Origin of pockmarks and chimney structures on the flanks of the Storegga Slide, offshore Norway

Authors

Charles K. Paull, Monterey Bay Aquarium Research Institute
William Ussler III, Monterey Bay Aquarium Research Institute
W. Steven Holbrook, University of Wyoming
Tessa M. Hill, University of California, Davis
Rendy Keaten, Monterey Bay Aquarium Research Institute
Jurgen Mienert, The Arctic University of Norway
Haflidi Haflidason, University of Bergen
Joel E. Johnson, University of New Hampshire, DurhamFollow
William J. Winters, United States Geological Survey, Woods Hole
Thomas D. Lorenson, United States Geological Survey, Menlo Park

Abstract

Seafloor pockmarks and subsurface chimney structures are common on the Norwegian continental margin north of the Storegga Slide scar. Such features are generally inferred to be associated with fluid expulsion, and imply overpressures in the subsurface. Six long gravity and piston cores taken from the interior of three pockmarks were compared with four other cores taken from the same area but outside the pockmarks, in order to elucidate the origins and stratigraphy of these features and their possible association with the Storegga Slide event. Sulfate gradients in cores from within pockmarks are less steep than those in cores from outside the pockmarks, which indicates that the flux of methane to the seafloor is presently smaller within the pockmarks than in the adjacent undisturbed sediments. This suggests that these subsurface chimneys are not fluid flow conduits lined with gas hydrate. Methane-derived authigenic carbonates and Bathymodiolus shells obtained from a pockmark at >6.3 m below the seafloor indicate that methane was previously available to support a chemosynthetic community within the pockmark. AMS 14C measurements of planktonic Foraminifera overlying and interlayered with the shell-bearing sediment indicate that methane was present on the seafloor within the pockmark prior to 14 ka 14C years b.p., i.e., well before the last major Storegga Slide event (7.2 ka 14C years b.p., or 8.2 ka calendar years b.p.). These observations provide evidence that overpressured fluids existed within the continental margin sediments off Norway during the last major advance of Pleistocene glaciation.

Department

Earth Sciences

Publication Date

2-1-2008

Journal Title

Geo-Marine Letters

Publisher

Springer

Digital Object Identifier (DOI)

https://dx.doi.org/10.1007/s00367-007-0088-9

Document Type

Article

Recommended Citation

Paull, C.K., Ussler, W. III, Holbrook, S.W., Hill, T.M., Keaten, R., Mienert, J., Haflidason, H., Johnson, J.E., Winters, W.J., and Lorenson, T.D., 2007, Origin of pockmarks and chimney structures on the flanks of the Storegga Slide, offshore Norway. Geo-Marine Letters, DOI 10.1007/s00367-007-0088-9. http://dx.doi.org/10.1007/s00367-007-0088-9

Rights

© Springer-Verlag 2007