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Journal : Journal of Applied Sciences, Management and Engineering Technology (JASMET)

Grain Maturity and Sedimentary Processes of the Early Miocene Semilir Formation, Ngoro-oro Gunungkidul, Yogyakarta Rizky, Aga; Isnani, Desi Kumala; Widada, Sugeng; Pratomo, Septyo Uji; Tony, Brian
Journal of Applied Sciences, Management and Engineering Technology Vol 6, No 2 (2025)
Publisher : Institut Teknologi Adhi Tama Surabaya

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31284/j.jasmet.2025.v6i2.8185

Abstract

The texture of sedimentary rocks is a fundamental aspect of sedimentation, reflecting the physical properties of particles and their relationships. Understanding rock texture is essential for interpreting depositional mechanisms and environments. Grain maturity represents a key property within sedimentary textures. The Early Miocene Semilir Formation is characterized by turbidite deposits with tuffaceous lithologies; however, the transport mechanism remains unclear. This study aimed to analyze the sedimentation process of the Semilir Formation by observing grain maturity. Granulometric analysis was conducted on three rock samples from the Ngoro-oro area, Gunungkidul Regency, Yogyakarta. The samples were ground, separated into size fractions, and statistically evaluated to determine quartiles, median diameter, sorting coefficient, skewness, and kurtosis. The results showed that the Semilir Formation consisted of immature grain sedimentary rocks, indicating that the sediments were deposited under moderate to high energy conditions. These findings suggest that the deposits were derived from a nearby source and were strongly influenced by volcanic slopes and underwater volcanic activity.Keywords: Grain maturity; Granulometric analysis; Sedimentary process; Semilir Formation
Hydrothermal Alteration and Mineralization in the Grindulu River Segment, Pacitan, East Java: A Study of the Geotourism Potential of the River Area Mineralization Kurniawan, Oki; Purwanto, Heru Sigit; Harjanto, Agus; Winarno, Edy; Fatchurohman, Dedi; Pratomo, Septyo Uji
Journal of Applied Sciences, Management and Engineering Technology Vol 6, No 2 (2025)
Publisher : Institut Teknologi Adhi Tama Surabaya

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31284/j.jasmet.2025.v6i2.8192

Abstract

The Grindulu River in Pacitan is one of the areas that exhibits manifestations of hydrothermal alteration and metal mineralization. However, the valuable metals found are relatively low, making it less economical to produce. This condition opens up other opportunities by utilizing the area as a natural laboratory for geological education and sustainable geotourism development. This study evaluates the potential for hydrothermal mineralization-based geotourism through geosite assessment. The study area comprises the Watupatok Formation and the Arjosari Formation, which show silicic, argillic, and propylitic alteration zones. The research methods include geological mapping, rock sampling, petrographic analysis, XRD, FA-AAS, and geosite assessment using the Kubalikova method, covering scientific, educational, aesthetic, and value-added aspects. The results show the presence of mineralization in the form of pyrite, chalcopyrite, sphalerite, and galena, with low levels of valuable metals (Au, Ag, Cu, Pb, Zn). Nevertheless, all three segments of the Grindulu River possess significant geosite value for educational and conservation purposes, with segment 2 considered the most ideal due to its superior accessibility and educational value. This study concludes that the Grindulu River is more appropriate for development as a sustainable geotourism destination based on conservation and geological education rather than mining exploitation.