Shallow Gas and the Development of a Weak Layer in Submarine Spreading, Hikurangi Margin (New Zealand)

Micallef, Aaron, Mountjoy, Joshu J., Krastel, Sebastian, Crutchley, Gareth and Koch, Stephanie (2016) Shallow Gas and the Development of a Weak Layer in Submarine Spreading, Hikurangi Margin (New Zealand) Submarine Mass Movements and Their Consequences : 7th International Symposium. Advances in Natural and Technological Hazards Research, 37 . Springer International Publishing, Cham, pp. 419-426. ISBN 9783319209784 DOI 10.1007/978-3-319-20979-1_42.

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Submarine spreading is a type of mass movement that involves the extension and fracturing of a thin surficial layer of sediment into coherent blocks and their finite displacement on a gently sloping slip surface. Its characteristic seafloor signature is a repetitive pattern of parallel ridges and troughs oriented perpendicular to the direction of mass movement. We map ~30 km2 of submarine spreads on the upper slope of the Hikurangi margin, east of Poverty Bay, North Island, New Zealand, using multibeam echosounder and 2D multichannel seismic data. These data show that spreading occurs in thin, gently-dipping, parallel-bedded clay, silt and sandy sedimentary units deposited as lowstand clinoforms. More importantly, high-amplitude and reverse polarity seismic reflectors, which we interpret as evidence of shallow gas accumulations, occur extensively in the fine sediments of the upper continental slope, but are either significantly weaker or entirely absent where the spreads are located. We use this evidence to propose that shallow gas, through the generation of pore pressure, has played a key role in establishing the failure surface above which submarine spreading occurred. Additional dynamic changes in pore pressure could have been triggered by a drop in sea level during the Last Glacial Maximum and seismic loading.

Document Type: Book chapter
Keywords: Submarine spreading, Shallow gas, Hikurangi margin, New Zealand
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence > FO-R06
Kiel University
Kiel University > Kiel Marine Science
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
DOI etc.: 10.1007/978-3-319-20979-1_42
Projects: Future Ocean
Date Deposited: 17 Dec 2015 08:13
Last Modified: 08 Mar 2017 11:22

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