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AAPG Bulletin

Abstract

AAPG Bulletin, V. 88, No. 6 (June 2004), P. 841-855.

Copyright copy2004. The American Association of Petroleum Geologists. All rights reserved.

Seafloor reconnaissance and classification of the Storegga Slide headwall region, Norwegian Sea, using side-scan sonar, video, and photographs acquired on submarine NR-1

Brian S. Parsons,1 Peter R. Vogt,2 Haflidi Haflidason,3 Woo-Yeol Jung4

1Marine Geosciences Division, Naval Research Laboratory, Washington, D.C. 20375; present address: General Dynamics, Advanced Information Systems, 540E Huntmar Park Drive, Herndon, Virginia 20170; [email protected]
2Marine Geosciences Division, Naval Research Laboratory, Washington, D.C. 20375; [email protected]
3Department of Earth Science, University of Bergen, Allegt. 41, N-5007 Bergen, Norway; [email protected]
4Marine Geosciences Division, Naval Research Laboratory, Washington, D.C. 20375-5320

AUTHORS

Brian Parsons has a B.S. degree in geology (1994) and a Ph.D. in oceanography (1999) from Old Dominion University. He joined Woodward-Clyde in 1998 and worked on subsea pipeline routes in the Black Sea and the Philippines. He received a National Research Council Fellowship (2000ndash2003) and studied continental slope stability on the Norwegian margin. His main interests are using sonar and seafloor data to assess sediment dynamics for subsea engineering projects.

A marine geophysicist working at the Naval Research Laboratory on subjects ranging from plate tectonics to methane hydrates and sediment dynamics, Peter Vogt obtained a B.S. degree from the California Institute of Technology in 1961, and a Ph.D. in oceanography at the University of Wisconsin. Vogt is a Fellow of the Geological Society of America. In 2000, he received an honorary doctorate from the University of Bergen and was elected to the Norwegian Academy of Science and Letters. In 2003, he was recognized as a Distinguished Alumnus by the University of Wisconsin. Vogt has authored or coauthored over 150 peer-reviewed papers, accumulating over 4000 citations.

Haflidi Haflidason is a professor of marine geology at the University of Bergen, Norway. He received his B.S. degree from the University of Iceland in 1978, his M.Phil. degree from University of Edinburgh 1984, and his Dr.Scient. from University of Bergen in 1994. His research interests are in Quaternary stratigraphy, continental slope stability, and paleoceanography vs. marine sedimentary processes.

Jung finished college at Seoul National University and studied marine geophysics at Columbia University. He received his Ph.D. from Texas AampM University and was awarded National Research Council Research Associateship at the Naval Research Laboratory. He has been working there since 1987. Jung's research area involves inversion/numerical modeling techniques related to geopotential field anomalies and recently to gas-hydrate stability under the ocean floors.

ACKNOWLEDGMENTS

We thank the Marine Physics Branch Head, H. Fleming, as well as B. Vermillion and I. Jewett for their support. We further thank the Officer in Charge (Charles D. Richard), the officers and crew of submarine NR-1 for their expertise, and two midshipmen from the U.S. Naval Academy for assisting the scientists. We thank the editor (W. Sager), J. Mienert, and M. Hovland for reviews. M. Richardson (Naval Research Laboratory) shared information on rates of colonization of sessile benthos on seafloor rocks. The first author was supported by a National Research Council Research Associateship. This research was supported by the Office of Naval Research, Program Element 0601153N. We further thank the Ormen Lange License Group (Norsk Hydro, AS Norske Shell, Statoil, BP, Exxon, Mobile, and Petoro) for permission to use Storegga multibeam bathymetry to plan the NR-1 dives. The field work by H. Haflidason was financially supported by the Continental Slope Stability (COSTA) of Ocean Margins program (EC 5th Framework project EVK-CT-1999-00006).

ABSTRACT

The U.S. Navy nuclear research submarine NR-1 was used to investigate the Storegga Slide (Norwegian Sea) shelf break, headwall, and upper debris-flow fields to a maximum water depth of 630 m (2070 ft). About 275 km (170 mi) of seafloor was traversed in 1 week, collecting 150-kHz side-scan sonar, current speed and direction, bathymetry, optic imagery, and visual observations. Side-scan imagery was used to identify four provinces, some corresponding to distinct optic-scale characteristics. We found the Storegga outer shelf streaked and locally incised by iceberg plow marks or otherwise ldquolineatedrdquo in the side-scan imagery. We attribute the ldquostreakingrdquo to the strong Norwegian-Atlantic Current and perhaps the Norwegian Coastal Current. Despite our short current-sampling ldquosnapshot,rdquo we found good agreement between measured current directions and current-generated seafloor features. Along the headwall, just seaward of the iceberg plow marks, are deep-water, coral (Lophelia pertusa) reefs. Recent instability (post-8.15 ka) along part of the headwall region is indicated by cobble/boulder fields devoid of sessile biota (such as sponges). No obvious fluid expulsion or extensional features were discovered in the small portion of the Storegga Slide that was investigated.

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