g activated carbon for 250 ml and 300 ml COD waste respectively. The agitation time of each experiment were 30, 60, and 90 minutes. Atomic absorption spectrophotometer (AAS) was used to analyze the COD waste. The result shows that 2.5 g activated carbon could absorb COD waste ranging from 6.9-67.5 %, while the utilization of 9 g could absorb COD waste ranging from 88.9 - 100 %. The more activated carbon and the longer time of agitation used in this experiment, the more the absorption of COD waste.
3-D Imaging of Cleat and Micro-cleat Characteristics, South Walker Creek Coals, Bowen Basin, Australia: Microfocus X-ray Computed Tomography Analysis
Authors: Permana Asep Kurnia 
Published: March 2024

DOI: 10.17014/ijog.v7i1.131The Permian coals of the South Walker Creek area have a moderately to highly developed cleat system. The cleat fractures are well developed in both bright and dull bands, and generally parallel, inclined or perpendicular to the bedding planes of the seam, with the spaces open or filled by mineral matter, such as clay and carbonate minerals. Microfocus X-ray computed tomography (CT) technique was performed to identify cleat characteristics in the coal seams. This technique allows visualizing of microcleat distribution and mineralization in three dimensional images. Cleat mineralization in the coal seam occurs either as single mineral (monomineralic) or intermixed mineral (polymineralic) masses. The cross cutting relationship was shown by X-ray CT scan analysis. The timing of microcleat formation in the coal seam from early to late is carbonate minerals, clay minerals (kaolinite) plus minor high density (rutile or anatase) phases. Thus, a high resolution of microfocus X-ray CT does not only provides a better visualization, but also could identify microcleat orientation, cleat mineralization, and generation of microcleat.
Nose Structure Delineation of Bouguer Anomaly as the Interpretation Basis of Probable Hydrocarbon Traps: A Case Study on the Mainland Area of Northwest Java Basin
Authors: Kamtono Kamtono , Wardhana D. D. 
Published: March 2024

DOI: 10.17014/ijog.v7i3.144Two important aspects in the exploration of oil and gas are technology and exploration concepts, but the use of technology is not always suitable for areas with geological conditions covered by young volcanic sediments or limestone. The land of the Northwest Java Basin is mostly covered by young volcanic products, so exploration using seismic methods will produce less clear image resolution. To identify and interpret the subsurface structure and the possibility of hydrocarbon trap, gravity measurements have been carried out. Delineation of nose structures of a Bouguer anomaly map was used to interpret the probability of hydrocarbon traps. The result of the study shows that the gravity anomalies could be categorized into three groups : low anomaly (< 34 mgal), middle anomaly (34 - 50 mgal), and high anomaly (> 50 mgal). The analysis of Bouguer anomaly indicates that the low anomaly is concentrated in Cibarusa area as a southern part of Ciputat Subbasin, and in Cikampek area. The result of delineation of the Bouguer anomaly map shows the nose structures existing on Cibinong-Cileungsi and Pangkalan-Bekasi Highs, while delineation of residual anomaly map shows the nose structures occurs on Cilamaya-Karawang high. Locally, the gas fields of Jatirangon and Cicauh areas exist on the flank of the nose structure of Pangkalan-Bekasi High, while the oil/gas field of Northern Cilamaya is situated on the flank of the nose structure of Cilamaya-Karawang High. The concept of fluid/gas migration concentrated on nose structures which are delineated from gravity data can be applied in the studied area. This concept needs to be tested in other oil and gas field areas.
Melanic and Fulvic Andisols in Volcanic Soils derived from some Volcanoes in West Java
Authors: Devnita Rina 
Published: March 2024

