Regional Geology

Ery Arifullah 1), Andang Bachtiar 2) , Djuhaeni 3)
1 Master Student, Department of Geology, ITB
2GDA Consultant Jakarta
3Department of Geology, ITB
earifullah@plasa.com

Abstract
Detailed analysis of Modern Mahakam Delta sediments concentrated on identifying ichnological and sedimentological characteristics of four deltaic environments. These include: 1) distributary channel, which are typically low diversity and bioturbation index with displaying Psilonichnus, Skolithos, Ophiomorpha, Monocraterion, Teichichnus Arenicolites, Planolites, Thallasinoides, escaping traces, and Glossifungites ichnofacies; 2) estuarine tidal bar which are typically balanced diversity and biotu rbation index with displaying Psilonichnus, Ophiomorpha, Arenicolites, Skolithos, Siponichnus, Monocraterion, Paleophycus, Helminthopsis, Teichichnus, Planolites, Chondrites, Paleodictyon, crawling traces, and vertebrate track; 3) interdistributary area which are typically medium diversity and high biotu rbation index with displaying dominated Arenicolites, Ophiomorpha, Conichnus, Skolithos, Scaubcylindrichnus, Diplocraterion, Rosselia, Teichichnus, Chondrites; 4) mouth bar sediments are displaying Ophiomorpha, Planolites, grazing traces, crawling traces, fecal casting, and abundance dwelling tubes Skolithos like.
Ichnological research in the Modern Mahakam Delta potentially improves our understanding of deltaic facies sedimentology. Our findings suggest that sedimentological processes, substrate types and salinity control ichnological characteristics.

From : The 33rd Annual Convention & Exhibition 2004 Indonesian Association of Geologist

Eko Soebowo, Kamtono dan Herryal Z. Anwar
*) Pusat Penelitian Geoteknologi – LIPI
Kompleks LIPI, Jalan Sangkuriang, Bandung. 40135
Telpon : 022-2503654, 2507771, fax. 022.2504593
e-mail : eko.soebowo@geotek.lipi.go.id

Abstract
Regional development program at hinterland area require an information of land capacity and sub-surface geology. Several boring have been done at Puring, South Gombong to investigate the sub-surface condition and the engineering properties.
The result of the study shows the stratigraphy of this area consisted of 3 litological unit, ie. Sand and coastal deposit unit, silty clay with mangrove environment until shallow marine and inter bedded clay-sand with marine environment (Upper Halang Formation). Drilling and engineering properties data shows medium to dense of slit- clay layer and denser to the north. Bearing capacity of this layer tend to decrease at the middle of the section, and increases to the north.
Base on soil index properties, this layer has a medium to high expansive potential index, and tend to more expansive at the bottom of bore hole 1 (Sugihwaras). Therefore, the sub-surface stratigraphical aspect and the engineering properties of the layer shows that the Suguhwaras area and surrounding has a low bearing capacity index.

From : The 33rd Annual Convention & Exhibition 2004 Indonesian Association of Geologist

Eko Seobowo, Adrin Tohari dan Hery Haryono
Pusat Penelitian Geoteknologi – LIPI
Jl. Sangkuriang, Kompleks LIPI, Bandung.40135
Tlp. 022-2503654, 2507771, Fax. 022-2504593

Abstract
In the development plan of a new and old road infrastructures, the understanding of lithology distribution aspect and fault structures are the most crucial factors on the road establishment. Geological aspects is the first thing to predict the geological hazard to prevent the negative impact on the environment, need to be evaluate.
According to the geological interpretation and field assesment along the lane of Ladia Galaska road are metamorf (sciss, phillite, quarzite) dominated and some sediment (intercalation sandstone-clay), intrusion rock (diorite) and vulcanic sediments. Presented fault structure along the road of Ladia Galaska is related to the active “Sesar Besar Sumatra” (west part) and some earth quake were occured in Blangkejeren (1997) as well. The fault structures orientation along the road are crossed and pararelled. The road lanes of Lhok Seumot – Beutong Ateuh – Ceulala and Uring – Pepela are crossed by the fault which has a local landslide problem. The road which are pararelled to the Takengon – Isaq, Ise-ise – Blangkajeren dan Pinding – Lokop fault has a tendency to the local landslide especially on the lane of the road. This research result can be use for the classification of the geological hazard and to prevent the unstable condition of the road on the future.

