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All Journal IJOG : Indonesian Journal on Geoscience
Adjat Sudradjat
Padjadjaran University
Earth & Planetary Sciences

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Sabang Submarine Volcano Aceh, Indonesia: Review of Some Trace and Rare Earth Elements Abundances Produced by Seafloor Fumarole Activities Hananto kurnio; Ildrem Syafri; Adjat Sudradjat; Mega Fatimah Rosana
Indonesian Journal on Geoscience Vol 3, No 3 (2016)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1442.696 KB) | DOI: 10.17014/ijog.3.3.173-182

Abstract

DOI:10.17014/ijog.3.3.173-182Geochemical analyses of selected coastal and seafloor samples from Sabang Area revealed abundances of trace and rare earth elements. The selected samples of element abundances were mostly taken from seafloor in the vicinities of active fumaroles either by grab sampler operated from survey boat above fumarole point or by diver directly took the samples on the seafloor especially at Serui - Sabang Bay. Results show that samples closed to seafloor fumaroles demonstrate plenty of trace and rare earth elements. The trace and rare earth elements mean values (n=10) are: Nb (4.33 ppm), La (16.52 ppm), Ce (38.82 ppm), Nd (19.15 ppm), Ce (38.82 ppm), Pr (4.907 ppm), Nd (19.15 ppm), Sm (4.04 ppm), Gd (3.95 ppm), Dy (3.38 ppm), Th (6.432 ppm), and U (4.335 ppm). Negatively, statistical correlations between Fe, Zn, and Ni as the main sulphide elements with sulphur is interpreted that sulphide minerals do not form in the Sabang Sea. Sea water influence in the mineralization process was shown by the good correlations between Fe, Zn, Pb, Ni, and Ba.
Geomorphic Analysis in Determining Tectonic Activity Affected by Sumatra Fault in Liwa Region and Its Surrounding Area, Lampung, Indonesia Yudhicara Yudhicara; Dicky Muslim; Adjat Sudradjat
Indonesian Journal on Geoscience Vol 4, No 3 (2017)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (3397.501 KB) | DOI: 10.17014/ijog.4.3.193-208

Abstract

DOI: 10.17014/ijog.4.3.193-208The study discusses about characteristics of Sumatra Fault and its tectonic activity in Liwa and the adjacent area. The research uses quantitative methods of verification hypothetical deduction, which starts from the general approach, then it pursues into more specialized and focused ones. While the research work includes field measurements, remote sensing with GIS, and geomorphologic analysis using morphometry, such as: sinousity of mountain front (Smf), percentage of facets, ratio of the width and height of the valley (Vf), bifurcation ratios of the river (Rb), drainage density (Dd), shape of the watershed basin area (Bs), hypsometric curves (HI), and gradient index of stream length (SL). Basically, two blocks separated by the Sumatra Fault do not have a significant difference in tectonic activity, but the tectonic activity change can be seen when the studied area is divided into three blocks (northwest, middle, and southeast), then the change in each part can clearly be seen. Apparently, the tectonic activity in the studied area starts from the southeast continues toward the northwest. It is proved by this research, that geomorphological parameters which are associated with mountain fronts and watershed systems demonstrate the value of the activity increases towards the northwest. Hypsometric curves and a river analysis show that the tectonic activity in the northwest is relatively in a young stage, while towards the southeast it is getting in a mature stage.
Sedimentation Process of Rambatan Formation in Larangan Brebes, North Serayu Range, Central Java Bernadeta Subandini Astuti; Vijaya Isnaniawardhani; Abdurrokhim Abdurrokhim; Adjat Sudradjat
Indonesian Journal on Geoscience Vol 6, No 2 (2019)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (2520.882 KB) | DOI: 10.17014/ijog.6.2.141-151

Abstract

DOI:10.17014/ijog.6.2.141-151Rambatan Formation in the western part of North Serayu Basin, Brebes, Central Java, comprises generally flysch facies of turbidite sediments deposited in a deep marine environment. This formation is equivalent to Merawu Formation found in the eastern part of the basin and deposited in the environment of tidal flat to subtidal. The turbidite sediments were highly controlled by a rapid downward movement taking place continuously during Early to Late Miocene. The variation of the depositional environment has been the object of this research which aims to understand the sedimentation process of Rambatan Formation in this type locality with a modern turbidite approach. Rambatan Formation was deposited in N13-N19, as a deep marine sediment channel, turbidite, and deep marine tidal zone. The sedimentation was affected by gravity flow and contourite. The sediments on N13-N14 were marked by turbidite sediments until Middle N17. The sediment supply increased on Middle N17, as a sediment filler on a channel marked by contourite mud layer (muddy slump) and debris flow, with sources from the north. The increase of sediment supply was followed by an environmental transformation from a deep marine channel into deep marine tidal area. In N19, the sediments were redeposited as turbidite sediment, starting with debris flow in Middle N18.
Co-Authors Abdurrokhim ⠀ Bernadeta Subandini Astuti Dicky Muslim Hananto kurnio Ildrem Syafri Mega Fatimah Rosana Vijaya Isnaniawardhani Yudhicara Yudhicara