Identification of Fault Structure in the Mount Tampomas Geothermal Area Based on Derivative Analysis and 2.5D Forward Modelling Using the Gravity Method

Sultan Ahmad Syarifuddin, Suharsono Suharsono, Iqbal Takodama — Sat, 28 Feb 2026 00:00:00 +0000

The Mount Tampomas Geothermal Area is located in Sumedang Regency, West Java Province. This study aims to interpret the distribution of subsurface fault structures based on gravity data analysis over an area of 14 × 14 km². Residual gravity anomaly analysis reveals the presence of a low gravity anomaly in the central part of the volcanic edifice, which is interpreted as a low-density zone associated with a magma ascent pathway within the volcanic system. The results of derivative analysis, correlated with surface geological data, indicate the presence of fault structures comprising normal faults, strike-slip faults, and reverse faults, which represent structural patterns predominantly controlled by volcanic activity. Forward modelling applied to several profiles yields the subsurface lithological density distribution, including the Subang Formation (2.40 g/cm³), Kaliwangu Formation (2.35 g/cm³), old volcanic lahar breccia (2.85 g/cm³), undifferentiated volcaniclastic tuffaceous sand (2.55 g/cm³), pumiceous tuff (2.60 g/cm³), breccia and agglomerate (2.70 g/cm³), and young volcanic lava (2.50 g/cm³).The results of this study provide a preliminary characterization of subsurface fault structures in the Mount Tampomas Geothermal Area based on gravity methods.

Keywords : Gravity, Geothermal, Tampomas, Derivative
Analysis, Forward Modelling

Determination of Coal Quality and Depositional Environment Based on Ash Content, Total Moisture, and Total Sulphur on Gross Calorific Value of Coal in the Batuah Village, Loa Janan District, Kutai Kartanegara Regency, East Kalimantan Province

Muhammad Afrizal Ie, Ahmad Helman Hamdani, Winantris Winantris — Sat, 28 Feb 2026 00:00:00 +0000

Coal is formed from the accumulation of plant material that undergoes decomposition, compaction, and deposition over millions of years due to physical and chemical influences. This study was conducted in the Kampung Baru Formation, Kutai Basin, to determine quality and depositional environment of coal. Data were obtained from three boreholes (DH-01, DH-02, and DH-03) with having coal thicknesses of 17.8 m, 9.8 m, and 4.8 m, respectively. The analyses performed proximate and ultimate. The results showed that huminite (densinite) was the dominant maceral component with an average of 36.6%, followed by liptinit (cutinite) at 6.8% and inertinite (semifusinite) at 3.03%. The mineral matter content was dominated by pyrite (1.8–6.8%) and clay (0.8–7.6%). The average values of the proximate and ultimate analyses show an ash content of 20.60%, total water of 12.25%, total sulphur of 0.66%, and a calorific value of 4,042.3 cal/g. Based on the United Nations (1998) and ASTM classifications, coal in the study area is categorized as a lignite B to low-medium rank coal. Depositional environment analysis is based on Lamberson diagram classification (1991), which shows that the coal was deposited in a limno-telmatic zone with a lower to upper delta plain facies.

Keywords: Coal, Kutai Basin, Kampung Baru Formation, Quality, Depositional Environment, Maceral

Jurnal Geologi dan Sumberdaya Mineral

Identification of Fault Structure in the Mount Tampomas Geothermal Area Based on Derivative Analysis and 2.5D Forward Modelling Using the Gravity Method

Determination of Coal Quality and Depositional Environment Based on Ash Content, Total Moisture, and Total Sulphur on Gross Calorific Value of Coal in the Batuah Village, Loa Janan District, Kutai Kartanegara Regency, East Kalimantan Province