Structures: Folds and Faults in West Kalimantan, Borneo

In West Kalirnantan, the E-W trending fold system is exemplified by the large synclinal structure that involves the Ketungau Basin sediments. It is a symmetrical fold with dips on both flanks around 30 degree. The situation is quite different in the Melawi Basin to the south, were the folding is asymmetric, with a steeply dipping north limb, and the dips decrease to the south. The fold axes extend NWSE. Similar trending folds have also affected Triassic to Cretaceous sedimentary formations to the west of the Melawi Basin.

In the northern part of Kalimantan, a number of thrust and normal faults have been identified trending E-W. The thrust faults may be associated with Late Cretaceous melange formation and were rejuvanated in the Early Miocene. The normal faults were formed after Oligocene time, probably in the Early Miocene.

There are north-trending faults in West Kalimantan, whose nature is ill defined. In Central Jawa, younger faults intersect the Plio-Pleistocene fold axes nearly perpendicularly.

A set of faults in West Kalimantan trends NE-SW, cutting the Cretaceous sediments and Boyan Melange. They are thought to be strikeslip.
 

Diamond in Kalimantan, Borneo, Indonesia

Like gold, diamonds have been known to exist in Kalimantan since the 18th Century. Diamonds have been obtained by panning in the Lardak and Kapuas rivers (Sanggau Regency) since 1836. The largest diamond ever found weighs some 6 carats. All the Kalimantan diamonds are derived from alluvial deposits, and the ultimate source rocks have never been established.

The diamond-bearing alluvial sediments are clastic rocks of 2 to 12 meter thickness, whose clasts are of quartz (yellow to pink color), hornblende, corundum, schist, slate and igneous rock fragments, in addition to magnetite, mica and gold. The slate and schist clasts are known to be pre-Permian. The other rock clasts are Tertiary in age. It was formerly considered that the Pamali Breccia of Southeast Kalimantan represents the primary source of the diamonds. However, Bergman et al. (1987) have shown that this diamondiferous formation is a sedimentary conglomerate of local Bobaris ophiolite provenance.

In 1984 Anaconda Indonesia Inc., together with PT Aneka Tambang, carried out explorations over 4,882,500 hectares of West Kalimantan, under K.P. Number DU 574 by PT Aneka Tambang. Samples were collected from the Landak and Sekayam rivers and examined in Denver, but none showed a positive indication of primary diamond. Only one sample location contained diamonds.

Diamonds are found only in streams that drain the Plateau Sandstone. There is also a correlation between diamonds in the neighboring stream and corundum-bearing rocks occurring as rounded pebbles in the basal conglomerate of the Plateau Sandstone. Paleo-current analyses were made of the Plateau Sandstone, which generally indicated a provenance from the east, but such studies were unsuccessful in locating the primary source of the diamonds. 8 Ma old minette dykes occur at Linhaisai in the northern Barito Province, but they are not considered to be the source of the alluvial diamonds, and the search for the lamproite or kimberlite sources must continue in Central Kalimantan or adjacent Southeast Asia.

It is also possible that at least some of the diamonds were derived from the olivine basalts of Central Kalimantan, and from ophiolites occurring in the Suruk river area in West Kalimantan. The diamonds found in the Tertiary sediments and present day rivers of Kalimantan, Thailand, Burma and Sumatra are characteristically similar. The present geographical locations of the diamond deposits are likely to have resulted from multiple cycles of erosion and sedimentation.

Geology of Sulawesi Island, Indonesia

Geologically, Sulawesi Island and its surrounding area is a complex region. The complexity was caused by con­vergence between three lithospheric plates: the northward-moving Australian plate, the west­ward-moving Pacific plate, and the south-southeast-moving Eurasia plate. The Makassar Strait, which sepa­rates the Sunda Platform (part of the Eurasia Plate) from the South Arm and Central Su­lawesi, formed by sea-floor spreading originat­ing in the Miocene. North of the island is the North Sulawesi Trench formed by the subduc­tion of oceanic crust from the Sulawesi Sea. To the southeast convergence has occurred between the Southeast Arm and the northern part of the Banda Sea along the Tolo Thrust. Both major structures (the North Su­lawesi Trench and Tolo Thrust) are linked by the Palu-Koro-Matano Fault system.

Based on lithologic association and tectonic development, Sulawesi and its surrounding is­lands are divided into 5 tectonic provinces:

• The Tertiary Western Sulawesi Vol­canic Arc
• Quarternary Minahasa-Sangihe Volcanic Arc
• Cretaceous-Paleogene Cen­tral Sulawesi Metamorphic belt
• Cretaceous Eastern Sulawesi Ophiolite Belt and its associ­ated pelagic sedimentary covers
• Paleo­zoic Banda Micro-continental fragments derived from the Australian continent

The contacts between those provinces are faults.

Coal Carbonization Process

Coal carbonization include the reform process with the state of anaerobic (without oxygen) at low temperatures 459-700 Celsius and at high temperatures produces 900-12000 Celsius and porous solid materials which are residues carbonization process called coke or charcoal and volatile gases (Tsai, 1980 ).

In general, the solid material consists of semi-coke is formed from the coal that is not experiencing maturation and coke derived from coal that has undergone maturation.

During the carbonization of coal through several stages of physical and chemical changes. Physical changes of softening, the flow of material, and hardening of the merger, while the chemical changes of cracking polymerization and evaporation. The factors above may affect the quality of coal in terms of petrography composition.

