Kajian Biomarka Fraksi Alifatik Aspal Alam Dari Pulau Buton, Daerah Lasalimu, Sulawesi Tenggara

Juliani, Selviar (2026) Kajian Biomarka Fraksi Alifatik Aspal Alam Dari Pulau Buton, Daerah Lasalimu, Sulawesi Tenggara. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Biomarka fraksi hidrokarbon alifatik aspal alam Lasalimu dianalisis dengan ekstraksi, fraksinasi, dan GC-MS untuk menentukan asal bahan organik. Keberadaan unresolved complex mixture (UCM), berkurangnya n-alkana dan isoprenoid menunjukkan biodegradasi lanjut dan pengaruh water washing. Interpretasi geokimia menunjukkan bahwa bahan organik diendapkan pada lingkungan laut dangkal kaya lempung dalam kondisi anoksik yang mendukung preservasi alga, sebagaimana ditunjukkan oleh rasio diasterana/sterana sebesar 0,59 yang mencerminkan sistem klastik-karbonat campuran. Distribusi sterana didominasi oleh input laut (sterana C₂₇ sebesar 24,20%; sterana C₂₈ sebesar 56,30%), dengan kontribusi terestrial yang kecil (rasio hopana C₂₉/C₃₀ = 0,59; rasio trisiklik terpana/hopana = 1,55). Parameter kematangan termal menunjukkan tahap awal hingga menengah oil window (early to mid oil window), yang tercermin dari rasio C₂₉ 20S/(20S+20R) sebesar 0,44; rasio Ts/Tm sebesar 0,53; dan rasio homohopana 22S/(22S+22R) sebesar 0,51–0,53. Alterasi sekunder yang kuat dibuktikan oleh rendahnya fraksi alifatik (1,77%); tingginya kandungan aspalten (15,39%); serta keberadaan 25-norhopana dan UCM yang menunjukkan biodegradasi berat (petroleum microbiodegradation level, PM 6–7). Kondisi ini diduga berkaitan dengan pengangkatan pada Neogen yang memicu biodegradasi dan water washing, sehingga menyebabkan hilangnya hidrokarbon ringan, peningkatan viskositas minyak, dan pembentukan aspal alam. Dengan demikian, sistem petroleum di daerah penelitian telah mengalami alterasi sekunder yang signifikan, yang menyebabkan hilangnya hidrokarbon ringan dan pembentukan aspal alam.
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The aliphatic hydrocarbon biomarkers of natural asphalt from Lasalimu were analyzed using extraction, fractionation, and gas chromatography-mass spectrometry (GC-MS) to determine the origin of the organic matter. The presence of an unresolved complex mixture (UCM), together with the depletion of n-alkanes and isoprenoids, indicates advanced biodegradation and the effects of water washing. Geochemical interpretation indicates that the organic matter was deposited in a shallow marine, clay-rich, anoxic environment favorable for algal preservation, as reflected by a diasterane/sterane ratio of 0.59, suggesting a mixed clastic-carbonate system. The sterane distribution is dominated by marine input (C₂₇ steranes: 24.2%; C₂₈ steranes: 56.3%), with only a minor terrestrial contribution, as supported by a C₂₉/C₃₀ hopane ratio of 0.59 and a tricyclic terpane/17α(H)-hopane ratio of 1.55. Thermal maturity parameters indicate an early to mid oil window, reflected by a C₂₉ 20S/(20S+20R) ratio of 0.44, a Ts/Tm ratio of 0.53, and C₃₁–C₃₂ homohopane 22S/(22S+22R) ratios of 0.51–0.53. Strong secondary alteration is evidenced by the low aliphatic fraction (1.77%), the high asphaltene content (15.39%), and the presence of 25-norhopanes and UCM, indicating severe biodegradation (petroleum microbiodegradation level, PM 6–7). This alteration is inferred to be related to Neogene uplift, which promoted biodegradation and water washing, resulting in the loss of light hydrocarbons, increased oil viscosity, and the formation of natural asphalt. Therefore, the petroleum system in the study area has undergone significant secondary alteration, leading to the loss of light hydrocarbons and the formation of natural asphalt.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Asphalt, Buton, Aliphatic, Biomarker, GC–MS.
Subjects:	Q Science Q Science > QD Chemistry > QD251.2 Chemistry, Organic. Biochemistry
Divisions:	Faculty of Science and Data Analytics (SCIENTICS) > Chemistry > 47201-(S1) Undergraduate Thesis
Depositing User:	Selviar Juliani
Date Deposited:	05 Aug 2026 04:29
Last Modified:	05 Aug 2026 04:29
URI:	http://repository.its.ac.id/id/eprint/143963

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