Cruise summary for P-1-02-SC: acoustic imaging of natural oil and gas seeps and measurement of dissolved methane concentration in coastal waters near Pt. Conception, California

Lorenson, T. D.; Dougherty, Jennifer; Ussler, William; Paull, C. K.

doi:10.3133/ofr03122

Cited by 2 publications

(5 citation statements)

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“…These observations provide ample evidence for seepage sites within the depth range required to explain the tar index record. In addition, hydrocarbon deposits are common along the California coast, and the tar index may incorporate hydrocarbons originating from outside of SBC (19). Comparison of the tar index between the two cores indicates that the deeper site (MD02-2503) has higher index values during the deglacial episode.…”

Section: Discussionmentioning

confidence: 99%

“…For example, seepage near Point Conception (northwest of SBC) may have contributed to the tar preserved in SBC sediments through transport in the California current (19). Changes in concentrations of petroleum compounds (hopanes) from ODP Site 1016 (3,846 m; on the continental slope offshore Point Conception) correlate with major shifts in climate, with the largest peaks over major deglacial warming during Terminations I and II (13).…”

Section: Discussionmentioning

confidence: 99%

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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: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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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“…B) Map showing the tracklines along which sidescan-sonar data were obtained for the collaborative study with MMS. Water-column methane anomalies from (Lorenson et al, 2003) are based on an earlier cruise in support of the MMS collaboration and were used in part to determine survey area. Open white rectangle shows area of sidescan-sonar image in Figure 5.…”

Section: Discussionmentioning

confidence: 99%

“…These anomalies could result from gas rising from the seafloor; a strong reflection is observed, particularly on 12-kHz echo-sounding profiles, and an acoustic shadow results from the efficiency of the reflection. A water sample with elevated methane concentration was obtained during a previous cruise (Lorenson et al 2003) from an area of circular features in the southeastern part of the image in Figure 5. The floor of these circular targets are typically 10 m to 20 m in diameter and exhibit stronger acoustic backscatter than the surrounding sea floor as would be expected from either coarser grain size of sediment or greater roughness.…”

Section: Overview Of Seismic-reflection Datamentioning

confidence: 99%

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Cruise report for A1-02-SC southern California CABRILLO project, Earthquake Hazards Task

Normark¹,

Fisher²,

Gutmacher³

et al. 2003

Open-File Report

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This section provides an overview of the restrictions on acoustic sources used during the cruise as well as information about the vessel, personnel (Table 1), equipment used, and key operational events during the cruise (Table 2). See Table 3 for types of data collected along each survey trackline. Restrictions on use of the acoustic sound sources The use of acoustic sources for seismic-reflection profiling is limited by regulations of both State and Federal agencies. The National Marine Fisheries Service (NMFS), which is the agency empowered to enforce the provisions of the Marine Mammal Protection Act (MMPA) requires that operations involving acoustic sources such as those used by the USGS for the 2002 cruise must be conducted under a permit granting Incidental Harassment Authorization (IHA). The IHA request process nominally takes 150 days and the request was submitted to NMFS in mid-January 2002. One part of the IHA process requires NMFS to make the application available for public comment, which is done through notification in the Federal Register. The California Coastal Commission (CCC) and the California State Lands Commission (SLC) both have additional issues and regulations that pertain to offshore surveys. The procedures for acquiring necessary permits to conduct seismic-reflection surveys off California using small sound sources are reviewed by Childs et al. (1999).

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Cruise summary for P-1-02-SC: acoustic imaging of natural oil and gas seeps and measurement of dissolved methane concentration in coastal waters near Pt. Conception, California

Cited by 2 publications

References 0 publications

Climatically driven emissions of hydrocarbons from marine sediments during deglaciation

Climatically driven emissions of hydrocarbons from marine sediments during deglaciation

Cruise report for A1-02-SC southern California CABRILLO project, Earthquake Hazards Task

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