Coal type is characterized by variation maceral and mineral content in coal (Cook, 1975; Stach, 1985). The formation of this type are controlled by various factors, including the spatial and temporal variation of the ancient climate, geological age, tectonic processes, the ecological conditions of sedimentation environment and the coal-forming plants in its community. Type of coal occurs in phase biochemistry.

 

Rank or rank of coal is the maturity level of organic material that starts from the lowest level of lignite, sub-bituminous, bituminous, semi-anthracite, anthracite to meta-anthracite. Carbonization stage is dominated by geochemical processes, so that the most important factor in the formation of coal rank is the temperature, pressure and time.

Observations by petrography in coal basically covers two things namely the identification maceral abundance and composition of maceral vitrinite, inertinite and liptinite. Coal with high inertinite composition and low vitrinite will tend to produce low-power one while if vitrinite high and low inertinite it will have the moderate-power, but coal with high strength obtained when the composition shows inertinite content and vitrinite was balanced. Strength of coal can also affect the rank of coal. Through petrography, coal rank can be known through its vitrinite reflectance value. The best range of vitrinite reflectance value is 1.2-1.4. The coal with good vitrinite value obviously can produce coal with high strength quality.

Regional Tectonic of Timor Island, Indonesia

Arc-continent collision between Eastern Sunda Arc (Banda Arc) and Southwest Australia continent formed the southern boundary of the tectonic elements. This collision zone is part of the evolutionary stages of young or early and more to resemble aspects of normal trench-arc system.

In the eastern part of Sumba Island, Indian Ocean crust has a complete experience of intense subduction and Australia now has been raised above the Banda Arc due this. To the west of the collision zone, Sunda Arc moved to the edge of continental Southeast Asia which make up one of the classic collision system features, in which the crust of the Indian Ocean-Australian (about >150 Ma) forces down along the Sunda trench, given that the Indian Ocean Plate, Australia moved northward relative to the Eurasian Plate with a velocity of about 7.5 cm/year (according to Curray, 1989). The island of Java, Bali, Lombok and Sumbawa expected forming this through the formation of the volcanic arc on the southern edge of Sundaland that initially passive. Sumba represents the bedrock that uplifted front of the arc and was trapped in front of the arc current basin (Reed et al., 1986). Some evidence suggests that the development of Sumba geology can be parallel correlated with Doang Borderland located at the end of the edge of the Sunda Shield (Wytze et al., 1991). However, Lombok front arc basin lies to the west of Sumba marked by the opening structures on certain stratigraphy horizon.

Transition zone Sunda-Banda arc is clearly recorded the existence of two straight thrust fault zone, both located in the front of the arc itself. One is represented by Savu fault (thrust type), and the other were behind the arc is called Flores back arc fault (back-arc thrust type). Both systems are connected (Silver and Reed, 1987). Area behind the arc shows laterally discontinuous zones of the back arc fault structures and produced younger accretionary wedges.

Timor Island is located outside the non-volcanic arc islands of Indonesia, between the Australia plates that move toward the north and the outer Banda arc as part of the Eurasian plate. The Timor Island is made by deformation of the northern Australia plate which had being thrust faulted, especially the southern part around Timor Trough.

The Non-volcanic arcs consist of the underwater ridge of Java Trench, Timor Island, Tanimbar, Kei and Seram up to the east. During the Tertiary age, continuous trench system was fairly active in northwestern Sumatra, Java Trench, the Lesser Sunda Islands, Timor, Tanimbar, Kei and Seram, accompanied by active volcanic subduction that can be found on the West Coast of Sumatra, South Coast of Java, Lesser Sunda Islands (Katili, 1990).

Component of plate tectonics collision involved in this, namely the Asian plate lithosphere that appear shaped by the continental crust (Sunda Craton), sea-marginal (marginal sea) of the Banda Sea, and Australian-Irian lithosphere plate (Gondwana), made by the oceanic crust Indian and Australian continental crust include elements from the island of New Guinea, Buru, Obi and others.

Tectonic evolution that began at the age of the Upper End of Perm, Middle Jurassic, Early Cretaceous until the Late Cretaceous and Neogene basin formation resulting from Paleozoic basin which had trending oriented northwest-southeast direction which then formed again (overprinting) by later Mesozoic basin of northeast-southwest trending direction. Meanwhile, the sinistral transform fault was rejuvenated by Neogene normal fault were related both sides (N. Sitompul, S, Wijanto, J., Purnomo, 1993).

Shape, Structure, and Volcanism Activity of Gunung Kelimutu (Kelimutu Mount), Flores Island, Indonesia

Shape and Structure 

This mountain is located in the Central Flores Island, Endeh District, also called Mount Geli or Mutu. It is at 1640 m above sea level. This mountain has 3 craters are: Tiwu Ata Mbupu, Tiwu Nua Muri Kooh Fai, Tiwu Ata Polo. Mount Kelimutu is belong to strato type volcano.

According to Neuman van Padang (1951) northeast caldera named Sukaria there is a compound volcano with a slope that can develop long straight lineament to the east. Granite buried here about 3 km to the north Kelido area and 2 km to the south of the Kelibara area which is height 1630 m.

Peak which extends 2 km to the west northwest direction, east southeast, and contains 3 pieces craters that all contain a lake.

Ata Mbupu Tiwu, northwest of the valley has a very steep wall of a crater with size of 850x700m rising in the east of an older crater with diameters of 600 m.

Double crater Nua Tiwu Kooh Fai and Tiwu Ata Polo surrounded by a dike ring with “C” shape. It is irregular with a diameter of 1200 m identified by Kemmerling (1929). In August 1932 Stehn (1940) found a large area of collapse sink outside the crater slopes of Tiwu Ata Mbupu and Tiwu Nua Muri Kooh Fai. Because of its embankment, the circle “C” shape is not present.

