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All Journal Jurnal Pendidikan, Sains, Geologi, dan Geofisika (GeoScienceEd Journal) Journal of Earth and Marine Technology (JEMT)
Wijaya, Muhammad Eval Juni
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Agriculture, Biological Sciences & Forestry Chemistry Civil Engineering, Building, Construction & Architecture Earth & Planetary Sciences Education Energy Physics Transportation

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Perubahan Iklim Kala Miosen Akhir Berdasarkan Analisis Palinologi Di Formasi Lemau, Bengkulu Mentari, Sakilla; Wijaya, Muhammad Eval Juni; Adesti Audina Ulfah
Jurnal Pendidikan, Sains, Geologi, dan Geofisika (GeoScienceEd Journal) Vol. 6 No. 4 (2025): November
Publisher : Mataram University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29303/goescienceed.v6i4.599

Abstract

Fossil pollen and spores can be used to determine the age and depositional environment of sedimentary rocks, as well as to reconstruct the paleoclimate at the time the rocks were formed. The use of pollen and spores for paleoclimate reconstruction in Sumatra remains limited. This study aims to identify the pollen and spore assemblages of the Lemau Formation and to reconstruct Late Miocene climatic changes based on these assemblages. Sampling was conducted through a measured stratigraphic section at 5–8 cm intervals, and laboratory analysis employed the hydrogen peroxide method. A total of ten rock samples were collected and analyzed. The results indicate that the study area experienced a warm climate with five episodes of humidity variation, interpreted from changes in the abundance of arboreal pollen, non-arboreal pollen, Graminae, spores, and montane pollen. The warm climatic conditions and humidity fluctuations are inferred to be related to the global Middle Miocene Climate Optimum (MMCO) event, as well as to uplift activity of the Bukit Barisan Range in the study area.
Petrology and Geochemistry of Volcanic Rocks of Kaba Volcano, Bengkulu Wijaya, Muhammad Eval Juni; Mentari, Sakila Gia; Pratama, Ridho Ramadhan; Sitohang, Victor Ranson
Journal of Earth and Marine Technology (JEMT) Vol 6, No 1 (2025)
Publisher : Lembaga Penelititan dan Pengabdian kepada Masyarakat - Institut Teknologi Adhi Tama Suraba

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31284/j.jemt.2025.v6i1.8571

Abstract

Mount Kaba is an active stratovolcano in Bengkulu Province, Indonesia, characterized by explosive magmatic eruptions and the presence of monogenetic volcanic centers, reflecting complex magmatic processes. This study focuses on the northern sector of the Mount Kaba area to investigate magma evolution and its relationship to volcanic development and hazard mitigation. Fifteen representative lava and pyroclastic rock samples were analyzed using petrographic observations and ICP-MS geochemical methods to determine major, trace, and rare earth element (REE) compositions. Petrographic results indicate basaltic to andesitic rocks with hypocrystalline textures, dominated by plagioclase, pyroxene, olivine, hornblende, and displaying porphyritic, trachytic, sieve, zoning, intersertal, and reaction rim textures that reflect disequilibrium processes and multi-stage magma evolution. Geochemically, rocks range from basanite/tephrite to dacite and belong mainly to calc-alkaline to high-K calc-alkaline magma affinities, forming two magma groups (Danau Mas and Kaba). Major element Harker diagrams show decreasing MgO, CaO, FeO, TiO₂ with increasing SiO₂ and increasing Na₂O + K₂O, indicating progressive differentiation. Trace element diagrams display positive trends of LILE and HFSE with SiO₂ and dual magma trends, suggesting multiple differentiation histories. Spider diagrams reveal LILE enrichment, HFSE depletion, and LREE enrichment relative to HREE, consistent with subduction-related magma sources. Integration of petrographic and geochemical data indicates that magma evolution was dominated by fractional crystallization, with additional influences from assimilation and magma mixing that produced compositional diversity and disequilibrium textures. Overall, the Mount Kaba magmatic system reflects a dynamic subduction zone environment characterized by multiple magma sources, progressive differentiation, and complex interactions within the crust, with implications for understanding volcanic processes and hazard potential in the northern sector.
Co-Authors Adesti Audina Ulfah Mentari, Sakila Gia Mentari, Sakilla Pratama, Ridho Ramadhan Sitohang, Victor Ranson