Seismic-scale funnel-shaped collapse features from the Paleocene–Eocene of the North West Shelf of Australia

Imbert, Patrice; Ho, Sutieng

doi:10.1016/j.margeo.2012.10.010

Cited by 26 publications

(15 citation statements)

References 48 publications

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“…First, if the bubble volume of methane in sediment exceeds a certain threshold value, these bubbles may reach the sediment-water interface, dissolve and oxidize to CO 2 (Archer & Buffett, 2005;Valentine et al, 2001). Although this can happen on small scales (cm-m), this scenario has also been connected to large (km) scale pockmarks, which have been found associated with Paleocene-Eocene sediments (Imbert & Ho, 2012). However, the exact age of these structures remains uncertain and the gas volume accounted for is equivalent to only~1% of the total volume required to explain the CIE.…”

Section: Methane Hydrate Presence and Dissociationmentioning

confidence: 99%

Widespread Warming Before and Elevated Barium Burial During the Paleocene‐Eocene Thermal Maximum: Evidence for Methane Hydrate Release?

Frieling

Peterse

Lunt

et al. 2019

Paleoceanog and Paleoclimatol

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Current climate change may induce positive carbon cycle feedbacks that amplify anthropogenic warming on time scales of centuries to millennia. Similar feedbacks might have been active during a phase of carbon cycle perturbation and global warming, termed the Paleocene‐Eocene Thermal Maximum (PETM, 56 million years ago). The PETM may help constrain these feedbacks and their sensitivity to warming. We present new high‐resolution carbon isotope and sea surface temperature data from Ocean Drilling Program Site 959 in the Equatorial Atlantic. With these and existing data from the New Jersey Shelf and Maud Rise, Southern Ocean, we quantify the lead‐lag relation between PETM warming and the carbon input that caused the carbon isotope excursion (CIE). We show ~2 °C of global warming preceded the CIE by millennia, strongly implicating CO 2 ‐driven warming triggered a positive carbon cycle feedback. We further compile new and published barium (Ba) records encompassing continental shelf, slope, and deep ocean settings. Based on this compilation, we calculate that average Ba burial rates approximately tripled during the PETM, which may require an additional source of Ba to the ocean. Although the precipitation pathway is not well constrained, dissolved Ba stored in sulfate‐depleted pore waters below methane hydrates could represent an additional source. We speculate the most complete explanation for early warming and rise in Ba supply is that hydrate dissociation acted as a positive feedback and caused the CIE. These results imply hydrates are more temperature sensitive than previously considered, and may warrant reconsideration of the political assignment of 2 °C warming as a safe future scenario.

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Section: Methane Hydrate Presence and Dissociationmentioning

confidence: 99%

Widespread Warming Before and Elevated Barium Burial During the Paleocene‐Eocene Thermal Maximum: Evidence for Methane Hydrate Release?

Frieling

Peterse

Lunt

et al. 2019

Paleoceanog and Paleoclimatol

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“…At least three processes might be responsible for the complex geometry observed in VFZ (see Figure 9a): (a) gas hydrate dissociation; (b) downslope processes; and (c) alongslope processes. Imbert and Ho (2012) interpret the V-shaped features as fossil hydrate pockmarks (i.e. collapsed pockmarks) initiated by methane hydrate emplacement along conical failures originating from the subsurface to Palaeocene-Eocene seabed.…”

Section: Interpretation Of Su-2mentioning

confidence: 99%

Tectonic and oceanographic process interactions archived in Late Cretaceous to Present deep‐marine stratigraphy on the Exmouth Plateau, offshore NW Australia