Kemmerling (1929) analyzed the rocks as follows:

1. A bomb from hyperstene alkaline andesite or basalt.
2. Obsidian.
3. Andesite lava flow or basalt hyperstene
4. Inclusion of the burned clay.

Tabel of Kelimutu Mount Details:

The size is based on Kemmerling (1929). The water color change from year to year, may be directly related to the magmatic activities. The color pattern is also caused by some kind of algae (Niloperbowo, 1972).

Eruption activity

According to old residents in the surrounding volcanoes, the three lakes have been there throughout history. Only the crater wall between the two eastern lakes was much wider and had the same height as the other wall. The eruption occurred between 1860-1870.

• 1938, in May-June occurred activities in Tiwu Nua Muri Kooh Fai. Neuman van Padang (1951) identify as phreatic eruption.
• 1967, in the September, water color of Lake Tiwu Nua Muri Kooh Fai changed from green to white. This is caused because more sulfur is deposited by fumarole uplifting or increasing its activity.
• 1968, Kusumadinata reported the eruption happened in water Tiwu Nua Muri Kooh Fai on June 3. This phenomenon is preceded by a hissing sound followed by a spray of blackish brown water in the west of the lake. Spray occurs in more than one place and reach the high altitude about 10 m.
• 1973, according Suryo there is no significant change, only the water of lake Tiwu Ata Mbupu look black.

Soil in Liwa, Lampung, Sumatra Island, Indonesia

In general, the southern region of Liwa (West Lampung, Sumatra Island) is covered by the residual soil. Soil residues in this region formed by weathering processes are in-situ in the parent rock without experiencing erosion or transportation. Condition tropical regions resulted in the formation of residual soil in Liwa area controlled by the degree of chemical weathering. Climatic and topographic factors also indirectly affect the soil formation process in Liwa area because of these factors helped determine the level of weathering and the thickness of the residual soil. Soil residues from the Liwa area derived from volcanic rock deposition filled up most of volcano hills and valleys. Residual soil weathering is the result of volcanic material such as tuff which has the highest plasticity and high compressibility. It also has a characteristic level of intensive consolidation (Wesley, 1988).

The residual soil in this area can be divided into two types based on their physical appearance. Brown residue on the soil top layer of 0-3 m, whereas below this layer is a red residual soils with a depth> 3 m. They are on the horizon E and B according to the classification of soil profiles according to Soil Survey Staff. Brown residue in the soil on eluviated horizon (E horizon) is characterized by light brown color, many lost their silicate minerals, clay, iron elements, or aluminum due to the washing process and leaving sand or silt particles of minerals resistant. Ground red residues are on illuviated horizon (B horizon) is characterized by red, mineral concentration washing process results in the form of clay minerals, carbon, sesquioxides of iron and aluminum elements.

DETAILS OF GEOTECHNICAL CHARACTERISTIC IN THIS AREA:

·                     Consolidation and compressibility tests showed a tendency to brown residual soil settlement properties (decrease in building construction) are high enough compared with the residual red soil. In accordance with the thickness, consolidation brown residue on the soil is estimated to occur up to 3 m.

·                     Based on the compaction test, natural water content of soil residues (brown and red) are high and are slightly above the optimum water content. As piling material, it is necessary to obtain some degree of drying for the maximum resistance power.

·                     The flow of water occurs vertically from top to bottom through the soil horizons. This process is triggered so that the leaching process of accumulation of minerals often found in the layer B (red residual soil) as enrichment. Lateral water flow at the surface and the erosion is minimal, so that the process of formation of sedimentary soil less than the residual soil widespread in this region.

·                     Soil residues in this region (brown and red) are loaded with halloysite clay minerals, high plasticity value, so that is sensitive to the effects of vibration and changes in pore water pressure. In saturated conditions can cause instability and prone to landslides, especially on steep slopes.

Tectonic and Structure Geology of Sumatra Island

Sumatra Island is located in the path of volcano (NW-SE). Sumatra volcanic arc was formed by the meeting of two plates, the Indo-Australian plate which plunge down into Eurasian plate. The converging between the two plates as more detailed formed tectonic elements as follow:

• Active subduction zone, manifested by the Java-Sumatra Trench.

• Non-magmatic arc as accretionary wedge that formed island of Nias, Simeule Island, Mentawai Islands, etc..

• Fore arc basin, manifested by Sibolga Basin and Bengkulu Basin.

• Magmatic arc, indicated by the Barisan Mountains. Volcanoes located in the Barisan Mountains including Mount Merapi, Mount Kerinci, etc..

• Back arc basin, manifested by the Malacca Straits.

• Continental shelf of Sundaland.

Structure Map of Sumatra Island (Darman & Sidi, 2000)

Important symptoms that occur in Sumatra, in addition to that described above is the presence of horizontal Sumatra fault, known as the Sumatra Fault System (SFS) which divides the island of Sumatra, and following the path of the Barisan Mountains from Aceh to the Sunda Strait. There are two thoughts about SFS:

• Allegedly as a consequence of oblique subduction occurred in Sumatera (Katili, 1985).

• The movement was done by collision between India-Eurasia plate which extruded blocks of Southeast Asia toward Southeast (Tapponier, 1982).

