Koros W.K.,University of Auckland |
Koros W.K.,Geothermal Development Company |
Agustin F.,Geological Agency
Journal of Spatial Science | Year: 2017
Subsidence is conventionally measured by comparing levels on benchmarks that are derived by survey levelling techniques from surveys carried out some epochs apart. Subsidence is usually expressed as an annual rate. The Olkaria geothermal field in Kenya has an extensive benchmark network established in 1983 that has not been levelled since. The field operator is tasked with accelerating generation of electricity from geothermal resources to meet the demands of the population. This may lead to environmental challenges like subsidence. The advent of digital levels and use of traditional precise levelling techniques can achieve high accuracies over short distances. The InSAR technique has been applied in the geothermal field to observe subsidence despite shorter periods of image acquisition. Subsidence levelling data can also be used for gravity surveys and for the design and setting out of geothermal engineering projects. Similar survey techniques have been used worldwide to monitor subsidence in geothermal areas. © 2016 Mapping Sciences Institute, Australia and Surveying and Spatial Sciences Institute.
Helnaria F.P.,Diponegoro University |
Agustin F.,Geological Agency
34th Asian Conference on Remote Sensing 2013, ACRS 2013 | Year: 2013
Timor island is a part of the Banda arc that lies between the Savu Sea and the Timor Sea, it is also part of the collision zone between the northwest edge of the Australian continent that moved north to the Indo-Australian plate and the Banda Sea. This study aims to explain the geological structures and its fault system developed in the Kolbano Block using remote sensing-based geological structure identification method. The geological structures recorded in the relief and topography of Kolbano Block were expressed from satellite images fusion of Landsat 7-ETM + and SRTM. The measurement of the mainstress is also made to support the interpretation of the fault system in the study area. Visual image interpretation are able to identify geological structures such as anticline, syncline, thrust fault, wrench fault, and normal fault. Fault system that developed in the study area is identified as imbricated thrust system shown by either younging age trending from the oldest thrust fault to the youngest one, and existance of several folds among the sheet of thrust faults. The main stress of study area is Northeast - Southwestern or preference to NNE - SSW.The results obtained from this study compiled in Geographic Information Systems (GIS) that uses corrected-satellite imagery Landsat 7- ETM+ as base map. Copyright© (2013) by the Asian Association on Remote Sensing.
Van Den Bergh G.D.,University of Wollongong |
Van Den Bergh G.D.,Naturalis Biodiversity Center |
Li B.,University of Wollongong |
Brumm A.,Griffith University |
And 14 more authors.
Nature | Year: 2016
Sulawesi is the largest and oldest island within Wallacea, a vast zone of oceanic islands separating continental Asia from the Pleistocene landmass of Australia and Papua (Sahul). By one million years ago an unknown hominin lineage had colonized Flores immediately to the south, and by about 50 thousand years ago, modern humans (Homo sapiens) had crossed to Sahul. On the basis of position, oceanic currents and biogeographical context, Sulawesi probably played a pivotal part in these dispersals. Uranium-series dating of speleothem deposits associated with rock art in the limestone karst region of Maros in southwest Sulawesi has revealed that humans were living on the island at least 40 thousand years ago (ref. 5). Here we report new excavations at Talepu in the Walanae Basin northeast of Maros, where in situ stone artefacts associated with fossil remains of megafauna (Bubalus sp., Stegodon and Celebochoerus) have been recovered from stratified deposits that accumulated from before 200 thousand years ago until about 100 thousand years ago. Our findings suggest that Sulawesi, like Flores, was host to a long-established population of archaic hominins, the ancestral origins and taxonomic status of which remain elusive. © 2016 Macmillan Publishers Limited. All rights reserved.
Van Den Bergh G.D.,University of Wollongong |
Kaifu Y.,National Museum of Nature and Science |
Kurniawan I.,Geological Agency |
Kono R.T.,National Museum of Nature and Science |
And 5 more authors.
