Did postglacial catastrophic flooding trigger massive changes in the Black Sea gas hydrate reservoir?

Poort, Jeffrey; Vassilev, A.; Dimitrov, Lyubomir

doi:10.1111/j.1365-3121.2005.00599.x

Cited by 27 publications

(47 citation statements)

References 24 publications

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“…The seepage itself is probably a consequence of higher sediment compaction and steepened pore-pressure gradients in front of the detached sediment ridges. Since the BGHSZ is outcropping at the base of both landslide areas we have to take into account that the sediment failure could have been facilitated by gashydrate destabilization due to temperature and pressure changes associated with climatically driven sea-level fluctuations (Poort et al, 2005), as has also been proposed for e.g. Storegga slide (Bouriak et al, 2000;Bünz et al, 2005).…”

Section: Submarine Landslidesmentioning

confidence: 99%

Geological and morphological setting of 2778 methane seeps in the Dnepr paleo-delta, northwestern Black Sea

et al. 2006

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The Dnepr paleo-delta area in the NW Black Sea is characterized by an abundant presence of methane seeps. During the expeditions of May-June 2003 and within the EU-funded CRIMEA project, detailed multibeam, seismic and hydro-acoustic water-column investigations were carried out to study the relation between the spatial distribution of methane seeps, sea-floor morphology and sub-surface structures.2778 new methane seeps were detected on echosounding records in an area of 1540 km 2 . All seeps are located in the transition zone between the continental shelf and slope, in water depths of 66 to 825 m. The integration of the different geophysical datasets clearly indicates that methane seeps are not randomly distributed in this area, but are concentrated in specific locations.The depth limit for the majority of the detected seeps is 725 m water depth, which corresponds more or less with the stability limit for pure methane hydrate at the ambient bottom temperature (8.9 8C) in this part of the Black Sea. This suggests that, where gas hydrates are stable, they play the role of buffer for the upward migration of methane gas and thus prevent seepage of methane bubbles into the water column.Higher up on the margin, gas seeps are widespread, but accurate mapping illustrates that seeps occur preferentially in association with particular morphological and sub-surface features. On the shelf, the highest concentration of seeps is found in elongated depressions (pockmarks) above the margins of filled channels. On the continental slope where no pockmarks have been observed, seepage occurs along crests of sedimentary ridges. There, seepage is focussed by a parallel-stratified sediment cover that thins out towards the ridge crests. On the slope, seepage also appears in the vicinity of canyons (bottom, flanks and margins) or near the scarps of submarine landslides where mass-wasting breaches the fine-grained sediment cover that acts as a stratigraphic seal. The seismic data show the presence of a distinct bgas front,Q which has been used to map the depth of the free gas within the sea-floor sediments. The depth of this gas front is variable and locally domes up to the sea floor. Where the gas front approaches the seafloor, gas bubbles were detected in the water column. A regional map of the sub-surface depth of the gas front emphasises this bgas front-versus-seepQ relationship. The integration of all data sets indicates that the spatial distribution of methane seeps in the Dnepr paleo-delta is mainly controlled by the gas-hydrate stability zone as well as by stratigraphic and sedimentary factors. D

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Section: Submarine Landslidesmentioning

confidence: 99%

Geological and morphological setting of 2778 methane seeps in the Dnepr paleo-delta, northwestern Black Sea

et al. 2006

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“…Averaged values for salinity, temperature, wind speed, and atmospheric methane concentration were taken from the literature (Table 1). Methane oxidation rates were calculated based on the dataset published by Reeburgh et al (1991). They have been shown to depend linearly on the dissolved methane concentration (Ward et al, 1987).…”

Section: Model Descriptionmentioning

confidence: 99%

“…The first Black Sea methane budget by Reeburgh et al (1991) determined the total water column methane inventory to be 96 Tg. Thus, the Black Sea represents the largest marine water reservoir of dissolved methane.…”

Section: Introductionmentioning

confidence: 99%

“…Hunt, 1974;Kessler et al, 2006;Reeburgh et al, 1991). The Black Sea water column stratification plays a key role in this complex cycle.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the Black Sea represents the largest marine water reservoir of dissolved methane. According to Reeburgh et al (1991), the major methane sources are shelf and slope sediments, which are balanced by anaerobic oxidation of methane as the major sink in the anoxic deep water (4.6 Tg yr −1 ). The second most important sink is the methane flux across the sea/air interface with 0.07 Tg yr −1 .…”

Section: Introductionmentioning

confidence: 99%

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Response of the Black Sea methane budget to massive short-term submarine inputs of methane

2011

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Abstract.A steady state box model was developed to estimate the methane input into the Black Sea water column at various water depths. Our model results reveal a total input of methane of 4.7 Tg yr −1 . The model predicts that the input of methane is largest at water depths between 600 and 700 m (7% of the total input), suggesting that the dissociation of methane gas hydrates at water depths equivalent to their upper stability limit may represent an important source of methane into the water column. In addition we discuss the effects of massive short-term methane inputs (e.g. through eruptions of deep-water mud volcanoes or submarine landslides at intermediate water depths) on the water column methane distribution and the resulting methane emission to the atmosphere. Our non-steady state simulations predict that these inputs will be effectively buffered by intense microbial methane consumption and that the upward flux of methane is strongly hampered by the pronounced density stratification of the Black Sea water column. For instance, an assumed input of methane of 179 Tg CH 4 d −1 (equivalent to the amount of methane released by 1000 mud volcano eruptions) at a water depth of 700 m will only marginally influence the sea/air methane flux increasing it by only 3%.

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Gas Hydrate Accumulations in the Black Sea

Bialas

Haeckel

2022

World Atlas of Submarine Gas Hydrates in Continental Margins

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Did postglacial catastrophic flooding trigger massive changes in the Black Sea gas hydrate reservoir?

Cited by 27 publications

References 24 publications

Geological and morphological setting of 2778 methane seeps in the Dnepr paleo-delta, northwestern Black Sea

Geological and morphological setting of 2778 methane seeps in the Dnepr paleo-delta, northwestern Black Sea

Response of the Black Sea methane budget to massive short-term submarine inputs of methane

Gas Hydrate Accumulations in the Black Sea

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