In general, the process of Barisan Mountains uplifting began in Late Miocene, probably reached its peak at the boundary between the Miocene-Pliocene. This uplifting process is not consistently going on until now as estimated by recent geological features followed by the pattern of tectonics in the Early Pleistocene. Tectonic activity along the island formed massive geanticlines that causing the temperature rise related to rapid intrusion of accumulated magma underneath. It is characterized by increasing of both volcanic activity and lateral movement along Sumatra Fault System. All active tectonic activity over the Sumatra region is considered as the main source of recent earthquakes.

Karst Landscapes

Chemical weathering of rocks rich in carbonates would form a unique landscape such as caves, rivers, underground rivers, and springs. Karst derives from the narrow plains means empty due to the dissolving of the work on the surrounding area. Karst developed in areas that have many limestone with little dolomite. Chemical solubility of limestone become more intense when there are cracks, cracks in the rocks so that erosion comes through the gap and continuous surface to the inside.

Limestone towers and conical hills Southeast of Guilin, China

In general there are four necessary conditions for the emergence of karst. First there must be limestone located close to the surface. However, karst is usually found in the dolomite layer was covered by the very lack of solubility when compared with limestone. Second, limestone be packed with lots of thick and thin layered. If the rock is too permeable then the water will continue to flow without reacting first with limestone. Third, the existence of rivers under the ground upon which consist of soluble rocks while also allowing a lot of heavy downward flow forming subsurface water flow is important in the formation of karst. And the last at least the area must have a rainfall conditions is high enough. Some areas with climate Arid or semi-Arid to form karst, karst formation, although some may appear in the previous period when the climate humid/wet.

Gunung Benau (Benau Mount), Type of Sedimentation and Lithology

Consist of interbedded marl and limestone with intercalation of fine grained sandstone conformably overly shoreface sandstone unit. Marl characteristic by grey, limey, frequent calsitic, rich concretions, and pyrite nodules, bioturbated, fossils, minor mica and carbon, concretion. The marl interbedded with light grey, hard, massive, calcite veined, micritic limestone. This well bedded micritic limestone indicate a platform environment. Some build up reef limestone and minor sandstone were also found in this unit.

There also reef limestone with a great amount of fossils including coral, foraminifera, and gastropod. The reef limestone growth in shallow marine environment and interacted with sea level change. Distribution of the reef limestone is not too far and just only found in several spot. It means that the reef can not grow optimally because the sea level change that makes reef can’t catch up or give up to the sea level. The lack of sunshine and nutrient or large influx of terigeneous clastic sediments could also disturbing the growth of reefal limestone.

The limestone is various. In some place, found grey, massive, micritic, very fine-fine grained (calsilutite-calcarenite), no fossil, calsitic, up to 1.5 metres and has a good thin and thick bedding with the marl. The others is fossiliferous limestone, whitish-yellow, texture compact, largely calsite, shells, gastropods, algae, coral. This unit deposited in shelf and shallow water environment. We can interpret the limestone that the massive, micritic limestone is deposited around the outer shelf, near reef, or barrier reef. The major frame building colonies, heads of algae, gastropods, poorly sorted calsirudite, shells, and very rich cavities, hollows is part of reefal (Biohermal Limestone) as a lense or boulder and surrounded by marl and the pelletal packestone, bioclastic wackestone, and limestone is only a local reef development, and growth after shoreface sandstone unit deposited because of drop sea level phase. This local boundstone with limey sand bodies is part of lagoonal or mid-shelf environment.

The middle section contains a tiny section of minor mica, very fine-grained sandstone that interbedded with limestone and marls. This sandstone indicates deltaic/tidal influence in the platform environment. Probably, this environment just occurred in a short time. The whole unit represents platform sedimentation with some localized reef. Sea level change and tectonic process play role during the deposition. The base of this unit is conformably overlies the shoreface unit .The upper contact is an uncomformity with volcanic rock sequence because airfall tuff overlies the marl-limestone unit.

Tanjung Redeb, North East Borneo Geology

Structure and Tectonics

Structures found in the Tj Redeb consist of folds, normal faults, strike slip faults and lineaments. Faults trend NW-SE and SW-NE. Folds trend NW-SE and SW-NE forming anticlines and synclines. This are presumed to have four tectonic events. First event inferred during Late Cretaceous time or older. This event made the Bangara Fm. sediments into folding, faulting and low grade metamorphic rocks. Depositions of Early Eocene shallow marine sediment within the Sembakung Fm. (middle and western part of  area) was also formed Tabalar Fm. in the SE mapped in Eocene-Oligocene and followed by the second tectonic event. Deposition of the Bangara Fm. took place in the middle, east, south and west in the Oligo-Miocene where it is locally intruded by Andesitic rocks, which have been altered and mineralized. Oligo Miocene volcanic activity formed the Jelai Volcanic Rocks in the west. After deposition of the Birang Fm. the Latih Fm was deposited. The Latih Fm. sediments were formed surrounding Teluk Bayur during Late Early Miocene up to Middle Miocene.

The third tectonic event seems to have been occurred after the position of the Latih Fm. Deposition of the Labanan Fm. in the SW and Domaring Fm in the east occurred during the Late Miocene up to the Pliocene whereas the Late Miocene sediments of the Tabul Fm was formed in the north and deposition of the Sinjin Fm. (in SW and N of the sheet). After deposition of the Sinjin Fm. the Sajau Fm. was deposited in the Eastern portion of the sheet in the Plio-Pleistocene.

The Late Pleistocene, after deposition of the Sajau Fm. sediments, the fourth tectonic event was presumed to have occurred. This was showing folding and faulting sediments of the Sajau Fm. and older sediments on the lower part to form the recent topography and morphology.

