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IJOG : Indonesian Journal on Geoscience

IJOG
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Published by Geological Agency of Indonesia

ISSN : 23559314 EISSN : 23559306 DOI : -

Core Subject : Science,

Earth & Planetary Sciences

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.

Arjuna Subject : -

Articles 796 Documents

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Berau coal in East Kalimantan; Its petrographics characteristics and depositional environment Nana Suwarna; Bambang Hermanto
Indonesian Journal on Geoscience Vol 2, No 4 (2007)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.vol2no4.20071To asses the characteristics of the Early to Middle Miocene Berau coal in the Berau Basin, leading to interpretation of coal depositional environments, some fresh outcrop and subcrop samples and also drill cores of the coals have been analyzed microscopically. Coal petrographic analysis was performed on twenty four coal samples from the Middle Miocene Lati Formation. Vitrinite, present in a high value, and ranging between 66.2 - 96.2%, is dominated by vitrinite B. On the other hand, inertinite and exinite, showing a similar value, exist in a low to moderate amount. Vitrinite reflectance, present in a low value, varies from 0.40 - 0.58%. Low mineral matter content is dominated by clay minerals (0.4 - 6.6%) with minor pyrite. Transitions from wet and very wet forested swamps to drier conditions with lower tree density are indicated by the higher content of vitrinite B, whilst a reverse trend is indicated by the lower content of vitrinite A. Petrographic indices obtained from facies diagnostic macerals show that an accumulation of the ancient peats under prevailing relatively wet limited influx clastic marsh to very wet forest swamps or moors is considered. The composition of the coal samples supports the interpretation of a system of fluvial to meandering streams in an upper delta plain environment. The original peat-forming vegetation was composed mainly of cellulose rich, shrub-like plants, tree ferns, herbaceous plant communities, with minor amount of trees. Thereby, the organic facies concept is thus applicable in basin studies context and has potential to become an additional tool for depositional environment interpretation.

Genesis endapan aluvium Dataran Purworejo Jawa Tengah; Implikasinya terhadap sumber daya geologi Sutikno Bronto
Indonesian Journal on Geoscience Vol 2, No 4 (2007)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.vol2no4.20072Purworejo is part of the Southern Central Jawa alluvial plain that is bordered by the South Sera- yu Mountains and Sumbing Volcano in the north, West Progo Mountains in the east, Indian Ocean in the south, and Kebumen-Banyumas plain in the west. This Purworejo plain comprises reworked allu- vial deposits, particularly from Tertiary volcanic rocks of the South Serayu and West Progo Mount- ains, and the Sumbing Quaternary Volcano. In the northern part older reworked material has formed Purworejo alluvial fan in the east and Kutoarjo alluvial fan in the west. Those alluvial fans developed from northeast side of studied area. The central part of Purworejo plain consists of older coastal alluvial deposits which have been covered by recent fluvial deposits that transported by Wawar River in the west, Jali River in the middle, and Bogowonto River in the east. The southern part of Purworejo plain, starting from the Lereng River until present coastal line is composed of younger alluvial coast- al deposits. It is suggested that groundwater resources are abundant under the Purworejo plain, and the young alluvial coastal deposits contain highly potential iron sand and associated minerals.

Multi-geohazards of Ende city area Igan Supriatman Sutawidjaja; Sugalang Sugalang
Indonesian Journal on Geoscience Vol 2, No 4 (2007)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.vol2no4.20073The Ende City is a steep mountainous area, of which the height of their peaks are above 1500 m asl. It has the limited extent of plain places, without coastal plains. Due to this condition, large parts of the area are vulnerable to mass-movements mainly debris flows, rock-falls and shallow translational and rotational landslides. On the other hand, Flores Island is a segment of the Banda Arc that contains eleven very active volcanoes and numerous inactive volcanic cones. Two of them, Mount Iya and Mount Kelimutu are included to Ende Regency. The northern foot of Mount Iya is only about 1 km away from the southern outskirts of Ende city. But the presence of Mount Meja and Mount Roja as the barrier, and the orientation of the active crater (K2), the highly explosive eruption of Iya Volcano may not directly endanger the city of Ende. Most pyroclastic flows of previous eruptions and other eruptive material emplaced into the sea, but due to a short horizontal distance between Mount Iya and Ende City, the ejected rock fragments can endanger the city of Ende especially its southern parts. A crack has developed around the active crater (K2) of Iya Volcano. It seems that the crack indicates a major weakness within the volcano, which could result in a giant landslide, entering the sea in future eruptions of Iya Volcano. The kinetic energy which is transmitted through the water may probably generate a tsunami. The Ende City also experienced significant damages in the 1992 earthquake. Luckily this city is located on a solid rock instead of alluvial sediments which can potentially undergo liquefaction.

