Active gas venting through hydrate-bearing sediments on the Vestnesa Ridge, offshore W-Svalbard

Buenz, S.; Vadakkepuliyambatta, Sunil; Polyanov, Sergey; Mienert, Jürgen

doi:10.1016/j.margeo.2012.09.012

Cited by 149 publications

(312 citation statements)

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“…The system is restricted to the upper stratigraphic sequence (YP3) and has a series of gas chimneys and pockmarks associated along the full extent of the Vestnesa Ridge. However, only pockmarks located toward the easternmost part of the ridge (where our 3D seismic survey is located; Figure 1) are actively seeping gas presently (Bünz et al, 2012;Smith et al, 2014). Gas chimneys toward the westernmost part of the ridge seem inactive presently, but foraminiferal records indicated past activity approximately 8000 my ago (Consolaro et al, 2014).…”

Section: Study Areamentioning

confidence: 90%

“…An inline has been selected from seismic data in which a BSR is clearly identified by high seismic amplitudes at approximately 1.9 s two-way traveltime in the seismic section (Figure 4a) (Bünz et al, 2012;Smith et al, 2014). The BSR separates hydrate-bearing sediments from an approximately 100-m-thick free-gas zone (Hustoft et al, 2009).…”

Section: Analysis Using the Centroid Frequency Methodsmentioning

confidence: 99%

“…Our study focuses on the active seeping segment of the Vestnesa Ridge, an approximately 100-km-long gas hydrate charged contourite drift developed over <20 Ma oceanic crust offshore west Svalbard (Figure 1) (Eiken and Hinz, 1993;Vogt et al, 1994;Bünz et al, 2012). The contourite drift is in close proximity to the Molloy and the Knipovich slow-spreading oceanic ridges, and it is located between the Molloy and the Spitsbergen transform faults (e.g., Ritzmann et al, 2004).…”

Section: Study Areamentioning

confidence: 99%

“…A gas hydrate system and an associated free-gas zone exist along the Vestnesa Ridge (Hustoft et al, 2009;Petersen et al, 2010;Bünz et al, 2012;Plaza-Faverola et al, 2015). The system is restricted to the upper stratigraphic sequence (YP3) and has a series of gas chimneys and pockmarks associated along the full extent of the Vestnesa Ridge.…”

Section: Study Areamentioning

confidence: 99%

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Gas hydrate and free gas detection using seismic quality factor estimates from high-resolution P-cable 3D seismic data

et al. 2016

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We have estimated the seismic attenuation in gas hydrate and free-gas-bearing sediments from high-resolution P-cable 3D seismic data from the Vestnesa Ridge on the Arctic continental margin of Svalbard. P-cable data have a broad bandwidth (20-300 Hz), which is extremely advantageous in estimating seismic attenuation in a medium. The seismic quality factor (Q), the inverse of seismic attenuation, is estimated from the seismic data set using the centroid frequency shift and spectral ratio (SR) methods. The centroid frequency shift method establishes a relationship between the change in the centroid frequency of an amplitude spectrum and the Q value of a medium. The SR method estimates the Q value of a medium by studying the differential decay of different frequencies. The broad bandwidth and short offset characteristics of the P-cable data set are useful to continuously map the Q for different layers throughout the 3D seismic volume. The centroid frequency shift method is found to be relatively more stable than the SR method. Q values estimated using these two methods are in concordance with each other. The Q data document attenuation anomalies in the layers in the gas hydrate stability zone above the bottom-simulating reflection (BSR) and in the free gas zone below. Changes in the attenuation anomalies correlate with small-scale fault systems in the Vestnesa Ridge suggesting a strong structural control on the distribution of free gas and gas hydrates in the region. We argued that high and spatially limited Q anomalies in the layer above the BSR indicate the presence of gas hydrates in marine sediments in this setting. Hence, our workflow to analyze Q using high-resolution P-cable 3D seismic data with a large bandwidth could be a potential technique to detect and directly map the distribution of gas hydrates in marine sediments.

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Section: Study Areamentioning

confidence: 90%

Section: Analysis Using the Centroid Frequency Methodsmentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

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Gas hydrate and free gas detection using seismic quality factor estimates from high-resolution P-cable 3D seismic data

et al. 2016

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“…Bünz et al, 2012;Sztybor and Rasmussen, 2017a, b). We discovered Rosaliella svalbardensis gen. et sp.…”

Section: Introductionunclassified

Cold-seep ostracods from the western Svalbard margin: direct palaeo-indicator for methane seepage?

Yasuhara

Sztybor

Rasmussen

et al. 2018

J. Micropalaeontol.

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Abstract. Despite their high abundance and diversity, microfossil taxa adapted to a particular chemosynthetic environment have rarely been studied and are therefore poorly known. Here we report on an ostracod species, Rosaliella svalbardensis gen. et sp. nov., from a cold methane seep site at the western Svalbard margin, Fram Strait. The new species shows a distinct morphology, different from other eucytherurine ostracod genera. It has a marked similarity to Xylocythere, an ostracod genus known from chemosynthetic environments of wood falls and hydrothermal vents. Rosaliella svalbardensis is probably an endemic species or genus linked to methane seeps. We speculate that the surface ornamentation of pore clusters, secondary reticulation, and pit clusters may be related to ectosymbiosis with chemoautotrophic bacteria. This new discovery of specialized microfossil taxa is important because they can be used as an indicator species for past and present seep environments (http: //zoobank.org/urn:lsid:zoobank.org:pub:6075FF30-29D5-4DAB-9141-AE722CD3A69B).

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Thermogenic methane injection via bubble transport into the upper Arctic Ocean from the hydrate‐charged Vestnesa Ridge, Svalbard

Smith

Mienert

Bünz

et al. 2014

Geochem Geophys Geosyst

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We use new gas-hydrate geochemistry analyses, echosounder data, and three-dimensional PCable seismic data to study a gas-hydrate and free-gas system in 1200 m water depth at the Vestnesa Ridge offshore NW Svalbard. Geochemical measurements of gas from hydrates collected at the ridge revealed a thermogenic source. The presence of thermogenic gas and temperatures of 3.3 C result in a shallow top of the hydrate stability zone (THSZ) at 340 m below sea level (mbsl). Therefore, hydrate-skinned gas bubbles, which inhibit gas-dissolution processes, are thermodynamically stable to this shallow water depth. This was confirmed by hydroacoustic observations of flares in 2010 and 2012 reaching water depths between 210 and 480 mbsl. At the seafloor, bubbles are released from acoustically transparent zones in the seismic data, which we interpret as regions where free gas is migrating through the hydrate stability zone (HSZ). These intrusions result in vertical variations in the base of the HSZ (BHSZ) of up to 150 m, possibly making the shallow hydrate reservoir more susceptible to warming. Such Arctic gas-hydrate and free-gas systems are important because of their potential role in climate change and in fueling marine life, but remain largely understudied due to limited data coverage in seasonally ice-covered Arctic environments.

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Active gas venting through hydrate-bearing sediments on the Vestnesa Ridge, offshore W-Svalbard

Cited by 149 publications

References 36 publications

Gas hydrate and free gas detection using seismic quality factor estimates from high-resolution P-cable 3D seismic data

Gas hydrate and free gas detection using seismic quality factor estimates from high-resolution P-cable 3D seismic data

Cold-seep ostracods from the western Svalbard margin: direct palaeo-indicator for methane seepage?

Thermogenic methane injection via bubble transport into the upper Arctic Ocean from the hydrate‐charged Vestnesa Ridge, Svalbard

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