Mineral and Energy Resources

Coal is one of natural resources having a good prospect in the studied area. The coal surveys were carried out since the Netherlands Indies Government and then continue investigating by the Indonesian Government. Coals are found within sediments of the Latih, Tabul, Labanan and Sajau Formations. The coal mining was formerly carried out by the NV Steenkolen Maatschappij Prapatan (SMP).

Previous geologists report 70 coal seams ranging from 20cm to 5.5 M in thickness. There are many varieties of coal grading from bituminous coal to brown coal. The bituminous and sub-bituminous coals have a quality of 6000 calories per gram. The Teluk Bayur coals have 7000 calories per gram. Building materials such as quartz sand and clays are widespread in Teluk Bayur and Labanan areas. Good quality limestone outcrops are found in Tanjung Selor but are limited in area. The limestone also crops out well in Siduung River upstream but it is hard to be mined because of bad transportation. Limited andesite outcrops were also found in the west and they were used by the logging company for building roads.

Situmorang, R.L. and Burhan, G., 1995

Regional Stratigraphy

• Qa – Quaternary alluvium, Mud, silt, sand, cobbles, pebbles and peat, grey to blackish colors, Unit thicknesses up to 40M..
• Ql – QUATERNARY REEF LIMESTONE, Reefal, coralline and brecciated corals, white to grey, brown, crystalline, hollows, containing corals, locally brecciated, deposited in shallow marine environment.
• TQps – SAJAU Fm. Alternations of claystone, siltstone, sandstone, conglomerate, intercalations of coal seams, contains molluscs, quartzite and micas. Shows cross bedding and lamination. Coal seams 20-100CM thick, black to brown. Unit thickness about 775M deposited in fluviatile and delta environments..
• Tps – SINJIN Fm. Alternations of tuff, agglomerate, lapilli, pyroxene andesite lava, silicified tuff, tuffaceous claystone and kaolin. Contains lignite, quartz, feldspar and black minerals. Unit thickness up to 500M.
• Tmpd – DOMARING Fm. Coralline limestone, chalky limestone, intercalations of marl and lignite; deposited in swampy-littoral environment, thickness is about 1000M. Of Late Miocene-Pliocene Age.
• Tmpl – LABANAN Fm. Alternating polymic conglomerate, sandstone, siltstone, and claystone, intercalations of limestone and coal seams (20-150CM thick) deposited in fluvial environment. Thickness is about 450M. Late Miocene-Pliocene age.
• Tmt – TABUL Fm. Consisting of sandstone, claystone, conglomerate and coal seam intercalations. Contains Operculina sp. Unit thickness about 1050M. Deposited in delta, regressive environment. Late Miocene age.
• Tml – LATIH Fm. Quartz sandstone, claystone, siltstone and coal in the upper part. Intercalations of sandy shale and limestone in the lower part. Black and brown coal seams 0.2 to 5.5M thick. Deposited in estuary, delta and shallow marine environments. Unit thickness is about 800M. Early Miocene to Late Miocene age.
• Tomj – JELAI VOLCANICS, Volcanic breccia, tuffaceous sandstone and tuff. Locally intercalated with coal seams, shows graded bedding and cross bedding structures. Andesite cleave intrusive. Unit thickness reached 200M. Oligocene to Miocene age.
• Tomb – BIRANG Fm. Alternations of marl, limestone and tuff in the upper part. Alternations of marl, chert, conglomerate, quartz sandstone and limestone in the lower part. Thickness is about 1100M. Fossils content: Lepidocyclina ephicides, Spiroclypeus sp., Miogypsina sp., Marginopora vertebralis, Operculina sp., Globigerina tripartite Koch, Globigerinita altispira, Globorotalina mayeri Cushman and Ellisor, Globorotalia peripheronda, Globigerinoides immaturus, Globigerinoides sacculifer, Pre-Orbulina transitoria, Uvigerina sp., and Cassidulina sp. Fossils range Oligocene-Miocene Age.
• Teot – TABALAR Fm. Lower part consist of grey marl, sandstone, shale and intercalations of limestone and basal conglomerate. Upper part consists of dolomite and calcarenite and marl intercalations. Deposited in fluvial-shallow marine environment. Thickness is about 1000M. Eocene to Oligocene age.
• Tes –SEMBAKUNG Fm. Claystone, siltstone and sandstone in the lower part. Quartz sandstone, sandy limestone, chert and tuff in the upper part. Contains fossils: Nummulites sp., Discocyclina sp. Operculina sp. Globigerina sp. Reusella sp. Nodosaria sp., Planulina sp., Amphistegina sp., and Borelis sp., Unit thickness up to 1000M. Deposited in marine environment. Eocene age.
• Kbs – BANGARA Fm. Alternations of metamorphic claystone, silicified claystone, black claystone and shale intercalated with laminated tuffs containing radiolaria. Flysch deposit.
• Tomi – INTRUSIVE ROCKS, Andesite, consisting of vitrophyre, prophyllitic andesite and pyroxene andesite lavas.

Geology of Lomblen Island, Indonesia

Regional Geology and Stratigraphy

Regional structure Lomblen Island include of Banda arc Volcanic belt, with structure terms as folding and faulting in NE-SW and SE-NW direction. The oldest rock formation is Kiro Formation (Tmk) in lower Miocene until upper Miocene. This formation consist of lava, breccias, agglomerate implied layered tuff. Kiro formation wedge with Nangapanda formation (Tmn) that consisted of sandy tuff, breccias tuff, and implied by limestone. Those old formation above were infiltrated by granodiorite (Tmd) in upper Miocene. When Pliocen-Plistocene there was volcanic activity such as lava, agglomerate, and tuff.


