cover
Contact Name
-
Contact Email
jag.ft@ugm.ac.id
Phone
+62274-513668
Journal Mail Official
jag.ft@ugm.ac.id
Editorial Address
Geological Engineering Departement Universitas Gadjah Mada Jl. Grafika No. 2 Kampus UGM Yogyakarta 55281 Phone +62-274-513668 Fax +62-274-546039
Location
Kab. sleman,
Daerah istimewa yogyakarta
INDONESIA
Journal of Applied Geology
ISSN : 25022822     EISSN : 25022822     DOI : https://doi.org/10.22146
Journal of Applied Geology – JAG focuses on the applied geology and geosciences with its key objective particularly emphasis on application of basic geological knowledge for addressing environmental, engineering, and geo-hazards problems. The subject covers variety of topics including geodynamics, sedimentology and stratigraphy, volcanology, engineering geology, environmental geology, hydrogeology, geo-hazard and mitigation, mineral resources, energy resources, medical geology, geo-archaeology, as well as applied geophysics and geodesy.
Articles 162 Documents
Cooling history (from magma ascent to lava extrusion) of the Watuadeg pillow lava, Berbah, Yogyakarta, Indonesia Indranova Suhendro; Agung Harijoko; Nugroho Imam Setiawan; Haryo Edi Wibowo
Journal of Applied Geology Vol 8, No 1 (2023)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jag.73942

Abstract

The Watuadeg pillow lava (WPL) is known as one of the most famous pillow lava outcrops in Yogyakarta, Indonesia, and its origin has been attributed to rapid-cooling process of subaqueous lava extrusion. However, there is no quantitative evidence that implies such hypotheses. Therefore, this study aims to reduce such a gap by revealing the cooling times (t) of WPL on the basis of a quantitative approach. In particular, we measured the size distribution (CSD) and number density (MND) of plagioclase microlites from the core, medial, and marginal (rim) domains of WPL. We found that the CSD slope significantly increases towards marginal zones, namely 30.4ᵒ for the core, 53.4ᵒ for the medial, and 228.1ᵒ for the rim. Because CSD slope is inversely proportional to cooling time ( ), by assuming a typical plagioclase microlite growth rate (G) of 1×107 mm/s, it is therefore inferred that the rim experienced the fastest cooling time (±12.1 hours), followed by the medial and core ((±52.0 and 91.4 hours, respectively). The fact that MNDs value increases toward the marginal zones also does not deny this idea (0.3×1016 m-3 for the core, 1.4×1016 m-3 for the medial, and 2.4×1016 m-3 for the rim), as higher MND with the domination of acicular-spherulitic habit represents a higher degree of undercooling. Because microlite is syn-eruptive product, our estimation represents the cooling time of magma since it migrated from the reservoir to the surface.
Source Rock Quality and 1D Maturity Model in Pendalian Sub-basin, Central Sumatra Basin Putri Dwi Afifah; Hendra Amijaya; Sarju Winardi; Widi Atmoko
Journal of Applied Geology Vol 8, No 1 (2023)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jag.78104

Abstract

Pematang Formation is well known as the main source rock in the Central Sumatra Basin (Mazied et al., 2008). The formation which acts as source rock has been studied thoroughly in the central and eastern parts of the basin, but research regarding source rock in the western part of the basin, which is the study area, is very limited. This paper aims to define the quality of source rock from a geochemical view through the determination of organic content quantity based on the Total Organic Carbon (TOC) data, determining the type of kerogen, and thermal maturity of the source rock according to the values of Tmax and Vitrinite Reflectance (%Ro). Burial history and thermal maturity models (1D basin modeling) were also constructed to understand the timing of hydrocarbon generation. The results show that Pematang Formation among Sihapas and Telisa Formation has good organic content with TOC ranging from 0.2 to 42.48 wt%, and the maturity parameters indicate that the Pematang Formation has reached the mature stage. Both formations are dominated by Type II kerogen. 1D modeling of the SHT-1 Well indicates that the Pematang Formation is currently in the oil maturity window starting from early oil to main oil at 20.61 Ma, but the model of the SMB-1 Well has not reached the oil maturity window. Tectonic activity is estimated to have a significant effect on this difference when the uplift activity of Bukit Barisan in the Middle Miocene increased the maturity in the northwest, but the inversion that occurred in the Late Miocene resulted in uplift and erosion of young sediments, thus lowering the temperature in some area.