Characteristics of volcanic gas correlated to the eruption activity; Case study in the Merapi Volcano, periods of 1990-1994 Priatna Priatna; Eka Kadarsetia
Indonesian Journal on Geoscience Vol 2, No 4 (2007)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.vol2no4.20074Volcanic gases, collected from Gendol and Woro solfatara fields, the summit of Merapi Volcano during 1990-1994, show an increase in chemical composition of H , CO, CO , SO , and HCl prior to the volcanic events, on the contrary to the drastic decreasing water vapour. The carbon/sulfur ratio of the volcanic gases lies between 1.5 and 5.7 which means that they were derived from the fresh magma. The Apparent Equilibrium Temperature (AET) which is calculated from chemical compositions of volcanic gases using reaction of SO +3H = H S+2H O showed an increasing value prior to the volcanic events. The Merapi activities lasted during August 1990 to November 1994 showed a significant increase in ratio SO /H S prior to the November 1994 pyroclastic flow. The isotopic composition of volcanic gas condensates indicates that water vapour in Gendol is directly derived from the fresh magma. On the other hand, the contamination and cooling by the subsurface water occurred around the Woro field at a shallow part.

Karakteristik batubara di Cekungan Bengkulu Rachmat Heryanto; Suyoko Suyoko
Indonesian Journal on Geoscience Vol 2, No 4 (2007)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.vol2no4.20075Bengkulu Basin is known as a fore arc basin, which located in the southwestern part of Sumatera Island. Bengkulu Basin is occupied by Oligo-Miocene siliciclastic, coal, and carbonate sediments. Coal, one of alternative energies which can substitute hydrocarbon, is found within the sedimentary rocks of the Middle to Upper Miocene Lemau Formation as observed in Ketaun, Bengkulu, and Seluma areas. The thickness of the coal seams in the Ketaun area ranges from 100 to 200 cm, whereas in the Bengkulu area it varies between 100 to 350 cm, and in Seluma area up to 450 cm. Megascopically, coal seams in the Ketaun area are black in colour, dull to dull banded, with brownish black in streak, whereas in the Bengkulu and Seluma areas show a black colour, bright banded, and black streak. The mean of vitrinite reflectant value (Rv) of coal seam in the Ketaun area ranges from 0.41 to 0.49%, whereas in the Bengkulu and Seluma area it varies from 0.44 to 1.12%. The higher vitrinite reflectance of the Bengkulu and Seluma coals is probably due to the influence of andesitic sill intrusion. In general, the coal in the Ketaun area was deposited in an environment of relatively more to marine direction or limited influx clastic marsh or lower delta plain, where the tree density decreased. However, the coal in the Bengkulu and Seluma areas occurred in an environment which was relatively more to land direction or telmatic, or upper delta plain or wet forest swamp, where the tree density increased.

Amblesan di daerah Porong, Kabupaten Sidoarjo, Jawa Timur Untung Sudarsono; Indra Budi Sudjarwo
Indonesian Journal on Geoscience Vol 3, No 1 (2008)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.vol3no1.20081On 29th May 2006, there was a huge mud outpouring in the Porong Subregency, Regency of Sidoarjo, East Jawa and for one year, it had flooded the area of more than 5 km2 including Porong, Tanggulangin and Jabon Sub-regencies. The mud known as Lumpur Sidoarjo. The impact of the mud outpouring was the presence of a subsidence around the main outpouring for the width of 6.3 km2 in ellipse stretching to the north. The subsidence area covered Tanggulangin Sub-regency: Kedungbendo Village, Porong Sub-regency: Siring, Jatirejo, Mindi, and Renokenongo Villages, and Jabon Sub-regency: Pejarakan and Besuki Villages. The rate of the subsidence is ap- proximately 2 cm/day.

Batubara Formasi Warukin di daerah Sampit dan sekitarnya, Kalimantan Tengah Kusnama Kusnama
Indonesian Journal on Geoscience Vol 3, No 1 (2008)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.vol3no1.20082The Warukin Formation in Sampit area, occupying the Barito Basin, was conformably deposited on top of the Berai Formation, but unconformably lies on the Tanjung Formation, Undifferentiated Metamorphic Rocks and Sepauk Granitic Rock. The formation consists of sandstone, interbedded claystone-mudstone, conglomerate and intercalations of coal, having Early-Late Miocene in age. Coal of the Warukin Formation at the Sampit area occurs within sandstone and interbedded claystone-mudstone facies. Two main seams, A and B, was deposited within sandstone and interbedded claystone-mudstone facies respectively. Generally, the coal is bright banded with partly dull lithotypes; brownish black in colour and it has a medium to light in weight. Physically, the coal recognized in two seams, is generally banded with brittle to friable in hardness; and has partings of claystone and mudstone. The thickness of the coal deposit ranges from 80 cm to 200 cm. On the basis of calorific value and lithotype, and also ash, moisture, and sulphur contents, the coal includes to subbituminous C - A rank. The coal was deposited in a wet-forest swamp occupied by high plants and shrubs.

