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Downslope-shifting pockmarks: interplay between hydrocarbon leakage, sedimentations, currents and slope's topography

Ho, Sutieng and Imbert, Patrice and Hovland, Martin and Wetzel, Andreas and Blouet, Jean‑Philippe and Carruthers, Daniel. (2018) Downslope-shifting pockmarks: interplay between hydrocarbon leakage, sedimentations, currents and slope's topography. International Journal of Earth Sciences, 107 (8). pp. 2907-2929.

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Official URL: https://edoc.unibas.ch/66645/

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Abstract

Pockmarks in Pliocene-Quaternary continental slope deposits offshore Angola show features related to: (1) fluid leakage craters that formed repeatedly, (2) authigenic methane-derived carbonates that indicate the (former) presence of hydrocarbons and (3) erosional-depositional structures that are clearly related to current activity. Depending on topography, the pockmarks show differing development: "Advancing Pockmarks" preferentially developed on regional slopes or inclined topography (>2.5°-3°). They arranged in a chain-like pattern and mimic the outline of buried turbidite channels below. These pockmarks and their infill migrated downslope in response to shifting vents. "Nested Pockmarks" occur in gently sloping areas (<2°). Their isolated conical infill records slope-parallel migration within a specific depth range pointing to the influence of contour currents. Both pockmark types are long-lived and they record preferential fluid migration along specific pathways, which developed at the downcurrent sidewalls of pockmarks due to flow separation initiating "cavity flow" within the pockmarks. The durable specific migration paths include pockmark sidewalls, vertically stacked erosional-interface of sediment waves, or entire pockmark bodies. The vertical extent of both pockmark types from End Miocene to the present-day seafloor documents various intensities of episodic fluid bursts followed by periods of quiescence and fill.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Ehemalige Einheiten Umweltwissenschaften > Sedimentology (Wetzel)
UniBasel Contributors:Wetzel, Andreas
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Springer
ISSN:1437-3254
e-ISSN:1437-3262
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
Identification Number:
Last Modified:08 Jun 2020 12:42
Deposited On:14 May 2019 12:54

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