 

Regional Stratigraphy of Lomblen Island (Noya, Y., and Suwarno, N., 1983)
 

Structure Characteristics

By regional investigation in field, map of topography and interpretation photograph air there are 2 especial structure direction that is: north-south direction and northeast-southwest direction. In this area (Atedai) there are 6 big structure they are lineament, volcano, cauldron, crater, caldera, slide and fault.

Lineament

This lineament structure have the direction NW-SE. This structure is the oldest big structure estimated cut the basement. Alongside this lineament have emerged the volcano network, such as: Watulolo, Atolojo, Watukuba etc.

Cauldron (crater of Atolojo)

This cauldron structure is the result of eruption mount Atolojo, which among other things yield fallout sediment of pyroclastic skoria andesitic. Cauldron diameter 750-1000 m encircling from NE till NW and open toward north.

Caldera Watukuba

This structure is the result of eruption Watukuba yielding dusty sediment of pyroclastic. diameter of caldera Watukuba 2500 m encircle from north direction to west till easterly. In floor of caldera there are geothermal manifestation like hot ground and alteration.

Debris Avalanches/sliding of Wai Teba

This structure represent the slide which have association with the weak area, form like horse poultice that opening eastwards of Watuwawer.

Fault of Wai Kowan

Fault structure have the direction NE-SW. Alongside this structure have attended the hot water source of Wai Kowan, hot ground of Koti and area of alteration Lowo Kebingin.

Fault of Lewoderoma

This structure have the direction NE-SW. As long as this structure have emerged the hot water source of Lewoderoma And hot water of Waiketi.

Geomorfology

Regional area of research by Volcanology Department of Indonesia divided in 5 morphology region:

1. Old volcanic
2. Mount Watuloko
3. Mount Watukuba and Atalojo
4. Debris Avalanches unit
5. Plain morphology unit

· Old volcanic
Set of this distinguished by circular hilly. The relief is smooth until middle. Dale instruct north-south direction. River have parallel semi pattern and sentence sharply form in high stadium erosion. Set of this reside in north formed of old rock volcanic.

· Mount Watuloko
Set of this distinguished by topography form which harsh, precipitous level of inclination and erosion river deeply. Set of this take possession of the middle until north of investigation area limited of old morphology volcanic. Set of this built by lava andesitic which is generally escaped because fault.

· Mount Watukuba and Atalojo
Set of this show the very typical topography form that is volcano crater and caldera. There are a crater with the diameter 750-1000 m ( Mount Atalojo) and a caldera with the diameter 2500 m ( Mount Watukuba). Set of this morphology is formed by fallout of sediment of pyroclastic and lava. The river have pattern radial with the narrow tight dale pattern making dominant vertical erosion.

· Debris Avalanches unit
Set of this have the wavy topography form with middle of level inclination. Generally weak river stream and a little erosion. Set of this formed by rock from landslide.

· Plain morphology unit
Set of this located in coast environment formed by rock alluvial. Set of this distinguished by smooth topography.

Geothermal, Atadai East Nusa Tenggara, Indonesia

Geological

Based on geological surveys the area is mostly covered by the Quaternary andesitic volcanic rock, while those rocks are uncomfortably underlain by Tertiary basement rocks of Kiro and Nangapanda formations. Volcanic products include lavas, pyroclastics and lahars. From thin section in petrography observation shows that the volcanic rocks are andesine pyroxene composition. The volcanic products can be divided into two groups; the old volcanic and the young volcanic. The crop outs were founded at the northern and the southern part of the area with unknown eruption centers and forms a high dissected terrain. Also those were the forms cones at the central and eastern part of the area along the NNW-SSE trending volcanic lineament.

The couple of NE-SW trending normal faults in this area recognized as Wolo Kebingin fault in the north and Mauraja fault in the south, these faults possibly control occurring thermal features in the area. There is also a major volcanic center known as Watuwawer caldera of about 2,5 km2 in diameter, located in the central part of the study area (Figure 4.1).


Figure 4.1: Geological Map of Atadai Geothermal Area (Sundhoro, et al., 2003)

Geochemical

Thermal features in Atadai geother¬mal area occur over an area about 25 km2 within the Watuwawer caldera, eastern and western flank of the volcanic lineaments. There are at least 9 locations of thermal features which are in an elevation between 170 m to 500 m above sea level. These include hot springs, fumaroles, steaming grounds/ hot grounds, and altered rocks. And then the flow rates of these hot springs are between 1 to 50 liter/minute. The temperature of six hot springs are up to 42 oC, however the temperature of three fumaroles and hot ground are up to 98 oC (Table. 4.1).