From : The 33rd Annual Convention & Exhibition 2004 Indonesian Association of Geologist

F a t i m a h
Directorate of Mineral Resources Inventory

Abstract
Indonesia coal resources have been updated annually. The most recent data (2003 publication) shows that the total Indonesian coal resource is 57,847.74 million ton. This number can be classified as 12,466.42 million ton measured resources, 20,533.56 million ton indicated resources, 24,314.96 million ton inferred resources, and 532.80 million ton hypothetical resources.
Data for coal resources calculation derived from government inventory reports as well as private company reports. The main problem appears in coal resources compilation is there is no standard format in reporting Reserves and Resources of coal in their concession area. Although the government has already published the National Standard (Amendment 1 – SNI 13-5014-1998) for Coal Resources and Reserves Classification, most of private companies have not applied the standard yet. Therefore, there is no certainty for classified coal resources. Moreover, most of the coal companies (both private and BUMN) never reported the total reserve of their exploration areas. This would affect the compilation on Indonesia coal resources.
It is suggested that the government should make guidance for reporting the coal Resources and Reserves. The government also should insist coal companies to follow this guidance. Regarding resources and reserves classification, the government should strongly socialize the standard for coal resources and reserves to coal business sector (private companies, institution, as well as universities).

From : The 33rd Annual Convention & Exhibition 2004 Indonesian Association of Geologist

By :
Hanik Humaida and Yustinus Sulistiyo
BPPTK-Direktorat Volkanologi dan Mitigasi Bencana Geologi
Jl. Cendana 15 – Yogyakarta

Abstract
SO2 is one of the volcanic gases that can provide information about the state of volcano activity. Commonly, SO2 flux is measured by COSPEC (Correlation Spectroscopy). This equipment has several disadvantages; such as heavy, big size, expensive. DOAS (Differential Optical Absorption Spectroscopy) is a new method for SO2 gas flux monitoring that has advantages compares to the COSPEC. Recently, this method has been developed.
This DOAS consists of 5 units; namely scan miler, condenser lens, detector, power supply, and a laptop. Its total weight is up to 11 kg. For operation of DOAS using traverse method, it need only lens unit, detector and laptop. The total weight is only 2 kg. DOAS can be operated as static or traverse method and can be mounted at anyplace.
Measurement of SO2 flux by DOAS has been done at G. Bromo on 12-15 June 2004, after the 8 June eruption. Location of measurement is about 2 km from eruption source using tripod. This angle of measurement ranges between 10 and 12o, width of scan is 45o. Data was analysed by HINAGATA software. The result showed that 30 minutes prior to the ash eruption, the flux of SO2 increased from normal condition until 135 ton/day.

From : The 33rd Annual Convention & Exhibition 2004 Indonesian Association of Geologist

H. Utoyo*, Mesker H.J Dirk* S.Bronto* dan Kaspar L.B
* Geological Research and Development Centre (GRDC); Jl. Diponegoro 57 Bandung
E mail: harryutoyo@grdc.go.id

Abstract
K-Ar age of volcanic rocks in Cipunegara, Subang is to reach of the absolute age dating, therefore to be easy to detect of the relation between volcanic rocks one to the other.
Generally volcanick rocks in the study area has been altered to sericite, carbonate and ore mineral. In which there are only three samples can be dated by the K/Ar method.
Andesite display the age of 58.99 ? 1.94 m.a (Upper Paleocene) and 36.88? 3.96 m.a ( Upper Eocene ) there are possibility show the oldiest of volcanic rocks in this area. The other rocks display of negative age, because of strongly alteration activities, and significance of the loss argon. Results of the K/Ar dating shows of magmatic activities have been two time periods, i.e during Lower Eocene and Upper Eocene in Cipu negara.

From : The 33rd Annual Convention & Exhibition 2004 Indonesian Association of Geologist

R. Hutamadi, Bambang Tjahjono S., Rudy G.
(Subdit Konservasi DIM)

Abstract
Mineral conservation as part of the management of national mineral policy focuses on optimization benefits of mineral resources and reduction of environmental impacts resulted from mining operations. The implementation of conservation policies that involves various institutions has met a number of difficulties.
The problems of mineral conservation include unavailability of laws and regulations related to conservation policies, utilization of by-product materials, and management of remaining reserves after mine closure. In addition, the existence of illegal mining practice has failed to optimize the benefits of mineral resources and affected environmental damages
Recently in mining practises show that aspects of mineral conservation have not been fully applied in either small-scale or large-scale mining industries. For examples; dirty coals, fine coal as part of tailings disposal have not been utilized; and small-size materials are not treated appropriately. Therefore it needs urgently the avaibility of the conservation regulations and law enforcement as aguide for the mining companies and government institutions for implementing for mineral conservation.