Nature | Year: 2016
The evolutionary origin of Homo floresiensis, a diminutive hominin species previously known only by skeletal remains from Liang Bua in western Flores, Indonesia, has been intensively debated. It is a matter of controversy whether this primitive form, dated to the Late Pleistocene, evolved from early Asian Homo erectus and represents a unique and striking case of evolutionary reversal in hominin body and brain size within an insular environment. The alternative hypothesis is that H. floresiensis derived from an older, smaller-brained member of our genus, such as Homo habilis, or perhaps even late Australopithecus, signalling a hitherto undocumented dispersal of hominins from Africa into eastern Asia by two million years ago (2 Ma). Here we describe hominin fossils excavated in 2014 from an early Middle Pleistocene site (Mata Menge) in the So'a Basin of central Flores. These specimens comprise a mandible fragment and six isolated teeth belonging to at least three small-jawed and small-toothed individuals. Dating to ∼0.7 Ma, these fossils now constitute the oldest hominin remains from Flores. The Mata Menge mandible and teeth are similar in dimensions and morphological characteristics to those of H. floresiensis from Liang Bua. The exception is the mandibular first molar, which retains a more primitive condition. Notably, the Mata Menge mandible and molar are even smaller in size than those of the two existing H. floresiensis individuals from Liang Bua. The Mata Menge fossils are derived compared with Australopithecus and H. habilis, and so tend to support the view that H. floresiensis is a dwarfed descendent of early Asian H. erectus. Our findings suggest that hominins on Flores had acquired extremely small body size and other morphological traits specific to H. floresiensis at an unexpectedly early time. © 2016 Macmillan Publishers Limited. All rights reserved.
Darmawan S.,Padjadjaran University |
Junursyah G.M.L.,Geological Agency
Near Surface Geoscience 2013 | Year: 2013
A region of east Indonesia with a big geothermal energy potential is Akesahu in the province of North Maluku. Akesahu is located on the island of Tidore. An integration investigation included geological, geochemical, and geophysical survey has been completed to determine of subsurface mapping in this area. There are seven hot springs are found in this area as a surface manifestation of geothermal system. Furthermore, Hg and CO2 mapping has been supporting an investigation due to of ability to indicate a heat fluid leak and structure zone mapping. The presences of these hot spring and also the other supporting data from geological and previously geophysical data could be help on magnetotelluric data interpretation. Based on these previous survey data, data compilation are consistent shown a reservoir prospect in Akesahu area is in the northeastern of Tidore Island. At least, there are three layers shown in LINE-01 and LINE-02 MT section. In addition, the presences of other structures or weak zones that appear on MT seem consistent with the interpretation based on the other data sets and it's proved by 1-D magnetotelluric data which show the top reservoir is 900 m.
PubMed | Geological Agency, Griffith University, National Museum of Nature and Science and University of Wollongong
Type: Journal Article | Journal: Nature | Year: 2016
The evolutionary origin of Homo floresiensis, a diminutive hominin species previously known only by skeletal remains from Liang Bua in western Flores, Indonesia, has been intensively debated. It is a matter of controversy whether this primitive form, dated to the Late Pleistocene, evolved from early Asian Homo erectus and represents a unique and striking case of evolutionary reversal in hominin body and brain size within an insular environment. The alternative hypothesis is that H. floresiensis derived from an older, smaller-brained member of our genus, such as Homo habilis, or perhaps even late Australopithecus, signalling a hitherto undocumented dispersal of hominins from Africa into eastern Asia by two million years ago (2Ma). Here we describe hominin fossils excavated in 2014 from an early Middle Pleistocene site (Mata Menge) in the Soa Basin of central Flores. These specimens comprise a mandible fragment and six isolated teeth belonging to at least three small-jawed and small-toothed individuals. Dating to ~0.7Ma, these fossils now constitute the oldest hominin remains from Flores. The Mata Menge mandible and teeth are similar in dimensions and morphological characteristics to those of H. floresiensis from Liang Bua. The exception is the mandibular first molar, which retains a more primitive condition. Notably, the Mata Menge mandible and molar are even smaller in size than those of the two existing H. floresiensis individuals from Liang Bua. The Mata Menge fossils are derived compared with Australopithecus and H. habilis, and so tend to support the view that H. floresiensis is a dwarfed descendent of early Asian H. erectus. Our findings suggest that hominins on Flores had acquired extremely small body size and other morphological traits specific to H. floresiensis at an unexpectedly early time.