No Location Manifestations Temp. (oC) pH Type of Fluid Remarks
1. Watuwawer (Koru Matek) Fumaroles, hot ground and altered rock 96 2-3 Sulphate Up Flow
2. Lowokebingin (Wai Kating) Fumaroles, hot ground and altered rock 98 2-3 Sulphate Up Flow
3. Lowokoba (W. Teba) Hot ground and altered rock 96 3 Sulphate Up Flow
4. Wae Kerata Hot Spring 40 6.8 Bi -Carbon¬ate Out Flow
5. Wae Tupat Kecil Hot Spring 40 7.6 Bi -Carbon¬ate Out Flow
6. Wae Kowan Hot Spring 40 6.8 Bi -Carbon¬ate Out Flow
7. Wae Tupat Hot Spring 35 7.2 Bi -Carbon¬ate Out Flow
8. Wae Keti / Lewogeroma Hot Spring 38 7.2 Bi -Carbon¬ate Out Flow
9. Wae Teba Hot Spring 42 6.5 Bi -Carbon¬ate Out Flow


Table 4.1: The Thermal Features in Atadai, Lembata, East Nusa Tenggara

Following the example of the hot water have been taken in order to be known the nature of physical and its chemistry. From chemical analysis result of example can be determinated hot water type in investigation area (Figure 4.2). According to diagram Cl-, S042= and HCO3 water in investigation area can become 2 system that is:

1. Bicarbonate system
2. Sulphate system


Figure 4.2: Types of Water in Atadai Geothermal Area (suparman, et al., 1997)

The first system and the second ones show out flow system and the up flow system. Both of the hot water system supposed have been contaminated by meteoric water. Quantitatively, temperature of under surface was determined with a few method such as: silica method, method Na-K, and method of gas (methane and ammonia). The Result of temperature measurement of under surface with the silica method ( SiO2) show the temperature between 129-147 oC, while using method Na/K relative more higher (> 300oC), with the method of gas show the temperature between 178-221oC.

Considering that the geothermometer Na/K higher level than the other, water type dominant is bicarbonate with the surface temperature 40oC. It is included in enthalpy intermediate (125-225oC). Hence temperature of under surface was used from geothermometer SiO2 as minimum temperature (129oC) and maximum temperature from geothermometer gas ( 221oC).

There are also surface alteration of advanced argillic type. Clay minerals present in both the active thermal features area of Watuwawer and Lowokebingin. Minerals are predominantly: Kaolin, Halloysite, Smectite and Alunite. However Phyrophillite and Dickite are also present, which probably represent the high temperature of clay minerals in the acidic condition.

The high contour values of soil mercury is concentrated around Lowo Kebingin, Lowokoba and Watuwawer hot springs, where the maximum concentration of Hg are up to 2566, 564 and 330 ppb. The high values of soil gas CO2 is 6,76 %, It is also concentrated around the active geothermal manifestation of Watuwawer (Figure 4.3 and 4.4).


Figure 4.3: Soil Mercury in Atadai Geothermal Area (Suparman, et al., 1997)


Figure 4.4: Distribution of CO2 in Atadai Geothermal Area (Suparman, et al., 1997)

Geophysical

To get more interpretation about depth investigation then Volcanology Department of Indonesia used Schlumberger geoelectrical method. From this method gained more information of lateral and vertical distributions using resistivity data. Resistivity data indicated that low resistivity zones which represent argillic alterations about 15 km. The lateral of the low resistivity boundaries (below 10 Ohm-m) are related with the active thermal features areas, such as: Watuwawer and Lowokebingin. The resistivity boundaries which represent a prospect area covers at least 7 km2 area. The vertical sounding data shows that the thickness of conductive layers which represent the clay cap of the Atadai geothermal system are estimated between 500 m to 600 m depth of the bottom surface. The models of geothermal system have been made by geophysical team member of Volcanology Department of Indonesia on period 1997-2000 (Figure 4.2 and 4.3).


Figure 4.5: Apparent Resistivity Map of Atadai Geothermal Area (Sundhoro, et al., 2003)



Figure 4.6: Apparent Resistivity Cross Section of Atadai (Sundhoro, et al., 2003)

The tentative model of the Atadai geothermal area is shown in Figure 4.4. It is looks that in the active geothermal manifestations strictly an up-flow system with elevation are between 300 to 500 m above sea level. Whereas out flow geothermal system is manifested by the hot springs, which are situated in the flank of caldera Watuwawer with the elevation are between 170 to 250 m above sea level.


Figure 4.7: Tentative Geothermal Model of Atadai Geothermal Area (Sundhoro, et al., 2003)

Prospects Areas

The prospect area in Atadai is decided from the result of the geological, geochemical and geophysical surveys, such as: thermal features of hot springs, fumaroles, steaming grounds/ hot grounds, altered rocks, the resistivity boundaries, the high contour values of soil mercury and soil gas CO2, and also the structure geology of Watuwawer caldera. The structure of the cones at the central and eastern part of area, the NNW-SSE trend volcanic lineament, and the couple of NE-SW trending normal faults of Lowo Kebingin fault in the north and Mauraja fault in the south are dominantly controlling the prospect area (Figure 4.5).
Base on the prospect area of about 7-8 km2, than the estimated of the potential energy in Atadai geothermal area is about 22 Mwe. The estimation of geothermal energy in Atadai area are:

1. Watuwawer = 21.347 MWe
2. Wolokebingin = 1.187 MWe



Figure 4.8: The Prospect Area of Atadai Geothermal Area (Sundhoro, et al., 2003)

Based on those data, concluded that the prospect area in Atadai covers into Watuwawer and Lowo Kebingin, which both of the areas are situated in the nearby of the surface manifestations. Comparing between these prospect area indicate that Watuwawer is the most attractively exposure up of thermal features rather than in the Lowo Kebingin. The surface terrain of both prospect area are very different, Lowokebingin lies in the medium to the high steeply valley, whereas Watuwawer lies in the flat area. It forms a high dissected terrain on the floor of the Watuwawer caldera and it is also boundaried by caldera rim.

Sikuai Island, West Sumatra Indonesia

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TITIK HITAM DI ATAS KERTAS PUTIH...