From : The 33rd Annual Convention & Exhibition 2004 Indonesian Association of Geologist

Igan S. Sutawidjaja

Abstract
Egon volcano, which had been dormant since 1907, became active in late January 2004. It was preceded by some crumbling sounds at mid night on January 27th , 2004 that heard by the people who live in Baokrengit village, close to the volcano. No experience of volcanic eruption in almost two human generations caused a panic for the people when they saw a smoke column above the summit in the morning.
A phreatic eruption resulted many small craters surrounding the main crater, erupted ash and mud and distributed within the main crater. Ash analyses show altered materials of alunite, pyrite, kaolinite and anhydrite, there was no magmatic materials erupted to the air. At least 12 craters were identified with a different dimension between 5 to 10 m in diameter.
Volcanic Hazard Map of Egon volcano that had been mapped in August 2003, have supported the Local Government to evacuate the people to the safe area and returning some refugees from Maumere city to the living area which was declared in outside of Hazard zone II and Hazard zone I areas

From : The 33rd Annual Convention & Exhibition 2004 Indonesian Association of Geologist

K.T. Dewi1, P.Frenzel 2 , A. Muller3, D. van Harten4
1. Marine Geological Institute, Bandung, INDONESIA
2. Marine Biology Department, University of Rostock, Germany
3. UFZ Centre for Environmental Research, Magdeburg, Germany
4. Department of Geology, Free University, Amsterdam, The Netherlands

Abstract
Surface sediments from water depths between 100 and 3070m along a transect off Timor Island between the Banda and Timor Seas contain more than one hundred species of marine ostracods. Generally, the number of species in each samples ranges from 2 to 112 and reflects a high diversity. The numbers of specimen is between 2 and 4942 individuals per 100 cc of sediment sample. The distribution of ostracod species clearly correlates with water depth. The abundance and diversity of the ostracod fauna tend to decrease with increasing water depth, except for one anomaly in station that was collected in the deepest part (3070m) of the study area. The highest numbers of individuals (>1000) occur in stations with water depth less than 100 m, i.e. in shelf zone and dominated by Paracytheridea, Polycope, Foveoleberis, and various species of Bairdiidae. The bathyal zone is characterized by Cytheropteron, Saida, Bradleya, Pelecocythere, Henryhowella, Krithe and Parakrithe. The unusually high number of ostracode in the Lower Abyssal zone (deeper than 3000m) is mainly caused by the high occurrence of shallow water ostracods. The abundance of ostracods in deep-water are strongly influenced by bathymetry and water mass characteristic that cause downslope transport of shallow water ostracods into deeper environments.
The results of this study clearly show that ostracods are an important component of marine sediments regarding the identification of paleoenvironments, and particularly paleobathymetry. They provide a new and promising tool for future studies of paleobathymetry based on ostracod distribution at continental margins. The results of this study and additional study on two other transects from continental margin could be applied as a model to reconstruct the paleoenvironments in Indonesia.

From : The 33rd Annual Convention & Exhibition 2004 Indonesian Association of Geologist

MAC. Endharto
Geological Research and Development Center

Abstract
This study attempts to analyse the depositional system of the Ngrayong Sandstone into the basin pattern with using the basin analysis approached, concerning the hydrocarbon explorations in Madura Island. The study area is divided into three main zones which initiated with the western segment of the island. There are some geological key traverses e.g., Gunung Geger, Gujug Laut, Waterfall, Gujug village, Tanah Merah, Torjun-Somber, Sapulu and Kombangan.
Along the Gunung Geger-Gujug Laut-Water Fall section (south margin-western portion) is remarked by the appearance of the depositional classic progradation which characterized by the sedimentary structures (i.e. lenticular bedding, flaser bedding etc), implicate that the Ngrayong Sandstone was deposited within the tidal sand flat (open coast) system subdivision, from supratidal-salt mars to the shallow portion of the subtidal. environment. At the open sand quarry outcrop near Gujug Laut Village, well exposed of the basal portion (2m thick) of the Ngrayong Sandstone sequence, dark grey silty sand and shale demonstrate ripple cross lamination and wavy bedding underlie bioclastic lithic arenite contains tabular cross bedding indicate the intertidal sand flat, lower portion of tidal flat under condition low current speed. Tabular cross bedding occurs in the bioclastic lithic arenite interpreted as the sand flat in the headward portion of the macrotidal estuaries. Shelf transgression of marine condition is shown by the occurrences of the sandy limestone, upper part of the sequence. The presence of the hexagonal gypsum crystal formed within the calystone indicates the evaporation process in subaquaceous of supratidal zone. Paleocurrents are measured from planar and trough cross beddings display southwest direction (200o- 190o). Based on the sedimentary structures and trace fossils found in the Ngrayong Sandstone unit, along the Torjun-Somber section.
Along the Sapulu traverses (northern part of the west segment), the sand unit of the Ngrayong Sandstone was precipitated and more influenced by fair-weather wave base to outer shelf-transition zones, the lithology is characterised by the presences of the coarsening upward of the sandy limestone and alternating mudstone and shalestone. Change gradually from low to high energy to the landward is also present in this area, which is evidenced by the occurrences of the packstone.
The Kombangan traverse exhibits subtidal type of sediment marked by trace fossil of Cruziana (Planolites.). Marine condition as shallow lower shoreface to deep upper shoreface usually associates with Skolithos and Cruziana

From : The 33rd Annual Convention & Exhibition 2004 Indonesian Association of Geologist