Journal of Earth and Marine Technology (JEMT)
Journal of Earth and Marine Technology (JEMT) ISSN: 2723-8105 is an international peer-reviewed journal published by LPPM-ITATS, in cooperation with IAGI and PERHAPI. The journal publishes applied and interdisciplinary research in geoscience, natural resources, mining engineering, environmental engineering, and marine-related systems. It emphasizes scientific rigor, methodological clarity, and technological contributions to earth system studies. It provides a platform for research on geological processes, resource exploration and management, environmental impacts, and engineering applications across terrestrial and marine environments. JEMT is committed to maintaining high standards of peer review, research integrity, and scientific quality. It publishes original research articles, reviews, and applied studies relevant to earth and marine sciences and engineering. Frequency: 2 issues per year (March and September) Editorial timeline (average): First decision ~1 week, peer review ~4–8 weeks, post-acceptance ~1–2 weeks Acceptance rate (2025): 64% DOI: 10.31284/j.jemt Indonesian Journal Accreditation: SINTA 4
Lembaga Penelititan dan Pengabdian kepada Masyarakat - Institut Teknologi Adhi Tama Suraba
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Deciphering Metamorphism of Tarap Formation through Petrographic Analysis
Detailed petrographic characterization aimed at constraining the metamorphic evolution of the Tarap Formation remains limited. This study presents petrographic analyses of 11 metamorphic rock samples collected from the Tarap Formation in OKU Selatan, South Sumatra. The results identify a range of metamorphic rock types, including metalimestone, metasiltstone, calcite–chlorite marble, muscovite–quartz phyllite, quartz–muscovite schist, muscovite–chlorite schist, and quartz–hornblende schist. The protoliths identified were calcareous rocks, quartz–feldspathic sandstones, and shales, which may be lithologically correlated to the Kuantan Formation and Gunungkasih Complex. The metamorphic facies identified are sub-greenschist, greenschist, and lower amphibolite facies. Prograde metamorphism and the subsequent development of mylonitic texture that overprints the main foliation are interpreted to be possibly related to the tectonic evolution of Sumatra during the Early Cretaceous, particularly subduction of the Ngalau Ocean (Meso-Tethys) beneath the Sundaland margin (West Sumatra). The subsequent arc-continent collision from the Late Cretaceous, causing reverse faulting and fold–thrust deformation, facilitated exhumation of the rocks, potentially resulting in retrograde metamorphism and cataclastic texture.
Copyright (c) 2026 Muhammad Alfath Salvano Salni, Idarwati Idarwati https://creativecommons.org/licenses/by/4.0
Geotechnical Planning for Slope Stability in Limestone Mining at PT Rahmad Makmur Abadi, Punggulrejo Village, Rengel District, Tuban Regency
This study focuses on optimal slope-geometry planning in the IUP area of Rahmad Makmur Abadi Ltd, Punggulrejo Village, Rengel District, Tuban Regency, to create a safe working environment and maximize material recovery. Slope stability is evaluated by analyzing the Factor of Safety (FoS ≥ 1.2) using the finite element method based on the Hoek–Brown failure criterion, as well as the Probability of Slope Failure (PF ≤ 10%) using Rosenblueth’s Point Estimate Method under the weakest slope conditions (saturated, with minimum UCS value), in accordance with KEPMEN ESDM No. 1827/K/30/MEM/2018. Through iterative geometric modeling (trial and error), the study produced recommendations for a single slope geometry (bench height of 20 m, width of 6 m, at a 90° inclination). It divided the overall slope into two blocks: Block 1 (bench height of 8 m, width of 4 m, at an 85° inclination with 9 benches, with the lowest bench at 7 m) and Block 2 (bench height of 8 m, width of 5 m, at an 85° inclination with 8 benches, with the lowest bench at 6 m). Rock mass quality analysis using Rock Mass Rating (RMR = 78) and Geological Strength Index (GSI = 73), along with Uniaxial Compressive Strength (UCS > 40 MPa) tests, supports the recommended mining excavation methods—drill & blast for optimizing productivity or the use of a breaker for cost savings.