Bertahun-tahun yang lalu hingga sekitar beberapa bulan yang lalu, terus terang saya menjadi seorang yang merasa kehidupan dunia ini datar-datar saja, tidak ada yang istimewa dan layak disyukuri. Bagi saya saat tidurlah suatu kebahagiaan terindah. Entahlah, saya begitu menyesal atas apa yang saya miliki, istri, pekerjaan, kehidupan, kemampuan serta fisik yang saya miliki sepertinya tidak sesuai harapan. Saya selalu merasa menjadi orang yang KEKURANGAN di dunia ini. Semakin kuat saya berusaha untuk merubah keadaan, yang saya terima adalah semakin banyak kekecewaan. Saya tidak tahu harus memulai dari mana, hingga suatu saat seorang sahabat memberikan suatu nasehat yang sungguh luar biasa dan memberikan suatu gambaran utuh tentang sebuah arti syukur dalam kehidupan. Di suatu tempat aku dan sahabatku berbincang-bincang :

Ya...aku mengerti apa yang kau alami, tidak hanya kamu akupun sendiri pernah mengalami dan mungkin banyak orang lainnya, sekarang aku akan ambil satu kertas putih kosong dan aku tunjukkan padamu, apa yang kamu lihat ?, ucap sahabatku.

Aku tidak melihat apa-apa semuanya putih, jawabku lirih.

Sambil mengambil spidol hitam dan membuat satu titik ditengah kertasnya, sahabatku berkata "Nah..sekarang aku telah beri sebuah titik hitam diatas kertas itu, sekarang gambar apa yang kamu lihat?".

"Aku melihat satu titik hitam", jawabku cepat.

"Pastikan lagi !", timpal sahabatku.

"titik hitam", jawabku dengan yakin.

"Sekarang aku tahu penyebab masalahmu. Kenapa engkau hanya melihat satu titik hitam saja dari kertas tadi? cobalah rubah sudut pandangmu, menurutku yang kulihat bukan titik hitam tapi tetap sebuah kertas putih meski ada satu noda didalamnya, aku melihat lebih banyak warna putih dari kertas tersebut sedangkan kenapa engkau hanya melihat hitamnya saja dan itu pun hanya setitik ?". Jawab Sahabatku dengan lantang,

"Sekarang mengertikah kamu ?, Dalam hidup, bahagia atau tidaknya hidupmu tergantung dari sudut pandangmu memandang hidup itu sendiri, jika engkau selalu melihat titik hitam tadi yang bisa diartikan kekecewaan, kekurangan dan keburukan dalam hidup maka hal-hal itulah yang akan selalu hinggap dan menemani dalam hidupmu".

"Cobalah fahami, bukankah disekelilingmu penuh dengan warna putih, yang artinya begitu banyak anugerah yang telah diberikan oleh Tuhan kepada kamu, kamu masih bisa melihat, mendengar, membaca, berjalan, fisik yang utuh dan sehat, anak yang lucu-lucu dan begitu banyak kebaikan dari istrimu daripada kekurangannya, berapa banyak suami-suami yang kehilangan istrinya ?, Juga begitu banyak kebaikan dari pekerjaanmu dilain sisi banyak orang yang antri dan menderita karena mencari pekerjaan. Begitu banyak orang yang lebih miskin bahkan lebih kekurangan daripada kamu, kamu masih memiliki rumah untuk berteduh, aset sebagai simpananmu di hari tua, tabungan , asuransi dan teman-teman yang baik yang selalu mendukungmu. Kenapa engkau selalu melihat sebuah titik hitam saja dalam hidupmu ?" dan juga........ ......... .

Itulah kamu, betapa mudahnya melihat keburukan orang lain, padahal begitu banyak hal baik yang telah diberikan orang lain kepada kamu.

Itulah kamu, betapa mudahnya melihat kesalahan dan kekurangan orang lain, sedangkan kamu lupa kelemahan dan kekurangan diri kamu..

Itulah kamu, betapa mudahnya kamu menyalahkan dan mengingkari- Nya atas kesusahan hidupmu, padahal begitu besar anugerah dan karunia yang telah diberikan oleh-Nya dalam hidupmu.

Itulah kamu betapa mudahnya menyesali hidup kamu padahal banyak kebahagiaan telah diciptakan untuk kamu dan menanti kamu

"Mengapa kamu hanya melihat satu titik hitam pada kertas ini? PADAHAL SEBAGIAN KERTAS INI BERWARNA PUTIH ?, sekarang mengetikah engkau ? ", ucap sahabatku sambil pergi (entah kemana).

"Ya aku mengerti", ucapku lirih.

Kertas itu aku ambil, aku buatkan satu pigora indah dan aku gantung di dinding rumahku. Bukan untuk SESEMBAHAN bagiku tapi sebagai PENGINGAT dikala lupa,..lupa. ..bahwa begitu banyak warna putih di hidupku daripada sebuah titik hitam. Sejak itu aku mencintai HIDUP ini. Bisa Hidup adalah suatu anugerah yang paling besar yang diberikan kepada kita oleh Perekayasa Agung... Aku tidak akan menyia-nyiakannya. Pak Mariopun juga pernah berpesan kepadaku :

Kadang-kadang Tuhan menaruh kita pada tempat yang sulit supaya kita tahu dan menyadari bahwa tidak ada yang sulit bagi Tuhan

Temukan cara bersyukur akan masalah-masalahmu dan semua itu akan menjadi
berkah bagimu ...
Rasa syukur dapat mengubah hal yang negatif menjadi positif ...

AKU TAK SELALU MENDAPATKAN APA YANG KUSUKAI oleh karena itu AKU SELALU
MENYUKAI APAPUN YANG AKU DAPATKAN.............