et al. 2018

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Deep‐marine deposits provide a valuable archive of process interactions between sediment gravity flows, pelagic sedimentation and thermohaline bottom‐currents. Stratigraphic successions can also record plate‐scale tectonic processes (e.g. continental breakup and shortening) that impact long‐term ocean circulation patterns, including changes in climate and biodiversity. One such setting is the Exmouth Plateau, offshore NW Australia, which has been a relatively stable, fine‐grained carbonate‐dominated continental margin from the Late Cretaceous to Present. We combine extensive 2D (~40,000 km) and 3D (3,627 km2) seismic reflection data with lithologic and biostratigraphic information from wells to reconstruct the tectonic and oceanographic evolution of this margin. We identified three large‐scale seismic units (SUs): (a) SU‐1 (Late Cretaceous)—500 m‐thick, and characterised by NE‐SW‐trending, slope‐normal elongate depocentres (c. 200 km long and 70 km wide), with erosional surfaces at their bases and tops, which are interpreted as the result of contour‐parallel bottom‐currents, coeval with the onset of opening of the Southern Ocean; (b) SU‐2 (Palaeocene—Late Miocene)—800 m‐thick and characterised by: (a) very large (amplitude, c. 40 m and wavelength, c. 3 km), SW‐migrating, NW‐SE‐trending sediment waves, (b) large (4 km‐wide, 100 m‐deep), NE‐trending scours that flank the sediment waves and (c) NW‐trending, 4 km‐wide and 80 m‐deep turbidite channel, infilled by NE‐dipping reflectors, which together may reflect an intensification of NE‐flowing bottom currents during a relative sea‐level fall following the establishment of circumpolar‐ocean current around Antarctica; and (c) SU‐3 (Late Miocene—Present)—1,000 m‐thick and is dominated by large (up to 100 km3) mass‐transport complexes (MTCs) derived from the continental margin (to the east) and the Exmouth Plateau Arch (to the west), and accumulated mainly in the adjacent Kangaroo Syncline. This change in depositional style may be linked to tectonically‐induced seabed tilting and folding caused by collision and subduction along the northern margin of the Australian plate. Hence, the stratigraphic record of the Exmouth Plateau provides a rich archive of plate‐scale regional geological events occurring along the distant southern (2,000 km away) and northern (1,500 km away) margins of the Australian plate.

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“…Other evacuation features have been described by Imbert and Ho (2012) for the Carnarvon Basin, Australia. Those features are conical, with diameters of a few kilometers and typical depths of a few hundred meters.…”

Section: Evacuation Upward Through Covermentioning

confidence: 75%

“…Consistent with the findings of Sultan et al (2010) on present-day hydrate pockmarks, the conical features were interpreted as collapsed hydrate pockmarks. In that case, no indication of the evacuated material could be found above; Imbert and Ho (2012) proposed that it was evacuated as sediment plumes, and redistributed over wide areas of the Carnarvon slope.…”

Section: Evacuation Upward Through Covermentioning

confidence: 96%

“…Kilometer-scale sediment evacuation under cover is a process that has been described in several contexts-for instance, chambers of mud volcanoes (e.g., Planke et al 2003;Stewart and Davies 2006;Deville 2009;Deville et al 2010), silica ooze "diapirism" (e.g., Riis et al 2005;Lawrence and Cartwright 2010), or hydrate pockmarks and collapsed pockmarks, their fossil counterpart (e.g., Sultan et al 2010;Imbert and Ho 2012). Sediment evacuation is usually observed through the collapse/foundering of a package of sediment below its initial locus of deposition, thereby occupying the space of series that are displaced or removed during the process.…”

Section: Introductionmentioning

confidence: 99%

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How to evacuate 10 km3 of mud: saturate with gas and decrease the pressure!

2014

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The crest of the Absheron anticline in the South Caspian Basin at a few hundred meters below the present seafloor shows a subcircular depression about 8 km in diameter and 200 m deep, bounded by steep edges dipping 15°to 45°into it. The depression and the surrounding series are respectively filled and overlain by a regional mass-transport deposit (MTD) 150 m thick outside the depression and 300 m thick inside, composed mostly of extensional blocks. Geometric and stratigraphic analyses indicate that 150 m of initially deposited sediment were removed from a closed area after burial. Seismic evidence of shallow gas accumulations below the crater-like feature suggests that gas likely played a significant role in its development. The model proposed for the emplacement of the crater is that the gas-bearing cover of a shallow gas reservoir underwent exsolution when its overburden thinned during an episode of extensional slope failure. This resulted in loss of resistance to shear and evacuation of the gas-bearing sediment, likely at the shearing base of the failed mass. This evacuation feature is considered an example where the presence of gas locally governs the morphology of an MTD. The interpreted process shows a positive feedback between slope failure and loss of strength at the base of the resulting MTD.

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Seismic-scale funnel-shaped collapse features from the Paleocene–Eocene of the North West Shelf of Australia

Cited by 26 publications

References 48 publications

Widespread Warming Before and Elevated Barium Burial During the Paleocene‐Eocene Thermal Maximum: Evidence for Methane Hydrate Release?

Widespread Warming Before and Elevated Barium Burial During the Paleocene‐Eocene Thermal Maximum: Evidence for Methane Hydrate Release?

Tectonic and oceanographic process interactions archived in Late Cretaceous to Present deep‐marine stratigraphy on the Exmouth Plateau, offshore NW Australia

How to evacuate 10 km3 of mud: saturate with gas and decrease the pressure!

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