Copyright (c) 2026 Yudho Dwi Galih Cahyono, Alifer Zalfani Ardiansyah, Rinaldhie Guntur Dharmansyah, Gilberto Amaral https://creativecommons.org/licenses/by/4.0
Petrology and Petrography of Tuffaceous Sandstones from The Cipacar and Genteng Formations in the Kadurahayu Area, Lebak Regency, Banten Province, Indonesia
This study analyzes the petrological characteristics and depositional mechanisms of tuffaceous sandstones in the Genteng and Cipacar Formations, located in the Kadurahayu area, Banten Province. By integrating field observations with quantitative petrography based on Pettijohn (1975), the research identifies distinct mineralogical and textural variations between the two units. The Early-Middle Pliocene Genteng Formation is classified as a lithic wacke, comprising quartz (25%), lithic fragments (28%), and volcanic glass (10%). In contrast, the Late Pliocene Cipacar Formation is categorized as a greywacke, characterized by higher volcanic glass (13%) and clay matrix (22%) content. The presence of massive structures, matrix-supported fabrics, and poor microscopic sorting indicates that these deposits originated from sediment gravity flows and subsequent volcaniclastic reworking rather than primary air-fall processes. Early diagenesis is marked by the devitrification of volcanic glass into clay minerals, which significantly influenced rock porosity and overall properties. Regionally, the Genteng Formation exhibits higher textural maturity due to more extensive transport and reworking, while the Cipacar Formation reflects distal volcanic facies with a dominant primary volcanic input. These findings enhance the understanding of the depositional processes and volcanostratigraphic evolution within the Java volcanic arc.
Copyright (c) 2026 Salsabila Salsabila, Dwi Vina Febrim, Harnani Harnani https://creativecommons.org/licenses/by/4.0
Paleosalinity and Paleoproductivity reconstruction based on Foraminifera Microfossil analysis: A case study of the Oyo Formation, Gunungkidul, Special Region of Yogyakarta, Indonesia
The Oyo Formation in the Southern Mountains of Java represents a neritic carbonate succession rich in foraminifera. This study aims to reconstruct the paleosalinity and paleoproductivity of the Oyo Formation and to evaluate their implications for depositional conditions associated with organic matter preservation. The study was conducted through micropaleontological analysis of foraminifera from three measured sections representing the Sambipitu Formation and the lower and upper parts of the Oyo Formation in Gunungkidul Regency, Special Region of Yogyakarta. Paleosalinity was reconstructed based on the relative abundance of Orbulina universa and Globigerinoides sacculifer, while paleoproductivity was interpreted using the benthic foraminiferal epifaunal–infaunal (E/I) index. The resulting paleosalinity and paleoproductivity trends were tentatively compared with the global Middle Miocene eustatic sea-level curve of Haq et al. (1987) to evaluate the possible influence of relative sea-level fluctuations on depositional conditions. The results indicate that the Sambipitu Formation was deposited under normal marine conditions characterized by low organic matter supply and well-oxygenated bottom waters. The lower part of the Oyo Formation also records normal marine conditions, interrupted by a localized hypersaline event. The upper part of the Oyo Formation exhibits decreasing paleosalinity toward brackish conditions, accompanied by the lowest E/I index values, suggesting increased organic matter flux and relatively reduced bottom-water oxygenation. These environmental conditions may have favored enhanced organic matter preservation compared with the underlying intervals. The results provide a preliminary micropaleontological screening of depositional conditions that may be favorable for organic matter preservation and identify intervals that warrant further evaluation using complementary geochemical analyses.
Copyright (c) 2026 Ihstar Andin Nur Fatiq, Esti Solehatun, Sapto Kis Daryono https://creativecommons.org/licenses/by/4.0
Foraminifera Biostratigraphy and Paleobathymetry of the Ombilin Formation in the Sumpur Kudus Area, Sijunjung Regency, West Sumatra, Indonesia
The Ombilin Formation in the Sumpur Kudus area, Sijunjung Regency, West Sumatra, is known for its abundance of foraminiferal fossils. However, studies on the relative age of the rock layers, particularly regarding paleobathymetry, still require more in-depth research. This study aims to determine the relative age and bathymetric environment of the Ombilin Formation. The research method used is foraminiferal microfossil analysis, which includes identifying planktonic and benthic foraminifera from rock samples in the study area. The data used consist of five carbonate rock samples. The results of the study indicate that the relative age of the Ombilin Formation in the Sumpur Kudus area, Sijunjung Regency, West Sumatra, based on planktonic foraminifera analysis, is Early Miocene (N5), and its bathymetric environment, based on benthic foraminifera analysis, is in the neritic margin to mid-neritic zone (11–175 fathoms). Thus, the results of this study not only confirm previous findings but also strengthen evidence regarding the relative age and depositional characteristics of the Ombilin Formation, in both regional and local contexts, thereby providing supporting data to understand the geological history and evolution of sedimentation in the Ombilin Basin.