DOI: 10.17014/ijog.v7i4.149Melanic and fulvic Andisols are the great groups in the classification of volcanic soils Andisols, which describe the soils with high organic carbon content in the epipedon. The organic C must be more than 6% in the upper 30 cm with the value and chroma are 2 or less for melanic and more than 2 for fulvic. Melanic epipedon also has to have the melanic index that is 1.70 or less. The objective of this study is to investigate the melanic and fulvic Andisols in volcanic soils that developed under pine forest vegetation (Pinus merkusii) from different parent materials and ages of Mount Tangkuban Parahu (andesitic, Holocene) and Mount Tilu (basaltic, Pleistocene). The method used was a descriptive comparative survey of three profiles in Mount Tangkuban Parahu and three profiles in Mount Tilu. Analyses were done for each horizon in the profiles comprising the investigation of andic soil properties through the analyses of organic C, bulk density, Al + ½ Fe (ammonium oxalate), and P-retention. The investigations were continued by further calculation of organic C content and by investigation of soil colour with Munsell Soil Colour Chart. The results showed that the two profiles in Mount Tangkuban Parahu and two profiles in Mount Tilu are fulvic Andisol. No melanic Andisols were found in both locations. Pine forest vegetation encourages the formation of fulvic Andisols were derived from andesitic-Holocene parent materials or basaltic-Pleistocene parent materials.
The Potential of Eocene Shale of Nanggulan Formation as a Hydrocarbon Source Rock
Authors: Winardi S. , Toha B. , Imron M. , Amijaya D. H. 
Published: March 2024

DOI: 10.17014/ijog.v8i1.152In western Indonesia, Eocene shale is generally considered as a potential source rock. The Nanggulan Formation outcropping at Kulonprogo Yogyakarta consists of a shale interval of Eocene in age. Analysis of its organic material content, kerogen type, and maturity level were conducted to know its potential. The laboratory analysis of eleven samples were done to measure its TOC content. Samples with TOC > 0.5% then were analyzed to measure its Rv and TAI. Maturity level was also calculated by TTI from burial history model. The result of analysis shows there are various TOC contents and seven samples of them are categorized into a good-excellent class (TOC > 1%). Kerogen content of those samples is type III (non fluorescene amorphous-humic kerogen). One sample has a good indication of hydrocarbon formation (PY = 9.0 mg HC/g rock). Unfortunately thermal maturity level of the samples is immature (highest Rv 0.39, Tmax 422oC, and TAI 2). Otherwise, TTI calculation result from subsurface burial history modelling indicates that some areas are mature having reached gas window since 0.4 mya, especially in the area which had been influenced by a volcanic intrusion at Oligocene (28.5 mya). Therefore, the Nanggulan Formation shale has a potential capacity as a source rock with some limitation in maturity level.
Maceral Characteristics and Vitrinite Reflectance Variation of The High Rank Coals, South Walker Creek, Bowen Basin, Australia
Authors: Permana Asep K. , Ward C. R. , Gurba L. W. 
Published: March 2024

DOI: 10.17014/ijog.v8i2.156The Permian coals of the South Walker Creek area, with a vitrinite reflectance (Rvmax) of 1.7 to 1.95% (low-volatile bituminous to semi-anthracite), are one of the highest rank coals currently mined in the Bowen Basin for the pulverized coal injection (PCI) market. Studies of petrology of this coal seam have identified that the maceral composition of the coals are dominated by inertinite with lesser vitrinite, and only minor amounts of liptinite. Clay minerals, quartz, and carbonates can be seen under the optical microscope. The mineral matter occurs in association with vitrinite and inertinite macerals as syngenetic and epigenetic mineral phases. The irregular pattern of the vitrinite reflectance profile from the top to the bottom of the seam may represent a response in the organic matter to an uneven heat distribution from such hydrothermal influence. Examination of the maceral and vitrinite reflectance characteristics suggest that the mineralogical variation within the coal seam at South Walker Creek may have been controlled by various geological processes, including sediment input into the peat swamp during deposition, mineralogical changes associated with the rank advance process or metamorphism, and/or hydrothermal effects due to post depositional fluid migration through the coal seam.