Kerogen/asphaltene/sulfur relationships in sulfur-rich Monterey oils

Orr, Wilson L.

doi:10.1016/0146-6380(86)90049-5

Cited by 427 publications

(164 citation statements)

References 15 publications

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“…Several lines of evidence support this interpretation. First, as discussed above, petroleum from the Monterey Formation that floats to the surface is readily weathered in oil slicks to the point of becoming negatively buoyant, presumably because of its unusually high resin, asphaltene, and heteroatom content (2,17). Consistent with this observation, hydrocarbon compounds have been detected in sinking particles collected in sediment traps in Santa Barbara Basin (18).…”

Section: Discussionsupporting

confidence: 66%

Climatically driven emissions of hydrocarbons from marine sediments during deglaciation

Hill

Kennett²,

Valentine³

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Marine hydrocarbon seepage emits oil and gas, including methane (Ϸ30 Tg of CH4 per year), to the ocean and atmosphere. Sediments from the California margin contain preserved tar, primarily formed through hydrocarbon weathering at the sea surface. We present a record of variation in the abundance of tar in sediments for the past 32,000 years, providing evidence for increases in hydrocarbon emissions before and during Termination IA [16,000 years ago (16 ka) to 14 ka] and again over Termination IB (11-10 ka). Our study provides direct evidence for increased hydrocarbon seepage associated with deglacial warming through tar abundance in marine sediments, independent of previous geochemical proxies. Climate-sensitive gas hydrates may modulate thermogenic hydrocarbon seepage during deglaciation.methane ͉ paleoclimate ͉ Quaternary climate ͉ hydrate ͉ tar

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Section: Discussionsupporting

confidence: 66%

Climatically driven emissions of hydrocarbons from marine sediments during deglaciation

Hill

Kennett²,

Valentine³

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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“…The second carbonate underwent a more exhaustive extraction allowing for the separation and identification of other compounds (all data presented in Table 1 and supplemental Table 3). Biomarkers typically associated with seep oils from COP were present in the chromatograms along with a broad unresolved complex mixture, as is typical of the Montereyderived oils at COP (Orr 1986;Wardlaw et al 2008;Farwell et al 2009). Dozens of other compounds were resolved but co-eluted with the unresolved complex mixture (UCM), which likely impacts the accuracy of assigned δ 13 C values.…”

Section: Lipid Biomarkersmentioning

confidence: 99%

Gas flux and carbonate occurrence at a shallow seep of thermogenic natural gas

et al. 2010

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The Coal Oil Point seep field located offshore Santa Barbara, CA, consists of dozens of named seeps, including a peripheral ∼200 m 2 area known as Brian Seep, located in 10 m water depth. A single comprehensive survey of gas flux at Brian Seep yielded a methane release rate of ∼450 moles of CH 4 per day, originating from 68 persistent gas vents and 23 intermittent vents, with gas flux among persistent vents displaying a log normal frequency distribution. A subsequent series of 33 repeat surveys conducted over a period of 6 months tracked eight persistent vents, and revealed substantial temporal variability in gas venting, with flux from each individual vent varying by more than a factor of 4. During wintertime surveys sediment was largely absent from the site, and carbonate concretions were exposed at the seafloor. The presence of the carbonates was unexpected, as the thermogenic seep gas contains 6.7% CO 2 , which should act to dissolve carbonates. The average δ 13 C of the carbonates was −29.2±2.8‰ VPDB, compared to a range of −1.0 to +7.8‰ for CO 2 in the seep gas, indicating that CO 2 from the seep gas is quantitatively not as important as 13 Cdepleted bicarbonate derived from methane oxidation. Methane, with a δ 13 C of approximately −43‰, is oxidized and the resulting inorganic carbon precipitates as highmagnesium calcite and other carbonate minerals. This finding is supported by 13 C-depleted biomarkers typically associated with anaerobic methanotrophic archaea and their bacterial syntrophic partners in the carbonates (lipid biomarker δ 13 C ranged from −84 to −25‰). The inconsistency in δ 13 C between the carbonates and the seeping CO 2 was resolved by discovering pockets of gas trapped near the base of the sediment column with δ 13 C-CO 2 values ranging from −26.9 to −11.6‰. A mechanism of carbonate formation is proposed in which carbonates form near the sediment-bedrock interface during times of sufficient sediment coverage, in which anaerobic oxidation of methane is favored. Precipitation occurs at a sufficient distance from active venting for the molecular and isotopic composition of seep gas to be masked by the generation of carbonate alkalinity from anaerobic methane oxidation.

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“…The high ratios of S org to TOC indicate that the paper shale samples have Type II-S kerogen sensu Orr (1986), i.e. atomic S/C ratios >0.04.…”

Section: Sulphur Contentmentioning

confidence: 99%

Organic facies variation in the late Kimmeridgian of the Boulonnais area (northernmost France)

Tribovillard

Bialkowski

Tyson

et al. 2001

Marine and Petroleum Geology

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Recent studies of the upper Kimmeridgian of the Boulonnais area (northernmost France) have provided a sequence-stratigraphical framework that is here used to help interpret variations in sedimentary organic matter (OM) content and composition in response to fluctuations in relative sea-level. The organic facies are characterised using a combination of palynofacies, bulk organic geochemistry (TOC, Rock Eval pyrolysis, and sulphur data), and the particlesize distribution of the total palynological residues. The organic facies show a good correlation with the sequence stratigraphy, exhibiting peak TOC, HI, total S and S org values in the lithofacies deposited around the two MFS. The palynofacies in these intervals is characterised by a high content of fluorescent, orange, marine AOM. There is a strong correlation between the orange AOM and the total and organic sulphur contents. Similar positive correlations between orange AOM and organic sulphur have previously been observed in the distal organic-rich sediments of the Kimmeridge Clay Formation of Dorset (lateral time equivalents of the Boulonnais facies), but there the sulphur contents are lower, indicating that organic sulphur content of orange AOM is not fixed, suggestive of preservation-related parallel but not intrinsically related trends. The S data can be used to estimate an apparent burial efficiency and hence the proportion of the primary productivity preserved; this allows a rough estimate of palaeoproductivity. Model calculations suggest that for a sulphide retention of 30-70% and uncompacted sedimentation rate estimates in the range 5-10 cm/ka, the mean palaeoproductivity was in the range 52-175 gC/m 2 /a (up to 6% of which was preserved). Thus, if the preservation is high, as is the case for MFS, the palaeoproductivity does not need to be above average for shelf waters to produce a given TOC.

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Kerogen/asphaltene/sulfur relationships in sulfur-rich Monterey oils

Cited by 427 publications

References 15 publications

Climatically driven emissions of hydrocarbons from marine sediments during deglaciation

Climatically driven emissions of hydrocarbons from marine sediments during deglaciation

Gas flux and carbonate occurrence at a shallow seep of thermogenic natural gas

Organic facies variation in the late Kimmeridgian of the Boulonnais area (northernmost France)

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