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    Rifting under steam – how rift magmatism triggers methane venting from sedimentary basins (2016)
    GSA (Geological Society of America)
    In:  Geology, 44 (9). pp. 767-770.
    Details
    Publication Date: 2019-10-24
    Description: During opening of a new ocean magma intrudes into the surrounding sedimentary basins. Heat provided by the intrusions matures the host rock creating metamorphic aureoles potentially releasing large amounts of hydrocarbons. These hydrocarbons may migrate to the seafloor in hydrothermal vent complexes in sufficient volumes to trigger global warming, e.g. during the Paleocene Eocene Thermal Maximum (PETM). Mound structures at the top of buried hydrothermal vent complexes observed in seismic data off Norway were previously interpreted as mud volcanoes and the amount of released hydrocarbon was estimated based on this interpretation. Here, we present new geophysical and geochemical data from the Gulf of California suggesting that such mound structures could in fact be edifices constructed by the growth of black-smoker type chimneys rather than mud volcanoes. We have evidence for two buried and one active hydrothermal vent system outside the rift axis. The vent releases several hundred degrees Celsius hot fluids containing abundant methane, mid-ocean-ridge-basalt (MORB)-type helium, and precipitating solids up to 300 m high into the water column. Our observations challenge the idea that methane is emitted slowly from rift-related vents. The association of large amounts of methane with hydrothermal fluids that enter the water column at high pressure and temperature provides an efficient mechanism to transport hydrocarbons into the water column and atmosphere, lending support to the hypothesis that rapid climate change such as during the PETM can be triggered by magmatic intrusions into organic-rich sedimentary basins.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1130/G38049.1
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Gas-controlled seafloor doming (2015)
    GSA (Geological Society of America)
    In:  Geology, 43 (7). pp. 571-574.
    Details
    Publication Date: 2019-10-24
    Description: The upward migration of gas through marine sediments typically manifests itself as gas chimneys or pipes in seismic images and can lead to the formation of cold seeps. Gas seepage is often linked to morphological features like seabed domes, pockmarks, and carbonate build-ups. In this context, sediment doming is discussed to be a precursor of pockmark formation. Here, we present parametric echosounder, sidescan sonar, and two-dimensional seismic data from Opouawe Bank, offshore New Zealand, providing field evidence for sediment doming. Geomechanical quantification of the stresses required for doming show that the calculated gas column heights are geologically feasible and consistent with the observed geophysical data. The progression from channeled gas flow to gas trapping results in overpressure build-up in the shallow sediment. Our results suggest that by breaching of domed seafloor sediments a new seep site can develop, but contrary to ongoing discussion this does not necessarily lead to the formation of pockmarks.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1130/G36596.1
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
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