Junursyah G.M.L.,Geological Agency |
Harja A.,Padjadjaran University
AIP Conference Proceedings | Year: 2014
The Manglayang mountain is one of volcanoes located in Bandung Basin area, it is limiting the Lembang active faults in the eastern part. Relationship between those can be interpreted by the information of volcanic deposit thickness and it has conducted by Magnetotelluric method (MT). This method utilizing the sources of natural electromagnetic wave that induce subsurface rocks and produce secondary fields which can be measured orthogonally on the surface. The results are presented in the form of resistivity rock variation resulting by one dimensional (1D) inversion. Interpretation of volcanic deposit thickness in the eastern of Manglayang Mountain indicated reaches 443 m (55-115 Ωm). It is unconformable on soft sediment (3-13 Ωm) with thickness 1,671 m. Those products covered the basement rock (11-42 Ωm). The subsurface geological conditions suggest that the dominated by low resistivity values (<1000 Ωm) suspected correlated with the soft rock as clay, sand, high porosity rocks, and the weathered rock. It is very different from western part of Manglayang mountain which consist of igneous rock dominantly, so that the relationship with Lembang active faults can interpreted separated by geological structure. © 2014 AIP Publishing LLC.
Costa F.,Nanyang Technological University |
Andreastuti S.,Geological Agency |
Bouvet de Maisonneuve C.,Nanyang Technological University |
Pallister J.S.,U.S. Geological Survey
Journal of Volcanology and Geothermal Research | Year: 2013
To understand the processes that made the 2010 eruption of Merapi much larger and more explosive than most dome-forming eruptions of the past century, we investigated the geochemistry, petrology, and pre-eruptive conditions of magmas erupted in 2006 and 2010. The juvenile rocks of 2010 are plagioclase, two-pyroxene basaltic andesites with seriate textures and minor amounts of reaction-free amphibole, Fe-Ti oxides, and rare crystals of olivine and biotite. The bulk-rock composition, mineral paragenesis, and textures are similar to those of juvenile blocks from the much less explosive eruption of 2006. One of the key differences is that most amphiboles in 2010 don't have breakdown reaction rims, whereas those of 2006 are largely reacted. We acquired >80 X-ray distribution maps of major and minor elements of large areas (>1cm2) and single crystals, backscattered electron images, electron microprobe analyse, and compositional traverses across crystals. The data reveal that both the 2006 and 2010 samples are heterogeneous at various spatial scales, with numerous reaction textures between pyroxenes and amphiboles, dissolution textures, and large variations of crystal sizes, morphologies, and compositions. These features record open-system magmatic processes involving the assimilation of carbonate rocks, and interactions between various parts of Merapi's plumbing system, including a degassed shallow magma system and deep hotter and more volatile rich magma intrusions.The petrological complexity of the samples makes unraveling the pre-eruptive conditions of Merapi magmas a petrological puzzle. We applied five different geothermobarometers and performed thermodynamic modeling with the MELTS algorithm, and we propose that there are at least three crystallization zones or environments below Merapi. A deep reservoir at about 30 (+/-3) km depth is suggested by some amphiboles and high-Al clinopyroxenes. Here is where the high-Al basaltic andesites from Merapi are generated probably by water-rich fractionation of more primitive magmas. Such deep magmas are volatile-rich and at near-liquidus conditions (≥4-6wt.% H2O, ≥0.15wt.% SO2, and an undetermined amount of CO2, at about 1050°C) when they start moving towards the surface. A second crystallization zone is recorded by another type of amphibole at about 13 (+/-2) km. Here high-Al clinopyroxene may also grow together with Ca-rich plagioclase. Assimilation of limestone may also occur at this level as recorded by the very Ca-rich plagioclases found in the cores of some crystals. At this location the water content of the melt must remain high enough to stabilize amphibole (4-6wt.% H2O) but CO2 and SO2 are probably already degassing and contribute to gas changes observed by the monitoring system at the surface. Finally, a shallower part of the system (<10km) is recorded by the lower anorthite plagioclase and low-Al in clinopyroxene, and perhaps also in orthopyroxene. This part of the system is probably crystal-rich and largely degassed, and is the likely source of the high-temperature fumaroles and the volcanic gas plumes that are commonly seen at Merapi.We propose that the 2006 and 2010 eruptions were driven by basically the same processes and magma types. The main difference is the much larger size of the deep and volatile-rich magma replenishment that took place in 2010, which had large effects on the kinetics and dynamics of the plumbing system and processes. In 2006, and perhaps also in most of the typical small dome-forming historical eruptions at Merapi, the direct ascent of deep and gas-rich magmas towards the surface is slowed down and partially