Petrologi - geokimia batuan Gunung Api Tampomas dan sekitarnya Mesker H. Dirk
Indonesian Journal on Geoscience Vol 3, No 1 (2008)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.vol3no1.20083Volcanic rocks of Mount Tampomas and its surroundings belong to low–K, calc–alkaline, and high–K series of basalt, basaltic andesite, and andesite suites containing 48.59 – 60.49 wt% of SiO and 0.31-1.67 wt% of K O. The rocks are typically formed in an island arc environment characterized by the high content of Al O (16.47 – 21.76 wt%), low to moderate content of MgO (2.37 – 8.84 wt%), low content of both titanium TiO (< 1 wt%) and high field strength elements (HFSEs), negative anomaly of Nb relative to K and La. The light rare earth elements (LREEs) enrichment but low abundances of heavy rare earth elements (HREEs) indicate fractionation process. The parent magma was an extensive removal of olivine and clino-pyroxene, plagioclase, apatite, and titanoferrousmagnetite from a basalt olivine magma of N-MORB character that was firstly enriched by LILEs such as Ba, Rb, Th, K, and LREE (La). The differentiation lasted, and the magma became water undersaturated at the crystallization phase of hornblende. The high content of incompatible elements such as Ba, Th, La, Ce, may indicate contamination by liquid derived from the subducted slab.

Gumuk gunung api purba bawah laut di Tawangsari - Jomboran, Sukoharjo - Wonogiri, Jawa Tengah Gendoet Hartono; Adjat Sudrajat; Ildrem Syafri
Indonesian Journal on Geoscience Vol 3, No 1 (2008)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.vol3no1.20084This paper discusses the study on the basalt volcanic rocks and the volcano morphology indicating the existence of an ancient submarine volcano in Tawangsari-Jomboran sub-regency, Sukoharjo- Wonogiri, Central Java. In general, this basalt volcanic rocks were identified as andesite breccia which might be grouped into the Mandalika Formation of Oligosen-Miosen age (Surono et al., 1992). The origin of the Mandalika Formation in relation to the classic sedimentation process and the submarine volcanism is still needed to be evaluated. The present study was based on the detailed descriptions of the rocks both in the field and in the laboratory. The autoclastic basalt outcrops consisting of breccias show the characteristics of the igneous rock fragment component embedded in the groundmass with the same composition, namely igneous rock, dark grey to black in colour; porphyritic texture, rough surface, brecciated; pillow structures, massive, fine vesicularities, amygdaloidal filled with calcite, and radial fractures; calk-alkaline andesite composition ( SiO = 54.71% , K O = 1.15% ). This rock body attains the dimension of 2 - 5 m length, and 40 cm - 1 m in diameter with the direction of the deposition varies following the direction of the eruption source. Brecciated structures on the surface was controlled by the high cooling rate and the low flow, while the interior of the rock is massive because it was not in a direct contact to the cooler mass outside. Autoclastic basalt breccias and or the pillow basalt lava was interpreted to be formed by the undulating low gradient of morphology with the average angle of <10o. On the other hand, the low basaltic magma viscosity produced the effusive eruption related to the formation of the low angle morphology. The distance between the hills generally composed of pillow basalt is between 500 m - 1 km. The typical pillow structure of the igneous rock as described above is interpreted to be the product of the lava flow related to the effusive eruption from a submarine volcano located under or close to the seawater surface.

Karakterisasi sumber gempa Yogyakarta 2006 berdasarkan data GPS Cecep Sulaeman; Lestari Cendekia Dewi; Wahyu Triyoso
Indonesian Journal on Geoscience Vol 3, No 1 (2008)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.vol3no1.20085The southern part of Central Jawa is one of earthquake hazard prone areas in Indonesia an earthquake occurred on May 27, 2006 and had the moment magnitude 6.3. Base on the GPS observation, the characterization of the epicenter and source of this Yogyakarta earthquake can be estimated using the displacement estimation and strain at the measurement point by using a simple kriging and sequential gaussian simulation method. The direction of the displacement and maximum shear strain anomaly in this research was shown by the fault of SW – NE direction and the displacement pattern shows that this fault is left lateral strike slip movement. The positive anomaly of the maximum shear strainis located about 10 km east of Bantul, which suggests as the position of Yogyakarta 2006 earthquake source, with the moment seismic and moment magnitude values are 8.1385 x 1025 dyne cm, and 6.5 respectively.

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Ivan Ferdian

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Contact Name Ivan Ferdian

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Contact Name
Ivan Ferdian

Contact Email
ivan.ijgbg@gmail.com

Phone
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Journal Mail Official
ivan.ijgbg@gmail.com

Editorial Address
-

Location
Kota bandung,

Jawa barat

INDONESIA