Copyright (c) 2026 Febi Annisa, Budhi Setiawan, Yogie Zulkurnia Rochmana https://creativecommons.org/licenses/by/4.0
Depositional Environment of the Rajamandala Formation Based on Foraminiferal Analysis from the Kemang Area, Cianjur Regency, Bogor Basin, West Java, Indonesia
The Rajamandala Calcareous Sandstone Member (Omc) and the Rajamandala Limestone Member (Oml) represent mixed siliciclastic–carbonate and carbonate deposits within the Bogor Basin. This study aims to determine the depositional environments and to evaluate the stratigraphic relationship between these two units by integrating geological mapping and micropaleontological analysis. Biostratigraphic analysis based on planktonic foraminifera indicates that both the Calcareous sandstone unit of the Rajamandala Calcareous Sandstone Member (Omc) and the Rajamandala Limestone Member (Oml) were deposited during the Early Miocene (Zones N7–N8). Benthic foraminiferal assemblages indicate deposition within an inner–middle neritic environment for both units. Field observations document a direct contact between the two lithologies, while geological mapping shows calcareous sandstone becoming increasingly abundant toward the southwest and limestone becoming progressively dominant toward the northeast. The equivalent ages, similar depositional environments, and observed field relationships are consistent with the interpretation that the two units were deposited contemporaneously and exhibit lateral facies variation within the same shallow marine depositional system.
Copyright (c) 2026 Sundus Ghaida Noor Azizah, Dianda Rahma Aulia, Budhi Setiawan https://creativecommons.org/licenses/by/4.0
Changes in Major and Trace Element Concentrations in Low-Rank Coal after Hydrogen Peroxide Pre-treatment: A Screening Approach Based on Enrichment Index
Low-rank coal contains minerals and associated major and trace elements that may be mobilized during processing, particularly under pre-treatment and leaching conditions. This study aimed to characterize the major and trace elements in low-rank coal, evaluate their relative enrichment in solid residues following hydrogen peroxide (H₂O₂) pre-treatment, and assess the potential implications of mobile Fe and Mn for groundwater quality. Elemental concentrations before and after pre-treatment were determined using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), while changes in elemental abundance were evaluated using an enrichment index (Δ%). The untreated coal contained a range of major and trace elements, including Fe, Mn, Yb, Er, Zn, Co, Ni, Mg, Al, Sc, Li, Na, Ga, and Ce. H₂O₂ pre-treatment altered the distribution of several elements in the solid residue, with Fe and Mn showing the most pronounced relative enrichment. These changes are likely associated with the oxidation and transformation of metal-bearing mineral phases under oxidative conditions, whereas other elements exhibited variable responses depending on their modes of occurrence and mineral associations. Leachate analysis by Atomic Absorption Spectroscopy (AAS) further confirmed the mobilization of Fe and Mn into the aqueous phase. Mn concentrations remained below the Indonesian mining wastewater standard (Permen LHK No. 5/2022), whereas Fe concentrations exceeded the regulatory limit in the 40- and 60-mesh samples. In addition, the leachates remained acidic, with pH values below 6. These findings indicate that oxidative pre-treatment can influence both elemental redistribution in coal residues and metal mobility into the aqueous phase, highlighting the importance of controlling pre-treatment conditions and neutralizing acidic leachates prior to discharge. Overall, the proposed screening approach provides a practical preliminary framework for assessing the geochemical mobility of elements in low-rank coal.
Copyright (c) 2026 Yulia Jamastuti, Shofa Rijalul Haq, Rika Ernawati, Hendriono https://creativecommons.org/licenses/by/4.0
Paleoenvironmental Reconstruction of the Sentolo Formation Based on Paleosalinity and Paleoproductivity, South Serayu Basin, Indonesia
The Sentolo Formation represents one of the stratigraphic units of the Kulon Progo Mountains within the South Serayu Basin and is distinguished by the widespread occurrence of limestone. This formation is interpreted to have been deposited in marine settings ranging from neritic to bathyal environments, thereby preserving valuable palaeoceanographic information that can be used to reconstruct past ecological conditions. The distribution of foraminiferal assemblages in the Sentolo Formation is closely controlled by environmental factors, with particular species serving as proxies for ecological parameters such as palaeosalinity and palaeoproductivity. Analysis of the planktic foraminifera Orbulina universa and Globigerinoides sacculifer suggests that palaeosalinity conditions during deposition ranged from brackish to normal marine. In addition, reconstruction based on benthic foraminiferal assemblages indicates oligotrophic palaeoproductivity, as reflected by the predominance of epifaunal taxa over infaunal taxa. Brackish to normal marine salinity conditions are inferred to have promoted relatively high oxygenation, which may have limited the preservation of organic matter. The resulting low accumulation of organic material, together with evidence of oligotrophic productivity, indicates that the Sentolo Formation has limited potential as a hydrocarbon source rock.
Copyright (c) 2026 Esti Solehatun, Ihstar Andin Nur Fatiq, Sapto Kis Daryono https://creativecommons.org/licenses/by/4.0