arrested by the shallower crystal-rich zones of left-over magma from previous events. However, this was not possible in 2010, where the much larger (up to 10 times) size of the magma intrusions overwhelmed the crystal-rich eruption filter. In 2010 the deep magma probably resided for only a short time at intermediate to shallower depths which allowed it to proceed to the surface still carrying most of its deep gas cargo. The larger magma intrusion probably induced higher rates of crustal carbonate assimilation and production of additional CO2 gas at shallow depths. This contributed to the much faster than usual ascent rates and larger explosivities in 2010 than in 2006. These inferences are supported by the shorter interaction times calculated from the diffusion models of clinopyroxene compositions for the 2010 magmas, by the fact that most amphiboles are not broken down in 2010 as opposed to 2006, and also by the much shorter times of escalating monitoring signals (seismicity and deformation) in 2010 compared to 2006.A puzzling observation is that despite the multiple explosive phases of the 2010 eruption, pumiceous materials are rare, and were only found in the last part of the eruption. This contrasts with the abundant tephra layers and vesiculated deposits of older historical explosive events like 1872, and suggest that syn-eruptive processes in 2010 were also different from standard models. The rarity of expanded pumices in 2010 may be due to rapid degassing and re-welding of magma as it ascended from intermediate depths. Given the near constant bulk composition of Merapi magmas erupted in the last decades, and the similarity of textures and minerals in 2006 and 2010, our study suggests that most Merapi magmas are intrinsically capable of explosive eruptions. Here we propose that whether they do so or not mainly depends on the degree of interaction and magma mass proportions between the upper crystal-rich parts of the system (including carbonates) and the deeper and more gas-rich replenishing magmas. Older historical explosive eruptions at Merapi such as in 1872 were driven by more mafic magmas than those erupted in 2006 and 2010 and thus might be caused by different processes from those discussed here. The still unanswered and vexing questions remain as to why in 2010 a much larger amount of magma was segregated from depths and whether this will happen again in the near future. © 2013 Elsevier B.V.
Kaifu Y.,National Museum of Nature and Science |
Kaifu Y.,University of Tokyo |
Zaim Y.,Bandung Institute of Technology |
Baba H.,National Museum of Nature and Science |
And 5 more authors.
Journal of Human Evolution | Year: 2011
Skull IX (Tjg-1993.05) was unearthed from the upper stratigraphic zone (Bapang-AG levels) of the hominin-bearing sequence in Sangiran. This remarkably complete cranial specimen of Homo erectus from the early Pleistocene of Java preserves substantial portions of the vault and face. However, the distortion present in the original reconstruction has hampered detailed documentation of its morphological characteristics. We here report a new reconstruction of Skull IX that successfully recovers the original morphology and significantly differs from previous reconstructions. Detailed morphological description and the results of initial comparative analyses based on this new reconstruction are provided.The endocranial volume of Skull IX was measured as 870 cc using micro-CT data. The neurocranium of Skull IX is slightly smaller than the so far recorded smallest cranium from this zone, suggesting this individual was female. In most, but not all, aspects of the cranial vault form, details of the external surface structures, and facial morphology, Skull IX exhibits numerous similarities to the other Bapang-AG H. erectus specimens, indicating that it belonged to the Bapang-AG H. erectus population. Drawing on the expanded fossil sample of this chronoregional H. erectus group, we discuss their evolutionary status, degree of sexual dimorphism, and facial morphological variation in Afro-Asian earlier Homo specimens. © 2011 Elsevier Ltd.
Robiana R.,Geological Agency |
Cipta A.,Geological Agency
AIP Conference Proceedings | Year: 2014
Jayapura city had destructive earthquake which occurred on June 25, 1976 with the maximum intensity VII MMI scale. Probabilistic methods are used to determine the earthquake hazard by considering all possible earthquakes that can occur in this region. Earthquake source models using three types of source models are subduction model; comes from the New Guinea Trench subduction zone (North Papuan Thrust), fault models; derived from fault Yapen, TareraAiduna, Wamena, Memberamo, Waipago, Jayapura, and Jayawijaya, and 7 background models to accommodate unknown earthquakes. Amplification factor using geomorphological approaches are corrected by the measurement data. This data is related to rock type and depth of soft soil. Site class in Jayapura city can be grouped into classes B, C, D and E, with the amplification between 0.5 - 6. Hazard maps are presented with a 10% probability of earthquake occurrence within a period of 500 years for the dominant periods of 0.0, 0.2, and 1.0 seconds. © 2015 AIP Publishing LLC.