Organic geochemistry of an oil and gas seep in northern Gulf of Mexico sediments

dc.contributor.advisorParker, Patrick L.
dc.creatorAnderson, Richard Kent
dc.date.accessioned2022-11-21T20:18:37Z
dc.date.available2022-11-21T20:18:37Z
dc.date.issued1984
dc.description.abstractDuring an extensive geochemical and geophysical survey of the outer slope of the northwestern Gulf of Mexico nine piston cores were recovered which had visible liquid organic deposits. In three of the cores deposits were observed concentrated in oblique fracture planes. Other occurrences included large deposits as liquid veins and smaller disseminated pockets in gassy and non-gassy sediments. The benzene soluble material (bitumen) was extracted and chemically and isotopically characterized. Bitumen content ranged as high as 8.6 percent in sediment samples. Gas chromatographic analyses of silica gel fractions showed that both the saturated and aromatic hydrocarbon components are highly biodegraded. The δ¹³C values for the whole oil and fractions were between -26.2 and -26.7 per mil on the PDB scale which closely resembles other Gulf coast oils. The δD values of the oil averaged -104 per mil relative to SMOW. Carbonate nodules found in the oil-rich zones were ¹³C depleted, indicating oxidized organic matter to be the source of the inorganic carbon. Several cores contained natural gas in concentrations high enough to result in large expansion gaps under the reduced ambient pressure at sea level. Hydrocarbon gases from methane through pentanes were sampled in nine cores. Chemical composition and δ¹³C values for methane, ethane, propane, and butanes (-30.5 to -61.9, -28.5, -24.5, -25.7 per mil) indicated that the gas has a major petrogenic component. δD values for methane, ethane, propane and butanes were -172, -101, -104, -101 per mil. Compositional variability of C₂⁺ gases among cores suggests the possible regional influence of gas hydrate formation. Compositional and isotopic variability of methane within and between cores does not conform to a two component mixing model (e.g. biogenic plus petrogenic methane). Instead, highly localized processes, possibly microbial, are implicateden_US
dc.description.departmentChemistryen_US
dc.format.mediumelectronicen_US
dc.identifier.urihttps://hdl.handle.net/2152/116763
dc.identifier.urihttp://dx.doi.org/10.26153/tsw/43658
dc.language.isoengen_US
dc.relation.ispartofUT Electronic Theses and Dissertationsen_US
dc.rightsCopyright © is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works.en_US
dc.rights.restrictionOpenen_US
dc.subjectOrganic geochemistryen_US
dc.subjectOil seepen_US
dc.subjectGas seepen_US
dc.subjectGulf of Mexicoen_US
dc.subjectSedimentsen_US
dc.subjectNorthwestern Gulf of Mexicoen_US
dc.subjectPiston coresen_US
dc.subject.lcshPetroleum in submerged lands--Mexico, Gulf of
dc.subject.lcshOil seepage--Mexico, Gulf of
dc.subject.lcshGas seepage--Mexico, Gulf of
dc.subject.lcshMarine sediments--Mexico, Gulf of
dc.subject.lcshOrganic geochemistry
dc.subject.lcshCore drilling
dc.titleOrganic geochemistry of an oil and gas seep in northern Gulf of Mexico sedimentsen_US
dc.typeThesisen_US
dc.type.genreThesisen_US
thesis.degree.departmentChemistryen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.grantorUniversity of Texas at Austinen_US
thesis.degree.levelDoctoralen_US
thesis.degree.nameDoctor of Philosophyen_US

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