An ancient linked fluid migration system: cold-seep deposits and sandstone intrusions in the Panoche Hills, California, USA

Schwartz, H.; Sample, J. C.; Weberling, K.; Minisini, Daniel; Moore, J. Casey

doi:10.1007/s00367-003-0142-1

Cited by 82 publications

(68 citation statements)

References 46 publications

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“…The occurrence and formation of carbonate minerals depleted in 13 C is common among marine methane seeps (Stakes et al 1999;Luff and Wallmann 2003;Gieskes et al 2005;Naehr et al 2007;Paull et al 2007), and is used as an indicator of seepage occurrence in the geologic record (Peckmann et al 1999;Schwartz et al 2003;Campbell 2006;Gontharet et al 2007). Carbonate minerals precipitate because of the high carbonate alkalinity associated with vigorous sulfate reduction common to methane seeps.…”

Section: Introductionmentioning

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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Section: Introductionmentioning

confidence: 99%

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

et al. 2010

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“…Rare tubes found as relatively straight broken segments at least 10 cm (0.3 ft) long and exhibiting perfectly circular sections less than 1 cm (0.4 in.) in diameter (enlarging progressively through the segments) are attributed to the Vestimentifera by Schwartz et al (2003). The density of fossils is approximately 1/m 2 (1/11 ft 2 ).…”

Section: Faunamentioning

confidence: 97%

“…Concretions interpreted as seep carbonates (Schwartz et al, 2003) are present in the Dos Palos Shale Member, up to the Cima Sandstone Lentil stratigraphic level (Minisini and Schwartz, 2007). However, they are isolated and rare in the Dos Palos Shale Member and are abundant only in the Cima Sandstone Lentil.…”

Section: Stratigraphymentioning

confidence: 99%

“…The Panoche giant injection complex has been extensively studied by many authors (Vigorito et al, 2008;Vétel and Cartwright, 2010;Vigorito and Hurst, 2010;Scott et al, 2013). Schwartz et al (2003) and Minisini and Schwartz (2007) described seep carbonates at the top of the Moreno Formation. The authors correlated seep carbonate distributions over several kilometers to the presence of underlying sand dykes emanating from the Panoche Formation, thereby providing evidence that the injectites served as hydrocarbon migration pathways.…”

Section: Introductionmentioning

confidence: 99%

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Mechanisms of biogenic gas migration revealed by seep carbonate paragenesis, Panoche Hills, California

Blouet¹,

Imbert²,

Foubert³

2017

Bulletin

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A comprehensive study of seep carbonates at the top of the organic-rich Maastrichtian to Danian Moreno Formation in the Panoche Hills (California) reveals the mechanisms of generation, expulsion, and migration of biogenic methane that fed the seeps. Two selected outcrops show that seep carbonates developed at the tip of sand dykes intrude up into the Moreno Formation from deeper sandbodies. Precipitation of methane-derived cements occurred in a succession of up to 10 repeated elementary sequences, each starting with a corrosion surface followed by dendritic carbonates, botryoidal aragonite, aragonite fans, and finally laminated micrite. Each element of the sequence reflects three stages. First, a sudden methane pulse extended up into the oxic zone of the sediments, leading to aerobic oxidation of methane and carbonate dissolution. Second, after consumption of the oxygen, anaerobic oxidation of methane coupled with sulfate reduction triggered carbonate precipitation. Third, progressive diminishment of the methane seepage led to the deepening of the reaction front in the sediment and the lowering of precipitation rates. Carbonate isotopes, with d 13 C as low as -51‰ Peedee belemnite, indicate a biogenic origin for the methane, whereas a one-dimensional basin model suggests that the Moreno Formation was in optimal thermal conditions for bacterial methane generation at the time of seep carbonate precipitation. Methane pulses are interpreted to reflect drainage by successive episodes of sand injection into the gas-generating shale of the Moreno Formation. The seep carbonates of the Panoche Hills can thus be viewed as a record of methane production from a biogenic source rock by multiphase hydraulic fracturing. A U T H O R S

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“…This is even more striking considering that only two more seep faunas from this time interval other than the above mentioned thyasirid-bearing faunas are known. These are some Maastrichtian seep faunas from Western Interior Seaway, USA (Metz, 2010); and Paleocene Panoche Hills seeps from California, USA (Schwartz et al, 2003). This common occurrence of large thyasirids at seeps during the latest Cretaceous and Paleocene is puzzling.…”

mentioning

confidence: 99%