Karakteristik Geokimia dan Biomarker Rembesan Minyak di Daerah Torete, Morowali, Sulawesi Tengah

Mon, 04 Nov 2024 00:00:00 +0000

Dua buah rembesan minyak bumi diambil dari daerah Torete, Morowali, Provinsi Sulawesi Tengah. Kedua sampel rembesan telah dilakukan analisis GC (gas chromatography) dan GCMS (gas chromatography and mass spectometry). Analisis geokimia biomarker dilakukan untuk mengetahui karakter minyak bumi berupa asal material organik, lingkungan pengendapan, dan tingkat kematangan. Pada kromatogram alkana normal, kedua sampel menunjukkan satu puncak (unimodal) sebelum nC20 dengan rasio Pr/Ph 0,87 dan 0,92. Fragmentogram m/z 217 menunjukkan sedikit dominasi pada sterana C29 dibanding sterana C27 dan sedikit kehadiran dari diasterana. Fragmentogram m/z 191 menunjukkan adanya dominasi pada terpana trisiklik C23 dan terpana tetrasiklik C24 serta kehadiran terpana trisiklik C26+. Pada terpana pentasiklik menunjukkan dominasi Tm terhadap Ts, hopana C29 terhadap hopana C30, kehadiran seri norhopana C30 dan gamaserana, serta homohopana C35 yang sedikit lebih tinggi dari homohopana C34. Biomarker petunjuk tumbuhan tinggi (oleanana dan bikadinana) tidak hadir pada kedua sampel. Hal ini menunjukkan bahwa kedua sampel minyak bumi berasal dari batuan induk karbonat dengan material organik alga, plankton, radiolaria, atau diatom lingkungan pengendapan anoksik-suboksik (lingkungan transisional), dan tingkat kematangan awal matang sampai level matang.

Katakunci: biomarker, GC, GCMS, Torete, Morowali, Sulawesi Tengah.

Geological Structures in The Formation of The Kendal Plains: Insights from Remote Sensing Imagery

Jamal Jamal, Indra Sanjaya, Dian Hari Saputro, Aji Suteja — Fri, 08 Nov 2024 00:00:00 +0000

Kendal Area in Central Java experiences rapid regional geology development. A wide flat area extending towards the Pantura, approximately 40 km wide and 20 km long, is influenced by the Bodri River. The Kendal basin formation is driven by Java’s regional compression tectonics. Major faults show the east-west direction as thrust faults and northeast-southwest direction as strike slip faults correspond to Java’s Regional Structures. Active and passive satellite imagery reveals geomorphic features such as deltas, coastal deposits, paleochannels, break slopes as faults zone, and topographic offsets of the area. The drainage pattern varies with deposit types: distributary channels in the north, meandering channels in the middle, and tributary channels in the south. Fusion image of Landsat 8 and National Digital Elevation Model (DEMNAS) produced by Badan Informasi Geospasial Indonesia (BIG) highlight distinct topographical boundaries and slopes. Residual gravity data shows subsurface contrasts, indicating dominant directions related to surface faults. Other supporting data used include magnetic anomaly imagery processed using the Reduce to Pole (RTP) method which are used to position the source of magnetic anomalies directly above their actual subsurface location. The RTP results enable more accurate interpretation of the distribution and depth of subsurface magnetic sources. The magnetic RTP model aligns with imagery, exhibiting east-west, northeast-southwest, and northwest-southeast trends. This structural interpretation is substantiated by field validation, with evidence of fault cliffs, lithologic offset, fault planes, mylonitization, and fault breccias corroborating the findings.

Keywords: Bodri River, gravity, Kendal, landsat 8, Java’s regional structures, magnetic anomaly.

Jurnal Geologi dan Sumberdaya Mineral

Karakteristik Geokimia dan Biomarker Rembesan Minyak di Daerah Torete, Morowali, Sulawesi Tengah

Geological Structures in The Formation of The Kendal Plains: Insights from Remote Sensing Imagery